# Building KEN I Rotary broaching tool



## coopertje (Feb 17, 2012)

Since its too cold to finish the painting work on the Tacchella grinder I decided to make a long desire happening, drilling square or hexagonal holes! There are several treads about this subject here and I decided to make the holder based on the design of KEN I. Thank you for sharing and the support so far Ken!

I will deviate a little from Kens plans because I do not have the mentioned material size available. The diameter of my holder will be 60mm instead of the mentioned 80mm in the plans. Since I am lazy I decided mine will be round instead of the more or less oval shape and last I will use the 6201 bearing with is larger and wider then the 6101.

Had a MT3-B16 shank laying around unused, nice base to start with. Tested before turing with a file how hard the material was, I was lucky it was not hard at all.
Put the shank between the centers 







And turned the end down to 14mm






Next part is the bearing housing. Chucked up a piece of 60mm steel, centered it and drilled a center hole for the tailstock center






Then turned the outside to shape, leaving the diameters about 1mm bigger then planned, they will be finished later to remove machining marks it might get during the process






Parting off with tailstock center, as you can see I parted until I had about 10mm in diameter left, un-chucked the piece and cut through with the bandsaw.






Placed the piece in the 3-jaw to machine the bearing seat for the 6201 bearing, round 32.00mm in diameter and 12mm deep. Also made the internal boring.











It was not completely successful, the diameter I got at the end was 32.02mm. To much for a press fitting of the bearing, need to use lock tide instead..

Now the part has to be swapped to turn the bearing seat for the 51202 trust bearing. To maintain centricity I decide to make some kind of collet. First turned down one side of a piece of round 40 aluminum back to 38mm. Swapped the part in the chuck, marked jaw number 1 and drilled and tapped M6 in the center. Last operation in the lathe is to chamber the hole and turn the diameter back to 34mm. Then took it to the mill to split the front side with a slit saw. As you can see I did not care too much to have an equal spacing between the cuts.






Mounted it back in the lathe and turned the diameter to 32.00mm. Now the part will have a snug fit on the collet meaning the the part can be fixed easily with the screw in the middle. Tested the runout and it was less then 0.01mm, good enough for me!






Tomorrow I will finish the bearing holder and maybe start on other parts for the holder if time allows. 

Have fun, regards Jeroen


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## vcutajar (Feb 17, 2012)

I will be following you every step of the way.

Vince


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## tel (Feb 17, 2012)

As will I - this could be a very handy thing to do!


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## Don1966 (Feb 17, 2012)

I think I will follow along also. This could be a interesting project.

Regards Don


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## ref1ection (Feb 18, 2012)

I'm very interested in this as well.

Ray


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## MawitÃ¶ (Feb 18, 2012)

Really nice project and thanks for sharing.

Mawito


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## coopertje (Feb 18, 2012)

Thank you all for your comments and interest! 

For who is interested on the background of the tool and working, here is some more info on the tool designed by KEN I (also check the links in the post, lots of info to find there as I discovered after asking Ken againsorry)

http://www.homemodelenginemachinist.com/index.php?topic=17289.0

Made some progress today, not too much, went to the tool store this morning (needed a 10mm machine reamer, just had the conical hand version) and just took it easy the rest of the day.

Fitted the bearing holder on the collet made yesterday and turned the seat for the 55202 trust bearing. Round 32mm, 11.5mm deep and made a relieve of round 33mm at the front end of the housing.






Swapped it again and made a relieve for the 6202 bearing, did not do that yesterday. Do not know if it is required but for sure it will not hurt.






Next was the backplate that will be mounted on the MT3 shaft. Did see it before and decided to make a very simple, though very effective tool. A piece of brass with a roller bearing. Had the blank running true in some seconds!






Faced the front and made a hole of 14mm with a boring bar to have better control over the end diameter






Could not help myself, just need to see how it will look when finished.






I decided that today it was time to make the first internal MT taper in my live. Could make an adapter to finish the other side (and OD) of the backplate, but the idea is to have the backplate fixed to the MT3 shaft, place it in the adapter and turn things true. The adapter will be useful in future projects too. Put a previous prepared (Stuart 10H build) blank in the spindle nose and have my MT3 reamer set ready (I put them very gentle on the bed to not damage them, better to have then on a piece of wood.)






And drilled a hole of 20.5mm (my god, what a difference a good drill makes.this is a resharpened professional drill, went trough like cutting butter!)






Below my set-up to set the support to the MT3 taper. Its 0.0502mm taper per mm on diameter, so the top slide should be set half this value for radius (that is what you are measuring with this set-up). I did set the taper a fraction to sharp, the final shape will be made with the reamer.






Made the taper with a boring bar as close as possible (checked many times the outer diameter, the finished taper should have a diameter of 23.825mm) and stopped turning when I reached 23.6mm. Since I had nothing to grab the reamer with my tailstock I used the reamer like below and it went really well! 20 RPM and lots of oil.






