Shop made Rotary broach holder and broaches.

[xalky]

After it cooled off, I put it in the band saw to slice off the extra bit of thickness.



Then I chucked it up in the lathe to face off the mating side. And turn the large OD to the size of the Rotary broach body. I also re-center drilled it for the next operation.



Turning the back side down. There was surprisingly, very little warpage from the welding operation. There might have been .002 at max warpage on the back side. I actually took off about .035 on the back. I also cleaned up the weld and cut that on a 45* angle to the shaft and plate.



Here's the part. The only thing left is to cut the length of the shaft to about 2" in length. and mill the slots for the tail adjustment.



Marcel

 

[xalky]

I haven't made much progress on the broach holder this week. My time is pretty limited with me working my buns off lately. I'm trying to come up with a good solid mounting for the tailpiece in the vice. To mill the slots I have to mount it shaft down, grasping by the shaft with the plate up. I don't have any v slots in my mill vice or really any good v blocks.

I've been wanting to make up a new set of soft steel jaws for the mill vice for some time now with a horizontal and vertical V milled into the jaws. I'll be working on those this week. Especially since I now have the surface grinder to be able to grind them in nice and straight.

Thats it for the progress report.

Marcel

 

[7HC]

I'm finding this thread fascinating as I've always been intrigued by rotary internal broaching.

However, I know nothing of rotary external broaching. I assume it puts splines on shafts?

I understand how an internal broach bit climbs around inside a hole to cut the shape, but I can't picture it externally except perhaps in the form of a knurl.

Little help?

M

 

[xalky]

External broaching works the same way as internal. The broaches have a 2.5* internal taper on them for clearance. The concept is exactly the same. The external broaches, however would be extremely difficult to make in a home shop. I'm not even sure how they make the external broaches. EDM maybe?

 

[xalky]

I finally had some time to work on this some more. I finished up the v-groove vice jaws for the milling vice last night and went right to work on the tailpiece. You can see the new jaws in the photo below. There's a horizontal and a vertical groove in them to hold round objects securely.



The plate that I used for the slotted part was a piece of hot rolled that I had laying around. It left a lot of heavy burrs after I finished milling the slots. So, it went back in the lathe for a final cleanup.



A photo of the completed back plate and the body. There's a 1/2 shank by 1/4"hex broach that i bought in the photo also. I bought it to grab dimensions from it for the other broaches I'll eventually be making for it. The little bearing and socket cap screw goes into the back side of the body and will eventually screw into the shaft. The cap screw draws the shaft back which holds everything together.



Marcel

 

[xalky]

I finished the broach holder shaft last night. I forgot to take pictures of the whole process. Hopefully you can figure it out by looking the completed part. I finished the setscrew hole and the zerk fitting this morning.

Here's a blow up of the parts as they would go together:






I removed the bearing seals on all but the outer bearing seals so that grease can flow from the zerk to all the bearings.


The completed assembly.





All that's left is to grease it up and give it a try in the lathe.)

 

[xalky]

I used this yesterday to make a 1/4" hex in a piece of scrap steel. It works great. No issues. I went for mild steel right off the bat.

Some things I might do differently if I were to make one again:
*I would use smaller ball bearings to make it a little more compact. I could have used 1" ID bearings which would have made the OD smaller too.
*I'd try to shorten up the body a little bit, by making everything a little more compact. ie: tighter thrust bearing, less meat behind the thrust bearing, instead of a socket head cap screw, I would use a button head. A small thin thrust bearing behind the retaining screw instead of a roller skate bearing.

With those changes, I could have shortened the whole assembly by about .75"...maybe a little more.

It's pretty easy to adjust it to center on the hole. I've seen some guys use indicators with a blank rod to get it centered. There's no need for any of that. I eyeballed it centered and away I went. Theres enough tailstock flex, that any small misalignment, within reason, self corrects.

Marcel

 

[john mullen]

XALKY,
Thank you for posting this project. I have started to make one for my shop from your idea. I could not afford one otherwise

 

[randyc]

Nice work ! Not to be overly critical but every shop-made rotary broach that I've seen is unnecessarily large and complex - here's a small one that took about two hours to make (not including the broach which took another two hours). One night's work for the entire tool.

http://www.hobby-machinist.com/threads/a-shop-made-compact-rotary-broach.32219/#post-272748



edited to add photo of disassembled tool

 

[xalky]

I love the simplicity of your design. I wish I would have seen it before I made mine.