# Bazmak - gearcutting



## bazmak (Sep 4, 2016)

Having spent all my working life in engineering I have never cut spur gears
I don't want to spend I long time learning all the technicalities but would like
to cut some spur gears.Just for the learning not for a any specific purpose
at this stage.I would like to cut some gears the same as the Sieg lathe change gears,which I think are Mod 1. A full set of involute cutters would be too costly
but I assume I can use a single hob??.Seen one on ebay from china for $40
Am I wasting my time.Cant make one economical as silver steel is too expensive here in Oz. General question. From my threads you can see I am in the process of making a dividing head.Is it feasible for me to buy a mod1 hob
and successfully make gears.Lots of comments would be appreciated


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## moerman (Sep 4, 2016)

Silversteel might be too expensive but how about old files? Or other hardened tools. Can't help you with advice about gear cutting. You're way ahead of me.


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## chucketn (Sep 4, 2016)

now that you have a rotary table and a dividing head, check out this link for all the info you need to make gears.

http://www.helicron.net/workshop/gearcutting/involute-gears/

Shows how to make the cutter and how to use it. 

Chuck​


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## Blogwitch (Sep 4, 2016)

Baz,

Cutting gears with a commercial hob requires the piece part to rotate in sync with the cutter.
The main advantage of a hob over involute cutters is that one hob will cut any number of teeth on a gear as long as the diameter for that gear is correct.

I have a full set of mod and DP hobs, plus I also have all the castings to make a gear hobber. 







The one shown next to the gear is a 1.25 MOD hob, the correct one for my change gears.

http://www.collegeengineering.co.uk/?product_cat=gear-hobbing-machine

These were a left over project when my shop was producing commercial items, which mine and my wife's failing health forced me to close.

One of the first jobs I will be doing when I get up and running again is a spring winder, which I will use on a freewheeling spindle similar to your latest indexer. Once that is out of the way, the freewheeling spindle will be used to hob gears, after gashing the blank to correct number of teeth. If you don't gash, and just wack the hob into the periphery of the blank, you usually end up with a couple less teeth than required.

John


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## chucketn (Sep 4, 2016)

The link I posted shows a method to cut gears where the cutting tool does not rotate the gear blank. I made a cutter and produced a set of change gears for an atlas lathe on aluminum blanks. I used my Vertex 4" Rotary Table controlled by an Arduino and stepper to step the blanks between cuts.
I won't call it hobbing gears because I got into a wizzing contest over the definition of hobbing. The resulting gears mated well with an original Atlas gear. I gave them to a former friend who never told me if they worked.

Chuck


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## bazmak (Sep 4, 2016)

This is where I am confused.When I said Hob I meant a multiple tooth cutter
where the gear does not revolve but work is turned for each cut and the trailing teeth
approximate the involute section.I now know the hob has a pitch and the job needs to revolve.I made a worm wheel for the Shaper using an M20 tap
and the workpiece revolved.Rough and ready but it did work.I also made a 3 tooth fly cutter from small dia silver steel with 3 teeth to cut 2 small gears
for the model V8.It did work but rough and ready.I would like to go one step further using my dividing head
ANYONE IN OZ know of a source for silver steel.I don't mind buying some and making a cutter.A very late in life learning curve for me


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## bazmak (Sep 4, 2016)

Thanks for comments everyone.Never thought of using my nearly finished indexer to freewheel for hobbing.One avenue to look at.When gashing,i assume the gashes have to be at the right pitch.(maybe by packing the 
head to get the angle ?)


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## Herbiev (Sep 4, 2016)

Pretty sure Hales at Kurralta park sell silver steel


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## gbritnell (Sep 4, 2016)

Hi Bazmak
I have made my own gear cutters for years using, single point from lathe tool bits (hardest to make) involute style cutters with forming buttons (pain in the butt for all that's required) and multiple toothed hob type (key word type) which I find the easiest to make and use. The only time there is an issue with this type of cutter is when you have to cut low tooth count gears. 
The following pictures are of the cutters I made when I made my T-5 transmission. They were made from drill rod, (silver steel) hardened and not annealed because I didn't feel like there was a thin enough area that might snap off from being overly hard. I had to make 3 different pitches and to have made involute style cutters would have been time consuming and laborious. The final gears pairs fit together very nicely, thank you. 
gbritnell


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## michael-au (Sep 4, 2016)

With the hob are the teeth of the gear cut to full depth in one pass?

Michael


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## Blogwitch (Sep 4, 2016)

bazmak said:


> Thanks for comments everyone.Never thought of using my nearly finished indexer to freewheel for hobbing.One avenue to look at.When gashing,i assume the gashes have to be at the right pitch.(maybe by packing the
> head to get the angle ?)



Baz,

You gash the blank on the level then adjust either the hob or the freewheeling blank to the degree setting shown on the commercial hob.

It would be a lot of trouble if you were just cutting one gear, but if you wanted to cut a lot of different sized gears or a lot of the same gear with the same DP or mod, then it would be worthwhile as it would be much faster than cutting individual teeth with an involute cutter. You could gang up the blanks on a mandrel and cut many of the same gears at the same time.

Basically, you cut all your blanks to the correct diameter for the number of teeth required first ( I use a little desktop program that does all the calcs for you in seconds, blank size, depth of cut etc.) and then using your indexer, dividing head or RT with plates you gash the blanks straight across so that the hob has something to bite into as it starts to cut and keeps the blank in sync with the cutter, so no lost or gained teeth.

Once that is done, set either your mill spindle to the shown angle on the hob or your freewheeling unit to the same angle. this ensures that when the hob is cutting, it is in fact cutting straight across the blank face.

