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Loose Chuck Check

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wcndave

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Something is not quite right here...

I have a 33 dedicated richard sorby chuck. I have a european Scheppach DMT 450

lathe.JPG


chuck.jpg


However if you watch the video, you'll see I appear to have significant wobble, and it's not a wobble chuck!

http://youtu.be/HNx3IBrPqq8

Before I go back to the toolpost, given it's taken 2 weeks and international delivery to get here, I thought I would seek out some opinions here...
It appears to be the diameter of the chuck that's wrong, not the TPI...
 

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chipmunk

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Hi Dave,
The looseness of the threads is not a big deal provided the back of the chuck can be tightened so that the back is flush against the step on the lathe shaft at the back of the threads.

If the chuck is still not running true when this happens then you have a problem but the video doesn't seem to get that far, does it?

HTH
Jon
 

wcndave

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I get the chuck on all the way, hence some video wobble while i try to hold the end with my elbow ;-)

However the first time i put on, i simply tightened fully (by hand, there is no other way), and it's not true at all.

I would have thought the threads would match pretty well, however if not, then the back of the head has to be exactly perpendicular, and also how would one center the chuck? gravity would have it down so that it runs parallel to bed, however in a loop...
 

jpt

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The wobble as the chuck is put on is normal and nothing to worry about.

The important bit is that the back of the chuck fits tight against the back of the register on the lathe. Looking at the video this doesnt happen and there is a small gap this is why you are getting wobble, make sure the thread of both the spindle and the chuck are clean and try it again and the two faces should meet as this is what makes the chuck run true.

If there is still a gap get back on the Toolpost and make sure they have sent you the correct insert, as there are different ones for M33 x 3.5 lathes.

Another thing to try is make a washer to go between the chuck and register out of a plastic milk bottle or similar.

john
 

chipmunk

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Oh hell Dave,it sounds as if you do have a problem but it could be lathe or chuck.

The Axminster catalogue has a diagram of the spec for a M33 x 3.5 spindle (T38). I would try measuring the lathe with some vernier callipers to see that it looks right. The thread pitch should be 3.5mm and the diameter of the threaded potion should be close to 33mm.

That may help you establish if it's the lathe or the chuck.
HTH
Jon
 

wcndave

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Thanks for speedy responses!

jpt":2m4428d4 said:
The important bit is that the back of the chuck fits tight against the back of the register on the lathe. Looking at the video this doesnt happen and there is a small gap this is why you are getting wobble, make sure the thread of both the spindle and the chuck are clean and try it again and the two faces should meet as this is what makes the chuck run true.
What i don't get is why a back registration is what's required. Imagine a deliberately exaggerated example, of hanging a hula hoop on the lathe. it could be as tight against the back as you like, however it's not going to run true...

or do you mean that the chuck should cover the lathe stock, ie that the lathe goes inside more than just the threaded part?

jpt":2m4428d4 said:
there are different ones for M33 x 3.5 lathes.
again slightly confused, as this must be "a size", is M33 different from 33? I ordered this online so any error is my fault, however i felt quite confident when I saw they had the 33 instead of the popular 8 and 16 versions...

The threaded portion is about 32.8mm, my calipers do not reach, however the deepest part, of the threaded portion of the chuck seems to be about 38mm

I now have 2 chucks for this lathe that do not fit, having ordered a different size a year ago when mistakenly looking at the UK version of the lathe online :(
 

myturn

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That's not right, from the video you have a significant runout, as though the internal thread is not parallel to the chuck body.

I have had exactly the same problem with a Patriot from Toolpost so send it back and ask them to send one that works properly. When I did this the replacement came direct from Sorby.
 

chipmunk

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The M in M33 just means metric thread and a pitch measured in mm rather than a TPI (teeth per inch).

The back registration makes sure that the chuck axis is parallel to the lathe bed but there is also an unthreaded register on the spindle behind the threaded part which should mates with a similar unthreaded part of the chuck before the thread begins when looking at the chuck from the back. In this case it should be 33mm diameter I think.

Jon
 

CHJ

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I must say the clearance on the thread form seems excessive to my eyes but as said by others not a killer if the chuck rear collar and the spindle nose step mate correctly to align the chuck.

