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Skew ChiDAMN!!
27th July 2005, 07:16 PM
I've been away from the shop for a few dyas, working on-site. The first thing I did on my return, before a cuppa even, was start up my mini-lathe to rough some pen blanks I picked up en-route.

Threw some pin-jaws on the reliable ol' Nova Midi chuck, spun it onto the lathe and powered it up for a quick speed check before mounting the blank. 'Twas on the lowest speed and... the chuck's wobbling! :( About 1mm deviation, I'd guesstimate... Remove the chuck and power up the lathe to eyeball the spindle, it seems to be running true, but to be sure I install a pen mandrel and everything still appears OK. No obvious slack in the head-bearings, no unusual bearing noise. Whisper quiet, as a matter of fact.

Reinstall the chuck and... instant wobble! Hmmm... I use a spacer to set the shoulders of the chuck. Maybe that's damaged? Remove the chuck and spacer, it eyeballs OK. Check the spacer thickness with verniers and 'tis a constant size. Strike 2 in my search for the cause.

Moving further afield, I remove the thread insert from the chuck for the first time since purchase and decide to field-strip the chuck to it's bare assemblies and do a full lube'n'grease. Reassemble, except for the jaws, power up and... Strike 3! I'm out! :mad:

Anybody got any ideas? The only thing I can think of is the head-bearings may be on the way out, so although they're fine with a mandrel they'll no longer handle the weight of the chuck. But before I go to the extreme of pulling this headstock apart too (the chinese bearings also failed in my MC-900 the other day!) I'm hoping someone can suggest other possible causes I may have missed. [fingers Xed]

Help?

DavidG
27th July 2005, 08:07 PM
Did you put the pin jaws on in the correct sequence.
Is the area under the jaws clean.
Are the jaws tight.
I don't know what else.

smidsy
27th July 2005, 08:16 PM
On the chuck insert, is there a locking bolt?
On the Vicmarc chucks the locking bolt is screwed in horizontally from the back of the insert and needs to be unscrewed before fitting the insert to the chuck.
Apart from what Dave said there is little more it can be - try refitting the stock jaws and see what that does.
Cheers
Paul

Cliff Rogers
27th July 2005, 08:33 PM
Try it without the spacer.

soundman
27th July 2005, 09:57 PM
I'd lay odds on the jaws not correctly fitted. Remember they are number stamped with their locations.
A common trap (apparantly). :D

Cliff Rogers
28th July 2005, 12:22 AM
I'd lay odds on the jaws not correctly fitted. ....Nope he said... "Reassemble, except for the jaws, power up and... Strike 3!"

I'm gunna put my money on the spacer. :)

Skew ChiDAMN!!
28th July 2005, 11:31 PM
No payout for anyone yet. :(

I tried it without the spacer today and still no joy. I also tried it with a newer Nova Precision Midi and that chuck didn't wobble, even though 'tis slightly heavier. Although it doesn't solve the problem, it relieves my angst about the headstock bearings. [Phew!]

The thread insert is the next obvious culprit, but...

It hasn't been removed from the chuck since being purchased way back when.

The locking grubscrew actually needed a bit of persuasion to release, so it certainly wasn't loose.

After careful inspection, (I used a jeweller's glass) both insert threads (inner & outer) appear undamaged & fit snugly to the relevant mating threads.
Similarly, both the spindle & chuck body threads appear undamaged.

Using a spare insert made no difference, the chuck still wobbles.


The only other thing it could be, that I can think of, is a warped chuck body. How this would happen is beyond me; the SWMBO admitted that the lathe was "borrowed" while I was away but I can't see how any misuse could warp the chuck without causing obvious damage to the lathe and/or tool-rest.

Has anyone ever encountered something like this? :confused:

Cliff Rogers
29th July 2005, 12:09 AM
....The only other thing it could be, that I can think of, is a warped chuck body. How this would happen is beyond me;
Did you leave it sitting on the dashboard in the sun? :rolleyes:



....the SWMBO admitted that the lathe was "borrowed" while I was away .....

ARH-HUH!!!! That'll do it everytime... somebody else touched it & it got all bitter & twisted. :D

Captain Chaos
29th July 2005, 12:13 AM
What was held in the chuck when it was " borrowed ". It may have been an irregular shaped piece of wood & a lot of pressure was placed on the jaws & scroll thread to hold it & this could have distorted the scroll thread & matching jaws. Threads are very powerful clamping mechanisms & can cause a lot of damage if overtightened.
That's my two bobs worth. Good luck.
Barry.