I have used involute cutters many many times, but have never tried the freewheeling hob method, but there is no reason for it not to work if things are set up correctly.
In my case, time will tell if I am correct or not.
If the freewheeling method doesn't work out as expected, then I can make the little hobbing machine instead.


John


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## bazmak (Sep 5, 2016)

Learning all the time,can the hobbing machine be made without castings
Do you have plans ? Could it be my next project ?


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## Cogsy (Sep 5, 2016)

michael-au said:


> With the hob are the teeth of the gear cut to full depth in one pass?
> 
> Michael


 
Sort of - at least with the ones I've made and used. The very first tooth is full depth but the surrounding teeth are 'started' with the first pass and get deeper as you index the blank and make successive passes. For the 5 'tooth' hobs you need to index the blank the number of teeth you need + 3 to completely cut all the teeth.

I second Chuck's link, it has all the info you need to make a hob quickly and easily.

I've bought lengths of drill rod (silver steel) off the shelf at Blackwoods, and from Bohler as well. Never found it to be overly expensive. I've also make a hob from mystery metal laying in my stockpile and successfully cut brass and aluminium gears with it.


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## Blogwitch (Sep 5, 2016)

Baz,

Of course the hobbing machine can be made without castings, as can most things, and not only that, it can be modified to cut all sorts of gears, not just spur.

I have nearly a full set of Myford change gears, which this little machine uses, but if you could borrow a set, then you can make all the gears you need for yourself, they could be made out of ali or nylon.

The plans and build instructions were shown in Model Engineers Workshop, plus a later modification series followed.

If you need further info then send me either a PM or email as I have everything needed to show how to build one.

John


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## bazmak (Sep 9, 2016)

On a previous thread I made a 3t cutter from a small piece of silver steel
Now in possession of Ivan Laws book on gear cutting and a little more 
knowledge I will make a 5t cutter.Again I had to make up from 3 pieces 
of silver steel


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## bazmak (Sep 9, 2016)

Next job was the above for when I start cutting gears
On a previous thread I described machining some pieces of rebar
I started by cutting 3 pieces and it machines really well


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## goldstar31 (Sep 9, 2016)

Thanks Barry! He has solved my problem which laughingly has nothing to do  with cutting gears- and if it was, they would be fibre ones!

I have a broken - rather cheap and nasty( badly designed?) set of tumbler gears bracket on my rather cheap, cheep little Myford lathe.

It isn't a Myford part, it's an addition which eventually will allow me to operate a dog clutch- which has nothing to do with dogs.

I await the next stage with baited/bated breath. I've also got a set of damaged twin gears which are designed to be reversed from gear cutting speeds to fine feeds and 'Vicky verky'

Whatever it was, it wasn't me  that filled the gear box with mahogany dust. Yuck!

Norman


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## John S (Sep 9, 2016)

There is currently a series on making a gear cutting machine running in MEW.
I think this months edition is episode 3 but not certain.


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## Hopper (Sep 10, 2016)

If you are going to do a lot of Module 1 gearcutting it might be worth buying something like this set of gearcutters for $80 delivered off eBay. Or $12 per individual cutter for specific sizes:
http://www.ebay.com.au/itm/Diameter...hash=item51d8649007:m:mEi1UTWuVuKm1Q0pnIGqrIw


Cheaper than you can buy the silver steel for in Oz to make your own. CTC tools also has reasonable priced cutters.

Yes, I know the dangers of buying cheap Fleabay tooling but I have been buying endmills and slot drills off these guys in HK and China and so far have not had a bad one. I'm thinking that with all the manufacturing going on over there they must use good quality cutters in their own factories to get the productivity levels required. Just avoid the stuff specifically built down to a price for the model engineer and home hobby market and buy their run of the mill stuff.


If you have Ivan Law's book you are off to a good start. There is a bit  more good info on making button-style cutter tools at http://mikesworkshop.weebly.com/designing-gear-cutters.html


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## bazmak (Sep 10, 2016)

Thanks Hopper,i have ordered cutters 4,5,6 and 7 for $48
covers nom 20T t0 135T. As you say cheaper than silver steel
Nothing specific in mind just want to cut a few gears and mod 1
to fit the sieg lathe seems logical.Dont think I need under 20t or over 135t
many thanks you made my decision for me


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## Hopper (Sep 11, 2016)

You're welcome, mate. I wish it were so easy for me. I'm looking to cut 14.5 PA gears for the old Drummond and for the worm gear on GHT's dividing head but do you reckon I can find cheap cutters for that? Pffft! Glad my researching helped somebody out anyway. Have fun making teeth!


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## bazmak (Sep 13, 2016)

Correlated my indexing head with the other bits and pieces and cut my first gear.The 5t cutter works but not to a good enough standard.Homemade and having to 
make multiple passes does not create a perfect tooth form.With a few thou play
in a couple of areas to be sorted and awaiting my order for some involute cutters before trying again,different materials etc.
Question. With my homemade cutter first pass was 1mm deep and then 2 more
to achieve 2.16mm tooth depth.Any comments ? should have made more lighter cuts or attemped 1 pass at full depth.
With the involute cutters cutting a full form single tooth ,should it be done in 1 pass or a no of smaller cuts. Obviosly multiple cuts accentuates and play in the index head.1 cut would be preferable but is the sieg mill rigid enough to cut
a full tooth form at a single pass with light feed ???


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## goldstar31 (Sep 13, 2016)

Hopper said:


> You're welcome, mate. I wish it were so easy for me. I'm looking to cut 14.5 PA gears for the old Drummond and for the worm gear on GHT's dividing head but do you reckon I can find cheap cutters for that? Pffft! Glad my researching helped somebody out anyway. Have fun making teeth!


 
Not wishing to spoil an excellent discussion, might I ask or comment but the old Drummond ( the RB) had 16DP gears and the GHT stuff( there was several) were 20DP- to mesh with Myford's  60 and 65 bullwheels.

