Myford thread

[AnsisParticipant @ansis]

Hi,

I recently bought ML7 lathe, but then soon after I got Super 7 an offer I just couldn't refuse. Super 7 came with various chucks and faceplates. problem with super 7 was that the spindle thread was damaged and thread on 4 jaw chuck was also visibly damaged 3 jaw chuck threded on all right but not perfecly, rather tight, faceplates and catchplate was threding on couple of spins and then it gets really tight. I didnt try to force anything, I replaced the spindle.. bought used spindle, which seems to be in fairly good condition.

Now 3 jaw chuck threads on perfectly (one which came with my s7, not original but HBM), but still none of my Ml7 chucks fit my Super 7.. maybe the old ML7 3jaw chuck but it also gets really tight towards the end. Although everything fits Ml7 spindle.

Does it means I got bad replacement spindle?

If so would it be possible to correct the tread? If yes, then could someone assist me on dooing it, as I have no experience on thread cutting, I have set of gears tho.

Any suggestions?

Thanks

[AnsisParticipant @ansis]

[John HaineParticipant @johnhaine32865]

You might be able to get a split die – thread is 1.125x12tpi – from Tracy Tools for example. That might allow you to very carefull remove just a tiny bit of metal to free the thread?

[Martin ConnellyParticipant @martinconnelly55370]

A set of thread gauges would be a useful tool to have. As well as checking what you have now they will come in useful in the future as well. Look for 55° Whitworth form, 60° Unified form and 60° Metric form. If you can get a chuck on to the point where you can do some work consider making a dummy spindle nose in aluminium that you can use to check backplates and faceplates without risking damage to the lathe's spindle nose. A dummy spindle nose is also useful if you want to machine your own backplates or faceplates.

Martin C

[JohnFParticipant @johnf59703]

Some close up photo's of both your spindles would probably be useful. Assuming your replacement spindle is an original Myford product it is extremely unlikely that the thread is at fault unless it too is damaged ?

My first thoughts are to suspect the threads and registers on your various chuck backplates, particularly when they have possibly been damaged when fitting to the damaged spindle you removed ?

I would no consider using a die on the spindle either because they are hardened, making a thread gauge and a plug gauge for the register are very worthwhile projects BUT you must make them to the correct spec and be as accurate as possible !

John

By the way where in the world are you ?

Edited By JohnF on 28/02/2023 13:34:36

[BazParticipant @baz89810]

Instead of buying a die I would buy a tap and run it into all the chuck backplates. I would be very wary of running a die down the spindle thread, you could easily wreck it, I would examine the spindle threads with an eye glass and very carefully stone any damage.

[Harry WilkesParticipant @harrywilkes58467]

Posted by Baz on 28/02/2023 16:20:30:

Instead of buying a die I would buy a tap and run it into all the chuck backplates. I would be very wary of running a die down the spindle thread, you could easily wreck it, I would examine the spindle threads with an eye glass and very carefully stone any damage.

I did what Baz suggested when I got my S7 it came with two 3 jaw chucks one of which was not the original and ot would not screw on I purchased a tap Chronos I think ran the tap through the back plate and it fitted a treat

H

[Tony Pratt 1Participant @tonypratt1]

I wouldn't buy a tap or die, just careful inspection should reveal where the 'problem' is, then bring out the files.

Tony

[Howard LewisParticipant @howardlewis46836]

When changing a chuck, I always clean both the internal and external threads with a toothbrush.

A tiny bit of dirt can make screwing on a chuck difficult if not impossible.

By all means, use thread gauges to check the Whit form 1 1/8 x 12 tpi thread on the Mandrel,. It may be that it has one or more bruises. These can be removed, ideally with a Whit Form thread file,or by very careful use of a small tringular or half round file.

BUT be very careful., and check frequently.

Howard

Edited By Howard Lewis on 28/02/2023 20:57:58

[Don CoxParticipant @doncox80133]

As mentioned above, a light touch with a thread file might clean off any "bruising" present, it has worked okay for me on my Myford ML7. I have three, metric, BSW/BSF and UNF/UNC and have used them to clean damaged automotive threads and others over the years.

Don Cox

[HopperParticipant @hopper]

If it screws most of the way on and then gets tight, it could be binding on the register collar, not the thread. Inspect for dings and bruises and file or stone any high spots or burrs down, on both spindle and chucks. A three-sided file can be made into a scraper to go round the edge of the register recess in the chuck, which is where most burrs occur.

