Keyway "broaching" on CNC lathe with no M19 / spindle lock?

[gregormarwick]

Oldwrench used to use his haas as a slotter. I never thought that was a good idea but he said he did it for years with no ill effects.

Maybe the old Haas's had a mechanical orient? I used to have a Hurco like that, I probably wouldn't have hesitated to try broaching on that machine, but it was long ago and I never needed to try...

But every mill I've ever had since has never been perfectly stationary with M19.

 

[EmGo]

But every mill I've ever had since has never been perfectly stationary with M19.

Yeah, I would not have done it, actually blew up a set of bearings on a manual vertical mill doing a ton of shaping (job was worth a lot more than the bearings) but just brought it up as a reference point. He said he'd done it for years.

Like everybody had that grandpa that smoked, drank and screwed till he was 93, I guess

 

[fmari --MariTool-]

Frank, you're right of course about mill spindles, but lathe spindles have correspondingly larger bearings, so I figure it wouldn't be an issue in that case?

Ive ruined a lathe sub spindle bearing by using the subspindle statically to drill 1" holes in brass. Was a batch of 20,000 pcs 1" long.
Was a Miyano BND42 S5, sub spindle was 7hp with 22sc collet system.

Most spindle bearings are surprisingly delicate when not rotating.

 

[Crowne]

Hell my conquest 42 from 1989 has a disk brake on the head.
I put a 8mm key way in a 30mm bore of 4140.

Can you reach in and rotate your chuck at any time? I have a setting on mine that lets me choose either free state, or locked in position.

Yeah, if the spindle is stationary, it's always free to rotate by hand, even mid-program.

 

[Stirling]

I've got a few hundred delrin parts with a 5/8" bore that need an 1/8" keyway. My new-to-me Cobra 42 doesn't seem to support spindle orientation (M19) or a spindle lock.

I assume that, without a lock, it would be a bad idea to try and broach (really, shaping) the keyways on the machine using one of those carbide insert tools which you feed in and out to shape the keyway?

I could make a rudimentary spindle lock myself, though having to place it on and off every part wouldn't be ideal.

Any suggestions?

Ive seen an air cylinder stop with a break pad on it. Pushed the pad against the chuck like a drum break

Can be activated by m code

 

[misty]

To report back on this, I was able to broach successfully without the spindle lock. I am taking 0.0015" each pass, and the spindle stays solidly put. It works really well, the only difficulty was chip management with the ID groove I need to do to provide relief for the broaching tool.

Have you tried cutting on the outward stroke, chips then exit the bore.

 

[Crowne]

Have you tried cutting on the outward stroke, chips then exit the bore.
View attachment 427994

It's a clever idea, is the tool custom made? If not, who makes it?

 

[misty]

It's a clever idea, is the tool custom made? If not, who makes it?

I made the tool - here is a video of it in action.

 

[dandrummerman21]

Good idea.
Although I do think since he's complaining about chips in the groove, that he has a pretty narrow groove. And with a tool like in your picture, he'd need a wider groove to get started?

Edit: actually watched the video, I see you have some sort of ramp at every pass. Slick idea.