Outside Jaw Grip Capacity of a 3" or 4" lathe chuck

projectnut

projectnut

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Earlier this year I purchased several PM model kits from another member. I'm getting closer to starting on one of them and thought it might be a good idea to purchase a small chuck that could be used on either of my lathes. Both have either a 5C collet chuck or 5C drawbar system so my first choice would be something with a mounting system like the one in the link below.


While the one in the link is a self centering (scroll) style I'm actually looking for one with independent jaws. So far I've looked at dozens ranging in price from less than $50.00 to nearly $200.00. The downside to all I've seen so far is the minimum grip range of the jaws when in the outside configuration. By in large the minimum grip range is .200". A few advertise as small as .160" but that's about it.

I'm wondering if anyone makes a quality chuck that has a minimum outside jaw grip in the .100" or less range?
 
I posted a similar thread on another board to see if other members of the community had experience with the type of chuck I am considering. One suggestion was to look at a Sherline 4 jaw independent chuck with a 5C mount. At least one member over there has been using them for over 20 years with good results.

This is the chuck I'm considering:

www.sherline.com

5C 3.1" 4-Jaw Independent Chuck - Sherline Products

3.1" dia. 4-jaw independent chuck with 5C back includes T-handled hex driver. NOTE: Not designed for use on Sherline lathes.
www.sherline.com

Does anyone here have experience with this or any similar Sherline products?
 
The Sherline chucks are well made small chucks, I have 3 and 4 jaw chucks for mine, but not with the 5C mounts. I've not tried to chuck something quite that small, and not at home to try, but the specs say min 3/32 / 2mm which is less than your requested 0.1". Sherlines are popular for small parts so if they claim to hold a 2mm part than it probably can.

If you are not in a hurry I can try to chuck up the small wire gauge drill bits and see where it stops holding solidly, but that won't happen until at least November 5th.
 
I'm currently in the process of fabricating an adaptor plate to marry a 5C mount and 4" 3 jaw chuck I have in stock. I should be finished with that project today. I also ordered a 4 jaw independent chuck with 5C mount from Sherline a few minutes ago.

www.sherline.com

5C 3.1" 4-Jaw Independent Chuck - Sherline Products

3.1" dia. 4-jaw independent chuck with 5C back includes T-handled hex driver. NOTE: Not designed for use on Sherline lathes.
www.sherline.com

I ordered it on the advise of members here and a couple from another board. One member of the other board just received his and confirms it's a good quality tool made in the USA.

The only downside is I'm wondering if it wouldn't have been cheaper to order the complete model kits already machined, and only needing assembly. Given the cost of the tooling needed, and the time spent converting existing tooling, I might have been money ahead.
 
Yesterday I "thought" I finished marrying an existing 5C mount to a 4" (3 jaw) Union chuck. I turned the adaptor plate "in situ" attached to the mount, then drilled the through holes for mounting the chuck. I assembled the pieces and was pleased that the unit had a total runout of .0002" on the 5C mount, adaptor plate, and the chuck body.

I marked everything for reassembly in the same location disassembled the pieces,, cleaned and reassembled them. NO JOY. Although they appear spotless, and were assembled in the exact original locations there is now a runout of .0015" between the 5C mount and the adaptor plate, and another .0015" between the plate and the chuck body. I tried several times to make adjustments to bring things back to spec, but so far the source of the problem has eluded me As time allows in the next few days I'll reinspect the assembly and hopefully find something obvious that I previously overlooked.

The next few days however will be spent doing the remainder of the seasonal yard work and getting the equipment ready for winter. We're supposed to have temperatures in the high 60's to low 70's for the next few days so it's time to get to work. Early next week the weather is supposed to turn to the 40's and 50's for highs with chances of rain or even snow. There's lots to do outside before the snow flies, so time in the shop will be limited.
 