And here the MT3 shaft steady in the lathes spindle nose






That was not so hard after all, glad I took the step to make this MT3 adapter today.

Tomorrow I will make the broach holder.

Have fun, regards Jeroen


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## Blogwitch (Feb 18, 2012)

Jeroen,

You really do need to invest in a set of soft jaws, especially if you are going to do more jobs like this.

They would have saved you hours on jig making and setting up, I use mine all the time. In fact I have a 3 jaw chuck set up with soft jaws permanently.

They are about the cheapest thing you can buy to get yourself into the high precision stakes.

Things are really looking good, and should really help me when eventually I get around to making one.


John


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## coopertje (Feb 19, 2012)

John,

Thanks for the tip! I have a chuck with removable jaws, nice start to make a soft jaw version. Its written down on my to do list (page 5 bottom :big.

The collet I made is really quick, did not spend more then 20 minutes in total. And it will be reused many times, now the diameter is 32mm, next time when I have something smaller I just turn down this one and I am ready to go. The best for me would be a nice collet adapter, thats also on my to do list, I believe it was page 3 in the middle...

I will go the shop to make some chips on the broaching holder.

CU later, regards Jeroen


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## Ken I (Feb 19, 2012)

Nice going Jeroen and thanks for letting us "look over your shoulder".

I'm watching.

I presume you are going to grind your broaches from solid 10mm HSS stock - or tool steel and harden perhaps ?

Ken


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## coopertje (Feb 19, 2012)

Hi Ken,

I plan to make the broaches from silver steel (drill rod), make them to shape oversized, try to hard them and then grind to dimension and give them the relieve angle. Lets see what will happen, I am not so good at hardening What about the front side of the broach, does that need to attention or can it be flat? I think I red somewhere that you should drill it with a oversized drill, but I think then the cutting points will become very weak.

Made a set-up which is far from perfect but with light cuts good enough. Clocked the bearing housing to 1 degree angle and took advantage to check my digital angle meter. 






And the digital device is 0.2 degrees off!






Took the sharpest mill I had and started to take cuts from 0.1 deep to not stress the set-up. As you can see it cuts nice and symmetrical meaning the set-up is ok.






Here it is deburred and finished.






And then I realized I made a big mistake! I should drill and tap M6 the 2 holes in the same set-up.

Took the part to the lathe and set my indicator on center height






And try to find the higher and lower part on the face, when found marked it with a tool.






Put it back in the mill, clocked it out again a drilled and tapped the 2 holes with M6. I made blind holes so the front of the tool will look nice and clean.






Then I made the slots in the back plate






Degreased the MT3 shaft and the backplate, took the green lock tide, and pressed the parts together using the lathes tailstock. Its machinable after about 45 minutes.






While the MT3 shaft was drying I made the broach holder. Chucked up a piece of round 40mm






And turned it to dimension. its 15mm for the trust bearing and 12mm for the 6202. At the end its 11.5mm with a 1mm groove for the clip. This is just before parting off.






I was eager to test my MT3 adapter so I let the 10mm hole in the broach holes for a later moment. Removed the chuck and mounted the adapter in the spindle nose. The fit is quite well, I am happy at least






I faced the back plate and made a chamber (3mm deep) in the middle to make space for the broach holder. 






Its starting to come together!






Remount the chuck and drilled the broach holder 9,8mm 20mm deep. Then took a 10mm reamer and reamed the hole to 10mm






I know they are unsafe but I just love long pieces of swarf!






Last thing for today I drilled and tapped M6 for the set-screw to hold to broach in the holder






This is what I got up to now, tomorrow I will assemble and start on the actual broach tooling






Thanks for watching, regards Jeroen


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## Ken I (Feb 19, 2012)

Jeroen, I would not reccomend drilling. I have broached hundreds of thousands of holes using that design and flat faced broaches. (VW Golf / Rabbit / Jetta front strut rods all have a 7mm AF and some Audi an 8 and even 10mm - EN30B high tensile rod.)

You can concave grind the face to give it some rake - this helps a little but to be frank is just not worth the bother.

Don't go nuts on clearance - with a "frictionless" bearing set up there is no torque applied to the tool (there's going to be some) - but as the bearing wears this torque increaces and starts to drag the broach producing a spiral broach - the more clearance, the worse this tendancy.

In production practice when the go gauge went in but wouldn't go to the bottom - it was time to change the bearings.

On my drawing the broach has a 2½° included angle which gives ¼° clearance on the 1° toolholder. Also on the drawing a R1 radius at the root - this to prevent the creation of a "stress raiser" caused by a sharp edge - again this helps to reduce breakages. If you grind it in a tool and cutter grinder just offhand dress the corner of the wheel - its not critical. If you mill it do it with the cutter radius as washout (Don't mill across leaving the sharp cutter corner in the root).

