Truing lathe jaws revisited

cueman said:
BORING THE JAWS:

Once you make sure the chuck opens and closes smoothly then you will want to bore the jaws if they have significant run out. The first step Is to open the jaws on the chuck all the way up. Then close them about 1/12 of a turn and turn the lathe on high speed. Then bore the jaws with your regular boring bar. Make sure you snug up your screw dial and the rear carriage thumb screw. You don’t want any carriage play or cross-slide backlash when boring the jaws. Take a few small in and out passes. Then on the last pass stop after you complete the inward pass and turn the lathe off. Back the cutter out without touching a jaw and check for run out again. Sometimes it takes a time or two to get it right. It usually can be trued up to turn within .002" or so. The above works best on the small bore headstock chucks. On the Deluxe large bore headstocks the above works well, but sometimes you can get a truer bore if you run a faced off piece of 1.375” Phenolic Butt size tubing in from the back side and chuck the metal rear part of the jaws down onto that. That allows you to still bore the entire aluminum part of the jaws. To bore the rear chuck, do not remove either chuck. Instead remove the front plate on the headstock. Then loosen the bottom back clamp that holds the headstock to the bed. Slide the headstock off and then slide it back on with the back side now up front. With the front plate removed and the headstock turned around you will now have the rear chuck on the right side so you can bore it just like the other one. Once it is trued up then turn the headstock back around and reinstall the front plate. If you bore the jaws too often or two much you will have to replace the set of jaws. The new jaws come to a point and have to be bored from scratch.
Click to expand...


I recently installed a new set of jaws. Just to add to what Chris said. IF you use the power feed instead of the had wheel, you will get a much cleaner cut. The same is true if you need to taper a Stainless Steel Joint. The only difference being that with the Joint, you can only take off a couple thousandths at a time, and you need to stop and let it cool every 1 or two passes or you will ruin the glue bond.
 
Tony Zinzola said:
I recently installed a new set of jaws. Just to add to what Chris said. IF you use the power feed instead of the had wheel, you will get a much cleaner cut. The same is true if you need to taper a Stainless Steel Joint. The only difference being that with the Joint, you can only take off a couple thousandths at a time, and you need to stop and let it cool every 1 or two passes or you will ruin the glue bond.
Click to expand...

I agree with Tony on this one if you have a Deluxe Large Bore headstock. But with the Mid Size or Micro lathes I would advise not using the powerfeed, because if you go even a little far you will crash the boring bar into the chuck. But with the Deluxe that is not a problem unless you go way to far.
 
Personally, I had better luck feeding by hand than with the power feed. Maybe I had the carriage too tight and it was jumping. I don't know.

I just did mine again last night. The first time I got sloppy and managed to cut a little taper in the jaws. This second time I got them better than .002" and I have solid contact along the entire jaw. That's about all you can really ask for from a scroll chuck.

If Chris ever offers a 4 jaw chuck, I'll first in line. :)
 
BHQ said:
i just bored jaws on my three jaw chuck
i do it the way a local machinist showed me
took some wire and wrapped around the outside of jaws and backed them off as tight as i could, leaving me an inside diameter of about 1.375"]
Click to expand...

i hate having to find a ring or bar to cut on a manual chuck jaws

I love the doosan puma I work on, hydrolic chuck
Set to od clamp and cut for grabbing id
Set to id clamp to jaws


This way I never have to search for anything to hold in the jaws,just cut them while they are open
 
Rem_Macs said:
Why is the cue man lathe sold with chucks that are not bored & true?
Click to expand...

Soft jaws, by definition, are designed to be trued after your machine is setup in your shop. That goes for cheap Harbor Freight lathes right up to the most expensive CNC lathes in the world. The whole point of soft jaws is to remove any residual runout in the system. Even the most expensive 3 jaw scroll chuck is not going to be accurate to better than .002" or so, and the fact that we can get Chris' lathe there is a testament to getting all of the important things right.

If you need better than that, you need to make collets, use a 4 jaw chuck or bore soft jaws at exactly the diameter you need for that particular part. It will run, more or less, as true as the bearing at that one setting...and when you chuck a different diameter, you'll be doing good if you can stay within .002" (which Chris' chucks/spindle setup does).

If you look up how a scroll chuck actually works, you'll understand why they never run perfectly. The entire scroll, the master jaws, etc...they would ALL have to me machined to ridiculous tolerances to hold .001" or better across the entire range. That never happens because no one would be able to afford the chuck for starters, and even if you could it would quickly wear out and you're be back where you started from.
 
Last edited:
You must log in or register to reply here.
Back
Top