Locking on a threaded chuck ?

[Bob Kelly III]

and to add to the bad part it is not a LOCK on the chuck... it just makes it harder to unscrew yah 4 set screws of beefy diameter would be a better idea than just 3 and once all is adjusted scinch them all down very tight.... I seriously doubt you could cut anything in reverse that would make the chuck unscrew but it COULD ! ( i think the v belt would slip on my lathe before the chuck unscrewed with that mod !
....
the modification is all done to the chuck BP so another chuck swap would change nothing...unless you did the same mod to it... like a 4 jaw chuck probably would not need the mod. but putting a chuck on that had the modification would no doubt take longer ..... but for guys with chucks that have alot of run out, I am sure they would love the opportunity to correct the runout on chuck installation ! I know I would on my 3 in 1 .... LOL.....it's chuck is cheap and hasn't ran true in it's entire life
....but I don't use it for turning any more, I use the good lathe for that ! <GRIN>
.....
bouncing ideas off one another has always been a fantastic method of coming up with a real good answer to the problem ! thanks for the input !
......
I went out to the shop about an hour ago only to find SNOW on the tailstock end of my lathe ! AURGH !
(at least I am happy that I left it drenched in oil ! )
when the storm is over I'll be out there with WD 40..... but a window that was covered over by a sheet of tin allowed in a bunch of snow... and the door to the shop is a big snow drift INSIDE the shop...... and that sux ! i gott'a seal that place up better !
first storm of the winter and it's a major blizzard .....go figure ! LOL.....


Bob........

 

[Bob Kelly III]

I think this Modification would take careful consideration ... I think boring out the BP to receive a brass insert cut to fit over the chuck register ever so slightly would be a touchy job .... but doable ! I'm thinking at this point that the brass insert would need a cut in it to allow the set screws to squeeze it closed eh ? i think one slice would be plenty as it shouldn't be flexing very far at all ....
i would make the brass insert at least 1/4" thick for strength purposes , and the set screws lined up to center on the insert's width.... would be ideal
but dealing with the limited space that may not be practical.
Sense your bearing on the brass insert there would be no need for lead tips on the set screws i don't think.
.....
a few days ago I repaired the compound dial on the Logan 922 and I put a short piece of bent over solder in the hole so it would stop tearing up the shaft on the dial.... that's been working good but it's not right yet as every once in a while I have to tighten the set screw or the dial does not turn with the handle.......
I need to make the mod Winky did on his logan for the compound dial !
.....
Bob..........

 

[stupoty]

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 !

I had it happen once, the 8" 3 jaw bison destroying everything in it's path has caused it to never happen again <----- (some mild exageration)

Stu

 

[matthewsx]

I had it happen once, the 8" 3 jaw bison destroying everything in it's path has caused it to never happen again <----- (some mild exageration)

Stu

Yes, having a chuck come loose would be a major problem....

I suspect those of us with older lathes are mostly set-up for the belts to slip before something like that would happen. I know there are lots of owners on here with screw-on chucks so if having them come loose was a major problem there would be more threads (no pun intended) on mods to keep it from happening.

1ohn

 

[Bob Kelly III]

I had it happen once, the 8" 3 jaw bison destroying everything in it's path has caused it to never happen again <----- (some mild exageration)

Stu

so what did you do to prevent it from never happening again ?
if I had that happen I'd be very tempted to weld the sucker on ! LOL......

 

[whitmore]

... a pin is a really good way to stop something from turning.....
the trick is to use a pin in such a way that it doesn't effect the other components !

A soft pin can shear, a hard one can shatter... without the operator noticing.

Another approach, for a rotating shaft, would be a collar and grooves.
Just make a groove (like for an O-ring) near the join line on both the chuck and
the spindle shaft (yes, this does depend on clearance...). Then turn a mating cylindrical
collar, that has (loose-fitting) internal constrictions that engage both grooves. You'll want to
saw the collar longitudinally, fit a hinge at one joint and a clamp or screw at the other, so it can be removed.

Even if the chuck were to come loose, it'd have to stretch the collar or shear that groove-engaging metal
before it got dangerously loose. This won't mean that the workpiece isn't ruined, though.

The clearance to mount such a safety-collar needn't be much (half an inch ?) but
it's clearance that has to be designed in from the start, on the chuck side as well as the spindle.

 

[Bob Kelly III]

and that is a sure fire cure.... thanks Whitmore ! fantastic idea ! .....
for me that would be tricky to machine...i don't think i am up to that yet but you could have the headstock facing lip just slip over the chuck redigister
and the front one machined into the back plate...... I am sure it would take some careful machining to get it right and as long as the groove in the
back plate is about 1/8" to 3/16" from the chuck register edge .... there would be plenty of meat there to stop the lathe dead in it's tracks !
......
...... I believe that is the idea of the other fella's method as well, back somewhere along the line .... using the strength of the metal to hold it captive not the bolts
as their there just to hold it on .....

someone could manufacture them and sell them I am sure, as chuck lock down clamps !
..... alot would depend on how much room you have to play with behind the chuck back plate and spindle chuck register......
..... in fact you could make it where the register lip is a ways back from the register and if the chuck did try to come off it would turn a few times and then bang to a stop.... that would definitely alert you to the problem ! ( probably not the best idea i've ever heard ! LOL) but some slop so the chuck would turn by hand and you would know there is a problem

and after you modified your other chuck backplates the one clamp would serve them all....
.....that is definitely better than a hole in the spindle ! and I think just as positive a lock too !

sense you would be clamping behind the chuck register no modifications would be needed to the spindle just the chuck back plate
which probably would consist of taking it down to the registry size or just a tad bigger and putting in a square groove for the clamp to set in
..... I was just thinking 2 allen head bolts to attach both sides of the clamp together perhaps star washers, or lock washers under them so they won't loosen up. no doubt the lips would be of different lengths the one on the spindle could extend the height of the chuck register and clamp on the spindle itself the other side on the chuck back plate would need to be shorter or you would weaken the cast iron ...i would want to leave at least 1/4" of cast iron on the thickness of the metal going to the chuck registry....UNDER the groove so that would mean a sizeable step in the
clamp..... but it would not change it's function at all........
surely a hinge at one side of the clamp would make it easier to put the clamp on there..... but I am thinking ease of construction at this stage !
LOL.....

great idea ! thank you !
Bob.......

 

[Bob Kelly III]

I've spent the last 2 days drawing the above idea of a clamp in Blender and I've made it about as narrow as I can but it still doesn't look like it will fit on the Logan 922..... there is about 1/2" to a max of 3/4" clearance behind the chuck back plate to the spindle head..... and I think the chuck register is
recessed a bit so the back of the clamp may well have to be machined to fit and if it's recessed it may be hard to get the clamp in there with the chuck on it....... but as long as the clamp clears the bearing face it would be good to go no matter how you get it on there
.....
this is one of those projects that will take good measuring equipment material and Lots of checking and double checking to get it right
.....but it is a darn sight better than a set screw in the back plate.
.....I think the procedure that would go into making the clamp would be to get a disk of 3/4" plate steel, say 3" in diam. and poke a hole in it the size of the spindle behind the chuck register. then cut a step to the top of the register.... then how ever you could...measure from the back of the chuck register to the front of the step in the chuck back plate then cut that lip into the ring.... when that is all done,.... cut it in half and put some bolts through it and see if it fits ! LOL...... I think there would be a need for several types of tips for the boring bars so you could make 90 deg corners
....
I'm thinking that a project like this is a LONG way off ....i need TOOLS to make tools ! LOL
Bob......