Truing lathe jaws revisited

Jaws

I have the Hightower lathe as well. I do just as you said. I chuck up a steel rod in the rear chuck and chuck it up just behind the jaws on the front chuck. Then just bore it. You don't have to take off much and there is no filing. I've done it many times with good results.

CamposCues said:

I have the Hightower lathe as well. I do just as you said. I chuck up a steel rod in the rear chuck and chuck it up just behind the jaws on the front chuck. Then just bore it. You don't have to take off much and there is no filing. I've done it many times with good results.

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Hi,

I assume you are doing this for a more perfect pin installation and greater accuracy for joint concentricity. If this is the case and you are trying to dial that thing in as true as you can get, then I suggest you use a thomson rod or at least a precision rod like they use for linear motion applications. You can buy both from McMaster Carr.

The thomson rod is better because it is case hardened and it runs true to an outrageous standard. The ends are not hardened and they can be center drilled and you can align your tailstock to your chuck also. If you buy one to use to dial in your lathe, you might want to consider having the centers drilled by a machine shop that has high standards equipment.

I recently did my six jaw and I bore with a rotary grinding tool mounted in my tool post with my jaws locked open with a precision collar. I have mine down to 1/2 a thousand run out which is close enough for the girls we date.

I have a back chuck and have that adjusted as close as I can get it but it is not half a thou. Because of that I like to do my pins and precision facing holding the part between the chuck and my steady rest. I seem to get the best results that way.

You might also want to check with Chris to get his input for your specific machine.

Best of Luck,

Rick Geschrey

i just bored jaws on my three jaw chuck
i had a guy make me an indexer,
it's made to go onto the spindle, behind the chuck
it was tight as hell going on, but somewhere along the line recently, it has shifted a little
which threw my chuck off a bit
i anchored indexer to the spindle this time, (shoulda did that in the first place ) and bored jaws
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".

using my router in toolpost, with kj's mandrel and a reinforced abrasive cutter wheel,
went in 2/1000ths at a time till all jaws were cut,
and then went back and forth , maybe a dozen times till no sparks were flying
everything is concentric once again

added> sorry stoney, i missed the part about what brand lathe you have

THREE JAW CHUCK REPAIR!

If your chuck has much more than .002” run out or it sticks every third of a turn when opening it here is the instructions on what to do. First off if the chuck opens freely but, has significant run out skip the following section on repairing the chuck and go to Boring the Jaws below.

REPAIRING THE CHUCK:

If the key is left in the chuck and the lathe is turned on it opens the chuck much to fast and slams the chuck scroll up against the side of one of the jaws. This bends the end of the scroll over and causes the chuck to stick every third of a turn when opening. It can even completely lock the chuck up. Here is how to repair it yourself.
To remove the chuck from headstock:
#1 On Deluxe headstock lock the headstock down with a indexing pin. On Small headstock machines use a thin wrench behind the chuck to lock head down or very cautiously use indexing pin.
#2 Then rotate the chuck counter clockwise to unthread off of the spindle.
#3 Pencil numbers on all chuck jaws and slots in case they come out of slots.
#4 Remove the snap ring from the back of the chuck.
#5 Then remove the back scroll plate from the back of the chuck.
#6 Turn the scroll plate over and you will see a spiral scroll. The inside very end of the scroll will be slightly bent or compressed from hitting the side of the jaws at high speed. Take a small diamond file or really coarse sandpaper and smooth up the burr or bent spot.
#7 Close jaws all the way until they touch each other and put scroll plate back on. If it opens and closes smooth then remove scroll plate again and grease inside of chuck with lithium or axel grease and reassemble.

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.

BHQ said:

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".

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Actually, it's better to tighten DOWN against something held in the rear of the jaws. The idea is to simulate the clamping pressure when chucked up on something and take up any slop between the jaws and the T-slots. If you back your jaws OUT against wire or tubing or whatever, you are taking out your slop in the wrong direction - the jaws will "tip" the wrong way.

Just so I understand......

cueman said:

THREE JAW CHUCK REPAIR!


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.

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I've always thought that it was a bad idea to run without the chuck jaws clamped onto something

You can actually bore the jaws with the jaws floating free?

While we're on the subject, I'm having a hell of a time turning the headstock around on my Enco 13x36. Do any of you guys have any suggestions on how to go about truing the rear chuck on that one?

