Loose Chuck Check

[CHJ]

Dave, with reference to your sketch no. 1.

The chuck should align on the collar (2) as you have drawn but pull up tight to the shoulder (1) and not bottom in the thread socket at (3)

The transition between (1) and (2) on the spindle nose should be machined at a perfect right angle and is the basis for true alignment. This then renders thread form discrepancies and in use damage as insignificant.

Some chucks have scroll mechanism exposure at (3) so clearance is essential.

 

[wcndave]

Ok, in the shop with feeler gauges and a ruler now.

Assuming my second picture with the black block is how it should be, when it's fully tightened there is a gap between chuck and "black blob". .2mm smallest and 0.65 largest. The coved register between threads and black block is 33.89 at widest part. The chuck had internal smooth pre threaded part of 33.93.

So even were I able to get it tightened at the back with zero clearance all around, nothing is going to centralise the chuck. Hence my feeling that either the threads or register should offer a tight fit?

 

[wcndave]

Dave, with reference to your sketch no. 1.

The chuck should align on the collar (2) as you have drawn but pull up tight to the shoulder (1) and not bottom in the thread socket at (3)

The transition between (1) and (2) on the spindle nose should be machined at a perfect right angle and is the basis for true alignment. This then renders thread form discrepancies and in use damage as insignificant.

Some chucks have scroll mechanism exposure at (3) so clearance is essential.

So I do have clearance at 3, however still fail to see how the difference in register and internal chuck diameters means I can have a centred chuck. Even so,I cannot get the chuck to sit flat against shoulder (1)

 

[12345Peter]

I have a Patriot chuck bought with an insert 24mm x 3, the chuck fitted well to the register, but had a pronounced wobble. I have just bought a Union Graduate that came with a Patriot and instead of a direct threaded chuck of 1 1/2 x 6 it came with an exsert that fitted to the headstock spindle and the chuck screwed onto that. There was no wobble that I could see, so I put my other patriot on it and that has a wobble, albeit not as much as when on the other lathe. When I have time I am sending it back.

 

[wcndave]

Further attempts show that the wriggle room means I can move through the right setting until the last turn, which pulls the chuck tight against the headstock at an angle. I can feel it forcing the angle. So either the depth of register is to great and I just hit the threaded part if the chuck too soon, or one is not machined right. I have put the supplied 10 cm faceplate on and that runs true, so next port of call must be toolpost I think. Thanks so much for all your input so far!

 

[CHJ]

The above is the ideal location areas so that the thread does not have an influence other than holding the chuck against the spindle face.

 

[myturn]

I've been out and taken some measurements. All my chucks are M33x3.5mm, so-called "German" type.

Conclusion:

The VM100 chuck is made to much finer tolerances. I have 4 of them and they are all consistent and as true as I could ask of a woodturning chuck. Two of them are direct-threaded and two have inserts but they are all as accurate as one another.

The Patriots (of which I have 3) are a lot less consistent, the one I used here is the most accurate, they all exhibit significantly more runout than the VM100s. They are all direct threaded. I had one exchanged that was wildly out and quite unacceptable. These 3 are acceptable but reverse-mounting on them still introduces some wobble on the wood despite taking great care in sizing spigot or recess.
You may notice I have machined the rear of the chuck to take a Vicmarc lock-ring, that is not standard on the Patriot.

Don't expect perfection from the Patriot !
But don't accept wild inaccuracies either.

 

[CHJ]

Looks like your 25 thou. min. clearance on the collar radius (50thou on diameter) means that the patriot is relying on the thread form to hold it central.
Not very significant for a lot of jobs but a real pain if you get a slight catch that moves the chuck a fraction or wish to reverse an item when the alignment will be a bit hit and miss.

 

[myturn]

Looks like your 25 thou. min. clearance on the collar radius (50thou on diameter) means that the patriot is relying on the thread form to hold it central.
Not very significant for a lot of jobs but a real pain if you get a slight catch that moves the chuck a fraction or wish to reverse an item when the alignment will be a bit hit and miss.

Is that not normal then?
Even the VM100's have play between the two register faces which is only eliminated once the rear face of the chuck is up against the headstock nose. Yet they run perfectly true and never move out of alignment during use, even in reverse rotation.

 

[boysie39]

I feel sorry for anybody with this problem re chucks .I had this problem with a lathe I had some years ago .
I got a direct thread chuck with the lathe when I wanted another chuck some time later I could only get one with an insert, thats when my problems started . Even now if I were to buy a chuck it would be supplied with an insert .
I have four chucks 2 Supernovas an Axminster K 10 and a Versachuck from The Toolpost. My go to chucks are direct thhread Nova and Axi. K 10 other two are for rough work .
Mike ,has a point about VM chucks everybody around swears by them ,more expensive but you get what you pay for.
Sorry Dave I know this wont help you with your problem ,but if you have a dedicated spindel thread why cant you buy a dedicated chuck to fit that thread , the answer is greed they sell you a insert and get another few quid out of the punter .
If it were possible I would send the lot back lathe and chucks .