Index reccomended regreaseing the bearings every shift's full production - Nuts to that we ran it until the bearings gave out (its as much trouble to change the bearings as it is to grease it and bearings are relatively cheap).

IIRC even without relubes the bearings used to last between 20000 to 50000 parts - and that was using soluable oil as coolant - it washes out the grease and is not a great lubricant for ballbearings.

The broach face needs to be smooth, the cutting edges sharp - flank finish good but not critical.

Obviously the "concentircity" of the profile to the shank needs to be good or you are going to introduce latteral forces that will want to snap the broach.

For hobby use add a dab of HP lube (the dark smelly stuff) and you should be good to go.

Hardened drill rod works well but you must temper it back - they will work fine glass hard but tend to snap if your alignment or tool concentricity isn't spot on.

Hope this helps.

Ken


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## Don1966 (Feb 19, 2012)

Great job jeroen I really like all your photos and explanations. Thanks for sharing with us.

Regards Don


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## mu38&Bg# (Feb 19, 2012)

Jeroen, Looks great. I might make one of these as well. What kind of mill at your working with there? Seems to be a Deckel or some clone there of?

Greg


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## steamer (Feb 19, 2012)

Hey Ken,

What would you think of using this on a turret lathe?

Dave


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## Ken I (Feb 20, 2012)

Dave,
    It works fine on a turret lathe, mill spindle etc.

Long answer version :-

When feeding from a screw or cam or power feed - you gain a mechanical advantage (over and above any drivetrain mechanical advantage) in that the drive is non-reversable - so it cogs in during the quiescent moments - the spindle torque is then translated into thrust against the non-reversable feed system as the corners of the broach dig in - so it feels like a lot less pressure than there really is.

Consequently on a mill quill or turret lathe (when hand fed) you are actually applying the force directly so it "feels" like quite a lot more - that said the intertia of the turret and quill also help in this regard - so it will seem "easier" at higher revs.

Since there is no real cutting velocity you can go nuts on revs but it is harder on the tool's bearings. Use higher revs when hand feeding a reversable drive like a mill quill or turret than when power feeding.

1000-1500 rpm for power feed, 1500+ for hand fed - when hand feeding, just apply a pressure that you are happy with and let it sink in. 

Feed rates are limited - at Tan 1° x Broach Diameter - you will be cutting on the entire face and the effect of the wobbly broach is lost and you may as well just push it in. For an 8mm Hex this would equate to 0.16mm per rev - in practice you want to be about a ¼ to ½ of that figure.

As mentioned in my prior post, errors in alignment and tool concentricity give rise to latteral forces which want to snap the broach - so using a tailstock or mill quill in the extended position makes it more forgiving.
That said, my experience on very rigid machinery was relatively trouble free.

Regards,
      Ken


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## steamer (Feb 20, 2012)

My expectations exactly, but I hadn't tried it. Having the ability to float the tool should help also to prevent side loading

Nice design Ken, as usual :bow:

Dave


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## Ken I (Feb 20, 2012)

Thanks Dave.

Jeroen, when you reamed the 10mm bore, I see you used the 3 jaw - were you using soft jaws ? is it accurate enough ?

The proof will be the measured runout on assembly against a 10mm pin.

Ken


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## coopertje (Feb 20, 2012)

Thank you Ken for your effort and time to clear my doubts and answers!
I will make a test bit just to see if the tool is working, when I have my Tacchella tool grinder finished I will make some decent broaches. 

When reaming the 10mm hole I used the dial indicator to check runout before drilling. It was 0.02mm which I assumed to be good enough. I will check the total runout tonight and let you know. 

With a little bit of luck I will have the first results tonight!

Thank you for your support Don and Dave, appreciate it! 

Greg, the mill is a Thiel 140. Its similar to a Deckel or Maho mill. I really love this machine, its very well build and very stable. Has power feed on all axis, scraped ways, SK-40 spindle nose with a drilling pinole, hydraulic axis locking and an automatic lubrication system.

CU later, regards Jeroen


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## Ken I (Feb 20, 2012)

Jeroen,
     0.02 is just fine - its just I have a pathological aversion to 3 jaw chucks for accurate work and never use them for finished diameter work or second op work.

Great going so far.

My earlier comments on reversable vs non-reversable applies where the drive efficiency is less than 50% then the drive is non-reversible - ie a screw driven tailstock quill - it doesn't matter how hard the work pushes back, the handwheel will not rotate backwards whereas a rack and pinnion drive can be pushed backwards with sufficient force.

That's probably cleared the murkiness to the consistency of mud ???


Ken


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## coopertje (Feb 20, 2012)

Hi Ken,

I know what you mean about 3 jaw chucks, they normally are not that accurate. I was lucky and got a accurate one with the machine, too bad the outside jaws are missing.

