Thread: 3 jaw chuck runout issue

Originally Posted by lucky7

My best 3 jaw on my 9” SB lathe has a tir of 2 thou. My worst is a Crown 3J (last time I bothered to measure) at least 30 thou out and bell mouthed. Guess which one I put on the lathe before the next door neighbor's kid comes over...?

L7

(The kid isn’t getting let loose on the bigger lathes yet)

LOL!

Good test. VERY!!!



When..... the first thing he does is dismount the silly f**ker and mount a 4-J like a grown-up.. and just carry on to do a bit of work, no drama?

Least of all imaginary "hydraulics work"?

... THEN he's prolly ready for a real lathe, too!

Show one photo of anything you can do, you fuck face troll.
I was here 8yrs before you, doing hydraulics work, after all this is a professional forum, but then there is you.
You have called ne a drug addict. a criminal, and also insane, but you termite are a very sick person that never could be a machinist, because you are basically lazy. Not a single thread have you started or a single photo have you posted.
These are the reasons I consider you a worthless piece of shit, simple as that.

I was over complicating machining the back plate. I'll buy a semi-finished one and just get a new chuck most likely a 6" bison.

Originally Posted by digger doug

Yes, however....I don't see anything about "get a 4 jaw chuck" in there....

Already covered a post or two previous to it.

Originally Posted by JST

Already covered a post or two previous to it.

Yes, but not in your "candidate for greatest hits" write up.

I never proposed it for a contest..... and I don't know that it is of that quality level anyhow.

BTW, per the comments by our local troll #2, I do not agree on his assessment of good chucks splitting down the pinion holes. I have a DE Whiton chuck that was also marked Rivett, and came with the 608. Not by any means a cheapo chuck, yet it does not split at all. Instead, a "plug" is dutch-keyed into the body. After removing the keys and the "plug", you remove the pinion toward the inside, IIRC (I have not had it apart for a while).

So I don't think that is a good way to separate good from bad chucks. It is just a design decision.

the little dinky chucks, do not split down the the center of the pinions, the bison 4" does not, having a back plate, but, all decent 6" and larger chucks do, as in cushman, skinner, union, buck and others, check it out. the better import chucks also are constructed the same way, of course one should look for themselves instead of depending of the moldy mouth pieces here
Without exception, the cheapest chucks on the market, are of the inferior construction, that is if one wants a long lasting chuck.

Well looking at the OP and the video.

1. Are the chuck jaw numbers correct, do they match their slots?

2. I notice you have got two piece jaws, can you adjust thejaws to make the part run true?

3. Is the chuck clean inside and out?


If you tried these and did not get anywhere, try loosening the chuck backing plate, a little but not all the way. Then put a dial indicator on the shaft and using something like a piece of bronze or lead or non marring hammer, tap the chuck until the shaft runs true, then tighten up the backing plate screws again.

This might not work because your chuck backing plate might be perfectly fitted to the chuck, but if there is some slop you can adjust the chuck so it runs true. I modified my chuck backing plate so I could do this. I can adjust anything to within 1 - 2 hundreths of a mm runout.

I hardly ever use the 4 jaw anymore.

Many good ideas here ..the op might try some just to gain experience.

all and indicating the chuck face and OD, and indicating the backplate face might be good.

Another one would/ might be to put a true round stock in a collet or between centers and try an indicator on the chuck backside when tightened on that part.

Indicating the chuck register might be good because a new best chuck won't help for problems there.
See how a test bar runs in a collet.

Try / indicate a 4" long true part in a collet.

Lathe could have a bent spindle tube...

try the 2x2 lift if the spindle under an indicator.

* To go buy a 2oo/400/600/1000 dollar chuck might not be the next thing to do.

Originally Posted by vicfi

I was over complicating machining the back plate. I'll buy a semi-finished one and just get a new chuck most likely a 6" bison.

Have you done any of the cleaning or checks suggested here? What were the results? Inquiring minds want to know.

The machining required on a semi finished backplate is the same machining that could well correct your existing back plate.

It's worth a try because it is A: free and B: good practice before cutting on the new backplate you've spent money on.

Yes, I have tried suggestions here. I'm going to pull the chuck off to do a better cleaning. I tried changing the order of the jaws and that makes the runout much worse. To eliminate the possibility of it being just my metal stock out of round. I am going to order some tight tolerance steel.

Originally Posted by vicfi

Yes, I have tried suggestions here. I'm going to pull the chuck off to do a better cleaning. I tried changing the order of the jaws and that makes the runout much worse. To eliminate the possibility of it being just my metal stock out of round. I am going to order some tight tolerance steel.

Save yer money! You have drills around? Shank on even a cheap one is good enuf for now. Better yet, 'coz they are handy in general, is a set of "drill BLANKS".

You do not NEED a full set by 64'ths or 1/2 mm.

Bought in twosies, only a few sizes, (Vermont-American are cheap and good enough..) one has handy pairs of rounds that are useful for LOTS of things. Measuring wear of dovetails and such one of many you might not have yet gotten to.

See also ground "dowel pins". Or a center in the spindle-bore taper.

or...

Even if the chuck is a 1/4" off-center, grab a large enough diameter of round stock you can TURN a true cylinder. Cut the true section off. Mic it for roundness. And taper.

This is not as straightforward as first appears. It MIGHT NOT be all that "round", let alone free of taper.

But that has the side-benefit in that it will ALSO give you an idea how good your spindle bearings are! Or are NOT!

Same again if you can separate the backplate from the chuck and measure TIR on the spigot.

IF.. the spindle bearings are nasty?

Time for a re-think.

