Toolpost (or other) grinding in the lathe

[petertha]

Sleykin - can you elaborate on the flat belt you used: material, dimensions, source... What kind of rpm is that motor spinning?

MRA - the 'sheet of abrasive' posted in my #2 is just a 1/4" wide surface grinding wheel, purchased from KBC. I suspect most machinery/abrasive suppliers will have them.

 

[user 43684]

Sleykin - can you elaborate on the flat belt you used: material, dimensions, source... What kind of rpm is that motor spinning?

The flat belt was just a vacuum cleaner belt I just picked one off the rack that looked good and made the wheels to match. The motor is a harbor freight trim router that spins at 25,000 RPM. The pulleys divide that in half and I use a router speed control to adjust lower if needed. I also use the speed control on the Dumor TPG. They work with just about any A/C brushed motor.

 

[MRA]

This has me thinking about bearings now for my hypothetical 25mm spindle with a collet chuck on the end. I don't suppose they'll take much load, but they need speed so I suppose that means a fair bit of power (torque x speed). 6905 ('normal' option)? Something fancy like 7905 (angular contact, in pairs)? Pair of tapers with end load set though a spring washer? I suppose it depends on what happens to clearances when they run that fast. If you've made one, perhaps you wouldn't mind making a suggestion.

 

[goldstar31]

Instead of a hypothetical 25MM spindle I have several ACTUAL 25.4mm ones. The 1" diameter cartridge spindles could be swopped about- here there and everywhere with the Quorn, the Stent and the Kennet grinders as prime examples and I added a Geo Thomas small dividing head and now the Potts milling spindle( referred to elsewhere) Sadly, getting 1" holders seems impossible in the Uk and I have no idea of whether 'one inch stuff' is obtainable in other countries.
Presumably, new starters should simply bore castings for 25mm and get on with life.
Having expressed my gripe, there seems to be no reason why a (say) Quorn spindle complete with high speeds bearings recommended by Chaddock. They are a 'bugger' to make nd probably the simpler ones a la Kennet and Stent should not be used.
Of course, the axial bearings suggested for the Quorn are metric but shrouded in a 1" ethos.
Yer pays yer money and you makes yer choice,

My thoughts, of course

Norman

 

[petertha]

MRA, there's a Workshop Practice Series #27 book called Spindles by Harprit Sandhu that contains a lot of different spindle designs; various OD & length sizes & bearing type/configurations. (My opinion) on the plus side the book is good in that its orientated to the practical hobby machinist. You can pick a drawing, adapt it to your machine & build it from his dimensions. But aside from 'conversational enlightenment', pretty light on engineering details as to why you would select one configuration over another. Mostly I was looking for specific guidance on bearing play setup & adjustment which is probably where the magic happens, but probably also at the expense of bearing life/heat etc. I see commercial spindles with adjustment nuts and wavy washers, but I don't see similar assembly components in the book designs, so I'm not sure what to make of it. Maybe a different path to the desired end result, or? It almost looks like the machining effort is about the same for all the spindle designs in the book +/- intended shaft details like whether it has a taper socket end to match some tooling purpose. Unless you go with uber precision AC bearings, I figure the overall materials cost doesn't vary too much so may as well build the best design - whatever that is.

I'm still on the hunt for a compact spindle design suitable for light but precision grinding using big wheels. There's lots of pictures & videos on the net that show a shiny part. But like the polished potato analogy, that's not the same as hitting a dimension to X decimal places with appropriate finish. I do think there is merit in a standalone spindle driven by external motor because a) you gain independent control of runout vs an integrated motor repurposed from another tool b) it removes a big bulky motor from the working area.

 

[petertha]

...Quorn spindle complete with high speeds bearings recommended by Chaddock...

Are you aware of any drawings and associated component specifications that one could properly replicate these designs? I'm not interested in castings or kits, just the information. And specific to grinding, not milling or general purpose.

 

[goldstar31]

Are you aware of any drawings and associated component specifications that one could properly replicate these designs? I'm not interested in castings or kits, just the information. And specific to grinding, not milling or general purpose.

