I'm new here!

[Iconoscope]

I am a retired engineer now enjoying my many hobbies, one of which is machining metals to make various devices. I own several machine tools. An Emco-Maier Maximat V10 lathe, a Southbend 10" toolroom lathe, a Harbor Freight 7X10 mini lathe, A Grizzly G1006 mill, a Bridgeport "M" head knee mill, the Emco Maier Maximat V10 mill which comes attached to the V10 lathe. Lots of machinery and a nice, clean, air conditioned shop to maintain them. Now I am looking for machining projects!!

[Jon]

Hi Iconoscope - welcome to HomemadeTools.net

Sounds like you'll fit in well here! What's next up on your project list? What can we help with?

[Iconoscope]

Hi Iconoscope - welcome to HomemadeTools.net

Sounds like you'll fit in well here! What's next up on your project list? What can we help with?

Thanks for the welcome, Jon!!
My next project is to finish making a tool post grinder so that I can clean up the chuck jaws on my ancient South Bend lathe. The old 8" three jaw chuck has small but serious damage to the jaws that prevent proper centering of the work piece. Regrinding the jaws should correct most of the problem. Making a small cylinder to clamp in the jaws for this purpose will be a challenge as the jaws must protrude through slots cut into the cylinder. Those slots must be perfectly 120 degrees apart and of uniform width. Any thoughts on how that can be accomplished? I do have a rotary table.

[Eagle_view]

Iconoscope, are you talking about dressing the inside of the jaws, the part that grips the material? If so, you might consider opening the jaws with a small ring around them (I believe the ring I used to even up my jaws was a 2" ID x 1/4" ring that I had turned) so that you can lightly bore the interior with a boring bar? The ring holds the jaws steady and true to one another while lightly boring the jaws. You can correct a lot of damage in that area this way. Keep us posted on what you do.

[Blogwitch]

I have reground a few jaws in my time, but found in reality they are not really worth doing unless you can't get replacement jaws and it is a last resort.

The first major problem is no matter how you hold the jaws apart, my favourite was a washer at the very back of the jaws on the inside where there is a step and it is closest to the spiral. You will find that the jaws will only be accurate at that open setting.

The other problem is reworking the jaws by hand afterwards. When the jaws are reground or recut, the faces on the jaw tips will be concave and the two outer parts of the concave groove will dig in and mark almost anything you put in there.
The only way around this is to dress down the concave groove to a flat, and by doing that, you will most probably lose everything you thought you had gained.

I have had more luck by mounting the jaws in a line in my mill vice and skimming across the top of the pack with a tungsten cutter, they are not as hard as you think they are.

Sorry to be so negative, but those are the facts of model engineering.


John

[brianhw]

Hi, Iconoscope,
I don't fancy the ring idea as the jaws are being pulled out rather than clamped inwards. This might be o.k. on a perfect newish chuck but scroll wear is not accounted for using this method, and this could be quite bad on an old chuck.
I recommend doing what I did and making a simple ring. You have a rotary table for your milling machine so you should be able to get the slots accurately 120 degrees apart. This is what I used to make this tool.
You can see what I'm talking about by having a look at my YouTube video :-

[gunner312]

Iconoscope,

HEre's the real scoop on regrinding Lathe Jaws. Don't bother. Three -Jaw chucks don't run true EVER, even new ones are .003-.005 out depending on the jaw diameter setting. They can be true, but usually only at one diameter setting. With three-jaw chucks, wear to the scroll changes with the diameter and because of Ham-fisted tighteners', the wear is uneven thru-out the span of the jaw adjustment. If you want a chuck to run true, convert your chuck to a dial-true and then you can dial in the chuck to run true no matter where the jaws are set. Where are you located? I'd be glad to talk to you about this in more depth. I've been a Machinist for 30+ years and own my own shop. I have done everthing from Sub-sea to Aero-Space. 3602758550

[Iconoscope]

Thanks for the suggestion of removing the jaws and then leveling them! That may be my most effective solution!

[Iconoscope]

I am well aware that typical 3 jaw chucks are rarely accurate for centering, but I have had good results from previous reworking of the jaws. This ancient 8" chuck is so far out that it is mostly unusable. I hope the scroll plate is not deformed!! I like the idea of a "dial true" chuck and saw one several years ago. Seems like an independent jaw chuck would be easier to use! I have a 6" with four independent jaws that fits the South Bend lathe but it is too small for some work. Thanks for your input!!

[rick9345]

["If you want a chuck to run true, convert your chuck to a dial-true and then you can dial in the chuck to run true no matter where the jaws are set."

Agree set true,dial-true how ever it is called. Or just learn to use a four jaw. The goal is the work piece running true.
Twiddling&fiddling with the jaws on old/worn 3 jaw is an exercise in futility,but it will keep one occupied if the goal is to get out of the house.