Shop made rotary broach for the Rivett

[mars-red]

I wasn't going to post this up here, but then I remembered my post about this in the Shop Made Tools thread some time ago. I had promised another member there that I would follow up with this video. The vid stalled out for a while after I lost *all* of my editing work due to, let's call them quirks, of the editing software I was using at the time. I finally mustered up the will to re-do the editing after learning some different software. The editing is kind of fun when you get used to it, and I think future vids will go smoother. A few friends have given me a lot of constructive feedback so far.

Anyway, for the sake of anyone on here who was interested in more details about the rotary broach I made to fit the Rivett toolpost, and seeing it in action, here it is:
https://youtu.be/grlPjZuDsso

[mattthemuppet]

neat, thanks Max! A couple of suggestions and Qs. First suggestion would be to do some more closeups, particularly for things like set up, perhaps cutting too. It's good to watch how you do things, but also good to see how I would need to do them for my set up. Don't forget to refocus for closeups, or the image comes out blurry. I'd also suggest shortening the turning segment - a couple of cuts will give the viewer the idea, then skip to when you do something different (chamfering, facing the shoulder etc).

I was also wondering a couple of things - when you were doing the facing cut, it looked like the chuck was slowing down when the cutting depth increased. Is the belt slipping? Do Rivetts normally come with a countershaft? Second, are the 2 main parts of the rotary broach holder steel? Just wondering how they do with side loads as there's no dedicated bearing to support it, just the thrust ball at the back.

[kitno455]

It is called a sex bolt, BTW.

allan

[mars-red]

It is called a sex bolt, BTW.

allan

Err well the sex doesn't really come into it for me, but what a guy gets up to in his own shop is none of my business.

Also if you watched much of the video you'll see I was not making a bolt at all. I was making a nut.

[mars-red]

neat, thanks Max! A couple of suggestions and Qs. First suggestion would be to do some more closeups, particularly for things like set up, perhaps cutting too. It's good to watch how you do things, but also good to see how I would need to do them for my set up. Don't forget to refocus for closeups, or the image comes out blurry. I'd also suggest shortening the turning segment - a couple of cuts will give the viewer the idea, then skip to when you do something different (chamfering, facing the shoulder etc).

I was also wondering a couple of things - when you were doing the facing cut, it looked like the chuck was slowing down when the cutting depth increased. Is the belt slipping? Do Rivetts normally come with a countershaft? Second, are the 2 main parts of the rotary broach holder steel? Just wondering how they do with side loads as there's no dedicated bearing to support it, just the thrust ball at the back.

Thanks for the feedback and the support, Matt!

Regarding the perceived slow down, no nothing slowed down, that's one of the spots where I sped up the video to reduce the boredom factor. The frame rate of the video caused an optical illusion, just like when something is spinning and it looks like it's spinning in the opposite direction. Regarding my drive setup, I have a 3 phase motor powered by a VFD, so the motor can directly drive the spindle and I never have to fiddle with belt changes. It's a beast for an 8" machine. I've got a video somewhere showing 0.130" depth of cut in some 2" diameter steel. Deepest I've cut is 0.140", no drama. To go much deeper I'd have to grind a tool with a longer cutting edge.

Regarding the broach, the outer body is aluminum but the next time I need to use it I'll remake it from steel. There is no need for anything else for bearing, these are pretty small broaches and the forces are nowhere close to being a problem.

[kitno455]

Err well the sex doesn't really come into it for me, but what a guy gets up to in his own shop is none of my business.

Also if you watched much of the video you'll see I was not making a bolt at all. I was making a nut.

I watched the video, and saw you make the female half of a sex bolt, while acknowledging that you did not know what it was called. Silly me, I assumed that meant you were interested in learning something.

Nice job on the broach, BTW.

allan

[mars-red]

I watched the video, and saw you make the female half of a sex bolt, while acknowledging that you did not know what it was called. Silly me, I assumed that meant you were interested in learning something.

Nice job on the broach, BTW.

allan

I stand corrected! Thanks! I thought autocorrect turned your hex into sex.

What a terrible thing to happen to a perfectly good joke.

[mattthemuppet]

ah, I wondered if that was the case, cool!

thinking about it some more, this should be adaptable to any lathe, even one without that neat eccentric toolpost, right? You set the broach to the centerline, center it in the work, then offset the compound by 1deg (ie. more than 0 but less than the relief ground/cut in the tool). After that use the compound to feed it into the work.

That sounds a lot simpler than the tailstock driven broaches, which always looked a little too involved to knock one out easily. Yours is a lot more feasible.

another Q - how did you cut/ grind the broach? Especially the 2 deg relief. Rotary table? I've read that people also cut front relief by facing the broach with the compound set at 2deg or so - did you do that? Then heat treat and stone? Did you heat treat the O2 with a torch or something more advanced? I've tried heat treating O2 before but I have a feeling that my propane torch didn't get it hot enough.