FIRST.... see to what you must / can / can NOT... do about the bearings.

If that proves too steep - or costly - a hill to climb at you present time, money, and skills "budget"?

TIME.... is the hardest one to "just buy"... an extra ration of...

You will have saved money wasted on a good 3-Jaw for a less-than-good lathe!!!

One that might not FIT the lathe .. you might have to replace this one with if roundly trashed or crashed!

I'm serious.

There's a point with 9" or 10" light-duty SB lathes where it is far wiser to cut your losses and find a better starting-point.

Same make & model, better condition?

Or a better lathe, outright?

Eg: "Most of them?"

When you pull the chuck, leave that backplate on the machine. Check IT for the things mentioned in post #11.

And remember, problems with the backplate are generally fixable. They are things you will have to get right on the next backplate, too.

DO make ALL the checks from post 11. Report the results.

The ONLY way to find this sort of problem is to be disciplined and methodical about it. Jumping from idea to idea is only going to get good results by chance. You made a good start with the checks, keep it up.

yes, drill blanks may be OK for checking purposes. So is a chunk of TGP rod.

Could be the chuck is shot but first go down the checklist Likely/perhaps you have and not reported your findings. (the target expected)
Indicate the chuck OD and face for run-out ( <.003 each)
Pull chuck and indicate the mounting plate face ( <.0002)
If the mounting plate has a register indicates its OD. (<.0002)
Pull the mounting plate and indicate the spindle face and register OD (<.0002 each)
Take 1 wood 2x2 and with one hand light pry the spindle nose up and sideways.(<.003)
Place a collet in the spindle with a straight 3" long rod and indicate the OD for run-out and wobble.(< .oo1)

Bargain brand test bars may be frowned on but are Ok for an old home hobby lathe IMHO.
A collet and a 3" long drill rod can be near as good.
Agree a drill or reamer shank is an OK straight bar and you need only test 3 or 4" to see results.
Good to choose something that will also be good to use once you have your lathe up and running.
A bar with having centers can be handy.

Lathe Alignment Test Bar Shank Size 1MT, 2MT, 3MT, 4MT, 5MT, 6MT Bluefox | eBay
(may have .0002 or so run out so just for ballpark check.) most lathe work is not in tenths or microns.

Originally Posted by JST

I never proposed it for a contest..... and I don't know that it is of that quality level anyhow.

BTW, per the comments by our local troll #2, I do not agree on his assessment of good chucks splitting down the pinion holes.

Got that shot right!

Not just D.E. Whiton, either. Taylor - perhaps the strongest self-centering scroll chucks ever made - anywhere - have been demo'ed holding their grip WITHOUT the body!

Taylor conical scroll lathe chucks

HIS problem? What with confusing "hydraulics work" and .. what is it? "Proctology and similar persuasions" as Jack Elam once put it???

..., is that he expects the "bilateral symmetry" of cheeks and such to "split down the centerline" of all holes... pinioned.. or otherwise!

Originally Posted by thermite

...Save yer money! You have drills around? Shank on even a cheap one is good enuf for now. Better yet, 'coz they are handy in general, is a set of "drill BLANKS"...

On that note you might also consider buying a few quality guage pins. I don't have any sets but I do have singles
in a few sizes that I can use in situations like this, Always handy to have some around...

Originally Posted by LKeithR

On that note you might also consider buying a few quality guage pins. I don't have any sets but I do have singles
in a few sizes that I can use in situations like this, Always handy to have some around...

I bought a large (when new..) but "incomplete" (now very OLD!) set a while back.
Used goods of that sort are often dirt cheap.

The small set of drill blanks gave me longer lengths than good-grade dowel pins and were cheap enough that two identical sets insured I'd have matching diameters when a dovetail was to be measured.

Sometimes longer is better. Sometimes SHORTER is better.

Bearing balls are another "nice to have".

All that basic stuff comes handy for LOTS of uses.

Just not very OFTEN!

So "the usual" applies. Yah forget what you have ... or where you stashed it ...and end-up fiddle-farting around with redneck jury-rigs anyway!

One might buy soft jaws and tool then good, but of the chuck is shot that may not help at different diameters.

Well, I got the chuck off. The spindle looks good. The backplate mounted to the chuck is aluminum which I don't think is causing an issue but just something weird I noticed. I'm going to buy a new chuck and back plate. But it'll be a while till I get to using it as I'm doing a teardown to replace wicks.

Originally Posted by michiganbuck

Could be the chuck is shot but first go down the checklist Likely/perhaps you have and not reported your findings. (the target expected)
Indicate the chuck OD and face for run-out ( <.003 each)
Pull chuck and indicate the mounting plate face ( <.0002)
If the mounting plate has a register indicates its OD. (<.0002)
Pull the mounting plate and indicate the spindle face and register OD (<.0002 each)
Take 1 wood 2x2 and with one hand light pry the spindle nose up and sideways.(<.003)
Place a collet in the spindle with a straight 3" long rod and indicate the OD for run-out and wobble.(< .oo1)

Bargain brand test bars may be frowned on but are Ok for an old home hobby lathe IMHO.
A collet and a 3" long drill rod can be near as good.
Agree a drill or reamer shank is an OK straight bar and you need only test 3 or 4" to see results.
Good to choose something that will also be good to use once you have your lathe up and running.
A bar with having centers can be handy.

Lathe Alignment Test Bar Shank Size 1MT, 2MT, 3MT, 4MT, 5MT, 6MT Bluefox | eBay
(may have .0002 or so run out so just for ballpark check.) most lathe work is not in tenths or microns.

those are very ambitious numbers you have there, even din 8605 is higher in some cases.