Locking on a threaded chuck ?

[Bob Kelly III]

Howdy Guys....and Gals if your out there !
...
I have been contemplating the threaded chuck coming off when using reverse on the motor problem.....
..... I would imagine a simple screw into the side of the chuck adaptor would cure this problem....
but I've never read where anyone has tried that or any results of that idea.
My 3 in 1 from Harbor freight has such a screw in it's tiny chuck adaptor and I have never had the chuck come off on me yet in all the years I've owned it.
.... and I've done some hard work with it in reverse too.... never thinking it could be a problem ! <grin>
....on my Logan it's chuck adaptor is much like everyone else's that has a threaded on chuck a flange that goes out about an inch from the chuck mounting plate toward the head stock..... which is about 1/4" thick and seams quite robust and able to handle a tapped hole
I was thinking of just drilling and tapping for a bolt or allen head grub screw and then drilling a indent into the spindle for the screw to bite into and not mar the rest of the spindle threads.....

has anyone ever done this with a screwed on chuck ?
evidently it is not a totally new idea because my 3 in 1 came with it already done on it. so why didn't Logan ? who knows ! LOL....
....
thanks for your comments !
Bob........

 

[mmcmdl]

In 43 years time I've never had a chuck un-screw itself , but , that's not to say that it couldn't . Once you get the feel for your machines you know what you can get away with and what you can't .

I will also add this . I'm in maintenance and see wiped out set screws and marred shafts everyday of the week . If that chuck releases because of a crash etc , that set screw ain't gonna help !

 

[Tozguy]

The idea of 'locking' the chuck to the spindle makes sense to me. It should give you some peace of mind when you need to be concentrating on the job at hand. Although I would not modify the spindle in any way.
Hopefully there are some ideas coming that only involve a modification of the chuck/backplate. Your idea of a grub screw could be modified to include a brass or hard plastic plug at the tip of a cup style set screw to prevent malling the spindle threads. More than one lock screw could also be considered.
My lathe has a D1-4 spindle and I really appreciate not having to wonder if and when the chuck will unscrew.

 

[ThinWoodsman]

In 43 years time I've never had a chuck un-screw itself , but , that's not to say that it couldn't . Once you get the feel for your machines you know what you can get away with and what you can't .

I had it happen for the first time a few months ago on the 14" logan. Wasn't even during any cutting - the job was set up, my brain sent my hand the "turn on" signal, my hand received it as a "turn off" signal and pushed the lever from park (heh) to reverse instead of pulling it to forward. Chuck spun off in about a second. Fortunately the workpiece was thick and extended into the spindle, so the chuck was suspended long enough for me to rescue it from hitting the ways.

Now, it probably shouldn't have just come right off like that, so maybe I screwed up somewhere, or maybe the threads on that (old and very worn) chuck are shot, but that cured me of any desire run the spindle in reverse with the chuck attached.

Agree on the set screw, that sounds like a good way to mar the spindle. If you want to do work in reverse on a threaded spindle, use collets.

 

[FOMOGO]

Just thinking out loud, but I would want the set screw to penetrate into the spindle far enough for positive locking. Of course that would probably only work for one particular chuck, as it is unlikely that a different one would seat in the same spot. It would be interesting to try several on the spindle and see where they land when tight. Mike

 

[Latinrascalrg1]

Ive thought about this a bit and ive come to the conclusion that, when needed and assuming the "Full" spindle bore is not needed i was planning on running a tube through the spindle that is flanged at the chuck side to catch the chuck and threaded on the left side with a double lock nut.

 

[brino]

Locking the chuck to the spindle has been discussed before.

Here's one such thread.......

In this reply Bob (@RJSakowski ) shows how his spindle has a groove to lock the chuck on:
https://www.hobby-machinist.com/threads/thread-crest-override.40895/post-351007

here, I suggested a draw bar type device too:
https://www.hobby-machinist.com/threads/thread-crest-override.40895/post-351035

...and here Bob suggests another way to do it:
https://www.hobby-machinist.com/threads/thread-crest-override.40895/post-351046
https://www.hobby-machinist.com/threads/thread-crest-override.40895/post-351047

Much depends on the particulars of your lathe.