[RB211]

You do sound like a mix between Topher Grace and Kermit the Frog!
Nice job, didn't know the Rivett was a small lathe.

[mars-red]

ah, I wondered if that was the case, cool!

thinking about it some more, this should be adaptable to any lathe, even one without that neat eccentric toolpost, right? You set the broach to the centerline, center it in the work, then offset the compound by 1deg (ie. more than 0 but less than the relief ground/cut in the tool). After that use the compound to feed it into the work.

That sounds a lot simpler than the tailstock driven broaches, which always looked a little too involved to knock one out easily. Yours is a lot more feasible.

I think I get what you're saying, but a couple of corrections: You'd need to center it after setting the compound angle to 1 degree, not before. And you'd need to feed it using the carriage, not the compound. The feed needs to be straight along the axis of the lathe center, and not at an angle.

I always liked the design of Mike's (from Mike's Workshop), personally. If I wanted to broach on a machine that had a more traditional toolpost, that's probably the design I'd go for

another Q - how did you cut/ grind the broach? Especially the 2 deg relief. Rotary table? I've read that people also cut front relief by facing the broach with the compound set at 2deg or so - did you do that? Then heat treat and stone? Did you heat treat the O2 with a torch or something more advanced? I've tried heat treating O2 before but I have a feeling that my propane torch didn't get it hot enough.

The broach itself was milled. It was pretty easy, I used a 6 sided collet block and shimmed under one end to get the relief angle. I did also cut the front relief you mention, all I did for that was drilled into the end a bit when I was turning the blank. So the front relief is the half angle of whatever drill bit I used for that.

I've never used O2, and don't know much about it, I would assume it's very similar to O1 but couldn't say for sure. It was O1 I used for my broach. I use O1 and W1 frequently for parts as well as my own cutting tools. If you were using a small torch and the part was large, that could have been the problem, but I typically use my little bernz-o-matic swirl head with a propane bottle, and it works great. Most likely you just didn't have the temperature quite right. If you want to be all scientific about it, you can use a magnet and when the magnet is no longer attracted to the part, you've got the right temperature. Easier said than done. I'd like to get a small heat treating oven some day, but until then I just go by eye, it's a very distinct orangey color you're looking for. O1 is decarb free so you won't get the release of telltale sparks if you take the temperature too high. You might see a few sparks here and there, but I wouldn't rely on them. It'll be obvious if it worked, by giving it the file test. How the scale builds up and then shocks back off can be very telling, as well. I can usually tell whether I got a good quench even before giving it the file test, just by examining the scale and how it has shocked off. It's especially easy to tell if you water quench. A little trickier with oil. O1 is oil hardening, but that doesn't mean you can't quench in water. The water quench is less finicky, but since it's a more rapid quench it's more prone to warping the part (some might say it's more prone to cracking but I have never once had a part crack while quenching), and the hardness won't penetrate as deep.

[mars-red]

You do sound like a mix between Topher Grace and Kermit the Frog!
Nice job, didn't know the Rivett was a small lathe.

Haha thanks RB!

Yeah I think a lot of folks don't realize they're only an 8" swing. But they'll turn that full 8" until the cows come home.

EDIT: Rivett made a handful of machines designated 1020 and 1030. They were a 10" or 10.5" swing over the bed, and weighed something like 2 tons from what I recall. Put it side-by-side with a 10EE and you'd think they were brothers.

[mattthemuppet]

thanks for the clarifications! I understand now, the compound is just being used to set the angle so that the cutter "wobbles" around in the cut. I checked out Mike's website, lots to read on there! I would make mine in a toolholder, similar to his. Looks fairly simple to make, I'll just have to add it to my long list of things to make.

Bah, meant to write O1, always write O2 for some reason. I'll keep those tips in mind for the next time I need to make a cutter. For that project I ended up making an indexable dovetail cutter instead which did the job.

[enginuity]

So often rotary broaching doesn't get the look it should in the home shop.

Maybe it is because people think you need a big heavy machine, or a heavy expensive tool that incorporates bearings and the offset angle (like Slater's Rotary Broach).

Making the cutting tool once you have the holder would take about the same amount of time as setting up a shaper / shaper attachment and rotary table.

The process fascinates me every time I watch it. I would really like to meet the people who invented the process.

[mattthemuppet]

for me it's one of those things I wouldn't use much but would make life a lot easier when I needed it. The simpler the tool build the lower the activation energy for building it and quicker pay off time

[ahidley]

I don't use mine often. But I I know what it'll do. That opens my shops capabilities. That's great.