Cliff Rogers
29th July 2005, 12:22 AM
& what if the borrower opened it up too far & then did it up again with the jaws in the wrong scroll threads or even worse, what if the took it apart & put it back together all out of order? :confused:

Captain Chaos
29th July 2005, 12:35 AM
Jeez Cliff, poor old Skew's probably had to take a couple of Bex & go for a good lie down after this lot eh?
Hopefully it's something really simple that we're all missing & will be a cost free fix ;-)
T.T F.N,
Barry

Skew ChiDAMN!!
29th July 2005, 01:22 AM
ARH-HUH!!!! That'll do it everytime... somebody else touched it & it got all bitter & twisted. :D
Nar, it's me that gets all bitter and twisted when someone else plays with my toys. :D


Just to clarify things, the entire chuck-body is running out of true, not just the jaws. Even if someone took a gas-axe to the scroll threads and mixed pin-jaws and 75mm jaws I doubt the resulting weight offset would mass enough to deviate the chuck. Not when I've had the same chuck mounted on my MC900 with an OOB load that walked the lathe a few feet w/out wobbling the chuck. That I noticed, anyway... I was probably more occupied with trying to avoid the lathe while hitting the off-switch at that particular moment. ;)

Hmmm... metal fatigue? I'll look into that on the morrow...

I doubt 'twas the result of a OOB load anyway; this is on a Ledacraft mini-lathe I use for pens. It's not even bolted down. Any load that'd do that damage would result in the lathe flying across the room and there's no dings or blood-stains in the wall, ceiling or concrete. No new ones, at any rate.

I've given thought to how I'd deliberately make this happen and I always end up with the chuck mounted on a solid 1" rod and a 4lb sledgie...

barnsey
29th July 2005, 03:52 AM
A 4 lb sledge won't do much damage really but a ham fisted persom may well have created more damage trying to do something you and I wouldn't.

He still alive???

What were they trying to turn???

I've done a few crazy things and given myself some damage but never managed to achieve any damage to a machine ( even a MC900 ) - only myself :rolleyes:

You should be able to determine where the damage is by making a few checks.

A thou or two in a bent headstock shaft won't be that obvious till you put the chuck on it. Try a centre in the morse taper and see if you get any runout.

FWIW

Jamie

Little Festo
29th July 2005, 10:20 AM
Have you tried changing the insert. I imagine that would be easier to damage than the chuck. I think that the insert from the larger Nova will fit??????? if the larger nova works ok the it cannot be the lathe it has to be a problemwith the chuck.

Hope this helps - peter

soundman
29th July 2005, 10:48 AM
Crikey Jack! :eek:
You'd have to be trying real hard to bend a whole chuck?
Have you stood it flat on its back & rotated it next to a ruler to check for true & run you calipers round it.
You've got us all fascinated now.
If it is bent, we'd all realy like to know how :confused:
cheers

Cliff Rogers
29th July 2005, 10:50 AM
Have you tried changing the insert. ......
Yesterday Skew said...
"Using a spare insert made no difference, the chuck still wobbles."

Ashore
29th July 2005, 11:01 AM
Skew
Run some dowel /rod from the new chuck to the tailstock when it is true move the tail stock back slide the damaged chuck on tail stock back on clamp the chuck to the dowel with the jaws and with a pointer or dial indicator rotate and see if its running true at the thread and the jaws. Wont fix it but may show you where the problem lies


Rgds
Russell




The trouble with life is there's no background music.

Skew ChiDAMN!!
29th July 2005, 11:14 PM
You'd have to be trying real hard to bend a whole chuck?
Have you stood it flat on its back & rotated it next to a ruler to check for true & run you calipers round it.
You've got us all fascinated now.
I hadn't thought of that. D'Oh!

Tried it and it suggested the chuck itself is out of true. I was beginning to think this was the case, but 'tis nice to have some confirmation. To be sure, I reassembled the MC-900 headstock (picked up the new bearings this morning) and mounted the chuck on that. A quick spin and... yup. Somehow, the chuck has been bent.

I asked he who borrowed my toy, it seems he was repairing a cheese knife, turning it down to take a new ferrule. He admitted to dropping the chuck when changing jaws, now that I think on it I did leave it with 50mm jaws instead of the customary pin jaws, but I really can't see how that would do it.