Carefull inspection and careful use of a very small triangular file or knife file or proper thread file can likewise fix most thread dings and burrs.

And there are production tolerances on those parts. Maybe the register collar is just a few tenths of a thou too big and needs cleaning up with some emery. But don't try that unless you are 100 per cent sure that is the problem. Its more likely there are burrs and dings with raised edges causing problems. .

Edited By Hopper on 01/03/2023 03:49:51

[AnsisParticipant @ansis]

Oh wow so much helping tips! Thank you all!

Actually while I was writing the post, ideas of what could be the issue arouse and while I waited for post to get verified I did have a closer inspection of threads.. and I noticed that the crest, especially towards the end, were kind of leaning towards headstock, so I grinded one side of three sided file flat so it files just one side of flank, set the lathe to run very slowly on backgear and carefully filed the bruising off and it worked! I just couldn't stop scrolling with great satisfaction my 4 jaw chuck on and off!

Posted by Martin Connelly on 28/02/2023 10:46:30:

A set of thread gauges would be a useful tool to have. As well as checking what you have now they will come in useful in the future as well. Look for 55° Whitworth form, 60° Unified form and 60° Metric form. If you can get a chuck on to the point where you can do some work consider making a dummy spindle nose in aluminium that you can use to check backplates and faceplates without risking damage to the lathe's spindle nose. A dummy spindle nose is also useful if you want to machine your own backplates or faceplates.

Martin C

I used to have thread gauges but with moving I have lost them. Definately will get them. Thanks Martin

Posted by JohnF on 28/02/2023 13:34:05:

Some close up photo's of both your spindles would probably be useful. Assuming your replacement spindle is an original Myford product it is extremely unlikely that the thread is at fault unless it too is damaged ?

My first thoughts are to suspect the threads and registers on your various chuck backplates, particularly when they have possibly been damaged when fitting to the damaged spindle you removed ?

I would no consider using a die on the spindle either because they are hardened, making a thread gauge and a plug gauge for the register are very worthwhile projects BUT you must make them to the correct spec and be as accurate as possible !

John

By the way where in the world are you ?

Edited By JohnF on 28/02/2023 13:34:36

Thanks for reply John. It turns out that replacement spindle had the same problem that the original, not so bad but still.. seller said it has good thread etc. and generally I like to trust people but Im not complaining it was just £50 compared to new one to for £300. at the moment I'm in Bristol.

Posted by Harry Wilkes on 28/02/2023 16:47:03:

Posted by Baz on 28/02/2023 16:20:30:

Instead of buying a die I would buy a tap and run it into all the chuck backplates. I would be very wary of running a die down the spindle thread, you could easily wreck it, I would examine the spindle threads with an eye glass and very carefully stone any damage.

I did what Baz suggested when I got my S7 it came with two 3 jaw chucks one of which was not the original and ot would not screw on I purchased a tap Chronos I think ran the tap through the back plate and it fitted a treat

H

Thanks Harry and Baz for replies, this tab would definitely be handy for Myford user, but I have heard they are a bit pricy.. probably like everithing in engineering I'll check chronos one.

Posted by Tony Pratt 1 on 28/02/2023 17:24:00:

I wouldn't buy a tap or die, just careful inspection should reveal where the 'problem' is, then bring out the files.

Tony

Thanks Tony that was just what I did, and it worked.

Posted by Howard Lewis on 28/02/2023 20:56:34:

When changing a chuck, I always clean both the internal and external threads with a toothbrush.

A tiny bit of dirt can make screwing on a chuck difficult if not impossible.

By all means, use thread gauges to check the Whit form 1 1/8 x 12 tpi thread on the Mandrel,. It may be that it has one or more bruises. These can be removed, ideally with a Whit Form thread file,or by very careful use of a small tringular or half round file.

BUT be very careful., and check frequently.

Howard

Edited By Howard Lewis on 28/02/2023 20:57:58

I always feel too picky when it comes to metal shavings on lathe I use compressed air gun to clean the threads but then Im afraid to blow on brass bushings, not to blow something in there. What are your thoughts on cleaning with air? I have seen people blowing with air all over the lathe. Thanks for tips Howard

Also thank you Hopper and Don for tips

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