M head spindle issues

[seanb]

I got my M head cleaned repainted and assembled.

I have a question about the spindle

I bought some import collets on ebay and a ER32 to B&S no.07 chuck

I am getting some serious runout with both.

After cleaning the taper I get .0015 with a .5 gauge pin in a 1/2 inch collet and the same when I use the ER32 chuck with the 1/2 inch gauge pin again.

I put an indicator just inside the spindle and get less than .00025

So do I need to have the spindle reground? Is that even an option?

 

[Bob Korves]

Indicating the spindle told you that it is OK. The runout is in your collet and/or pin.

 

[Bob Korves]

Nice job on the rehab, by the way. Looking good!

 

[chips&more]

Like said, it’s probably not the taper in the spindle. But more like the tooling you bought is causing it. The runout of 0.0015” is not that bad, it’s livable. Yes, life would be better if more like 0.0002”. If making NASA parts maybe a different story. But for the HM I would just run the mill and see how it performs. Tomorrow is a new day!...Dave.

And yes noted you said cleaned the taper. But maybe go back and look closer. Look for raised metal/burrs on all the mating surfaces.

 

[seanb]

Wow these collets really suck, I tried a 3/8 collet with a .375 pin and got .003 runout. I think you guys might be onto something with the collets. The runout varies based on what collet i use.

Anyone know where I can get some GOOD B&S No.7 collets that dont cost $50 a piece?

 

[Bob Korves]

I think it makes more sense to settle on several sizes of quality collets and then use straight shank tooling that fits them. A 1/4, 3/8, 1/2, 5/8, and 3/4" would really be all you would need, and at least a couple of those could be left out with the correct choices for tooling. Beyond that, tooling with short, straight shanks the length of the clamping portion of the collets, can be exchanged quickly and without so much fuss of lowering the table to make room for removing the collet. If you put index marks on your tooling marking the high spots (or low spots) you can index them with the marks on opposite sides when installing them for accurate work, removing much of the runout. If you have a collet with .002" runout and a drill chuck with .002" runout, you can get anywhere from .004" to zero runout depending on how they are indexed.

Another thing is to listen carefully to chips&more's comment on checking for burs and damage (and rust and swarf) in your spindle and on the tooling shanks, repairing or cleaning anything you find. I don't think B & S collets have keyways in them and a locating pin in the spindle, but if they do, that could also be a source of your problem.

 

[seanb]

Well, I feel embarrassed. I cleaned out the spindle (again) and now am getting less than .00025 at the spindle with my 1/2 gauge pin.

I swear I cleaned it out before with scotchbrite and wiped it down with a old T-shirt. But there was obviously something up there.

Not bad for a 70 year old machine.

Thanks Guys