Again, in Cleeve's Screwcutting in the Lathe,, he cut the gears with a sort of two ended flycutter  made from a single hss lathe tool.

The stock answer is that :-

He hadn't a milling machine and he hadn't enough money to patent his swing tool. Oddly, his Myford was only half a Myford!

'Fraid his stuff is no longer available.

Barry, thank you for your tolerance- I hope

Norman


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## John S (Sep 13, 2016)

Drummond gears are 14 DP 14.5 PA, made 100's of them including the tumbler reverse gears for the conversion that the Yahoo group did.

Might still have some tumbler reverse gears kicking about ?


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## Cogsy (Sep 13, 2016)

Baz,
I used a different looking tool to yours, made from drill rod with a series of 6 v's turned on the lathe then the diameter of the shank reduced to leave 5 upright v's. 4 longitudinal passes on the mill and a little clean-up filing and I had 4 sets of 'teeth'. Hardened than used like that. Anyway, I imagine they work the same, but mine did not have flats between the upright v's.

So the first pass, or passes, to full depth creates a full depth valley at the middle of the cutter and 2 smaller 'valleys' each side of the cutter. The next index of the blank should mean your cutter is now centered to cut on a valley that is already roughly half final depth, meanwhile the shallowest vally is deepened and the start of a new valley is made by the first tooth of the cutter (of course the trailing teeth on the cutter are making shallow forming cuts on the trailing valleys to approximate the involute form at the same time). So there isn't really a 'full depth' pass (unless you do it the very first cut that is). The only time I make multiple passes on a gear blank is when I index 3 extra teeth past one full turn so I can be sure all the teeth have had the extra 'forming' required by the trailing cutting teeth.

Hope this helps - it's easier than I make it sound.


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## Hopper (Sep 13, 2016)

Sorry I was unclear: yes two different sets/cutters for Drummond change gears and GHT's secondary wormwheel. 14DP and 32DP respectively but both are 14.5 deg pressure angle was what I meant. 
I have since found RDG has 14.5 PA cutters that I had overlooked -- but at a price. $55 per cutter. A one off HSS flycutter is still on the cards at that price. Plus I don't want to wait three weeks or more for them to get here. Must reread Martin Cleeves' book and see how he did it. I figure making a template based on the button method of making gear cutters and freehand grinding and diamond filing a lathe tool blank to fit the button template.

Bazmak, (and Cogsy) I am still trying to figure out the geometry of the multi-tooth cutter you made. Is it made to a rack profile with straight sided teeth and you then move the gear blank around in tiny increments and take lots and lots of tiny cuts, sort of like on an old gear planer, thus doing away with  indexing one tooth at a time while generating the involute curve as a series of tiny flats?


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## goldstar31 (Sep 13, 2016)

John S said:


> Drummond gears are 14 DP 14.5 PA, made 100's of them including the tumbler reverse gears for the conversion that the Yahoo group did.
> 
> Might still have some tumbler reverse gears kicking about ?


 

Apologies John but I have both 'some' 14's and some 16s as well as a full set of 20's

Long time since I had a RB Drummond or a reliable memory:wall:

Regards

Norman​


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## bazmak (Sep 13, 2016)

Hi Hopper,the 5 teeth are cut in this case at 40o included angle (2xPA) at a pitch of PI or 3.142mm,2.16mm deep to suit a rack profile
When I say 1pass I mean to the full depth in one cut which means the adjacent teeth are partially cut at the same time.I thought that the centre tooth cutting at full depth and the adj. teeth also being cut at the same pass
would be too heavy a cut.So I cut at 1mm depth and moved around 1 pitch at a time x 54 then moved the cutter I .5mm and did another 54 cuts before repeating again.A total of 162 cuts + an extra 3 at the end.Ball aching
Because its a homemade tool and there is a little play in the detent the cuts
were not as precise as I would have liked but in the end it did work
From what I understand as Cogsy explained to me is that the first cut
the centre tooth is cut as a rack form with adjacent teeth being part cut
when you move round 1 tooth it repeats so the adjacent teeth partially cut again to gradually form the involute shape.All simple clever stuff


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## Brian Rupnow (Sep 13, 2016)

Bazmak--I have a complete set of 24 DP gearcutters, The full depth of cut is 0.089" deep. I cut to the full depth with each cut, in brass, bronze, or steel. It works fine, and you only have to go around the blank once.---Brian


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## bazmak (Sep 13, 2016)

Thanks Brian,that is the answer I was hoping for.The 24DP and .089" depth
are almost the same as MOD1.What size mill are you using? as machine rigidity
will also play a part.Will wait for the cutters to arrive before giving it a go
Congratulations on your project of the month.I have never attemped an IC engine,a little fazed by the electrics but you never know.I am confident
about making the mechanical parts but spark plugs etc uugg.I remember my first and only motor bike.A little 2 stroke BSA Bantam
Cogsy I can see how your tool works there is no need to machine the full acme
profile as the flats do not cut the work if the OD is correct.I also would have preferred to make from a solid dia piece of silver steel but the cost did not warrant it.1m of say 3/4" was over $100 plus my little MAP touch would not be man enough to harden a big lump.I have bought 4 involute cutters for $50
don't know what the quality will be,and I will have to make a holder for the mill
Maybe I can remove the collet chuck or boring head from the R8 spindle and make/screwcut an adaptor to fit??


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## Brian Rupnow (Sep 13, 2016)

I am using a "tabletop" mill, a CX601 by Busybee tools. Previously I used the same cutters on a CT129 mill from Busybee tools.  It doesn't require a large mill to use these cutters. For specs on these mills, go to Busybeetools.com


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## Hopper (Sep 14, 2016)

Hi Bazmak, OK I see. It would cut the involute curve as a small number of flats, depending on how many teeth were engaged with the cutter at a time, it seems. I think if you indexed by less than one pitch (if you had infinite patience!) you would get a greater number of smaller flats, the way the old Sunderland gear planers did it, that would be a closer approximation of the true involute curve. Interesting.


