I have an older 12x24 Grizzly lathe, it's ended up being a really good machine for what I do, but I've recently discovered a flaw. I'm currently playing around with a QB HPA conversion, and needed to turn some new valve parts. Problem is, my chuck won't hold anything under about 1/4" diameter, but I'm working with 1/8" O1 tool steel for valve stems. I've actually resorted to using my mill as a vertical lathe, stick the stock in a collet and clamp a lathe tool in the vise. It works, sort of, but it's a lot of by guess and by god . And it makes a simple little valve stem and head more work than turning a new valve body would be.
So how do you guys handle small stuff? Am I going to have to invest in a collet chuck, or is there a less expensive alternative? Thanks.
You can make up a split sleeve & then chuck on to the sleeve.
Jig grinedrs use collets in standard inch sizes & are very precision & pretty small.
Use a drill bushing but you would have to put a split in it for it to compress.
Just 3 options, hope this helps
I have to imagine that with 1/8in stock you're not doing much to generate cutting pressure. I've gotten away with clamping small stock in a drill chuck and then clamping on the OD of the drill chuck with the lathe chuck. Quick. And. Dirty. But it works.
I also made myself an adapter that clamps in the lathe chuck but accepts R8 milling collets. Again, not ideal, but versus buying the adapter, collets, and drawbar for a 5C system I think it's worth it.
This message has been edited by Airgunner4life on Mar 3, 2012 9:03 PM
As I understand the terminology, a closer has a lever on the outside of the head stock that pulls the collet closed. A chuck, on the other hand, uses a scroll and key just like any other chuck. I've looked seriously at a collet chuck, both at CDCO and elsewhere. Big difference in prices!
I'm currently leaning heavily towards a set of 5C collets and a couple of collet blocks for now. That would give me some options for both the lathe and mill, and I'd already have the collets when I can afford to buy a chuck.
I'm also considering one of the quick change sets with a Morse taper adapter, I think they're ER series collets. My concern there is run-out stacking up, the biggest Morse taper available is a 3, my spindle is an MT-5, so I'd have to use my adapter. Seems like it's just asking for concentricity issues. And of course, I'd have to make a draw bar, but that's not a big deal.
Re: CDCO, seems to be a pretty hit or miss outfit. Lowest of the low in Chinese import tooling, and a hit or miss rep for CS, too. What's your experience been like?
To the rest of you that responded, thank you, there's some good ideas here, and I'll very likely try most if not all . Later.
If you're able to machine the mounting plate accurately, I believe you'll be able to get the same results as I have which is .0007 max run out 1" from the collet face. I bought one brand new Hardinge %C collet to try and eliminate variables in checking my mounting of the chuck. I am able to maintain those tolerances even with my other imported collets. When doing really close work that requires near perfect concentricity, I bore a soft collet. I goofed around with all the work-arounds and I have decided my time is worth the investment.
"Silence is the only thing that can hinder the Truth"
This message has been edited by jlucas50 on Mar 5, 2012 10:27 AM
Even doing CNC lathe work, we make bushings to hold odd sized pieces, or when doing second opps on parts that we don't want to mess up the threads.
Making a bushing is quick and easy. The guys giving this tip are right on the money. You can split only one side but it will usually run even more true when splitting both sides. I cut a little OD groove for an O-Ring which acts as a rubber band to keep both halves together after it's been split or cut into two pieces.
I like to make the bushing a step bushing. Start with something like 1" OD, Face material, and drill your hole. turn one OD down to .625" for a length of say 1", cut a groove for an O-ring, then part it off for an overall length of 1.25" Now saw one side or both sides. Slip your O-Ring on, and your small material inside. Now the step will let you align it straight with the jaws in chucking on the .625 with the 1" facing the jaws.
Personally, a 5C collet system is an investment that I would recommend making if you have the money. They are very nice and handy.
I've ordered a set of 5C collets and collet blocks, one square and one hex, plus a set of ER type collets and an MT 3 taper chuck. I rolled the dice and ordered from CDCO, considerably cheaper than anywhere else for the same stuff, will report my impressions once the stuff gets here. Hopefully, the 5C collets will be good enough that I can use them when I can afford a 5C chuck down the road. Like I said before, big price gap on chucks, ranges from $139 to almost $500. Later.
You can buy one of the import ER-type collet sets for about $60. They aren't as accurate as a 5C setup, but they are much better than a 3-jaw chuck, or anything clamped into a 3-jaw chuck. They come in MT3 taper, so you would need an adapter from your spindle bore to MT3.
They may also make a straight-shank model you could chuck up in your 3-jaw. The problem with using anything you chuck in your 3-jaw is you lose the advantage of collets, which is low runout compared to a 3-jaw chuck. On 2" stock .005" runout may not matter, but it's a bigger deal on a piece of 1/16" drill rod.