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

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.
 
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 :)
 
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.
 
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.
 
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
 
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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.
tool bare3.jpg
 
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.
 








 
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