I cant give any specific tips, but this old Tony made a video series about rotary broaches some years ago. He bought a comercial rotary broach with included hex broaches, and also managed to grind a working square broach from an old end mill. He also used the same broach in the lathe and on the mill, so this should not make a difference.

Some parts look homemade, and some parts look factory made. Hmmmm. And I love the self-trimming planes the most!

The inherent machine shop cleaning video was really inspiring

It doesn't matter weather the job is still and the tool rotates or vice versa, its just a change or reference plane. The tool stickout from the broach holder is critical - if it sticks out past the point where the two axies intersect then the tool tip experiences some radial movement into the work piece as it cuts (stick it out way to far and you can see this movement) - guaranteed to chip the tips of the tool. This may not be your problem but it just might... cheers

That thing doesnt look badly made, but man does it look banged up

I like the look of that old indexer.

The lighting in that last shot of the lathe is great!

That was built out of a hexagon 5C collet block and some welding, plus a collet adaptor style insert. Pretty cool!

You can try to broach the square holes in 2 steps to reduce the load on the broach. The first broach with chamfered edges to remove the majority of the material and the second broach with regular square edges to just cut the corners of the square hole. You can grind the broach for the first step out of the slightly damaged broach, just grind the damaged corners off.

Happy Sunday. Dunno why I'm up at 3am, but here I am... watching this video. =D

Hi Mark rotary broaches absolutely work that way on lathes. I have been involved in setting them up on cnc lathes (long ago and far away). If you have not already done so, spend some time looking at the slater tools videos and documents lots of information there. there are other manufacturers as well (edit) just a thought, are you certain that the tool is set to exactly the right length? if its off it will orbit the centerline and that could cause breakage.

Inheritance Machining is an absolute must to watch, just like your channel

Don't rest your ultrasonic cleaner basket on the bottom of the tank, suspend it. It's common to have some hooks on the basket handles that fit over the tank sides. The transducers are fastened to the bottom, and anything sitting on the tank bottom makes it harder for them to vibrate the tank bottom as well as they should.

Made my camlocks using allen bolts, built up the threads with weld and machined. The only downside you have to make a chuck key to suit. My rotary broach is in the cabinet gathering dust.

I made one of this same style. As far as the actual broach goes the tip length is very important! When I designed mine out in cad I worked from the cutting tips back and designed the rest of the tool off that specific length. That way when the cutting tips are rotating they are “on center” at the cutting plane to avoid the tips going “over center”. You probably need to either ask the tool maker what the tip length he designed the tool to or grind a tool then measure the tip “action” at center and cut the shank back until you get the tips rotating at 0.001” TIR or less. This style tool works better when the body is rotating and the cutting tip is “stationary” in the work piece. To use mine in the lathe I had to Chuck the tool in the lathe Chuck and clamp the work piece in the tail stock. This style works really well in a mill though!

Ya, if the bearing set and broach holder are bored in on an angle to the broach body, then its a rotating type meant for a mill. You could prove this by reversing your setup. Chuck the RB in the lathe chuck and hold your work piece stationary in the tool turret. That's a neat little indexer, good example of never judge a book by it's cover. I have an old Hardinge 5c indexer that looks like it was ran over by a Tank, but it still functions flawlessly.

The stickout on the broaching tool matters. There is a sweetspot for the broaching tool if it is too near the the square will not be centered with the workpeice and same if it is too far. If it is too near and far it will ficght the bearings and the chuck to bent the tool over and over again and chip the end of the broach

NZer here - I don't say it with a hard g. We NZers make a few funny sounds, but I don't think that's one of them (lol). I think it's more to do with the vowel that follows the g. When a y follows the g you use the soft sound - so gyrate has the same sound as gymnastics.

Molybdenium Disulphate Grease may not be the best choice for the plain bearing indexer. I would recommend installing a zerk fitting and use way oil to flush dirt out when you use it on the Clarkson.

The axial position of your broaching tool may not be set correctly. It needs to be spot on at the position of 0 runout, since otherwise the cutting edges experience very high side loads (meaning radially), they are not able to withstand. You already sort of demonstrated that setup in you last video.

I vaguely remember Stefan or TOT using a similar broaching tool in the lathe as well.. but can’t pinpoint the video yet

I don't know anything about broaching so I'm just wishing you luck!

I think ToT made a Video with rotary broaches, there he used the same tool in the mill and the lathe. So i believe it should work eather way

I'd try broaching something really soft like lead, to see what kind of deformation you get. It should be easier to see if something is rubbing or banging, or whether broach edges dig in too deep or to shallow maybe.

Inheritance Machining has just posted a clip on broaching, including building a metric (!) tool holder. Not totally without encountering some challenges, though...

Hi Mr. SMP, a couple of things that you may find helpful is drilling out the corners first undersize, then the bulk of the material in the center. The other one would be an internal groove to help with chip compaction at the bottom, which will do an absolute number on your cutter.