Started with assembling the parts of the holder. Put bearing grease for the trust bearing







And mounted the broach holder with light tapping with a plastic hammer. I bought some shims to set the trust bearing to tension, I needed 0.6mm in total. Its running easy and there is no any play on the head






Tool finished!! Put the broaching holder in the tail stock and mounted a piece of 10mm silver steel in the holes. The total run-out is 0.02mm, not bad for a home made tool, I am happy! If I had took the effort to make a collet for drilling and reaming the 10mm hole it could have been even better.











Then I cutted 11 pieces (1 trial piece, hope 10 good ones) of 10mm silver steel and chamber them in the lathe on one side











And milled a flat surface on them, 8mm mill, 1mm deep











I decided to make a 6mm Hex broach, first made 2 parallel side so I could check the dimensions easily






During the machining I made a mistake by having the collet holder not flat in the vice, so now it will be a 5mm broach!

Here it is milled and I tried to harden it. Heated until red and dropped in a bucked with old motor oil. Then heated again until just becoming red and dropped it in cold water. 











To bring the relieve I took my Clackson grinder and try to set-up the angle with a protractor (the grease on my jacked is just to make it water resistant). Its a great machine but a real pain to set-up angles accurate. 






To get the broach back parallel in the collet I used a parallel and flat table (Tacchella bed), have the flat side of the broach on the parallel and tighten the collet






Then tried to grind the broach by pressing the collet holder agains a flat and sliding it up and down. At the second face I hit the stone with the tip..so now it will become a 4mm broach!

Took the already finished dividing head of the Tacchella and bolted it to the Clackson table.











I set the angle by eye (big mistake, but I got impatient).and grinded the broach. This worked out well. Here it is after grinding, and with a way to large relieve angle.






Chucked up a piece of aluminum and drilled a 4mm hole and gave it a light chamber. Put the broach in the tailstock and brought it in position with the 2 screws fixing the bearing holder to the MT3 shaft loose. Let the lather run on very low rpm and put some pressure with the tailstock. Switched off the lathe while keeping the pressure on the tool. Then tightened the 2 screws on the back, this should be center. This is the procedure described by Ken. Started the lathe and hold my breath. I was able to keep the tailstock moving in nice and steady. I checked several times if I was not pressing the tailstock backward, but no, the broach is CUTTING!






Put in an allan key and it a very nice and tight fit. My goal has been achieved, I drilled a hexagonal hole!






Then tried a piece of brass. It worked ok for the first 3 to 4mm and then the broach got rotated or damaged I think. Also the hardening did not worked out well, I guess with my method you just harden the surface and I reduced the size with grinding. The broach has now some rounded corners. Can it be an option to harden it after grinding?? So now this broach will become the 3mm version :big:






Thank you so much Ken for sharing your design, its a perfect tool and but a little but of practice and experience it work great :bow: :bow: :bow:

Thanks for watching, regards Jeroen


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## swilliams (Feb 20, 2012)

This is really cool. Great stuff Jeroen and Ken. I think I'll have to build one of these

Steve


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## kf2qd (Feb 20, 2012)

What was you material, and how did you harden it? Case hardening would be only on the surface, and could be ground off. If you used a quench hardening material the hard should go all the way through.


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## Ken I (Feb 21, 2012)

Very cool Jeroen.

The broach was not hard enough - once the corners go it will jam as yours did.

Drill rod need to be heated to carrot red / bright orange (dull red doesn't cut it) and quenched - it comes in air, oil or water hardening grades.

I don't get why you heated it twice.

Ken


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## arnoldb (Feb 21, 2012)

Good going Jeroen Thm:

If you want to temper the silver steel after hardening it, it must not get anywhere near red hot again; that will just anneal it and lose nearly all hardness.

After hardening and grinding it, gently heat it on the shank side with a torch, and keep a close eye on the ground end. You'll see the metal changing colour from the heated end - the colour will travel slowly toward the ground end. The moment the ground end turns a bit yellow in colour, stop heating and quench it again. This should give a good temper for a broach without softening it too much.

Kind regards, Arnold


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## coopertje (Feb 21, 2012)

Hi Steve, you should build one, its a really fun project and most off all a very useful one!

kf2gd, I used silver steel (think its called silver steel in the USA). As Ken already indicated my fault is most likely the temperature, it was not hot enough for hardening. I need to get some heat resistant stones to be able to get more heat in the material, now I need to hold it with a pliers, sucking up part of the heat applied. 

Thanks for the tip Arnold, indeed I was "Trying" to temper it after hardening.....

I will make a square broach just for testing and playing in the below mentioned sequence:

- Heat the tip until carrot red / bright orange
- Quench it in cold water
- Grind it to shape and dimension
- Heat again on the shank as described by Arnold

I will keep you informed about the results, thank you all for your comments and tips!

Best regards Jeroen


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## swilliams (Feb 21, 2012)

One question. Will this work ok in a small lathe? Mine is 9" swing and weighs about 200kg


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## Dan Rowe (Feb 21, 2012)

Jeroen,

I was going to suggest using a magnet to indicate the quench temperature but that method does not work for all alloys.

