View Full Version : Chuck stops

Ian B
12-29-2008, 06:50 AM
In the collet stops posting, Mark posted a link to Royal products, and one of the items they have are these: http://www.royalprod.com/img/category/upload/Page_00%2093.pdf

I've seen them in use at a local engineering company. Very nice. However, at $200 for a set of 3, they're a bit out of the reach of the average HSM'er (if such a creature exists).

We all have a need for something that accurately spaces work away from the face of the chuck, keeping the work's back face parallel. I usually lay a couple of lengths of ground HSS across the jaws, grip the work with the chuck and then slip the spacers out. This obviously works on both 3 and 4 jaw chucks (which the ones from Royal don't - 3 jaw only).

Machining up soft jaws is always an option, but that means swapping jaws or bolting the soft ones on. Also, I've never seen soft jaws for a 4 jaw chuck. The stops in the link are very quick to use. How do others do their spacing?


12-29-2008, 08:36 AM
Wow, that's pricey!!

I think I'll continue to use pieces of plate left over from cutting discs of various sizes.


12-29-2008, 10:23 AM
I use old bearing races of different diameters and thicknesses.

12-29-2008, 06:20 PM
There was an article in one of the early HSMs or PMs on casting a bunch of these spacers, and they looked remarkably like the ones Royal sells, except there were no rare-earth magnets-too early I guess.

12-29-2008, 06:32 PM
GAH! How expensive can a surface ground aluminum extrusion be?

Perhaps one could make money on a mini-lathe sized one for jaws up to 1/2 inch or so, a bit large for my chuck. Tooling is a problem though,

Or they could be cast. What's his name, the person who always uses metric and who made the side lever engine in the magazine (recent HSM mag) made one out of folded aluminum sheet.

I wish there were soft jaws for my 4-inch 3-jaw. Maybe I could anneal a set of replacement hard jaws, make them into master jaws, and re harden them.

Ian B
12-29-2008, 11:35 PM
As far as the price of the commercially available ones is concerned, my thought was that they've had to have that extrusion profile purpose made. I have no idea of the costs involved, but it can't be cheap; maybe they're trying to recover their investment?

I was thinking about getting pieces of scrap aluminium plate in various thicknesses, machining them to 6" diameter circles, milling 3 or 4 slots in them and then facing them flat & parallel (in my 3 jaw with soft jaws...)

Easy enough to epoxy 3 or 6 neodymium magnets in to hold the spacer to the chuck.


12-29-2008, 11:49 PM
Here's one solution: http://www-personal.umich.edu/~mrwizard/macgyver/machine/chuckspacer.html

Ian B
12-30-2008, 02:53 AM

Yes - that's exactly what I meant, thanks.


12-30-2008, 04:01 AM
saying that each set is parallel within 0.0004" is one thing - but to be effective it would need to be flat to at least that accuracy - and the errors for parallel and flat may be additive and not subtractive. This will be compounded by the use of two or more sets.

They do nothing for or about any eccentricity in the chuck.

I'd be more inclined to dismantle the chuck and drill and tap three holes in the front face of the chuck for hex bolts and lock-nuts. I'd re-assemble the chuck, install the bolts, secure them with the lock-nuts and then face them off - job done. Accurate as you can get, costs nothing and bolts are replaceable in minutes.

There are a couple of problems with the indexing/zero-ing.

There had been no account taken of:
- "end-float" in the machine/lathe spindle; nor
- "movement" of the spindle head relative to the tool-post as the gear-box and spindle heat up.

It would be better if the "zero-ing/indexing" were made to a stop on or near the tool-post - after the part was inserted into the chuck. Those should cancel-out most of the errors and variables and would work just as well for/with collets as the variations in axial movement would be negated.

This is fairly basic turret/capstan lathe stuff.

John Stevenson
12-30-2008, 04:47 AM
Why do they have to be aluminium?
Get a set or 5 laser cut and wang them on the surface grinder, job done.


Virgil Johnson
12-30-2008, 07:31 AM
Once I had to face some 1 1/2 "alum. rounds off to a dimension that was +-.005 in the 3 jaw chuck. Not having any suitable plate around to make a chuck stop I used a piece of 1/2 cabinet grade plywood. Worked great for that job.

Spin Doctor
12-30-2008, 11:32 AM
I'd be more inclined to dismantle the chuck and drill and tap three holes in the front face of the chuck for hex bolts and lock-nuts. I'd re-assemble the chuck, install the bolts, secure them with the lock-nuts and then face them off - job done. Accurate as you can get, costs nothing and bolts are replaceable in minutes.

Another option is to make up a set of spacing blocks all ground to the same height with pass holes and c/bores for SHCSs. Did this a lot when I was doing a lot of CNC lathe work

12-30-2008, 11:56 AM
I see Sir John has already posted on this topic, but did not include a picture of a solution he showed here once before. Its saved in my "stuff to make" tooling folder and is extraordinarily simple. I was all set to cast some blanks next time they go to pour aluminum in the shop down stairs from me. I showed the Royal product to the guy in charge there and he bought a set and I was just going to push them into the sand and pour.

After seeing John's method, I think its much simpler. It simply involves a piece of threaded rod roughly a bit longer than the lathe headstock with a turned "plug" to go in the outboard spindle end and a similar one that goes in the recess in the chuck (behind the jaws). The threaded rod itself can serve as a stop, or you can make various diameter bored and threaded "buttons" to screw onto a "spigot" of the threaded rod protruding into the chuck jaw opening.

The two plugs, threaded toward each other lock the threaded rod in place (in case that's not obvious).


12-30-2008, 12:13 PM
Today I had to face off to length a set of 3/8 brass parts. I used a piece of 3/32 oxy/acetylene welding rod as a spacer/bump stop. I bumped the part on the wire, tightened the jaws, removed the wire. and faced the part. This works well on small diameter parts. The bent aluminum sheet works well also except sometimes you have to leave them in place while turning. This morning I was working on Mogens Kilde's "Side Lever " steam engine built to 1.5 :1 scale.

12-30-2008, 02:13 PM
Do you think that it is possible to turn chuck jaws into master jaws?