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## bazmak (Sep 14, 2016)

Yes it seems to create a small no of flats which approximates the curve
However if you rotate by less than one pitch you would remove the tooth


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## Hopper (Sep 14, 2016)

Of course it would. I'll get my head around it eventually. Might have to give one of your cutters a try myself. Would be eaiser than trying to hand grind the involute curve on a 32 DP cutter - about 1/8" wide at the top of the teeth and with a depth even less. Getting pretty tiny to grind accurate curves.


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## Hopper (Sep 14, 2016)

Just thinking about it some more, it should be possible to make a single tooth flycutter to rack form and achieve a similar result to a three-tooth cutter by going around the gear and cutting the teeth to full depth in one go, then move the gear to the left by one rack pitch then go around again, then move the gear to the right  one rack pitch past the original position and go around once more. 

The second and third go arounds would in effect be cutting the same profile as the two outside teeth on a three-tooth cutter, thus giving the relief angle on the top halves of the teeth, as would be done by Cleeve's double-ended cutter that Norman referred to earlier. 

Does this make sense? I know it is a lot of extra cutting, going around 60 teeth two extra times. But it allows the use of a single, very simple to make HSS toolbit ground to 29 degrees using an Acme gauge and does away with expensive silver steel lumps, or stacking smaller sections together and hoping they don't move under load. 

As Cleeve says in one of his articles, the involute curve can be far from perfect and still function useably well in low-speed, low-load applications, so should be ok for a dividing head worm wheel. He in fact recommends just using a straight sided rack-form tooth for any gears 59T and upwards.

Just a thought.


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## goldstar31 (Sep 15, 2016)

Of course, it isn't Hopper or even Cleeve. Gear cutting was done by chisel in the Middle Ages. No, the USA and Australia didn't have one. It was done in Germany by Johannes Gutenberg, a goldsmith who invented the printing press. No, we Brits didn't either. Sorry to spoil your day.

There is a lot about how it was done and the BBC did a programme using Stephen Fry. There is a UTube or whatever you call it now on the topic. Incredible stuff, almost forgotten but that is what enabled us lowly mortals to 'read and write' instead of some lonely cleric with time on his  lands-hands like the Venereal(?) Bede down the road at Jarrow. 

For those with more of a sense of humour, TV has just repeated one of the Last of the Summer Wine series where the hapless trio in RDG Country get involved in an old mangle with- cast, cast iron gears. 

Who says TV repeats are boring?

Another Norman


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## Fluffy (Sep 15, 2016)

G'Day All,
I thought that I would put my two bob's worth in here Re; homemade gear cutters. This method is *not my idea*, & it works very well. 
I stumbled on this site a few years ago (www.metallmodellbau.de), while looking for ideas for homemade gear cutters. The article needed to be translated via Google translator for me to be able to read the more important parts of the text.
I found this method to be simple & very cost effective when considered to the price of gear milling cutters. 
The multi tooth cutters have been turned & relieved from high carbon steel. Heat treated by using a gas flame & water quenched, then honed on the cutting surfaces. Important to note that the cutting face must be on the centreline of the blank.


The pitch of the teeth is calculated by multiplying the gear tooth module x pi, the included angle of the teeth is 40&#730;(for 20&#730; pressure angle) & the depth calculated by multiplying the gear module x 2.25 + 0.05mm for 20&#730; PA.
With the cutter held vertically, the centre of the cutter is centred on the dividing head height, the gear teeth are then cut to depth with several passes of the cutter. I used 4 cuts for a 1.5 module gear. As the cutter is cutting with several teeth at one time, an approximate involute form is cut via a numbers of small flats. 
To further improve the profile of the teeth, I then made a simple jig & ran the gears together with 600 grit lapping paste in both directions until the work surface of the tooth looked OK. 
I have used this method for a number of differing gear modules & all of the gears ran well in the required application with no excessive noise.
The two gears in the image are 0.6 module & were as test to try this method.
Don.


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## goldstar31 (Sep 15, 2016)

Might I add a bit of help to those whose German is somewhat limited?

Simply Google 'Metallmodellbau' and  then 'translate this page' and it comes up in very good Englische.

I recall some very good stuff like the Bonelle tool and cutter grinder on the same site.

Thanks, Don, I'd forgotten its existence. Doing too much in Catalan and French but neither have owt to do with model engineering malarkey. My private Hell is yet to finish:fan:

Cheers

N


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## bazmak (Sep 15, 2016)

Well described Fluffy.Basically what I have achieved thru trial and error
From the book I worked the pitch for a mod1 as PI but the depth was
given as 2.16mm,your formula would give 2.3mm for mod1.Single tooth 
flycutter not the best but all I could manage with max 10mm dia silver steel
Your cutters would be the next step up for me but I have decided to buy involute
cutters rather than larger silver steel.Its all a learning curve,thats why I am doing it.Thanks for your input


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## bazmak (Sep 21, 2016)

In order to speed up the learning curve,iron out minor niggles with the tool and index head,help out a friend who lives round the corner and to get 
the required education to enable me to become a professional gear cutter
before I hit 85yrs.I accepted an order for 2  brass spur gears 15 and 30 T 24DP
I annealed my homemade 5T mod 1 (25.4DP) gear cutter and remachined to
to suit.3.3mm pitch and 2.35mm dp.I first tried cutting MS blanks but the cutter was not up to scratch.Remade and cut 2 brass blanks to supplied drg.Also made a small test jig for meshing and checking the centres.Everything to my satisfaction.The gears mesh well at +3thou centres and should be spot on
with a little titivation. Hope the client is happy.Learning all the t

ime


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## Hopper (Sep 21, 2016)

Well done mate! If you can cut the smaller gears like 15DP you are doing well indeed. Well, you should be ready to hang up your shingle and make a living at gear cutting now!