Im pretty certain those feeds and speeds were way off. I have a rotary broach from Hoffmann Group and have used it quite a bit also with selfmade silver steel cutters. The Hoffmann people actually advice on going fairly slow (maxbe 150 RPM) at the beginning with a really high feed for the first millimeter because otherwise the tool doesnt really seem to bite instead it drags across the workpiece surface a whole lot which breaks down the edgeds. After the first millimeter i usually speed up to about 500 RPM and slow down the feed. Cant give mm/min as Im using the tailstock unfortunately.

Thanks for sharing.

I thought about making a video about my quick shop fixtures and special purpose tools but looking at them I realized I’d be embarrassed to show them to anyone. The other day I made a follower rest for the lathe by supergluing a piece of oak to the carriage.

Can’t wait, that indexer looks nice

Hi Mark. Check the other comments about broach length, it has to be correct for your broach holder. This may be your problem with chipped cutting edges.

I believe the size of hole really matters and it needs to be a certain amount bigger than the flats of your broach, and the amount that you dish the front of the broach is important too, feeds and speeds I’m sure need to be right but I don’t know where to start with that

Just right for Sunday coffee ☕️! I plan to return to the comments later, after they’ve accumulated, to try to gain comprehension of this lathe/mill broaching situation. I hope someone can elaborate…🤔

Looks like a hex collet block welded to a mount and indexer. Bolt hole pattern made on a mill maybe?

Yaaay awesome! I love your videos!

Thank you for the airplanes

9:30 in Australia, it's definitely JYE-RATING. That said, I lived in NZ for a year and can confirm, they do say a lot of things weirdly.

Perhaps the back angle taper needs to be larger...could be stress on the withdrawal phase of the rotation that flakes the front face off. OR perhaps the "corners" need to be relieved a bit more before the final cut ... eg drill round, broach octagonal, broach square. Definitely "Jai-rate" in the UK.

hi about the feeds and speeds, i'm "often" broaching at 1000rmp with 0.01mm per rotation in stainless steel but it's with a tool from garant so not the same as an home made tool. Have a nice day.

I think i would understand it so that if you drive the holder the broach are always concentric with the holder but if you drive the part you can introduce shear forces into the broach if the center of the holder and the center of the part are not exactly aligned. maybe thats the case

Corner breakage indicates dragging. Have you thought about trying a different gage length? Originally you set up for the focal length, but that means zero stroke (I think). Maybe the tool needs projection to take advantage of the clearance and get more action.

I never clicked so fast! 👍👍👍

I thought it was the J sound in gyrate, but it is a matter of preference.

Is the workpiece in the lathe subject to work-hardening? Either way looks a lot like workpiece too hard and cutter too soft. Maybe it needs a sharper cutter (ie; more end-concave giving more rake angle). Interesting project, thanks for sharing.

Hi mark was just wondering if the two locking pins were one for each indexing assembly as you only have the eight pin mechanism. Hope that makes sense as you wouldn’t want to disassemble it to change from eight to six .

The rotary broach I made after watching some youtube videos has slots, to move the rotating part to center. (I guess the design makes it easier to get the cutter on center) The tool does not care if the workpiece or the tool rotates. kzfaq.info/get/bejne/hZiXn7mqupbDc2Q.html I think the starting hole size might be a big influence kzfaq.info/get/bejne/jM1nhqaJtM6Re40.html

I wonder if a carbide insert on top of your cutting tool could solve your breakout problem? Did you or Mr. Gotteswinter show how to grind Carbide bits? If it was you, you should be able to bring an insert and mount it on your cutting bit. However, I think a slower rotation speed should help too. Good luck!

There seems to be a fundamental difference between the tool being driven and the work being driven. Isn't the loading on the tool edge going to be different if the work is 'pushing it around' as opposed to the tool 'pushing' into the work? (Full disclosure, i'm an idiot.)

Someone must have got out of bed early this Sunday

Havd you tried using a larger pilot hole?

If the broach just needed to be cocked at an angle, then the eccentric tooling would be unnecessary, just rotate the compound a bit with a parallel/concentric tool...?

Just like you, I don't see the differance between spinning the work or spinning the tool. It should work just the same and give the same results. Or maybe I'm missing something here.

Speaking as a physicist it makes no difference if the broach is rotating or the work is rotating, it's all a matter of reference frame. If you want to get exotic: kzfaq.info/get/bejne/ipqha8p01cu9YXU.html (But I think that tool clearance would be difficult with a square)

Are you able to mount it in the tailstock on the Bolly so you can 'feel' what's happening? It might give you a chance to try out various feeds and speeds before the cutter is ruined.

Your tool looks flat bottomed, you need to grind some relief into the face that approaches the work piece. The face approaching the work needs to be concave so the corners are more like points. It should work then. Slow the spindle down too, 1000rpm is a bit on the quick side.

Speaking of one minute jobs. Why didn't you take the horrible finish off the indexer body? That's why we have lathes 😂