Hi Folks,

I am in the process of grinding the jaws of the original 5" 3-Jaw chuck (Logan #431) for my 10" Logan lathe (SN 6774A, 1952, Montgomery Ward). Please see my question about grinding the OD of the jaws in a separate post.

In the meantime, I ground the ID of the jaws in an interesting way that might be of interest to the group. The outside-grip jaws seemed to have a diameter of about 1" originally, but they were badly mangled, and stock was so far out of true I had to shim it just to take a rough cut. So I set up a tool post grinder and chucked a 1" diameter piece of stock in the jaws to pre-load them against the scroll.

One normally builds a jig to hold the jaws in the pre-loaded position, but I did not want to go through that effort. Alternatively, one could clamp a thin disk near the bottom of the jaws (deep in the chuck) but I still wanted to grind the entire length of the jaws clamping surface.

So, here's the part for which I am probably going to go to hell: I crazy-glued the jaws in place. I knocked the piece of stock out with a rod (easy to do because the jaws are bent and worn) and then ground the jaws true. After grinding, I just broke the jaws free by turning the key, took them out and scraped the dried glue off with a razor blade.

Easy as pie, and it worked great. Now I just need to figure out the OD needed on the outsides of the jaws (see my other post) and I will probably repeat the crazy glue process.

As long as I don't use too much glue, a bit of force is all that's required to free the jaws, but if they get stuck, heat and acetone should also work to loosen the glue.

So, hope this trick is of use to others.

Dan

On 3/23/2018 1:46 PM, Daniel Koller wrote:
Hi Folks,

I am in the process of grinding the jaws of the original 5" 3-Jaw chuck (Logan #431) for my 10" Logan lathe (SN 6774A, 1952, Montgomery Ward). Please see my question about grinding the OD of the jaws in a separate post.

Â* I happen to be the owner of #6615A ... a 94TLC2136 with the 2139 gear
box .

In the meantime, I ground the ID of the jaws in an interesting way that might be of interest to the group. The outside-grip jaws seemed to have a diameter of about 1" originally, but they were badly mangled, and stock was so far out of true I had to shim it just to take a rough cut. So I set up a tool post grinder and chucked a 1" diameter piece of stock in the jaws to pre-load them against the scroll.

One normally builds a jig to hold the jaws in the pre-loaded position, but I did not want to go through that effort. Alternatively, one could clamp a thin disk near the bottom of the jaws (deep in the chuck) but I still wanted to grind the entire length of the jaws clamping surface.

So, here's the part for which I am probably going to go to hell: I crazy-glued the jaws in place. I knocked the piece of stock out with a rod (easy to do because the jaws are bent and worn) and then ground the jaws true. After grinding, I just broke the jaws free by turning the key, took them out and scraped the dried glue off with a razor blade.

Easy as pie, and it worked great. Now I just need to figure out the OD needed on the outsides of the jaws (see my other post) and I will probably repeat the crazy glue process.

As long as I don't use too much glue, a bit of force is all that's required to free the jaws, but if they get stuck, heat and acetone should also work to loosen the glue.

So, hope this trick is of use to others.

Dan

Â* I went to the effort as suggested by Scott and made the 3-hole
preload fixture to grind mine . Interesting that the original chuck
that's now 66 years old will still hold an average runout of under .003"
throughout it's range . They don't make 'em like that any more . I use
the 4 jaw more though , depending on what I'm holding . You might
consider joining the Lathe List over at Yahoo groups - if you're not
already signed up .

--
Snag
Ain't no dollar sign on
peace of mind - Zac Brown

On Friday, March 23, 2018 at 11:46:36 AM UTC-7, Daniel Koller wrote:

I am in the process of grinding the jaws of the original 5" 3-Jaw chuck...

One normally builds a jig to hold the jaws in the pre-loaded position, but ... I crazy-glued the jaws in place.

Actually, that's in the finest of machining traditions; fine collets are manufactured, routinely, by
roughing, heat-treating, external grinding, slitting, then
soldering a washer onto the face, and grinding the internal bore to finish.

It's not crazy glue, more of a hot-melt variant... but only a variant.