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## Brian Rupnow (Sep 21, 2016)

Sensational Bazmak!!!


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## Foozer (Sep 21, 2016)

Those look nice - Got the feeling you'll love the cutters you ordered, less interrupt cutting, less thump thump thump going down the backbone . . .

Recent cousin Tim visit reminded me - Could you please put some large dia, hardened washers and flange nuts on your gizmos slotted hold-downs?  Got that abstract image in my head of it rocking back and forth which brought the reality of cousin Tim and his rocking motor mount, busted fuel pump oil leaking truck to my door step . . .

In a reverse sort of manner - what happens when the pinch area is insufficient, it rocks - in this case to the point of failure - - - Carriage bolt for hold down, Ah No . . Solution is crude but a full length t-nut and holder, hardened washer and flange nut thingy - No more busted parts on the boat anchor that is an AA109 . Should be of steel but nothing of substance to whittle one out with . . .


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## bazmak (Sep 21, 2016)

Don't fully understand your post Foozer are you refering to my hold down bolts to the RHS index head.I am looking at minor mods to the head to increase rigidity and the fixings are one area.I was thinkinking of making some deicated large heavy washers and your post has talked me into it whether intended or not. Regards barry


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## Foozer (Sep 21, 2016)

bazmak said:


> Don't fully understand your post



That's normal - I and the language of communication don't always see eye to eye - One of the thumb rules from Boeing body structures was whenever a slot was encountered, fastening became one of a tension application - Use a washer of substance at least 2D the size of the fastener . . .


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## bazmak (Sep 24, 2016)

I successfully made a pair of brass gears for Herbie using a 5T homemade cutter.Very primitive but my thoughts turned to making a simple single tooth cutter from HSS. The initial cut at full depth would give a rack form.The cutter could then be raised and lowered a full pitch and further passes taken in order to approximate the involute form.This cutter could be used to cut any metric or imperial gear.Would be of benefit to anyone who wanted to make a few odd gears
without buying or making more expensive cutters Will give it go and let you know.I have some spare gears .I will machine one down to a suitable dia
and cut a single gear of yet to be decided DP and no of teeth.Will keep you posted
Sorry the sketch is upside down and I have just realised the cutting face must be flat and on centre line as per a D bit


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## bazmak (Sep 25, 2016)

Made a start on the cutter.Started with a broken 6mm carbide endmill
Rough ground with the bench grinder and finished in the mill with 
a diamond cup wheel.Must say easy peasy so far and the finish is
almost professional.Hope it works.TBC Missing photo here don't know why


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## bazmak (Sep 26, 2016)

I finished the single point carbide cutting tool,machined 2 surplus gears
and fitted keyed to my mandrel.Next is to try to cut the gears
May or may not be successful but will try tomorrow ,need a good fresh start
The gears I cut for Herbie were DP24.The mod 1 gears are DP 25.4
I decided to cut some with larger teeth so chose DP20 which I think are
for the Myford.Kept the PA to 20o as std and chose 2 surplus gears
to give me 44t and 30t .No particular reason other than that what I have
on my deviding plate.TBC


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## John S (Sep 26, 2016)

Just a note that Myford gears are 14.5 degrees PA


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## bazmak (Sep 26, 2016)

Thanks,yes I thought they were,but these are just test pieces to 
mesh with each other and nothing else.I decided on the now,more common
20o PA which decides the included angle of 40o on the cutter.14.5o Pa
would mean grinding to 29o included (ACME) profile for the rack cutter
Something else I have discovered.An acme thread profile is the same as 
a rack for a 14.5PA gear less  the thread pitch of course
This means that an acme tap could be used as a hob to cut both spur gears
and a worm wheel ? Long learning curve.If I was 20 and not 70


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## Hopper (Sep 27, 2016)

Yes. You can use an Acme thread gauge or screwcutting tool gauge to grind up a 14.5* PA gearcutting tool of the rack variety. 

However, I broke down yesterday and ordered a proper 32DP 14.5PA gear cutter from RDG so I can complete my GHT dividing head. Single point cutter on steel gear of that size is just too time consuming and too hard on my poor old lathe's already worn cross slide and headstock, I decided in the end. 
I probably could have just bought the gear from Hemingway kits for about the same price, if they ever bothered to answer their emails. 
Too bad that eBay supplier with the cheap module cutters does not do 0.8 module, equivalent(ish) to 32DP!


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## bazmak (Sep 27, 2016)

Yes I have the 14.5o gauge for acme threads,but these 2 gears will only mesh with each other.Just going thru the motions of proving the single point tool concept
I have just successfully cut the 44t gear in mild steel and will post details when I have done the 30t and checked mesh and centres etc.Will keep you posted


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## bazmak (Sep 28, 2016)

