New Chuck won’t screw on

[Richard JarvisParticipant @richardjarvis95040]

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 JarvisParticipant @richardjarvis95040]

[Ian ParkinParticipant @ianparkin39383]

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

[Tony Pratt 1Participant @tonypratt1]

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

Tony

[Harry WilkesParticipant @harrywilkes58467]

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

[Richard JarvisParticipant @richardjarvis95040]

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

[Richard JarvisParticipant @richardjarvis95040]

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

[bernard towersParticipant @bernardtowers37738]

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

[Richard JarvisParticipant @richardjarvis95040]

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

[Richard JarvisParticipant @richardjarvis95040]

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

Thanks Richard

[Richard JarvisParticipant @richardjarvis95040]

Posted by bernard towers on 21/07/2021 18:24:17:

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

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

[Maurice TaylorParticipant @mauricetaylor82093]

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

[FlywheelParticipant @flywheel]

Richard, check your inbox I have sent you a message

Peter

[Harry WilkesParticipant @harrywilkes58467]

Posted by Maurice Taylor on 21/07/2021 19:40:29:

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

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

H

[not done it yetParticipant @notdoneityet]

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.

[SteviegtrParticipant @steviegtr]

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.

[duncan webster 1Participant @duncanwebster1]

Posted by Richard Jarvis on 21/07/2021 16:50:43:

………, told supplier only to be told that they are machined on a myford and then checked on two other spindles to check fit. ………

Thanks Richard

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

[Richard JarvisParticipant @richardjarvis95040]

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.

[Richard JarvisParticipant @richardjarvis95040]

Posted by duncan webster on 21/07/2021 22:23:29:

Posted by Richard Jarvis on 21/07/2021 16:50:43:

………, told supplier only to be told that they are machined on a myford and then checked on two other spindles to check fit. ………

Thanks Richard

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

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.

[Howard LewisParticipant @howardlewis46836]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Richard Jarvis on 21/07/2021 16:50:43:

[…]

told supplier only to be told that they are machined on a myford and then checked on two other spindles to check fit. …

any thoughts please.

.

That’s the disappointing bit ^^^

Supplier needs to understand GO/NOGO gauging

MichaelG.

[Richard JarvisParticipant @richardjarvis95040]

Posted by Howard Lewis on 22/07/2021 09:30:27:

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

Thank you for that but it’s way out of my capabilities at this time, I do believe the problem is the root of the thread and or the fact that the start is not fully formed. I did ask from which side the backplate is threaded from because I think the end I am trying to screw it on from is the finish of the thread and it has not been formed fully.

[Mike CrossfieldParticipant @mikecrossfield92481]

-Are you quite sure that the problem is with the thread? I agree that it is most likely the thread being tight, but I have seen situations where the problem was with the register on the backplate being a tinch (technical term) too small. In fact in the "old days" Myford used to supply chucks with registers which needed to be lightly scraped to suit individual spindles. Since it would be quick and easy to check by knocking up a gauge with exactly the same diameter as that of your spindle, why not try it, if only to rule this out as the problem?

Mike

[Rod RenshawParticipant @rodrenshaw28584]

Richard

Howard is absolutely right but it's possible to interpret his instructions as "The thread is a bit tight and if you can scrape it out a bit it will fit better"

The fit of the chuck, both alignment and concentricity, is determined by the register (The parallel part behind the thread ) and not by the thread itself. So the thread is only there to keep the register engaged and stop the chuck falling off.

So it does not matter much if the thread is a bit of a loose fit as it screws on, it will tignten up as the register engages.. So feel free to poke about and scrape about inside the backplate with whatever you have to see if you can remove a bit of metal and any burrs etc to enable the backplate to screw on. Try not to damage the register.

Failing that, return it to the supplier as not fit for purpose and see if that wakes them up.

Rod

[Adrian DownesParticipant @adriandownes83818]

Before jumping in & modifying a brand new item in the hope that it might work it would make more sense to find the cause of the problem first!

I would suggest good old fashioned marking blue to highlight exactly where its binding.

[Author]

Posts