How to smooth a 5C Collet bore?

[lazylathe]

Hi All,

I managed to pick this 5C collet chuck up for a really good price!



It all works very smoothly and is made by a machinist from castings.
There are two issues i have with it is: the bore is not very smooth.



And it has a slight runout.

Is there a way to hone it on the lathe to get it smoother and to lessen the runout?

Apart from those two issues it seems to be very well made!

Andrew

[f350ca]

Tool post grinder while its mounted would be the best. Should reduce it to zero run out till you remove it. Then it would be the repeatability of the chuck mount. What about an aluminum lap mounted to the tail stock? With very little pressure would it remove the run out or just follow it?

[Sunset Machine]

Look close and you can see a lot of chatter. Try giving it a lick with a decent sized boring bar. Use a tiny bit of radius on the tip and hone the edge razor sharp with a small hard stone. It should come out pretty smooth, probably good enough. A strip of 120 grit emery wrapped around something-other-than-your-finger would polish it a bit further.

Oh, to be clear. Try a HSS bit.

[PixMan]

It may be a little too hard for a HSS tool to bore it.

The angle of the taper is also very critical. I would suggest using a sine bar and indicator to dial in the taper of the compound slide or taper attachment to the correct angle for a 5C collet closer rather than matching whatever might be there as it no longer appears to be the original grind finish.

Once aligned to the correct angle, the tool post grinder would definitely be the best option, but not everyone has one of those. I know I don't....yet.

If the part is hardened, I have some inserts of a very hard carbide grade and/or a couple of CBN-tipped ones. If you don't have similar tooling, tell me what holders you have and I can probably send you something. It's very nice-looking collet closer, and well worth fixing it.

[Sunset Machine]

(06-19-2012, 09:46 PM)PixMan Wrote: It may be a little too hard for a HSS tool to bore it.

"Machined from castings". Cast iron can be hard, maybe it should be tested with a file before getting in too deep. If it turns out to be good machinable cast iron, I'd like to also suggest using an existing collet with some length-wise chalk marks to get that taper just right. Lacking sine-bars and grinders and stuff, it's just a thought. Old school.

And yes, what's there pretty rough. I don't even see a taper.

[PixMan]

Ah yes, casting. I should have noticed that.

I've never seen one. All the collet closer nose pieces I've ever used were hardened steel.

[TomG]

Andrew,

It appears that this MLA-21 collet chuck was machined from a kit of castings supplied by a company called Lathe Accessories. It is made of ductile iron, which will machine very well. Unfortunately if the bore is already machined to size, but not concentric, machining it more will only make it oversized. It looks like there is plenty of meat in the casting, so I would suggest boring it out for a press fit sleeve then re-machining the bore concentric and to size. You can buy just the drawings from the company to get the proper dimensions.

The company also sells a number of lathe and mill accessory kits, even a kit for a small diesel engine, at very reasonable prices. I may pick up a kit or two myself since the castings alone are be worth the price of the kits.

Tom

[krv3000]

hi just my bit as its cast i wood lap the taper mack up a hard wood taper then cuver every thing up well get sum fine valve grinding past and hand lap the taper till the colets fit nice