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View Full Version : Is spindle runout adjustable ?



TR
12-07-2010, 09:57 PM
I have two three jaw chucks which both show a runout of 0.3mm. A few months ago, it was 0.1mm which is acceptable. I have geared head 13/40 lathe. Is spindle run-out adjustable ? Is something wearing out ? Any ideas ?

Thanks,

Ken_Shea
12-07-2010, 10:06 PM
TR,
Th efirst place to start would be to completely disassembled including backing plate, evertyhing/every where cleaned and inspected.

huntinguy
12-07-2010, 11:04 PM
if they are threaded on... they could change with each on and off. If they are cam loc or long taper, I would think there may be some junk on the taper or back surface. I usually stone the back of the chuck and the locking surface on the back of a cam loc.

Ken is right. A good cleaning never hurt.

TR
12-07-2010, 11:12 PM
D1-4 cam lock

RobbieKnobbie
12-07-2010, 11:20 PM
.1mm to .3mm? Eh, you just need a bigger hammer:D

Ken_Shea
12-07-2010, 11:33 PM
Look closely at the jaws for raised nicks.

Speaking of hammers, I have seen guys really abuse chucks, way over tighten while short gripping stock etc, not good.
Yes, they are a big chunk of steel but a precision big chunk of steel.

Forrest Addy
12-08-2010, 12:13 AM
Cleanliness is a goof place to start with any spindle tooling, especialy with a 3 jaw. You have to keep craap vrom being centriguged into the jaw cleartances. Stuff the inside jaw gaps with bits of rag to prevent chip infiltration when boring. Often times a chip can imbed and hold the chuck from registering. It has to be picked out with a scribe.

A little obsessive cleanliness is not a bad trait when it comes to chucks and tapers and measurements and machinery fit-ups in general. Old toothbrushes and a hook scribe are a machinist's best friends come chuck changing around a lathe. The tapers on my lathe chucks show a little wear except for a couple of tiny and promptly remedied chip bruises. My 38 year old 10" 3-jaw still runs within 0.002 gripping 2" dia work.

TR
12-08-2010, 01:23 AM
Good advise. Back to the original question, is the spindle adjustable ? Could something inside the lathe be loose ? Does 0.1 mm TIR seem okay ?

Black_Moons
12-08-2010, 01:28 AM
Yea just adjust the TIR knob at the back untill its at 0.

oldtiffie
12-08-2010, 02:02 AM
Good advise. Back to the original question, is the spindle adjustable ? Could something inside the lathe be loose ? Does 0.1 mm TIR seem okay ?

Scrolls are not as accurate or as consistent as some may wish or imagine.

If I recall correctly, you have D-1 cam-lock mounting and an "Adjust-True" adjustment (on the back of your chuck/s).

Ideally the same pin/should go into the same hole/s on your D-1 mount.

I suggest that you re-adjust your Adjust-True at or about your most frequently used size - and note and/or mark the pins/holes.

Your chuck manufacturer's site should have the run-out etc. specs on it.

Here are some typical specs for 3-jaw chucks:
http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/3-jaw_chuck_specs1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/3-jaw_chuck_specs2.jpg

willmac
12-08-2010, 06:59 AM
TR -

I'm a bit confused about your question.

You were talking about the runout on your 3 jaw chucks. Some run out is quite normal, and depends on a lot of factors, including abuse, cleanliness, quality of chuck, wear etc.

Then you are asking about the spindle on your lathe.

This is an entirely different issue. You should not try to assess spindle runout by the run out you get when gripping a part in a three jaw chuck, even two different chucks. The spindle should be orders of magnitude more accurate than your chucks, so if you have doubts about your spindle you need to take the chuck right out of the picture. Take it off the spindle and check the spindle run out on the taper or a suitable register. Having said that, accurately assesing spindle condition takes a fair amount of care and knowledge so unless you find clear evidence of significant problems I would resist the temptation to strip and attempt to adjust the spindle bearings.

I'm sure that you understand Black Moon's humour, but just to be sure, there is no simple dial in adjustment that will reduce TIR. Wish it was that easy.

TR
12-08-2010, 08:16 AM
Thanks for the replies. I did some more measuring. The spindle is more or less perfect. My 6" 3 jaw chinese has TIR of 0.07mm using the test bar. My new 3 jaw Gator chuck TIR of 0.30mm. Not happy. Using my 8" four jaw I can get zero runout.

JoeLee
12-08-2010, 08:58 AM
Thanks for the replies. I did some more measuring. The spindle is more or less perfect. My 6" 3 jaw chinese has TIR of 0.07mm using the test bar. My new 3 jaw Gator chuck TIR of 0.30mm. Not happy. Using my 8" four jaw I can get zero runout.


CHINESE............. thats the problem.

JL....................

vpt
12-08-2010, 09:15 AM
Time to grind it.

J Tiers
12-08-2010, 09:42 AM
if they are threaded on... they could change with each on and off.
Ken is right. A good cleaning never hurt.

I hear this regularly, and of course it "could". But the problems with threaded chucks are not necessarily due to some inherent wild inconsistency.....

Keep the threads clean and the spindle mating surfaces clean, and your threaded chuck will repeat well. threads are harder to keep clean than a cam-loc etc.

But it sounds like the real problem is not the taper or threads, rather something to do with the chuck. If chinese, it may not have been finished well. When the "high spots" wore off, it became less consistent, perhaps.

While "china" tools do not HAVE to be trashy, there is a lot of stuff coming out of china to service the "cheap-ass" end of the market.

ammcoman2
12-08-2010, 10:46 AM
I have a few TOS chucks that have a "0" stamped next to one of the keys. This is the one that is tightened last and results in the lowest runout.

A few years ago I picked up a no name chinese made 6", 3 jaw that had no such marking. So one day I ran a test on runout. Marked each key position with a sharpie, tightening each of the jaws as the last one and recorded the results. Can't remember the piece of rod I used but I think it was about 2" diam shafting material.

Ran the test 3 times and there was one jaw position that consistantly gave the best result.This was stamped with a "0". This chuck had previously been was mounted on a D1-4 backplate by me and I always mark the backplate so that it is set to the spindle on the same pin position. Then the final setup is done per the following.

I also use the technique of having about 0.010" clearance on the backplate to chuck register and set it to minimum runout before doing the final tightening of the mounting screws.

Geoff

P.S. I now have a 6", 3 jaw Pratt chuck that has no such marking on the keys and the results are consistant whichever key is snugged up last. It is not new by any means but I guess the original build quality still comes into play.