Locking on a threaded chuck ?

a very good possibility indeed ...perhaps a pinching collar with more than one bolt might help in that regard eh ?
.....
Bob.......
 
That's a good idea, just a note about my Clausing that has 1.5" x 8 tpi spindle threads. I have mounted it by rapidly spinning it by hand that I had to use a 12" Cresent wrench on a jaw to loosen it. On another occasion I spun it in reverse about 1/3 turn against a wood block on the back way. Hopefully some experienced hands will get involved with what I have done to the register. After checking to see that the cross slide dove tails are running at right angles to the spindle I took a light cut on the register. I did this over 20 years ago and think the cut was 0.002" with a really sharp HSS bit.
Have a good day
Ray
 
i took the 6" 3 jaw chuck off the logan 922 yesterday just to see how hard it was on there.... I put a 12" crescent on one of the jaws after tightening them together in the center, and had to hit it fairly hard with the palm of my hand to pop it loose.... I also put it in back gears but not "locking it in backgears ( there is a big difference! that will snap off teeth on the bull gear!!!!! ) but the resistance to turning the motor was enough to make one hard hit pop it off !..... I thought it would be much harder to take off than that....
putting it back on I threaded it on and turned it on till it stopped by hand and noted the position of it.... backed it off and gave it a really hard spin and let it bang to a stop.... the chuck went about 1/4 turn more than I could tighten it by hand.....
and with all my playing around in reverse and all I have yet to make it come loose yet !
this time I did not put oil on the threads..... last time I did..... because I wanted it to stick on there hard.... I just hope I can get it off when I want to now ! LOL.....
i don't know what the size is on the spindle , but I think it is 1.5" it's thread pitch is unknown as my gauge doesn't go that big ! LOL...
( probably 8 tpi as well )
catch'a later Ray !
Bob.....
 
Bob Kelly III said:
, and had to hit it fairly hard with the palm of my hand to pop it loose
Click to expand...
Bob , I would suggest using a soft hammer rather than your hand , you'll thank me in the years to come . Sounds like you're making progress . :encourage:
 
Well My conclusion on "locking on a threaded chuck " idea is this ....
to me it is my humble opinion that it is far easier to drill a hole through the chuck back plate and into the spindle.
go through the spindle wall, into the inner through hole of the spindle
and if your going to do this you just as well use a big enough bolt to be worth doing..... I'm thinking 3/8" for the smoothed down trimmed end of the bolt that will set in that hole in the spindle bore probably a grade 8 bolt should be used ....
my idea would be to take a grade 8 bolt probably the size that fits a 1/2" end wrench or 9/16".... drill the hole through the chuck back plate, and touch the spindle take the chuck off and check where that hole would be.... making sure it doesn't interfere with the chuck register or threads....
i was thinking a 1/16" drill for this exploratory surgery (as there may not be enough room to do this without messing up the entire spindle !)
the hole will no doubt be back as far as physically possible, and still have room for the threads to be tapped into the back plate
no doubt a allen headed bolt would be a good choice here as milling a flat area on the back plate for the tapped hole...
the hole in the spindle wouldn't need to be any larger than the end of the bolt/pin but, it needs to go all the way through so it does not bottom out in the hole and twist the chuck out of true.
it's possible that if the chuck register is in the way on the spindle and where the hole resides, and that it could be done in front of the register... near the end of the threads.....but that is not my first choice....i am fairly certain there is room behind the register for a hole there.
this method would lock the chuck on in either direction as the only way to get it off without taking the bolt/pin out is to sheer the bolt off.
and with all the torque developed in the lathe in back gears that could be a problem so a big enough bolt/pin to handle that torque should be used
.......
Myself I would want the bolt to go all the way down and set on a lock washer, but you could use a longer bolt and put a locking nut on it....
though how you would turn that locking nut is another problem... maybe with a crow foot on an extension....but space is very limited between the chuck and headstock.
......
Yes that means drilling a hole in the super expensive spindle... and that in itself may well take a carbide drill bit !
but if it fixes a dangerous problem on the lathe I am all for it
.... putting another chuck and backing plate on the lathe and marking where that hole needs to be in the backplate of the new chuck would have to be approached very cautiously ! no doubt ! perhaps sprey paint inside the hole through the chuck and using a flexible tube, sprey the hole ...would mark it on the inside....of the back plate...... i dunno... that is problematic at best.
....
As long as the pin is centered in the hole it will not exert any misalignment to the chuck.
however, if all of a sudden your run out changes drastically the chuck probably tried to come off .... pull the bolt/pin and tighten the chuck and put the bolt/pin back in. it's there to prevent the chuck coming off and landing on your foot or worse ... that heavy thing spinning at 300 rpm could do a person a lot of damage before all is said and done if it came off there and got ya !
....... it's not the ultimate cure to the problem, but may well be able to stop the chuck coming off in reverse.
.....
Myself, I will wait and see if it needs this modification or not.... so far I've not had a problem threading in reverse with my chuck coming off.
.....i hope I am just worried about nothing !
Bob.........
 
Why not drill and tap the hole in the chuck and drop in a dollop of copper to cushion the point of the set-screw against the spindle?
I've seen this done in other applications and may work here.
 
Honestly, if the manufacturer didn’t see a need for this what application will you be doing that requires it?

Waiting is a good idea, I always try to think about the next person to get my stuff and what would they think about modifications I did. If you really do have the need then just drilling the back plate doesn’t mess with the spindle, there are plenty of materials that will work beneath a set screw to prevent thread galling. JMHO


John
 
Whenever a need comes up to run the work in reverse, I use a 5C collet. So far, I have not needed to run anything in reverse that was big enough to require using a chuck. And they make 3 and 4 jaw chucks with 5C shanks if the need ever arose to go bigger.

I'm not going to part stock much bigger than 2". The only other thing I would entertain for turning in reverse is for metric threading to a shoulder. That can also be done in forward.

Best Regards,
Bob
 
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well, the problem with just putting in a set screw into the back plate of the chuck is that it will force the chuck out of true and you don't want to INCREASE the runout of the chuck.... which that would do.
.....I would even go as far as drilling a hole all the way through to come out the other side of the back plate to remedy this problem....
but ....it really doesn't seem to BE a problem at all.... so I will wait !
you can't have the chuck coming off... that is very dangerous for you and the machine....but as long as the potential for it to come off exists ....the potential is the problem...even if it never does.... you'll approach the machine not knowing if the chuck will come off today or not.... and that just takes away all the fun ! I want my lathe as safe as possible...within reason.... I see no need for a chuck guard or safety switches on/off is good enough
though a stout brake to stop the chuck immediately would be a good addition.
....
to me the best answer is what I have already outlined here.... I think considering all the options it is the easiest and arguably the best solution.
the second best would have to be the locking ring machined in a groove into the back plate. but that could still unscrew....
i've had an arrangement like that on a bush hog on my tractor, drive line a pieced together nightmare ...that was supposed to cure it from unscrewing
it didn't at all, i ended up welding it and that cured it !
....
Bob........
 
Bob Kelly III said:
well, the problem with just putting in a set screw into the back plate of the chuck is that it will force the chuck out of true and you don't want to INCREASE the runout of the chuck.... which that would do.
....
Bob........
Click to expand...

What if you turned a Brass (or other soft non marring metal) ring that would fit perfectly into the non threaded space that completely surrounds the spindle so that it in and of itself was a snug enough fit to keep the chuck in place and then lightly lock it down with the set screw to be sure? You will most likely need to split the brass Ring bushing to get it into position but that shouldn't be a problem....id probably make the cut diagonally though im not sure if that would matter or not but my inner voice says it does!
 
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