Here is a link to a blacksmith approach to heat treatment of carbon steel.
http://tidewaterblacksmiths.net/2.html

Dan


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## Ken I (Feb 21, 2012)

coopertje  said:
			
		

> - Heat the tip until carrot red / bright orange
> - Quench it in cold water
> - Grind it to shape and dimension
> - Heat again on the shank as described by Arnold (to straw colour)



That's it Jeroen - since you heated it red on the second go around I presumed you were trying to reharden it - that would not be tempering - the way Arnold suggests is correct.

Tip: Don't use pliers for holding - wrap a length of wire around the shank and use that for "dangling" or pick up.

Swilliams - it will work on even the smallest lathe - power is generally not the issue - tailstock thrust is the limiting factor - I would guess your lathe would handle up to about 8mm AF Hex in mild steel.

Ken


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## Don1966 (Feb 21, 2012)

http://mikesworkshop.weebly.com/rotary-broaching.html 
I have attached the above link for a rotary broach this will work on a small lathe for SWilliam. Great project Jeron I really enjoyed you work and your affords to show us how it is done. Thank you for sharing all your photos.

Regards Don


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## swilliams (Feb 21, 2012)

Thanks Ken and Don, great stuff

Cheers
Steve


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## steamer (Feb 21, 2012)

Jerone,

I would do just that with tool steel. Grind it and then harden! It only takes a very small rise in temperature to blow the temper of the steel with tool steels. Without coolant on the grinder...you'll blow the temper for sure. The part is so small, that I don't think it's going to distort much during quenching.

I would grind it, harden and then draw the temper to straw yellow.

Harden as others have stated. Wrap it in wire and then dip it in liquid soap. It will keep the scale down

POLISH the tool nice and bright....this is important for the next step!

Holding the tool vertical, heat the tool from the shank side and carefully watch the color...straw will appear pretty quickly near the back and start to climb up the part towards the cutting edge...The Cutting edge is all that matters!

When it gets to the cutting edge...immediately quench it in oil again.  The shank will be blue and tough, while the cutting edge will be very hard but not brittle.

Spend some time honing the edges with a stone....then give it a try.

Dave


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## coopertje (Feb 22, 2012)

Thank you for your response and help guys, I really appreciate it. I have some things to learn here, (accurate) tool making is a new dimension for me. Yesterday I visit a friend, he has a beautiful Shaublin 102. This thing is new, he had it send to Shaublin factory to have the machine re-grinded to original specifications. Digital readout system with a resolution of 0.5 micrometer!! He is able to make parts with an accuracy of 0.002mm. Damn, I was so happy that I could make parts within 0.01mm (tried better but without success). But is was very educational, first thing to do is get a more accurate dial indicator and start measuring my machine better. Then I know what I can expect out of my machine and what errors are from the operator (very frustrating when you try to achieve accuracies above machine specifications!). After that it will be playing time! When I get to that stage I might start a topic on this if people are interested.  

Back to the broach, In the article mentioned by Don you see the drilled tip of the broach, I knew I have seen that before, did not remember where. According to Ken this is not necessary so I will safe myself the trouble of making it. 

I do not know what grade of silver steel I have, some mention quench in water, some in oil. What would be advisable here, or does it not matter so much? 

To Dave, would it be enough to polish (emery paper?) and after hone just the front side of the broach? I am a little scared about the hexagonal sides, do not want to make a radius on them when polishing and honing...

Thanks in advance for sharing your wisdom!

Happy machining, regards Jeroen


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## Ken I (Feb 22, 2012)

The drilled point produces excessive rake (± 26°) unless you grind the drill point to a shallower angle - in any case the surface finish is generally lousy and I consider good finish more important for smooth chip flow. I have ground spherical depressions (good finish) to give different rakes - it does reduce the force very slightly - but as I have said before not worth the bother - it's far easier to get a good finish on a flat face. Additionally, raked broaches are weaker and more prone to chipping - especially with the "grooves" of a poor drilled finish close to the edge acting as stress raisers - that's just asking for the edges to fail quickly.

Use a flat face and live with the slightly increaced force.

You only need to polish the area you are interested in - in this case make it the flat face and watch the colour change on that although the sides give you a better view of the heat "creeping" towards the face.

It takes a lot of elbow grease to remove any significant amount off glass hard stock with fine emery paper - even on the corners - wrap the emery around a flat stick or file to avoid going around the corners. You need only "polish" one side not the entire hex.

Regards,
      Ken


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## coopertje (Feb 22, 2012)

Ken I  said:
			
		

> You need only "polish" one side not the entire hex.



Just to be absolutely sure, with this you mean the tip (front side) of the broach. So I will not touch the grinded hex side with a stone....

