New Chuck won’t screw on

I decided to fit a new Chuck to my ml7, being a relative newcomer to precision work I opted for the easy way of purchasing a Chuck complete with fitted backplate. Well it will only screw on half a turn, told supplier only to be told that they are machined on a myford and then checked on two other spindles to check fit. When looking at the thread on my backplate you can see a full turn of the thread before it is fully formed, but on the new one the full thread is formed at just over half a turn. If anything I would have thought my spindle thread would be worn not larger than original, any thoughts please.

Thanks Richard

Richard

do you have thread gauges to check that your new backplate has the same tpi as your spindle?

if not a piece of blutack or plasticene on your finger will make an impression so you can check against your spindle

Edited By Ian Parkin on 21/07/2021 17:16:25

A picture paints a thousand words. In the meantime check both threads are completely clean.

Tony

Hi Richard firstly may I say I've purchased two back plates from different companies and neither have screwed on my S7, what would help members to advise you would be a photo if possible and in the meantime make sure the thread on your ML7 is clean and undamaged also would you like to tell us the company who supplied your chuck.

H

I am trying to post two pictures and a video of me trying to screw on the Chuck but am struggling, just reading the info on posting pics. I have done the thread impression and it seem to be the same tpi but I don’t think it’s cut deep enough.

Edited By Richard Jarvis on 21/07/2021 17:46:27

Right it says file for video too big, but I managed to do pictures, I have marked the start of thread with pen it starts at 12 o’clock position and my chuck is a full turn to form the thread whereas new chuck seems to have it formed just after half a turn. The way I have written that is not very clear hopefully you can decipher my poor explanation. I have managed to post the same picture twice but I can’t see how to delete the second copy.

Edited By Richard Jarvis on 21/07/2021 18:07:17

All backplates that I have bought from non genuine suppliers have needed work!!!

The Chuck on the left is the new one, the first thread is nearly square but on my old one on the right it seems to be formed correctly or does that not matter. I found a thread gauge and they both read at 12 tpi but I am sure the gauge hits the top of the threads on the new chuck but I think the gauge has a small gap between it and the top of the thread on the old one, I think the thread is not deep enough.Thanks Richard 

Edited By Richard Jarvis on 21/07/2021 18:40:14

Edited By Richard Jarvis on 21/07/2021 18:42:43

You will all be getting fed up with me now, only one picture downloaded, here goes this is the new Chuck.

Thanks Richard

Without mentioning where it came from, they should know how to make the backplate fit a myford.

Hi ,I had the same problem with a backplate for an ML7, I bought a tap ,tapped the hole and backplate went on ok by hand

Maurice

Richard, check your inbox I have sent you a message

Peter

Snap that's what I did with the one's for my S7

H

I think you need to speak with a supervisor, rather than the ‘phone answerer’, for a more sensible response to a customer problem with their product.

I have a new plate somewhere that will not go on more than a couple of threads. Best of luck getting it sorted out.

Steve.

If I were making backplates for a living I'd use something more 'industrial' than a Myford. Don't get me wrong I'm on my second, but only as a hobby

Not that this helps, but the backplate I bought from RDG/Myford fits lovely. If you divulge your approximate location there might be another Myford owner near you and you could try it on their machine. With a bit of care you can do this Covid secure

Edited By duncan webster on 21/07/2021 22:23:50

Edited By duncan webster on 21/07/2021 22:24:25

This seems to be a common fault, I sent them some pictures earlier so I will see what tomorrow brings. Thank you for the replies.

Richard.

Thanks I’m in Orkney, I did not realise that was not shown. I have tried two face plates and a spindle nut from an Amollco mill so am sure it’s not my spindle at fault because they all fit ok.

Richard.

Maybe the thread needs to be truncated by a couple of thou, to prevent root / crest interference?

Put a substantial bar into an existing chuck.

Skim to obtain a concentric diameter.

Clamp the new chuck to the bar.

If the chuck on the mandrel is a 4 jaw, clock the register of the new chuck and centre as accurately as possible..

Skim the thread of the new chuck, to take out just a thou or so.

With a thread depth of 0.053", the core diameter should be 1.019", so you are looking to enlarge the ID of the thread to about 1.022 / 1.023.

Possibly, before you start work on the new chuck, turn up a piece of bar to 1.022/3" to use as a plug gauge.

Hopefully, the truncated thread will allow the chuck to screw fully onto the mandrel.

Howard  WHY do I only spot the typos after posting?

Edited By Howard Lewis on 22/07/2021 09:31:40

.

That’s the disappointing bit ^^^

Supplier needs to understand GO/NOGO gauging

MichaelG.