No offense,,,,,, but you’re talking about a hobby. Ain’t nothing cheap when doing a them! Like restoring old cars, antique tractors etc,,, almost always cheaper to find one already done than do it yourself.
 
twraska said:
No offense,,,,,, but you’re talking about a hobby. Ain’t nothing cheap when doing a them! Like restoring old cars, antique tractors etc,,, almost always cheaper to find one already done than do it yourself.
Click to expand...

In this case money isn't the issue. I have well over a dozen chucks for my lathes, and have made backplates to fit them to a variety of machines. It should have been a straight forward relatively simple operation. This particular chuck was purchased nearly 20 years ago when the internal jaws for a similar size one were temporarily misplaced. Eventually the missing jaws showed up so I have 2 nearly identical chucks that currently only fit one machine.

I also had the 5C mount in stock. It was part of a purchase of a large lot of repair parts several years ago. Both pieces have been setting on the shelf unused for some time. I thought the best course of action would be to marry the pieces and use them rather than have them continually gather dust. When the project is finished I'll be able to use the chuck on both lathes, and a spin indexer. I don't look at the current problem as a defeat or waste of time, just a frustrating minor setback.

As you mentioned "This is a hobby". The hobby is creating useful things from raw stock. In my mind it wouldn't be practical or prudent to purchase another unit when I have everything I need in hand. It's just a matter marrying the pieces. I did it once with no problems. The challenge is to understand why I'm currently unable to replicate the original assembly. I'm sure when I figure it out I'll have to give myself a dope slap for missing something obvious.
 
Just for grins, have you put a dowel pin or some drill rod in a 5C collet to rule out something happening there?

If this happened to me, I would suspect that something was wacky with the initial 5C setup, but some skim passes would set things right and it sounds like you tried those.

What would worry me most is the error between the 5C mount and the adapter plate. If the chuck is like the ones I have, it uses screws to mount to the adapter, and screws can be ... a bit screwy. At least when mounting those chucks to the 7x16 spindle.
 
I have checked the lathe spindle, 5C collets, and collet holder. I've chucked up 1/4", 1/2" and 3/4" dowel pins (.0001" runout) in the appropriate collets and consistently get readouts between .0001" and 0002" which is within the tolerances of the spindle, collet closer, collets, and materials. The 5C chuck mount alone measures .0001" each time.

All was well with the complete assembly with a runout of .003" on a 3/4" dowel pin sticking 1" out of the chuck jaws. It all went to pot after disassembling the original setup. I thought it was prudent to make sure everything was clean and Loctite the screws holding the chuck to the adaptor, and the adaptor to the 5C mount. Maybe I should have left well enough alone. This is another case where the search for perfection has turned out to be the enemy of good.

Not sure where the error has been introduced yet as I have been working cleaning up the garage since early this morning. I must admit I've found things I thought were long gone, and other things I wish I had disposed of many years ago. I'm sure if I leave the project set for a couple days the problem will be obvious when I return to it. Right now I've been so involved with it for so long I'm afraid I couldn't see the forest for all the trees.

At this point I'm inclined to agree with the error being in some way introduced by the screws. I can run them almost all the way in by hand, but from time to time I feel some resistance. It might be a case of a close tolerance in one of the counter bores in the 5C mount, and a slightly imperfect socket head. At the time I didn't think it was necessary to relocate each screw to it's original hole. There could also be an imperfection in a counterbore that causes a slight interference.
 
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The new Sherline 4 jaw chuck arrived late yesterday. It looks to be excellent quality, and it's even "Made In The USA". Things have been a bit hectic around here lately getting things cleaned up and put away for the winter so I haven't had a chance to run it through it's paces yet Hopefully I'll finish with the outside work by the weekend and will have some time to give it a try.

So far this weeks activities have consisted of the final yard cleanup of the year, edging all the walkways and driveway, fertilizing the lawn, power washing a couple north facing sections of the house that were covered with green goo, changing oil & filters on the mower, edger, tractor, and power washer, washing the windows on the ground level of the house, and a few other nondescript jobs.
 
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