Regards Jeroen


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## Ken I (Feb 23, 2012)

Jeroen, You can do either.

If you are unhappy about polishing one side of the hexagon then you can do just the face.

The side of the hexagon works better because you can see the colour "creeping" towards the face as you heat the shank - as suggested by Steamer.

If you only polish the face you will have no idea of how fast the heat is coming towards it and it might change from straw to blue before you can react - but this method will work if you are carefull - pactice on a piece of unmachined unhardened stock to get a feel for how much heat to apply and for how long.

Ken


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## coopertje (Feb 23, 2012)

Thanks for your answer Ken, I was completely wrong in my understanding :-[ You polish one side to just see better the color change creap up from bottom of tool to the cutting tip when tempering the broach! I though we where talking about finishing the cutting edges after grinding and tempering. 

If nothing comes inbetween I will make another broach tonight. Since my grinding machine is not operational yet I will take a different approach. I will set my milling table to 1.25 degrees and mill the relieve in the broach, harden and temper it and then hone the front side of the broach with a stone. 

Regards Jeroen


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## coopertje (Feb 23, 2012)

Made a little progress this night. Started with modifying a indexer I bought last year. Its very reasonable build and very cheap, 45 euros. I did not want to change the table of the mill to 1.25 degrees since it is set to zero quite accurate. I had the idea to add 2 M5 screws at the front of the indexer to set the angle in a more accurate way and could leave my mill table at 0 degrees. Dis-assembles the indexer and cleaned the typical smelling chinese grease. Put it in the mill, drilled and tapped the 2 M5 holes. As you can see in the pictures the sides of the base look like a banana, not so good for clamping it in a machine vise.






Flipped the part in the vise and made the sides of the base straight






Assembled it and before mounting a collet checked the run-out in the spindle, it was a little over 0.01mm which is better then expected and very acceptable for making a broach.






Spend quite some time in setting the angle accurately, I calculated 0.253mm movement in height when moving the dial indicator 10mm over the blank of the broach. When found locked the vise and mounted a mill with a chamber on the cutting edges and start cutting. I am quite happy with the result, no need to grind it when making it this way. 











Its not hardened yet, I will do that tomorrow. 

Regards Jeroen


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## steamer (Feb 24, 2012)

Looking Good Jeroen! 

Watching intently!  I intend to either A, Mod my indexer like yours, or B, mount my indexer on a sine plate in the vice.
Considering I have the sine plate....I'll probably do that.

Dave


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## coopertje (Feb 24, 2012)

Thanks Dave! For sure, if I had a sine plate available I would go for option B too. I probalby will drill 2 extra holes on the back too, yesterday I had to fill out the back to have the indexted tilted forward (collet side needed to be lower then the backside)....

Regards Jeroen


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## coopertje (Feb 24, 2012)

We are getting somewhere! Remade the broach yesterday and followed the advice given in hardening. It seems to work, made 2 hex holes, one in aluminum and one in brass. Not a single sign of use on the broach and it went in like cutting butter (could rotate the tailstock with one hand easily), thanks for the help!







If you look closely to the aluminum bar you will see that the hole was oversized, the broach cutted at the darker parts at the side inside the hole. 






Procedure followed to make the broach:

1) mill the hex to size at 1.25 degrees angle
2) Wrap a piece of wire around the broach and heat it until carrot orange. Put it in cold water and keep moving until it cooled down
3) Clean up the shaft with sanding paper and the tip or with sanding paper over a file or a honing stone. Be careful to not damage the sides, just make them clean.
4) Heated from the back of broach and watch the straw color go up until the tip (this is not so easy to see) and again put it in cold water and keep moving until it cooled down. Now its tempered.
5) Clean up again the shaft with sanding paper and I honed the front side of the tip and the 6 cutting edges slightly with a fine honing stone.

Tomorrow I will make some different size of broaches. What would be the correct tolerance on broach cutting sides?

For example a 6mm hex broach, should it be spot on 6.00mm or make it slightly oversize like 6.01mm?

Regards Jeroen


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## steamer (Feb 24, 2012)

Glad it worked out Jeroen!

I think .01mm clearance is fine for socket, but I wouldn't go any more than that...

Dave


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## mu38&Bg# (Feb 24, 2012)

Very good. I will need one of these for sure. Especially seeing you don't need any special grinder to make the broach.

Machinery's Handbook says the ANSI/ASME spec for a 6mm hex socket is 6.02-6.095. I found this online. http://www.greensladeandcompany.com/pdf/Inspection-Hex Recesses.pdf

Greg


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## steamer (Feb 25, 2012)

Thanks Greg!  I stand corrected! :bow:

Dave


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## coopertje (Feb 25, 2012)

Thanks Dave and Greg, that very useful information! I have printed the ISO table, now lets go to the shop to make some broaches!

Have fun, regards Jeroen


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## Ken I (Feb 25, 2012)

Well done Jeroen - a couple more pointers.