 

[CHJ]

Looks like your 25 thou. min. clearance on the collar radius (50thou on diameter) means that the patriot is relying on the thread form to hold it central.
Not very significant for a lot of jobs but a real pain if you get a slight catch that moves the chuck a fraction or wish to reverse an item when the alignment will be a bit hit and miss.

Is that not normal then?
Even the VM100's have play between the two register faces which is only eliminated once the rear face of the chuck is up against the headstock nose. Yet they run perfectly true and never move out of alignment during use, even in reverse rotation.

Unfortunately it becomes the norm because the lathe manufactures and the chuck manufactures don't hold tight enough to the specifications, erring on extra clearance rather than risk binding. Why else would it be in the design of a wood lathe spindle nose if it was not there to provide as good an alignment as possible. Given that it is not possible to machine a chuck register in situ as you would normally do on a metal working lathe.

Admittedly works fine for most woodturning as long as both lathe thread and chuck thread are good. Get one of them made at the lower end of the quality spectrum and we see folks having lots of aggro.

I have poolwood that has a no longer catered for spindle nose collar diameter. (see the diferences TO2 -TO2P)
My main user Axy precision chuck and faceplates etc. are of an age that they have the correct back plate and I have spares, and can turn my own if necessary.
My 125mm Axy chuck does not have the correct collar register and relies on the thread angle for centralizing but is well made and a reasonably close tolerance thread and does not give me any problems in use as long as I make sure the threads are clear of debris.

Another (unknown by me as to make) chuck I have does not have a suitable register but a slim line stepped adaptor collar takes care of keeping it true.

 

[cambournepete]

I tested one of my Stronghold chucks and there was very little wobble once it was screwed on a couple of turns and none at all when screwed on completely.
My Sorby eccentric chuck is a much looser fit, although it doesn't wobble when screwed on properly.

 

[wcndave]

Sorry Dave I know this wont help you with your problem ,but if you have a dedicated spindel thread why cant you buy a dedicated chuck to fit that thread , the answer is greed they sell you a insert and get another few quid out of the punter .
If it were possible I would send the lot back lathe and chucks .

Well, i) the chuck I bought is dedicated insert to match the lathe to avoid issues of adaptors / inserts, and ii) i thought the sorby was sort of the rolls royce of chucks. if £160 does not buy one a decent chuck with just the one set of jaws included, then one's looking at a mortgage to get a decent lathe and chuck set + various jaws and bits and pieces...

I will ask toolpost what they think, but again, amazing response from my friends on the forum, thank you all!!

 

[Noggsy]

I'm lucky in that I don't have any issues with the chucks that I have (K10, K8 and Multistar), but I have still read this entire thread, because this is what I love about this site...people trying to help and being interesting and informative whilst doing so. Nice one to all involved, I've learned things which may help me in the future and enjoyed the usual banter.

 

[cambournepete]

I will ask toolpost what they think...

It's the Toolpost show tomorrow and Saturday, so you might not get a very quick response this weekend.

 

[paulm]

Thanks for mentioning that Pete, I might make a trip over there tomorrow.

Would have missed it, yet again, as they don't seem to have any email distribution list or mailshots, and as I don't bother with the mags these days I never know they are on unless I happen by the website......

Sorry for the hijack Dave !

Cheers, Paul

 

[wcndave]

Thought a close up of the lathe thread might help.

I have all the dimensions, however left in the workshop, doh!

 

[CHJ]

Looks as though the locating collar is just fractionally greater diameter than the thread.

I believe the grove in the locating collar is to allow a chuck securing grub screw to engage without causing any location disrupting burrs.
Why one would do that on a lathe that does not have a reverse facility as far as I know is a bit of a mystery unless the component is common across differing lathe models.

The spindle nose has a Tomy bar or C spanner hole to aid in removing faceplates etc.

 

[wcndave]

Yes, I don't have a c spanner that goes with this. I was wondering if the threads in the chuck were just touching the locating collar, causing it to twist at the last moment. however having taking some rough measurements it seems there should be room..

 

[myturn]

referring back to a previous post you said....

Assuming my second picture with the black block is how it should be, when it's fully tightened there is a gap between chuck and "black blob". .2mm smallest and 0.65 largest. The coved register between threads and black block is 33.89 at widest part. The chuck had internal smooth pre threaded part of 33.93.

If as you say there is a gap between the rear of the chuck and the vertical face of the headstock nose (the black blob) the chuck will not be held in place nor will it be held straight. It would seem, as I believe someone has already mentioned, that the nose thread is bottoming out in the chuck.
To verify this put some paint on the inside face of the end of the threaded part of the chuck and test-fit to see if any paint comes off on the headstock nose.

One possible remedy is to file/grind a bit off the end of the headstock nose. (hammer)
Then, assuming the chuck is correctly machined, it should tighten up flat against the "black blob".