Home Model Engine Machinist > Showing Them > A Work In Progress > Building KEN I Rotary broaching tool
Reply
 
LinkBack Thread Tools Display Modes
Old 02-20-2012, 08:10 PM   #21
coopertje
Project of the Month Winner!!!
 
Join Date: Jul 2010
Posts: 278
Liked 48 Times on 48 Posts

Default Re: Building KEN I Rotary broaching tool

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



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

Thanks for watching, regards Jeroen



__________________
coopertje is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 12:58 AM   #22
swilliams
 
Join Date: Mar 2010
Posts: 239
Liked 12 Times on 12 Posts

Default Re: Building KEN I Rotary broaching tool

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

Steve



__________________
swilliams is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 02:45 AM   #23
kf2qd
 
kf2qd's Avatar
 
Join Date: Apr 2008
Posts: 404
Liked 25 Times on 30 Posts
Likes Given: 1

Default Re: Building KEN I Rotary broaching tool

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.

__________________

KF2QD, South Texas
HF MiniMill
HF 7x10
Hardinge UM

kf2qd is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 05:34 AM   #24
Ken I
Project of the Month Winner!!!
 
Ken I's Avatar
 
Join Date: Oct 2010
Location: Cape Town, South Africa
Posts: 1,225
Liked 100 Times on 97 Posts

Default Re: Building KEN I Rotary broaching tool

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

__________________

I'd rather have a bottle in front of me than a frontal lobotomy.

Ken I is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 06:36 AM   #25
arnoldb
 
arnoldb's Avatar
 
Join Date: Apr 2009
Location: Windhoek, Namibia
Posts: 1,793
Liked 91 Times on 176 Posts
Likes Given: 6

Default Re: Building KEN I Rotary broaching tool

Good going Jeroen

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

__________________

"Necessity, who is the mother of invention" - Plato

arnoldb is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 10:51 AM   #26
coopertje
Project of the Month Winner!!!
 
Join Date: Jul 2010
Posts: 278
Liked 48 Times on 48 Posts

Default Re: Building KEN I Rotary broaching tool

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

__________________
coopertje is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 11:52 AM   #27
swilliams
 
Join Date: Mar 2010
Posts: 239
Liked 12 Times on 12 Posts

Default Re: Building KEN I Rotary broaching tool

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

__________________
swilliams is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 12:48 PM   #28
Dan Rowe
 
Dan Rowe's Avatar
 
Join Date: Feb 2010
Posts: 590
Liked 29 Times on 28 Posts
Likes Given: 5

Default Re: Building KEN I Rotary broaching tool

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

__________________
Dan Rowe is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 03:05 PM   #29
Ken I
Project of the Month Winner!!!
 
Ken I's Avatar
 
Join Date: Oct 2010
Location: Cape Town, South Africa
Posts: 1,225
Liked 100 Times on 97 Posts

Default Re: Building KEN I Rotary broaching tool

Quote:
Originally Posted by coopertje
- 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
__________________

I'd rather have a bottle in front of me than a frontal lobotomy.

Ken I is offline  
 
Reply With Quote Quick reply to this message
Old 02-21-2012, 04:46 PM   #30
Don1966
Senior Member
 
Don1966's Avatar
 
Join Date: Jan 2012
Location: Morgan City, Louisiana ( along the Gulf Coast)
Posts: 487
Liked 38 Times on 38 Posts
Likes Given: 7

Default Re: Building KEN I Rotary broaching tool

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


__________________

How Many times I did that?

Don1966 is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Building a 120mm rotary table arnoldb Tools 158 01-11-2014 06:46 PM
Rotary Broach Tool Design excalibus Plans 28 04-09-2013 02:20 AM
Rotary Broaching question? Chitownmachine Questions and Answers 21 02-19-2012 09:13 PM
Scratch Building a QCTP (Quick Change Tool Post) for my Myford ML7 BenPeake Machine Modifications 6 08-29-2010 02:55 PM
Building Elmer's #46 rotary arnoldb A Work In Progress 77 07-13-2010 07:23 PM




- Top - Member List