When tempering cool down in liquid soap as suggested by Steamer) or oil - just slightly less of a thermal shock.

The chamfer needs to be at least as big as the corner to corner distance of the broach.
Imagine you had no chamfer and your toolholder is a bit worn and droops - it will snag the face off centre and be whirled around in an orbit until the cutting forces (tend to) centralise it. This imposes uneccessary stress on the broach and can snap it. (with a brand new holder like yours its not really a problem.)

If you want a sharp corner then make allowances to face off the chamfer later.

Ken


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## coopertje (Feb 25, 2012)

Ken, I am sorry but I do not understand what you mean. If we call the grinded end of broach the tip length, do you mean that the tip length should be at least the corner to corner distance of the broach? In other words, don't make the tip length too short?

I have made my broaches before reading your comments, lets see what you think of them, I am open for any comment!

Measured my allen keys and they are all or spot on or below the mentioned key number. So I felt that I will have a lot of play when making the broach too big. My goal when making them was to be on the lower limit of the Iso Norm, 0.02mm oversized. I ended up with broaches that are between 0.015 and 0.03mm oversized which should be quite acceptable.






When the milling was complete I took the broaches to the lathe and made a small chamfer 






For the smaller sized I prepared the blanks in the lathe so less material needed to be milled away






Here is my set after milling and before hardening. The dimensions (without tolerance) are 8, 6, 5, 4, 3, 2.5, 2 and 1.5mm (The 1.5 version looks really fragile, seems that it will snap off on the first use, did not try it yet.)






Then I harden them all and try to temper them accurately. Its quite difficult to see the straw color, one need some practice in this. I believe with most of them it went ok (second from left a bit too warm and 4th from left a little too cold)






Cleaned the sides with a honing stone and to hone the tip I put the broach in a collet such that the tip came out the back of the collet (to not damage the front of the collet). The collet is used as a guide to keep the tip straight on the hone. 






Made a nice storage box (old Clarkson collet holder box) for the tool including the broaches. There is also room for the spare bearings and the prepared drills with asymmetrical tips (maybe new chinese drills have this feature as standard?). 






It has been proven that you can make the broaches without a grinding machine. However next time I will make them on the tool grinder (hope the weather becomes better soon, want to finish it!). It much quicker in setting up the angles and also the cutting sides will be better finished (sharper) then when made on the mill. Especially the small broaches are a pain to hone with a stone!

I got an offer from Peter from polygon solutions. He offered me to send me a professionally made broach for me to try in my holder. I have discussed this with the moderator, after all this is a place to share our hobby! I am very pleased that they agree with it, I am eager to test the difference between a professional broach and a shop made version. I will try to make a test with a 6mm hex broach, 1 made on the mill as I did today, one made on the tool grinder and one supplied professionally. It will take some time, but when I have the results I will post them here. 

Regards Jeroen


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## mu38&Bg# (Feb 25, 2012)

How do these wear Ken? By making broaches something larger than the minimum, would it allow for sharpening of the cutting face of the broach before scrapping the tool?


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## Ken I (Feb 25, 2012)

Jeroen, you broaches are just great. That's a really lovely set you've made yourself there. You might reduce the length to width aspect on some of the smaller broaches on future replacements.

My comments were related to the drilled & chamfered hole in the material being broached - that is the hole you must predrill must be a bit bigger that the across flats distance and the chamfer must be a bit bigger than the across corners distance.

Dieselpilot - at one stage I used to have the broaches made top limit specifically for regrinding - in practice the edges tend to crumble and were not worth regrinding - remember this was in a production environment so no one noticed the broach was dull until it was buggered - for home use regrinds would be practical - removing as little material as neccessary - if the edges appear to be bit dull.
Hard material like HSS tends to chip away at 45°, material like hardened drill rod tend to go dull and generate "lands" on the clearance - like Jeroens earlier pictures of an insufficiently hard broach.

Sorry - kind of a yes, no, maybe sort of answer.

A professionally made HSS broach will require a little less force, last much longer and the hole will most likely be better (more a function of your accuracy & finish than anything else) but for hobby use that's not the point of the excercise.
Like many cutting tools they are cheaper bought than made yourself - but again doesn't provide the sense of acomplishment that doing it yourself does.

Ken


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## ref1ection (Feb 25, 2012)

This has been an interesting and very informative project to watch.

Ray


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## mu38&Bg# (Feb 26, 2012)

Jeroen, a box and spares! Excellent.

Ken, that makes sense. I'll probably buy the broaches once the time comes. There is a small volume product I'm thinking of making.


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## Ken I (Feb 26, 2012)

Jeroen,
     I trust you are going to post your finished box-set and a video of it working under finished projects ?

Ken


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## coopertje (Feb 26, 2012)

Thanks for the comments and interest Ken, Greg and Ray! You sure know what you are talking about Ken! Glad that my broaches look ok, and the chamfer on the prep-holes is received loud and clear this time.