I suspect that the spindle nose is bottoming on the bottom of the chuck threaded socket. (I.E. To long for the recess)

Fitting a washer as suggested would overcome this but looking at the video I'm afraid it will hold the chuck away from the spindle nose location collar and you will be relying on the threads alone to align the chuck.
Not something I would like to put my money on not moving under load such as a catch with threads with so much clearance.
 

chipmunk

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I agree with Chas and your measurements of the thread diameter on the lathe at 32.8mm suggest that it's the chuck that's at fault.

Mick's experience seems to suggest that Sorby have "form" on this issue.
Jon
 

wcndave

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looking at the post i made when i got the 1" 8TPI (the other wrong chuck for this), the one thing that's missing is the picture of my spindle. However we seemed to come to the conclusion that it was a standard T38. Mine is 33. I have not seen anything advertised as T38, so how do I know which flavour of 33 I have got, and whether that is available.

in my case the register is about 40mm, and there is no recess in the chuck for that.

Mick, I think the runout is due to simple tightening against the back whilst having huge wobble due to the threads having lots of "wiggle room", so where i reach when it's tight is arbitrary. I can see how this is the case in my head, hard to explain, however the chuck being "properly made" is irrelevant at this time :-(
 

chipmunk

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Hi Dave,
Looking at the video, your spindle seems to have a half-bead and a full bead between the reference face and the start of the threads.

If these are 33mm diameter then they will act as a diameter reference (as unthreaded portion) for the chuck. It may be that the Sorby chuck's 33mm diameter register is somehow not compatible with this form of shaft?

Jon
 

CHJ

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AxminsterThreads.jpg


The above is an image from an earlier Axminster catalogue, the current one does not have some of the older forms listed.
 

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wcndave

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Trying to clarify,

from the axminster picture, i added a red line where the chuck is, this would make sense, that the register keeps the chuck central and true, and the back of the register does nothing really to align. I have put arrows to what i think is the "aligning factor"

chuck1.jpg



In my case, the register is wider than the threads, so the chuck "stops" there, you have slop in the threads, and I am simply friction tightening against the big black part. nothign i can see in this picture keeps the chuck true...

chuck2.jpg


So question is, what chuck do i need to ask sorby for?
 

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wcndave

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Chas just beat me to it with the catalogue page... i wish i'd never got this lathe, nothing but problems, an M2 taper light pull friction centre is the only thing i have bought that fits! And that's despite spending over £400 on accessories so far :cry:
 

jpt

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There are several parts that make up a spindle as can be seen in the diagram below which comes from the Axminster catalogue.


3 = M33
5 = 3.5

These two measurements are common to all M33 x 3.5 spindles where the difference comes is in the other measurements. Unfortunately there is no standard for lathe spindles so manufacturers do their own thing. If you look at the Toolpost site on this page http://www.toolpost.co.uk/pages/Chucks_ ... _data.html you will see they list 5 different M33 x 3.5 references for different lathes. The difference is down to different manufacturers using different measurements for parts marked 1, 2 & 4 in the diagram above. If any of these measurements on your chuck dont match your lathe the chuck wont fit properly.

john
 

paulm

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Try calling Peter at The Toolpost, he has an engineering background and is a good guy and will want to help rectify the situation I am sure.

Hope you get it sorted, must be very frustrating, especially with the extra delivery time !

Cheers, Paul
 

wcndave

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mm, i went here,
toolpost.jpg

and just selected the 33 directly threaded, it does not state there are further options.

The page you put link for at toolpost doesn't specify which of the other measurements equate to which of the other types of chuck....
You think i am best to send them a picture / diagram with dimensions on?

Thanks Paul, one reason why my mitre problems thread was perhaps more vitriolic than normal, just had everything go wrong all day.... I'll have to get a job instead to take up my time ;-)
 

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myturn

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My Patriots wobble the same as yours when I thread them on. It is not until the back of the chuck hits the nose of the headstock (part 1 in your diagram) that it is secure and correctly located. So the register in my chuck bodies is not a tight fit over the register (part 2) on the headstock, but rather a loose fit.

Assuming that the larger diameter register on your headstock is true then the rear of the chuck should butt up to that in the same way. It is the two rear faces that make the friction contact that stops the chuck loosening during use.

But speak to Peter Hemsley and he will sort you out.
 

flh801978

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A friend of mine had a graduate threaded patriot chuck that was significatly out sorby swapped it over with no quible
 
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