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Step chuck question

JC Price

Aluminum
Joined
Oct 21, 2007
Location
Boulder, CO
I need to get some 5c step chuck tooling for my HLV-H. The part diameters are around 1.60 inch. One option would be to buy a Hardinge 2-inch closer and some of their machinable collets, but it’s a bit pricy. Lyndex and others make 2-inch 5c machinable collets that don’t require a closer. But what does 2-inch mean in that case? Is it the head O.D. or the maximum capacity? Will they work for 1.60 diameter? I can take very light cuts so I don’t think I need the extra grip provided by the closer-style step chucks.
 
Step chuck model sizes, as used by Hardinge, indicate the maximum holding capacity, so the actual OD of the chuck is greater. The three 1/8" pin holes are outside of the nominal grip size. The Hardinge 2" step chucks work without a closer, but will not work as well. In addition to the grip issue, not using a closer subjects the big end of the step chuck to bending loads when gripping, so the end can permanently deform, hurting accuracy and further limiting grip on the part. They make standard and deep step chucks. Do not buy an emergency step chuck that does not have the three pin holes.

Larry
 
Get the closer. It really makes a difference in accuracy, grip, and convenience.

As other noted, ebay is a good source for cheap materials. Though be careful buying the closers - get one with good photos of both sides. Somtimes these do wear out in production environments. They get a lot of scoring, or sometimes coolant pitting on one side or another. Usually if there is damage it will be obvious. If the person does not show the mounting or closer taper surfaces, they may be hiding something. Or just ignorant. You can re-grind the closer taper in situ, of course; or possibly hard - turn it (I have ground various tapers on the Hardinge with a die grinder mounted to the compound. I have hard turned custom tooling. I have not tried hard turning a closer)

If it is a true e-collet (soft, not hardened) there is no problem using one without the holes. Just mill a strip of Al vertically in the vise so both sides of the projection are parallel. Make it the same thickness as the base of the slots in the collet. bandsaw it off the thick part you held in the vise, clean up the burrs, and clip (& de-burr) 3 short lengths out of it to put in the collet slots near the rim. Keep them with your collet stuff for re-use.

I like the 2 & 3" deep closers and collets, because you can use one collet bored to a "standard" size and then make shop inserts from a piece of bar stock, for various short run jobs that com along. One "master" collet can then be used for dozens of job specific tooling sets.

smt5cworkholding.jpg


smt
 
I need to get some 5c step chuck tooling for my HLV-H. The part diameters are around 1.60 inch. One option would be to buy a Hardinge 2-inch closer and some of their machinable collets, but it’s a bit pricy. Lyndex and others make 2-inch 5c machinable collets that don’t require a closer. But what does 2-inch mean in that case? Is it the head O.D. or the maximum capacity? Will they work for 1.60 diameter? I can take very light cuts so I don’t think I need the extra grip provided by the closer-style step chucks.

Get the closer type and closer mount and closer for it ELSE consider just DIY'ing a split ring collet/bushing with a step to be held in an ordinary chuck.

The Hardinge supplemental closers are as much about deformation / not and accurate repeatability / not as they are about raw grip. Poor 5C struggles even in its native sizes, so NEEDS that help.
 
Thanks for all of this great guidance! I have ordered a used-but-looks-nice 2" closer and a new 2" step chuck for it. Stephen, thanks especially for that picture. It's worth a 1000 words.
 
Thanks for all of this great guidance! I have ordered a used-but-looks-nice 2" closer and a new 2" step chuck for it. Stephen, thanks especially for that picture. It's worth a 1000 words.

Good move, hope it works well for you!

For future reference, as these goods tend to grow as new opportunities appear. Hardinge catalog LISTS the buggers clear up to seven inches!

I consider that optimistic, and highly so, for a 5C mount, even WITH the Hardinge threaded-nose adapter I acquired for the closers, so have stopped acquiring at the 5" size.

It will have to be pie jaws on a chuck if I need anything larger.
 








 
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