-brino

 

[Bi11Hudson]

On both machines, a Grizzly 1550 and an Atlas 12X36, I have used a setscrew in the hub. To prevent a really non-existent problem. I have several chucks that are interchangable between the machines, more or less. I do lose some accuracy, but not much for what I do.

The first chuck was drilled off the machine, then mounted the chuck and marked with a Sharpie. Removing the chuck and then transferring the mark to the outside of the spindle. So I could match the other chucks. Then I cut (ground) a sort of keyway in the spindle. To protect the rest of the threads.

I used this system for a long time, but I honestly don't think it made any difference. Even when tapping a 5/8X8 LH ACME hole. Once the chuck seated, it stayed there. Through several pieces of the 5/8 ACME.

I've never used reverse that much, beyond the followers, but it seems to have been an exercise in wasting my time. Of course, tommorow I won't set the setscrew and it will come loose. No saying when preventative will pay off, better to have and not need than otherwise.

.

 

[hman]

I have an old Grizzly 12x24 with a threaded nose. I'm hesitant to use a set screw, for two reasons. 1. Tightening the screw might pull the chuck sideways, thus off-center, and cause increased runout. 2. Though this might be avoidable by drilling a "receiver hole" in the spindle, it would be difficult to get the setscrew in the same place on multiple chucks, face plates, etc.

My solution is to add a ¼-20 threaded hole to the chuck boss behind where the treads are (ie, between the end of the threads and the register on the spindle) and just barely snug down a socket head cap screw after the chuck is mounted. It's not there to prevent unwinding ... just to act as a limit stop. If the chuck wants to unwind, it will only do so until the side of the screw encounters the spindle threads. This will keep the chuck from unwinding all the way, falling down and damaging the ways (or my foot!)

 

[Bob Kelly III]

Some very enlightening answers guys thank you !
I thought myself also that a set screw is " just for looks" that if there is no indent you just as well not bother and yes that means drilling into the spindle which I am reluctant to do ! and I've thought about the sideways pull that might make the chuck run off center as well....
but Mostly I've been thinking if it was a serious problem they wouldn't have manufactured the lathes like this for so long, perhaps naive but in the real world I've only needed reverse a few times since I've gotten the lathe !.
I've taken the 6" chuck off about a total of 3 times and I've never had a problem getting it off ...but someone did, as the bull gear has been repaired
and the only way to damage the bull gear that I know if is locking it in back gear and whaling on the chuck ! so far I have been able ro remove the chuck just by putting a wrench on the chuck jaws and thumping on the wrench with the palm of my hand while it's in gear ... there is enough resistance in the drive train to do that.
but that does not mean it will never Lock on so tight that I can't get it off for love nor money ! I expect it in fact ! but I will cross that bridge when I come to it..... but never lock it in back gears that is what brakes the gear teeth !
my 10" 4 jaw independent chuck has not been on the machine yet that I know of .... but I do have it !
......
I came home with the switch I have been waiting for for over a month today,.... so I can now hook up reverse to the motor.....
if I turn it on in reverse and the chuck shoots across the shop, I will obviously have to do something about the chuck coming off but I have a feeling
that once that chuck hits the ends of the threads it's on there and it ain't going anywhere !
.....
if it is a problem.... I will either make up a internal expanding mandrel to hold the chuck on or try the setscrew idea
but for now I think I will leave it as it is and see what the lathe wants !

.....
My fear is that a set screw is not near enough holding power.... to hold properly it would have to be a through hole and a special bolt
that is just long enough when set to not protrude into the spindle hole
and if that holding pin is going to hold all that torque it will need to be about 3/8" in diameter .... that's a big hole in the spindle !
.....
Personally I think I am worried over nothing.... we'll see,....... now that I should have reverse by tomorrow !
thank you very much for all your help !
Bob.........