I have a Buck 3 jaw adjust tru chuck. I can put a .750 pecision pin in it and indicate it to about 1 thou. I think the repeatability is only for that size. By that I mean if I put a .875 pin in it would not be concentric. My question is can I get jaws that are soft enough to bore and set this thing up right or do I have to keep adjusting it for the size material I put through the headstock. I Have a threaded spindle on my lathe and I faced the headstock before I mounted the chuck and it was zero so I know the chuck was mounted tru. What is considered tru enough for cue making a half a thou or what?

kiinstructor said:

I have a Buck 3 jaw adjust tru chuck. I can put a .750 pecision pin in it and indicate it to about 1 thou. I think the repeatability is only for that size. By that I mean if I put a .875 pin in it would not be concentric. My question is can I get jaws that are soft enough to bore and set this thing up right or do I have to keep adjusting it for the size material I put through the headstock. I Have a threaded spindle on my lathe and I faced the headstock before I mounted the chuck and it was zero so I know the chuck was mounted tru. What is considered tru enough for cue making a half a thou or what?

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It sounds to me as though the chuck is worn out if there is much of a discrepancy. Scroll chucks are notorious for not being able to have more than .002 or so accuracy at multiple sizes. They can be honed and be dead on at that size but be out quite a bit at any other size. It is because of wear and the precision that the scroll parts have themselves. It is for this reason I laugh to myself when I see some of the numbers many on this forum post about their machines accuracy. They post numbers that there 50.00 chucks maintain that 1000.00 chucks won't hold. At any rate, we are turning and working with wood, not heart valves or such. .002 or .003 will not turn a good cue into a bad one. You try to keep all of your tolerances as close to 0 as possible as a little out here and a little out there can add up to a lot. Dead nuts is needed for facing any joints in a cue ( shaft joint, A-joint and such ) so in this case just face off at the tail stock.

Dick

dzcues said:

Actually, it's better to tighten DOWN against something held in the rear of the jaws. The idea is to simulate the clamping pressure when chucked up on something and take up any slop between the jaws and the T-slots. If you back your jaws OUT against wire or tubing or whatever, you are taking out your slop in the wrong direction - the jaws will "tip" the wrong way.

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that does sound logical,
but it got it to within .002"

Sometimes it is better to tighten down onto a tube in the front of the jaws, grind through the back of the jaws, and then cut the front portion off. This reduce the overhang tilting moment and makes them true to that diameter.
Some chucks come with jaws that are almost flush with the body of the chuck and are designed to only work wiithin the bore diameter of the chuck body to be very precise chucks .
Softjaw sets are fairly cheap and allow easy maching to make them correct.
Neil

Bill the Cat said:

I've always thought that it was a bad idea to run without the chuck jaws clamped onto something

You can actually bore the jaws with the jaws floating free?

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Yes, provided you are running fairly fast. 1500 to 2000 rpms.

Stoney said:

Regards,
Stoney

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The regular 1/4" $8 boring bar that I sell is all you need.

> Just typical,Chris comes up with an explanation that gets the job done,LOL.

I haven't had to do it yet,all my Hightower chuck does is hold lathe pins for shafts and a joint protector for polishing butts.

I can tell you this though. If you are replacing the jaws,and boring from scratch,don't get crazy with the depth of cut,even if it takes a bunch of small passes. I can see in a situation like this,you're dealing with a 3 flute interrupted cut,so to speak. Too deep of a cut like this and the inside corners of the jaws will beat the top of your boring bar to death,causing chatter,and more work removing it. Don't forget to deburr the edges either.

The chuck on my Enco tip lathe is the smallest Bison I've seen,and was bored or ground by the original owner,and I've never even had to take it off. My collets run nuts in the 5/8 range,and chucking up on round rod runs pretty sporty in the 3/8-1/2 range. I can't recall more than .002 on anything I've ever put in it,and that is rare. I can re-chuck and maybe tap a jaw here and there and get within .001 so often unless it's a shaft I've never worked on,I no longer indicate everything I put in it. I have to accept that not every machine I'll encounter will do this,but that little machine is a gem. Tommy D.

Dick said it best. Chris's Cuesmith is a grand piece of equipment I do not know what I would do with out, but we need to consider what we are trying to perfect. Get the jaws within .002", then indicate your work piece in using rolling papers to shim it to under .001". Works for me.

For the guys shimming with paper, have you ever tried a 4 jaw chuck? It is so easy to use once you get the hang of it. I never had luck with the 3 jaw. Every shaft you put in there has some wobble. With the 4 jaw, all it takes is an extra minute to chuck up on something. But if you guys are indicating things anyway, AND then putting papers under the jaws of your 3 jaw, the 4 jaw chuck should be way faster than the way your are doing it, and BETTER.