After a few minor mods to reduce play and increase rigidity
I set up the dividing head in the mill and the single point cutter
Starting with the 44t and depth set at .5mm I cut a few teeth
Cutter seems to work well so increased to 1mm and then 1.5mm 
depth of cut.Still Ok.Then tried 2mm deep but started to get bounce
Set back to 1.5mm depth and finished all teeth.Then cut again at 1.25mm
to get full depth of 2.75mm.I then raised the cutter x 1 tooth pith (4mm)
and skimmed the teeth,lowered x 8mm and repeated.Tooth form looks ok but bad burrs.I then tried raisig and lowering x 2 pithes 8mm but no cutting
Conclusion is that except for large gears a 3t cutter will suffice and a 5t is not needed.For the 30t gear I repeated except first cut at 1mm,2nd at 1mm and
3rd at .75mm depth.Much easier but cutter starting to blunt.Touched up with a diamond file and took the 2 more involute passes
Conclusions.A 3t cutter from silver steel is ok for alum brass etc but not steel
A single t cutter from HSS or carbide is ok for steel
The cutter is easy to shape 40o included angle for 20DP,29o for 14.5DP etc
The width of the front end of the tool needs to be ground 1/4 of tooth pitch
PROS A single tooth can be easily made cheaply to cut any gear satisfactory
CONS A satisfactory but not Proffessional job.Too many cuts ball aching job
Works well for a small no of self meshing gears or replace for existing
Next job is to turn 2 cast iron blanks and make a pair of larger tooth gears
for a better idea of tooth form TBC


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## Hopper (Sep 28, 2016)

Nice work there Bazmak. Thanks for sharing your results. Saved the rest of us some time consuming experimenting. Would you maybe get less spring in the tool at heavier cuts if the shank holding the HSS toolbit were shorter?


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## bazmak (Sep 28, 2016)

Probably,i am still experimenting.Larger dia carbide or HSS and larger dia stubbier holder would help.Most of the bounce seems to be in the index head
I have always found it easier to make improvements in stages,then you know which ones are the most effective.TBC


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## bazmak (Oct 5, 2016)

When I first bought my mill one of the tools I wanted was a 50mm
RCT face mill.The cost was about $130 and my homemade flycutter
worked well so I never bothered.When browsing ebay I saw the same face mill
with R8 arbor and 10 carbide tips for $65.What also caught my eye was
that the arbor had a 22mm spigot,the same as the bore on the involute cutters
Could as use the same.You betya so I ordered one.All arrived,so I made a keyed blank to fit the arbor and silver soldered a half key to fit the cutter
Also made a clamping nut.Works well.Now to try the facemill and the involute cutter arbor.2 tools for half the price of one


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## Blogwitch (Oct 6, 2016)

That's the way to do it Baz, if you ain't got it, adapt it.

John


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## bazmak (Oct 6, 2016)

Next test was to cut a larger tooth gear in cast iron
So I turned up a couple of blanks to make a pair
of 16DP - 30 tooth gears.First I reground the single point tool
at the front to give me a width of pitch/4 and honed the edges
I also made a new detent pin for the indexer and 2 10thk clamping washers
for a more rigid fix to the table.I started with a depth of cut of 1mm for the 
first couple of teeth.Then I cut a couple more at 2mm,finally tried the full depth
of cut at 3.43mm.The setup was much improved and much more rigid so 
I proceeded to cut all the teeth at 1 pass.Then raised the cutter 1 tooth and took the second cut all round,lowered by two teeth and repeated.Teeth were not perfect but much improved.Very happy with the result.Any minor niggles are down to the homemade indexer and not the basic principle of the single
point cutter.In a few weeks I have gone from knowing nothing to be confident
in cutting any size/pitch gear with a homemade single point tooth
I have cut Mod 1,16-20and 24 dp gears.That would require 32 involute cutters.Next I will try the 4 involute cutters I bought for Mod1


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## Foozer (Oct 7, 2016)

Love that fresh cut cast iron - Organic Artwork . . .


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## bazmak (Oct 7, 2016)

I love cutting cast iron,the crisp finish with no burrs far outweighs the
dirty mess the chips leave.Cutting like butter,soft to cut yet hard for the application and it seems to absorb the vibrations more even when cutting dry
I think I would use CI over steel for all gears.Brass is also good and alum
acceptable.Havent tried plastics or tufnol yet,will leave that until I have a purpose
for the gears


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## Hopper (Nov 16, 2016)

How are you going with those Mod 1 cutters you bought, Bazmak?

Just to throw in my two cents' worth, here's a few pics of my latest gearcutting, using a 32DP cutter from RDG tools to make the secondary worm wheel for my GH Thomas dividing head I am making from welded-together bits of scrap. I used a Myford 60T changewheel for the main gear and turned a worm to fit it. I got away from having to offset the worm at the helix angle to mesh with the straight gear by turning the thread a bit thin and angling the worm around straight. 

But to cut the second, smaller wormwheel for the ultra fine adjustment on this dividing head, I ended up angling the blank at 4.2 degrees to the cutter and so the teeth are at the right angle to match the helix of the worm. Not a helical gear, but more a straight cut gear with angled teeth! And it works a treat.

Cutting the gear teeth in the lathe (1937 Drummond M-type). The vertical slide is stretched about as high as it can go. Should really have a spacer block underneath, but hey we got away with it! Used a jury rigged plunger on the main wormwheel for direct indexing.




The resulting gear, with 4.2 degree "helical" teeth




And matching worm




How it all fits together




Index plates will attach to the small wormwheel on the left. A graduated micro-adjustment goes on the worm spindle on the right for dividing prime numbers etc, and making the dividing head's own indexing plates from scratch.




In the end, I was glad I spent the money on the commercial cutter. The two inch diameter steel gear, 5/16 thick would have been a long slow job with a single tooth flycutter and I don't think the vertical slide would be stout enough to take much of a cut, it was bouncing about enough under the smooth sailing of the commercial cutter.


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## goldstar31 (Nov 16, 2016)

Great stuff to see another GHT Versatile Dividing Head. After the roof came off( twice) during the winter storms, my division plates are really corroded and along with the Gibraltar casting and the Cleeve thing, I got 3 division plate blanks for drilling from Hemingwaykits. At least the second  worm is usable. Probably I'll get away with the  single hole division plate which seems OK.