I have the Harprete book but have never read it The reason is that I've done my spindles earlier!
So there is the Quorn Book by Dennis Chaddock which gives the 'words and music; for the 1' spindle but the main stuff- whilst it is perfectly usable and I have my Quorn from that.

What might be of use is to get the Bonelle drawings from the net for free- and maybe join the Quorn group as well. Currently, they are discussing Belleville washers for spindles but I must advise that I
have no comments good or otherwise for that. However some of the contributors have been at the tool and cutter game for almost as long or longer. There is a wealth of first class experience which might help you

Best Wishes

Norman

 

[Jerr46]

I am building Ron Colonna’s 1/4 scale offy and it calls for a 14.5 degree 48DP gear train. I am having trouble finding this size gear cutter. Is there a metric size gear cutters that would work? or does anyone know where I may able to purchase already made gears. Any help on this would be great.Thanks

 

[Asm109]

Precision and Commercial 48 Pitch Spur Gears | SDP/SI (sdp-si.com)
Spur Gears & Ratchet Gears | WM Berg

You can use 20 degree pressure angles in place of 14.5 degree. You can't intermix them tho.

Metric gears you might find something that is close but you will probably need to tweak your design to change shaft center distances to compensate for the differences in pitch diameter.

 

[MRA]

'Helichron' is good on this - I am working up to cutting some Boxford change gears this way

http://www.helicron.net/workshop/gearcutting/
By the way, I think we are in a tangent on this thread!

 

[L98fiero]

I have also acquired a Dumore TPG

I've also acquired a Dumore TPG, model 57-031, but it has only 2 pulleys, a #1 and a #3 and I don't know if they are even the correct ones for this machine, does anyone have the proper sizes for this TPG?

 

[trlvn]

Dumore has some resources for repair parts:

https://www.dumoretools.com/parts/series-57/tool-post-grinder?osCsid=b1hl1bjrk1krcnoqe05uae7o05
Craig from Oakville, ON

 

[L98fiero]

Dumore has some resources for repair parts:
Craig from Oakville, ON

Thanks Craig, I already have that but I was looking for the sizes so I could make them. I have a friend with the capability to balance them so it's just a matter of machining if I can get the OD sizes.

 

[Brian Rupnow]

I very seldom have a use for a toolpost mounted grinder.---but---Every time I machine i.c. valves for one of my small engine projects, I wish I had a grinder to finish the contact face on the valves. I get by using a sharp cutting tool, but under high magnification the resulting surface always looks a bit like the surface of the moon. Lapping the valve into the seat cleans the valve and the seat up sufficiently to make them seal, but I do wish I had a grinder for finishing the valve faces.---Brian

 

[user 43684]

Thanks Craig, I already have that but I was looking for the sizes so I could make them. I have a friend with the capability to balance them so it's just a matter of machining if I can get the OD sizes.

If you look at the list of parts in that link it lists the pulleys (62-68) by size starting with a .75" pulley and going up to the 5" pulley. I would go with what pulleys you have and add a router speed control. As long as you can get the high end with the pulleys you have the speed control should fill in the blanks nicely. You do loose some power over the correct pulley, you don't need much power for the grinding.

 

[user 43684]

I very seldom have a use for a toolpost mounted grinder.---but---Every time I machine i.c. valves for one of my small engine projects, I wish I had a grinder to finish the contact face on the valves. I get by using a sharp cutting tool, but under high magnification the resulting surface always looks a bit like the surface of the moon. Lapping the valve into the seat cleans the valve and the seat up sufficiently to make them seal, but I do wish I had a grinder for finishing the valve faces.---Brian

I built my first TPG and then traded a milling attachment for the Dumore. My first thought was also finishing and facing valves. Then, once I had one I found lots of other uses for it in finishing hardened pieces, like punches and dies or reamers. I have made several reamers that I turned on the lathe to get the shape then milled flutes. I hardened them and the ground the cutting edge and relief with the TPG. The TPG I built was made from billet aluminum and a piece of plate. The parts were made with a bandsaw and I used a wood router to make the edges rounded. Then the holes were bored on the lathe. Guarantees your spindle is on center-line of your lathe.