Worse, I don't feel I can hit him up for damages for something I've probably done a hundred times myself. :(

I'm not a happy chappy.

DavidG
29th July 2005, 11:31 PM
How the .... did the chuck bend????? :confused: :confused:

gatiep
30th July 2005, 12:09 AM
This thread is not updating on my computer seems to be stuck on Silent's post??????????????

:mad:

gatiep
30th July 2005, 12:10 AM
Ok, that fixed it!

:D

gatiep
30th July 2005, 12:16 AM
No payout for anyone yet. :(

I tried it without the spacer today and still no joy. I also tried it with a newer Nova Precision Midi and that chuck didn't wobble, even though 'tis slightly heavier. Although it doesn't solve the problem, it relieves my angst about the headstock bearings. [Phew!]

The only other thing it could be, that I can think of, is a warped chuck body. How this would happen is beyond me; the SWMBO admitted that the lathe was "borrowed" while I was away but I can't see how any misuse could warp the chuck without causing obvious damage to the lathe and/or tool-rest.

Has anyone ever encountered something like this? :confused:

Did you use the chuck on a Newer Nova Midi Lathe and it didn't wobble................. Thats how I read your post.
Well if that is so then there is a problem with either the shoulder or the thread on the spindle of your lathe. If the spindle doesn't show signs of running out, check if the insert screws on 'faily loosely' onto the spindle of the lathe.

rsser
30th July 2005, 08:53 AM
Might be worth a chat with Teknatool's Oz distributor.

Cliff Rogers
30th July 2005, 10:44 AM
Did you use the chuck on a Newer Nova Midi Lathe and it didn't wobble................. Thats how I read your post......
Nope, he used a newer chuck on his old lathe & that didn't wobble.

The chuck must have landed on it's back at a bit of an angle & slightly depressed one side of the back were the insert goes in. :eek:

gatiep
30th July 2005, 04:00 PM
It may be a good idea to try the chuck on another lathe to see if it still runs out.

Skew ChiDAMN!!
31st July 2005, 12:50 AM
It may be a good idea to try the chuck on another lathe to see if it still runs out.
I did and it did.

I've also finally located the root of the problem!

Having finally determined the body itself was skewed, I stripped it down again, paying more attention to the body itself. On this chuck the scroll is held in place by a circlip(sp??) around the threaded section of the body. Close inspection shows a hairline crack hidden inside the circlip's rebate (which is the thinnest part, of course) and running about half-way 'round.

No wonder 'twas running out of true!

Now I'm unsure whether or not I should attempt to weld it. If I knew that I could jig the chuck true I wouldn't be concerned, but my metal-working skills are of the bash-it-til-it-fits type. Come to that, so are my woodworking skills. :D Still, I guess I've little to lose by trying...

Captain Chaos
31st July 2005, 01:18 AM
G'day Skew,
Glad you found that crack in the circlip groove. Dunno that I'd be welding it though. I believe that Teknatool use a special high grade steel that may not be easily welded. I think that you may be better off to get it back to Teknatool for them to check it out + you may be able to get it repaired / replaced under warranty. It may possibly be a fault in the machining process that has caused the failure.:eek:
The address of their Australian office (?) is;
Teknatool International,
P.O. Box 1321,
Horsham, Victoria.
3402.
Phone: 1-800-140-761
Fax; 1-800-140-755
E-mail: [email protected]
[email protected]
The e-mail address goes to Teknatool In N.Z. I think but you will still find them to be very helpful.
Regards,
Barry.

Skew ChiDAMN!!
31st July 2005, 07:16 PM
I don't think their tooling dept. has any need for concern... I bought it second-had a couple of years ago and I believe 'twas a hand-me-down before then. Methinks any warranty attached has well'n'truly lapsed.

Thanks for the info just the same. I hadn't given a moments' thought to the steel grade, nor that I'd need to be able to clean up the circlip groove, etc after welding in order to reassemble it! And clean it up accurately! I'll buy a replacement anyway and although I doubt it'd be economical to send it back to Teknatool for repairs, enough people owe me favours that hopefully it'll be back in service soon(ish). Either that or resurrected as a doorstop.

soundman
31st July 2005, 10:19 PM
It might be worth trying to order a replacemnt part for the bent bit.
You've nothing to lose :D