# Shop made Rotary broach holder and broaches.



## xalky

This is the thread starter for a Rotary Broach holder. For those of you that don't know what a Rotary Broach is, here's a video showing the capabiliies of a Rotary broach: [video=youtube;BuT6mrAMOxE]https://www.youtube.com/watch?v=BuT6mrAMOxE&amp;feature=c4-overview-vl&amp;list=PLC06981055019FA8B[/video]

There are quite a few home shop made rotary broaches out there on the net. I will be building mine loosely based on all of them and to my own liking. :whistle: I will be making , what I Believe to be, some improvements on some of the designs. It will take .500 diameter shank broaches, store bought or shop made. It will have a 3/4" straight shank so that I can mount it on my tailstock drill chuck or be able to use it in a Bridgeport R8 3/4" collet.

Here's a picture of the bearings That I just got in the mail today for it. From right to left. 2-   1 1/4" ID Sealed Ball bearings, 1/2" ID thrust bearing, 5/16" ID sealed roller bearing.




I already had the 5/16" ID bearing left over from another project.

That's all I got for now...Stay tuned


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## DAN_IN_MN

What shape are you going to be broaching?

Interesting video.


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## xalky

Probably internal hex for now. Once the Broach holder is made just about any shape is possible. Making the external broaches is probably beyond the capability of a home shop, but they can be purchased. That's the reason why I'm going to be making it to be able to accept the commercially available broaches.

Marcel


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## astjp2

Will you be using a MT arbor to us it in a tailstock or set it up for use in a mill?  I am thinking that I want one for my lathe.  I was going to do it with a MT3.  Tim


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## xalky

It's gonna be 3/4" straight shank so that I can use it in my big drill chuck in the tailstock. I thought about making interchangeable shanks, but decided against it for simplicity sake. I'll be able to use the 3/4" shank on both the mill and the lathe. If it doesn't work out in the lathe I'll just make a whole back plate assembly with the mt3 shank. The Back plate and shaft is pretty quick to make.


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## xalky

I won't be making plans for this, because a lot depends on what bearings you decide to use. I just picked some bearings based on the size of the broach diameter and worked backwards for there. I wanted to have enough meat left on the collar for the set screw to tighten to the 1/2" broach shaft. Which was my reasoning for using an 1.250" ID roller bearing. Here's a couple more videos showing how it's made. The key to this is getting that 1* offset at the back end and making it adjustable at the tail end so that the broach can always land on center of the hole regardless of the length of the broach (within reason). 

[video=youtube;wpx76-_lPkM]https://www.youtube.com/watch?v=wpx76-_lPkM[/video]

[video=youtube;sso8Jpf4s30]https://www.youtube.com/watch?v=sso8Jpf4s30[/video]

In the last video there's actually a link to one persons build.

Marcel


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## Charley Davidson

I have 2 of the Slater rotary broaches (Internal&external) with matching metric hex broaches plus a couple blanks for making custom broaches. Never used it. But I have it.


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## xalky

I chose aluminum for the main body because it's lightweight and easy to work. It started as a 3" rd aluminum bar.





Center drilled.




Drilled it all the way thru with a 9/32 drill. This hole serves as the pilot and also it will see a 1/4" bolt through the back side at assembly time.




I drilled a series of larger and larger drill holes, bing careful not to be too deep with the point of the drill. I then flattened out the back of the hole at close to the right depth for the bottom of the thrust bearing. This will make it easier for me to clean up the back of the hole with a boring bar.




Boring in progress.




The Bore is complete with all steps and bores to the correct size and distance to each other. Chamfered all the edges. A quick sanding to open up the bore about .0005 to allow the bearings to slide in just nice. Trying the bearings periodically until it's perfect. A clean up pass on the outside for a nice finish.




Here's a picture of the bearing body with all the bearings fitted inside.




That's it for now. 

I have some more lathe work to do on the back side to fit the little bearing which retains the shaft with the 1/4" bolt. I did this first part on the 3 jaw, never unchucking it. Now that I have to flip it around, I'll do it in the 4-jaw and indicate it true for the back side work.

Marcel


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## JoeSixPack74

Every day this week I check out this site there is a new to me tool.    You have probably also seen this site http://www.docsmachine.com/projects/rotarybroach/rb01.html.  If not he uses a turret lathes floating holder to make a rotary broach holder and old broken endmills for the broaches.


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## xalky

I did see that one. If I had a floating tool holder I would have made it that way. )


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## lawlessman

This is an interesting thread that I will be watching. I have a question. Has anyone ever seen or built a homemade rotary broach that could broach a DEEP 1/8" square? I need to broach about 3/8" deep in ordinary steel and even Slater Tools, the self-proclaimed rotary broach "experts" tell me that is very small and somewhat impractical. The price they quoted for the necessary tooling was outta' sight. I have even tried just pushing a square broach in with a press, but all I got was a broach stuck in a part. I also need to broach a .150 square about 1/2" deep.
Any ideas?


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## pestilence

Is there a reason why this is a rotary broach and not just a broach?  Does rotation help with something, or do these exist just because people want to broach a part without removing it from a lathe?


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## xalky

lawlessman said:


> This is an interesting thread that I will be watching. I have a question. Has anyone ever seen or built a homemade rotary broach that could broach a DEEP 1/8" square? I need to broach about 3/8" deep in ordinary steel and even Slater Tools, the self-proclaimed rotary broach "experts" tell me that is very small and somewhat impractical. The price they quoted for the necessary tooling was outta' sight. I have even tried just pushing a square broach in with a press, but all I got was a broach stuck in a part. I also need to broach a .150 square about 1/2" deep.
> Any ideas?