So I look forward to your next gripping instalment out of the George Thomas stable

Norman


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## bazmak (Nov 16, 2016)

Great input,good to see someone else flying by the seat of their pants
I haven't used my involute cutters,will save them for when I need to make gears to be used


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## goldstar31 (Nov 16, 2016)

I missed the bit on first reading of 'thinning' the worm( To overcome the helical messing problem, folks)

Then I suddenly recalled that the late Martin Cleeve wrote it up in Engineering in Miniature. If my aged memory is working today, it was on the Alan Timmins dividing head which was serialised in an early EIM. The castings and whatever were sold by  Blackgates Engineering. Hopper, I haven't the articles now- sorry.

A lot easier than the GHT affair!

Hint-- the Stent t&C  from Blackgates Engineering is quite possible without castings. We were discussing mine which another old geyser made- by welding .Quite a toy- which is easier than the Quorn  but is really a diminutive Clarkson.

N


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## Hopper (Nov 16, 2016)

Norman, yes I think it was in Cleeve's book on screwcutting that he mentioned thinning down the Acme thread so the worm could mesh straight on with a straight cut gear.  The thing I like about GHT's design, fiddly as it is, is the ability to make its own index plates by using the micro-adjustment attachment.  I just saw a picture of the Timmins design for the first time the other day, it looks quite rugged and simple. Also uses a Myford change gear for the worm wheel.
I have thought about a fabricated Stent but shed time is limited these days so it will have to wait. FWIW, here's a  pic of the fabricated GHT body under construction. Yes, talk about flying by the seat of the pants!






Now, I never claimed to be a welder!

After a good heat soaking to cherry red and a night in the lime bucket to stress relieve and anneal:




Nothing a little bit of die grinding, body filler and paint won't fix though:



LOL, I never claimed to be a painter either! You can see the result of painting over putty in 90 per cent tropical humidity around the base of the legs there. We live and learn!


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## goldstar31 (Nov 17, 2016)

Hopper, I continue to be amazed at your approach to making this dividing head.  Of course, for other readers, Thomas published I the back of his book 'WorkshopTechniques' and earlier in 'Dividing and Graduating' the plans for the castings - should one be stuck on a desert island or something. I'm certainly more than impressed.

As I remarked earlier-somewhere, I had his fabricated Universal Pillar Tool and now have the Mark2 machine. Again, I suggested that the 'legs' might well be from a scrap set of full size conrods. Somewhere in my heap of things, there are the drawings of an automatic thing to graduate divisions. I'll dig them out and e-mail them to add to your collection. 

I 'made' Hong Kong' and then onto 'Fiji' in June and I wonder if I can make another trip- further South.

Meantime, Best wishes

Norman


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## Hopper (Nov 17, 2016)

Thanks Norman. Model engineers always welcome on this rather large desert island. Con rods for the pillar tool - brilliant idea. I have a motorbike flywheel truing stand made from two conrods bolted to a bit of steel channel. Been truing Harley crankshafts on it for decades without a problem. 
I'm still having many enjoyable hours reading through Cleeve et al in the treasure trove.

I have some drawings from Harold Hall's book on Dividing for a graduating tool with a ratchet mechanism to automatically vary the stroke length on every fifth and tenth stroke for making graduated handwheels. I am about ready to make the graduated thimble for the GHT micro-adjustment and thought about making the HH graduting tool, but once again in danger of completely disappearing down the rabbit hole  of making tools to make tools to make tools recurring. So I will probably bodge something out of  a toolmaker's clamp and a bit of allthread rod, or something. That's tomorrow's project so I'll worry about it then.

Bazmak, sorry about the thread hijack mate. I guess it's all gearcutting related so maybe will be helpful to someone?


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## bazmak (Nov 17, 2016)

No problem enjoying the input.Your casting looks good,still not syre how you fabricated it ?


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## goldstar31 (Nov 17, 2016)

I guess that I am also guilty of 'High Jacking' your thread but frankly, you have opened up a very important topic.
I'm sure that many will appreciate it in addition to me

Regards

Norman


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## bazmak (Nov 17, 2016)

This thread has opened a new line of thought for me with a sleepless night
(design time).Can I make and fit a worm/wheel to my index head for 
more accurate dividing.
Can I use a std mod1 spur gear and offset the worm to the helix angle
Can I hinge the worm from the far bearing to allow the worm to disengage
when using the plates and also allow adjustment to reduce eliminate backlash
Still thinking,keep this thread open


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## Hopper (Nov 17, 2016)

Bazmak, you certainly could do that. Easiest way is to do what I did and cut yourself a 60T gear using your module 1 cutters, but set the blank at the helix angle so the teeth are a the right angle to match the worm helix. Or you can do what I did on the main gear and use a straight cut Myford (or any other) change gear and when you turn the worm thread, a standard Acme profile, cut it a bit deep and wider than normal. This allows you to twist the worm to the straight position but still mesh properly with no backlash. 

The tricky bit is working out the pitch to turn the worm at so it matches the circumfrential pitch of the gear, THEN, working out the change gears to cut the oddball resulting pitch (8.37tpi or some crazy thing like that). Martin Cleeve's book on Screwcutting in the Lathe covers it a bit, but not sure if he includes metric for module 1. He does include DP20 etc. And does include the outline of how to calculate it yourself. (Makes my head hurt though.)
Also GH Thomas's books include details on doing it for the two gears, DP20 and DP32 on his dividing head.

I have some pics somewhere of the fabrication process for the body, I will dig them out when I have time later and post them. Basically it was two pieces of 1-5/8 round bar welded together to make the main body to hold the spindle and the tailstock bar. I machined a curved scallop out of one side of one piece of the bar so it matched the OD of the other piece and then welded them together and milled a flat on top of the second piece. Then the cross piece for the locking mechanism was turned from a piece of 3/4" bar, again with a scallop machined out of it to fit up to the main piece. Then the base and the legs were cut from flat plate and welded together.  Clear as mud? Will post the pics later today.


