seized backplate pros and cons
#1
The lathe purchased 2017 at a reasonable price came with a broken bull gear tooth and a seized threaded on spindle back plate on which was mounted a three jaw chuck, the reason for said seizure as can be seen here, although the absence of oil and/or grease on the threads was confirmed later:
    and here    

Being a relative newbie, although i had some experience back around late 1960's at Repco with brake lathes, i took up a course in u-tubing and lo and behold to my amazement i retained enough knowledge offered by the many savants to tread very carefully through this metal minefield. Spindles are precious.

Long story short, my first machining job made sense whilst the spindle's 8TPI 2.25" thread was well and truly seized the back plate.  The project was to make a 1" draw bar (the largest material on hand) in an attempt to wrestle the back plate off the spindle. As it turned out even with one metre (oops one meter - for our American friends) breaker bar on one end and a three meter (i'm learning) piece of 2" dia. thick walled galvanized work pipe on the other end there was no movement no matter what was done. Including using a 1" hex bar mounted in the three jaw 6" chuck and a 1/2" drive rattle gun. But i digress, now back to the draw bar.

For whatever reason occurred to me at the time i resolved to have a right hand thread on one end and a left hand thread at the other end, and with the confidence misplaced by the experience with the back plate decided to undertake the more difficult of the two tasks, that is to turn a left hand thread on a spindle threaded back plate chuck with no other locking mechanism save the seized back plate. So off to the Nuts and Bolts supplier for a 1" nut (about eight dollars two years ago) whereupon I returned with a left hand nut.

Here is the picture of the machined part and said bought nut.    

Unfortunately the draw the draw bar made no more head way than precious attempts so i resolved to do the following, with VERY light cuts:     .

Fortunately the lathe came with a 8.25" threaded face plate and a 8.5" four jaw chuck mounted on its own threaded back plate:
    and    

In home workshop machining of a new back plate for the 6" 3 jaw chuck is in the works. In the meantime the four jaw chuck is used. Need to make the spacers tool jacks and clamp down tools for the face plate but have the dogs and Dividing head for the hole circle holes placement.     and     .

If the back plate was not removed the Head stock could not be dismantled, the bull gear (driving the back gears) could not be repaired and the bearings and seals could not be replaced. (Projects forum - Lathe Bearings and Seals replaced).

Will update this thread as i progress the machining.

john aka castellated nut
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#2
(01-24-2019, 01:04 AM)castellated nut Wrote: For whatever reason occurred to me at the time i resolved to have a right hand thread on one end and a left hand thread at the other end, and with the confidence misplaced by the experience with the back plate decided to undertake the more difficult of the two tasks, that is to turn a left hand thread on a spindle threaded back plate chuck with no other locking mechanism save the seized back plate. So off to the Nuts and Bolts supplier for a 1" nut (about eight dollars two years ago) whereupon I returned with a left hand nut.

If you don't put the left hand thread on the draw bar end, then it will tend to unscrew itself during rotation.  I made a draw bar for my lathe, but that little voice didn't tell me to put a left hand thread on the end.  Once I discovered my error (the nut fell off during operation), I ended up putting a second nut to lock the first.  I intend to remake the draw bar with the correct threads.  I make my nuts from hex stock, so I had to order a LH tap for my thread.

You say that the reason for the seized chuck can be seen in the pictures.  Okay, where?  Did you find swarf under the threads at disassembly?

I take it that you removed the chuck from the backplate, then turned the backplate to dust.  Did you use forward rotation, or reverse?  I wonder if reverse rotation would eventually loosen the remains of the backplate.  

A trick that the British Navy machinists used to use to minimize stuck chucks, was to cut a washer from wax paper or parchment paper (cooking paper) and place that between the spindle shoulder and the chuck.  My spindle thread is the same as yours and it really works.  Mind you that it won't help if there is swarf in the threads and you "power" thru them to seat the chuck.
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#3
SLK001, Welcome to the forum!!!
Logan 200, Clarke 7x12, Index 40H Mill, Boyer-Shultz 612 Surface Grinder, HF 4x6 Bandsaw, ...
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#4
Welcome to the forum SKL001.

Ed
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#5
Thanks, all, for the warm welcoming! I've been metal working for close to half a century. I found this site on a D-D-G search and thought that I should join the community. Where have ya'all be hiding? I had never heard of this place before!
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#6
We've been hiding from all those other places. Big Grin

Welcome aboard!

Tom
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#7
(01-19-2020, 12:04 AM)SLK001 Wrote: D-D-G search

I'm going to show my ignorance but what is a "D-D-G search"? 17428

Ed
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#8
(01-19-2020, 11:33 AM)EdK Wrote: I'm going to show my ignorance but what is a "D-D-G search"?  17428

Ed

Duck-Duck-Go.  It's my preferred search engine.  I refused to be tracked/manipulated by Google (you know, the evil company whose motto is "Don't be evil" (ironic, I know).
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#9
(01-19-2020, 12:04 AM)SLK001 Wrote:  I had never heard of this place before!

I believe Tom once described it as the land of misfits. And he wasn't wrong! Rotfl

Welcome SLK001. (Slick one?) Chin

Big Grin
Willie
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#10
(01-19-2020, 11:39 AM)SLK001 Wrote:
(01-19-2020, 11:33 AM)EdK Wrote: I'm going to show my ignorance but what is a "D-D-G search"?  17428

Ed

Duck-Duck-Go.  It's my preferred search engine.  I refused to be tracked/manipulated by Google (you know, the evil company whose motto is "Don't be evil" (ironic, I know).

OK, I also use DuckDuckGo as my search engine.

Ed
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