With these rotary broaches you can only go 1.5 times the diameter of the broach. Its just the nature of the beast, because of the 1 degree tool offset, the broach runs out of practical shoulder room after a certain depth.


pestilence said:


> Is there a reason why this is a rotary broach and not just a broach?  Does rotation help with something, or do these exist just because people want to broach a part without removing it from a lathe?


The rotation helps clear some of the chips away and not very much pressure is required. These are designed for shallow, blind hole broaching. The above poster just pointed out what happens when you try to force a traditional broach down a blind hole.

Marcel

- - - Updated - - -

I put it in the 4 jaw and indicated it true. Then drilled and bored the back side and finished it to length and cleaned up the outer diameter.




After I finished all the lathe work I set it up in the vice on the bridgeport with a 1 degree angle block under it.





Taking the final pass on the back face for the 1 degree angle.




That's it for now.

Marcel


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## melsdad

I am subscribed! I would like to make one of these myself. The price to buy the tooling is out of the question for most home shop guys like us. 

I have a project coming up that requires a pentagon shape with and I.C. of .745 dia.


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## xalky

While it was setup in the mill for the 1 degree incline, I drilled and tapped the holes perpendicular to that face. I'm not sure if it makes much difference but I wanted to prevent the nuts from walking the chuck adapter adjustment. If i had drilled the holes parallel to the bore the nuts would have been touching on one side of the thread and not the other when it was clamped down. A small detail, I know, but one I had to iron out for myself.





I'll be using studs that will be set with lock-tight in the aluminum body, and nylock nuts with flat washers to tighten the adjustable chuck adaptor to the body. I don't want to be screwing bolts in and out of an aluminum piece.





I probably won't be doing much on this for the rest of the week. I gotta go make some money to pay for all this stuff.)

Marcel


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## astjp2

lawlessman said:


> This is an interesting thread that I will be watching. I have a question. Has anyone ever seen or built a homemade rotary broach that could broach a DEEP 1/8" square? I need to broach about 3/8" deep in ordinary steel and even Slater Tools, the self-proclaimed rotary broach "experts" tell me that is very small and somewhat impractical. The price they quoted for the necessary tooling was outta' sight. I have even tried just pushing a square broach in with a press, but all I got was a broach stuck in a part. I also need to broach a .150 square about 1/2" deep.
> Any ideas?



You need someone with an EDM, if its not a large quantity, it may not be too expensive.  Tim


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## DaRiddler

This is one of the better threads I've ever seen on this or any other machinist boards -- I'm following it with great interest, as are many others! It involves something that had seemed out of reach for the average machinist/budget and makes it very doable. 

Don't even consider not finishing this project -- the masses will be out with pitchforks and torches!

which is my way of saying Thank You . . .


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## xalky

DaRiddler said:


> This is one of the better threads I've ever seen on this or any other machinist boards -- I'm following it with great interest, as are many others! It involves something that had seemed out of reach for the average machinist/budget and makes it very doable.
> 
> Don't even consider not finishing this project -- the masses will be out with pitchforks and torches!
> 
> which is my way of saying Thank You . . .



Well Good! I'm glad I can help someone out. You're right, There isn't a whole lot out there on this subject. Don't expect much on this for a few days. As soon as I have some free time I'll jump back on this project. I'm busy as hell right now with work...I wasn't doing squat last week!  It's feast or famine.

I probably have about another day worth of work left to go on it, with no distractions , maybe less. I still have to make the broach arbor shaft and the the tail arbor. 

Marcel


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## xalky

I had some time to work on this a little bit tonight. I'm working on the tailshaft assembly. The tailshaft will be 2 pieces welded together, although it could be made in one piece, I didn't want to wast all that material I started with a piece from my scrap bin a 3" diameter piece of cold rolled steel cutoff. I indicated it roughly, faced it center drilled it and then I drilled and bored it to .754". I also cut a 45 degree chamfer, about 1/8" for the weld bead to sink into. The shaft will finish out at .750" to fit into a 3/4" collet or a 3/4" drill chuck on the lathe.





I then turned the shaft to .754". Its a snug fit in the tailstock plate.




A picture of the 2 parts mated together.





The shaft will be welded around the circumference on the back side and plug welded on the other side.

Once everything has slowly cooled down,the whole assembly will be trued up in the lathe, the plate will be turned down to size, and faced on both sides, and made thinner. The shaft will be turned down to .750". 

Marcel


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## xalky

I welded the 2 pieces together this morning.  I was gonna tig then together, but my tig doesn't have enough juice to weld this heavy stuff. According to the chart I needed 275-300 amps, my tig only pushes 250, plus I didn't have large enough rod for it. I used the mig at 210 amps and 210 ipm of wire feed. The shaft was not pushed all the way through so as to alloww it to put a deep penetrating fillet weld inside the plug.





On the other side I made a deep penetrating fillet weld. 





The part is left to air cool slowly before any machine work.





All these welds will be cleaned up on the lathe as well as turning the plate and shaft down to size and trued.

Marcel


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## 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


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## 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


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## 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


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## 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?


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## 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


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## 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.)


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## 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


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## 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


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## 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


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## xalky

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


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## randyc

xalky said:


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



Many thanks.

You know, I'd thought about these broaches for several years and likely would have built something similar to yours.  But I wanted to adapt an old Jacobs 18N chuck and make it a live tailstock chuck.  I used a long oilite bearing for alignment and a 1/2 inch hard ball for thrust.  I was quite satisfied with the way that it worked.  Thinking about it later that night a tiny little light went on upstairs, LOL.

 Next day I made the sketch and that evening made the broach.  I colored the parts on my gas range and dunked them in oil, as usual


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## magu

Wow Marcel, thanks for sharing! I never new such a tool existed before tonight. Onto the "someday" list it goes. Your progress looks great so far, I look forward to watching the rest of the build.


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