When the box is finished I will show it here. Also will try to make a video (don't have to big expectations, my video making capabilities are even worse the my machining ones). Probably it will take a week or 2, I am leaving tomorrow afternoon for work abroad. If I remember I will also try the broach in the mill, then its better to see the action.

CU, Regards Jeroen


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## coopertje (Apr 1, 2012)

Took a little bit more then 2 weeks, is quite busy at work and the RC helicopter season has started again.

Yesterday I made a storage for the QC tool holders. I collected quite a bit (18 in total) over the years and still I am changing tools in the holders. I believe you will never have enough of these.











As promised below some pictures of the finished box. As you can see needed to make some space in the cover to have the broach holder fitted.











I have tried to make a movie of the tool in work in the lathe as well as in the mill. If you look closely to the broaching in the mill, the tool rotates a little at the beginning. I think I need to give it more pressure from the start, even though the fit of the Allan key is the way I like it, nice and tight.

[ame]http://www.youtube.com/watch?v=sso8Jpf4s30[/ame]

Got the broach from Polygon Solutions. Must admit that the finishing and quality is top level! Below the professional broach on the left and the home made on the right (as if the difference would not be obvious). Note the hole in the Polygon broach, in this way the air can escape when mounting the tool in the holder but also during the broaching process. Since my prep holes are quite oversized I do not miss the hole in my home made broach. 











Made an adapter for the Polygon broach, this has an 8mm shaft were I need a 10mm one






I have tried both broached in the lathe in Aluminum. To my surprise I could not detect any noticeable differences between both broaching bits. The force to cut is similar and also the finishing of the hole is the same. Maybe in steel there is a noticeable difference, or it might be the life time of the tool. Since I will only make a few hole per year it will take me a long time to find the answer.. I am sorry Peter, I will not become a customer, but thank you again to give me the opportunity to test the differences :bow:

Its hard to photograph, here is the best I could do for the polygon broached hole






and the home made broached hole






I am happy that I made this tool, I can only encourage others to do the same!

Have fun, regards Jeroen


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## vcutajar (Apr 1, 2012)

Jeroen

A fine bit of kit you have made for yourself.  :bow: It will last you a lifetime.

Vince


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## Ken I (Apr 1, 2012)

Well done Jeroen - nice to see someone actually build and use it - thanks for the vid.

When using it in a mill you can see how it got the name "wobbly broach".

Regards,
       Ken


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## coopertje (Apr 1, 2012)

Thank you for your comment Vince! Ken, special thanks to you for making this tread possible, I really enjoy the tool :bow:

Regards Jeroen


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## steamer (Apr 1, 2012)

Nice Job Jeroen!

gotta build me one of those!

Dave


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## Lesmo (Apr 7, 2012)

Nice one Jeroen

Safely tucked away for the future.

Les

PS Your video making skills are much better than you said they were.


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## coopertje (Apr 11, 2012)

Thanks Les! Using Imovie makes live a little more easy.

Regards Jeroen


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## polygon (Apr 24, 2012)

Jeroen, you've done some beautiful work I agree! Thanks for trying out our rotary broaches and let me know if you have any other questions. Even though our broach holders are for production shops, we were very interested in your results. If you ever bump production up to 1000 parts per year let me know.


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## kustomkb (Apr 24, 2012)

Nice job Jeroen, Thanks for documenting the build and use of the tool.

Thanks for the design Ken.

Man, the list just keeps growing...


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## ksor (Jun 9, 2012)

I think i once saw a drawing for this project - or something similar - but I can't find it now !

Do you know a link to a drawing for such project ?


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## Ken I (Jun 9, 2012)

It's in the downloads section.

At the bottom of page 24.

Ken


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## ksor (Jun 9, 2012)

Ken I  said:
			
		

> It's in the downloads section.
> 
> At the bottom of page 24.
> 
> Ken



Thx Ken - I never used that section before - didn't know of it at all !


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## snowshooze (Aug 1, 2014)

That bearing on a stick you used to true the face was shown to me many years ago, and I have saved a lot of setup time with it. 
  But there is another application I have used it for:
  Chuck your shaft... end chuck... get the shaft turning and crash into it with trusty bearing in a stick. 
  Trues stock for subsequent center drill. 
  Start with moderate chuck pressure, when she is running true, tighten down.   
 If you accidentally cut a sloppy screw thread, put this in the tool post and actually roll down the major diameter of the screw threads... swageing them as you go. It might take you from a 70% to a 60% but sometimes that isn't too important. 
  Just beat down the top of the thread form....
  And another, in straightening bent shafting...sometimes heat is used, buy push the bearing against the shaft between centers, and throw it in feed. 
  Keep your hands on the cross-feed and keep consistent but not excessive pressure against the shaft.. you could hurt your lathe. 
  But it works that shaft back to straight.


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