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## bazmak (Nov 17, 2016)

thanks for your post Hopper,i have made a start.I don't have a spare suitable
mod1 changegear the tooth pitch would be 3.142mm and then I would have to cut an acme thread to suit and offset the worm by the helix angle
A far simpler way I have decided is to cut the gear using an M20 tap as a hob
and an M20 bolt as a worm.2 screws remove the dividing plt and detent assy
easily replaced with the worm and wheel.More room and less complicated than
trying to fit both.I am making a 120t gear which will give me 3o with a full turn of the worm,from cast iron. Will posted


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## Hopper (Nov 17, 2016)

Good idea. I guess with a 120T gear you could use a standard chart for a 60T as far as number of turns plus holes and then double the result.


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## Hopper (Nov 17, 2016)

OK, the fabrication process.
Showing the two main pieces, machined from 1-5/8 round bar. Holes bored to rough undersize at this stage. I printed out GHT's drawings at full size and used them to make templates adn mark out materials to correct size.




The scallop in the one piece of 1-5/8 bar was machined like this: offset on faceplate and "bored" to 1-5/8 diameter to match the other bar OD




This allowed the two pieces to be very easily aligned and welded together in the vice. You could just as easily make the second piece from flat plate and machine a flat on the main piece for it to mate to, but I had no access to flat plate that thick so used what I had, the large round bar.




Next, the barrel for the locking mechanism was similarly machined from 1" or 3/4" round bar, scalloped to fit to the main barrel so it can later be drilled and reamed for the locking mechanism to go inside it. 




Here it is tacked into position



You can see in the above pic that I milled the top and bottom of the second piece of 1-5/8 bar flat, mostly just so it duplicated the look of GHT's casting. Final welding on thos surfaces was done after the milling. (The weld on the ends held the piece while milling was done.)

Next, some bits of scrap 5/16 plate were marked up, hole bored to match the above piece it will mate to. The end piece was cut off and discarded after boring to size. The ends of the two vertical support plates were bevelled to mate up to the main 1-5/8 barrel. The small piece is the "web" that runs between the two uprights, just like the web in the casting.




Web welded in place




Legs added




Welds cleaned up while access is clear with no base plate in place.




Final welding to the base.




The resulting "casting" was then machined as per GH Thomas's instructions in his book "Workshop Techniques". I can tell you from experience that you ignore his advice at your own peril!

Base plate tacked before welding





The whole thing welded to the 3/8" base plate


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## Hopper (Nov 17, 2016)

Oops, last pic is out of sequence but I missed the time limit to edit post. You can see my $50 garage sale welder in the background. Came with 5kg of rods I am still using!

Also, meant to mention the rough-bored undersize holes up the middle of the two main pieces are essential to use for alignment when doing the machining. The original casting comes with the two holes cored. I bored the main hole to a nice fit on 3/4" BMS bar which was inserted though the hole and used to set the "casting" straight on the boring table of my lathe for machining.
Holes were then bored with a between centres boring bar so they are perfectly at centreheight for my lathe.


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## Hopper (Nov 17, 2016)

Durn, missed the timeframe to edit post again. How weird is this site? Anyhow here is the pic meant to go with previous post showing how the holes were machined using between centres boring bar. The G clamp is holding the brass locking plugs in place while they are being machined in place to perfectly match the bore of the main barrel.


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## goldstar31 (Nov 17, 2016)

Back to Thomas again? I did my Quorn with mine as well.

Perhaps it should be mentioned that regardless of the wear in the old lathe, an in line boring bar will bore DEAD parallel. Not necessarily the CORRECT DIAMETER however. 

Confession- I angled the tool bit at  45 degrees and it should have been 40. If it had been 40 I could have used the 40 tpi thread to read in thous. Silly me!

Regards

Norman


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## Hopper (Nov 18, 2016)

Norman, I did not even fit adjustment to the boring bar. Just drilled one hole in it at 45 degrees for the HSS tool bit to go through and another for a clamping grub screw. Used a micrometer over the tool point and the bar to measure size. Bored the hole first, nice and true and smooth but ended up some few thou bigger than teh nominal size. No problem. Just turrned the spindle to fit the hole.


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## goldstar31 (Nov 18, 2016)

Hopper
I enjoyed the approach- which obviously works:thumbup:

Moving off a little( Hope Barry will accept) I noticed your 3 jaw etc and would add that one of mine is drilled around the periphery to accept a detent. True, it's old fashioned and I didn't do it, but it is very useful on the lathe and the universal dividing head.

I've been playing with a little digital angle thing- which is a good substitute for lots of angle things.
Thinks, I'll spend the Children's inheritance on a 6" 180grit CBN wheel:wall:

Regards to All

N


-----------------------------------------------------------------------------------------------------------------------

Apparently I have been blocked from other posts.

The reasons are not even 'vague'

Thank you for putting up with me in the past.

All that I can say? Well- politely

Norman


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## Hopper (Nov 18, 2016)

Norman, I've made a little angle bracket to mount the plunger off the GHT dividing head on the change gear quadrant and engage with a gear on that end of the lathe spindle, so no need for drilling the chuck backplate. Will be using it to make the graduated collar for the micro adjustment so will keep you posted.


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## goldstar31 (Nov 18, 2016)

Laughingly, the chuck - complete with its little perforations- came with Myford ML10's knitting.

Of course, ML10's and ML7's have 65 tooth bull wheels instead of the more sensible 60's on the Super7's.

Factorising 65 only gives 5 and 13. Say no more!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

N


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## bazmak (Nov 22, 2016)

I have made  a successful start to making a worm and wheel for my
index head so I will continue the post description to the indexer thread
where it will make more sense


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