# 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........


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## 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 !


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## 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.


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## ThinWoodsman

mmcmdl said:


> 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.


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## 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


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## 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.


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## 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


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## 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.

.


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## 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!)


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## 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.........


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## Bob Kelly III

brino said:


> 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


I understand the concept of a Draw bar type device .... in fact I have the material to complete such a tool right now ( a rarity around here..LOL ) 
I really dislike loosing the through hole of the spindle when locking the chuck on by a device like this.... so it would have it's limited use and probably not even be on the lathe when you need it !!!! ....there has got to be a better way to lock the chuck on !
RJ's suggestion is a really good one, however it is hard to do without a full blown workshop !
.....
your suggestions on the links is greatly appreciated but, they all point to different responses in the thread.....
 Having read the entire thread, it helps to see other possibilities !  and seeing what BamBan encountered by moving the forward /reverse lever
teaches me Not to mess with that !!!!! LOL....
 his one miss in synchronicity is what I was getting at random times for no reason..... I think I found it in the slop of the lead screw sense I tightened up the lead screw collar I have had no further problems !  the mark on the thread dial is easy to hit and it is always in sync now !
.....
thanks for your help !
Bob.......


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## Bob Kelly III

hman said:


> 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!)



I have been thinking about going in with a hole through the chuck itself and bolting it to the spindle  or just into a notch at the tip of the spindle
if you put the end of a bolt in that notch it is essentially Locked !
..... however drilling through the chuck is extremely risky and apt to destroy the chuck..... you'd need better equipment to do that job than I have !
so the more I thought of that idea the less I liked it ! 
....
so far RJ's idea of clips on the back of the chuck adaptor to clamp onto a groove in the spindle look like the best idea, problem is my lathe does not have a big flange to cut a groove into ! 
.... so if the chuck coming off is an immediate problem, I will whip out a draw bar type of chuck holder.
the chuck I have on the lathe is a heavy one.... lot's of mass ( a Sanou 6" 3 jaw) but with the VFD controling the motor
shock of start and reverse is minimal and I can increase the slow start if needed !
......
so the plan is now to try it like it is with reverse on the motor..... and go from there ! 
Bob........


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## hman

I guess there's no ideal retrofit solution for a threaded chuck.  At least I haven't come across any.  Sounds like you've come up with a workable strategy.  Soft start with a VFD is a wonderful thing!


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## Bob Kelly III

Well, I got the "SWITCH" installed , VFD programmed for it and I now have Reverse.... that I didn't have before ! so that is very cool !
now if I use my die follower on the lathe I don't have to back it out by hand !!!  and I can leave the half nuts locked and not have to open them and reduce one more possible error in the chain of single point threading ! which is very cool ! 
....
I tested the reverse at a low RPM for obvious reasons, but everything seams to work great
I bumped up the speed to normal cutting speed and put it in reverse and the chuck stayed on .... so I have a feeling I am worried about nothing !
especially with the soft start of the VFD !  although I have it set to 2 or 3 seconds to reach speed that is still much better than the standard motor that would hit it with full torque  when starting.
.....
So,.... I put the switch in a 2"x2"x6" aluminum tube left over from my gyrocopter  and drilled 2 holes in the Logan hood to mount the switch box on
and bolted it down then I plugged the open ends of the tube with small squares of 1/4" plywood and J.B.Welded them in place to keep out the dust and chips !
I put a "F" and a line and a "R"  for forward and reverse on the switch box with a sharp chisel.... it will be hard to forget if it's marked ! 
....
then with that all done I continued work on the rebuilding of the expanding mandrel for the lathe indexer ! got the pipe to fit it nicely and now
I want to clean up an area on the piece to make it look better ( it has a band of rust around it and I want to take that off !)
my careful measurements the other day when cutting the thing to size paid off, as I test fitted the part in the end of the lathe and it fit like a glove !
I was quite pleased with that ! .... ( I had black tape on the last one LOL....)
so all I have to do is bore the 5/8" hole through the piece which is bound to be a job as I don't have a 5/8" drill bit so it looks like boring bar time !
....a while back I took a carbide cutter and cut a notch near the tip and bent the tip and then welded it.... later I welded it to another one for a longer reach...... well, over the years the carbide on that cutter has chipped several times and is almost gone now but it still cuts !
it took extensive grinding to make it useable again though !
I made a nice boring bar for the tailstock that uses a drill bit as the cutter ...but it is 5/8" in diameter ! so I may have to fiddle with my boring bars to get it to 5/8" ......a normal person would just go buy a 5/8" drill bit.....but where's the fun in that ?  Use what ya got !!!!
besides that means spending money that I don't have ! HAHAHAHAH

.....
later all !
Bob........


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## hman

Bob Kelly III said:


> I bumped up the speed to normal cutting speed and put it in reverse and the chuck stayed on .... so I have a feeling I am worried about nothing !


Fantastic!  Soft start is your friend.  

I recall visiting a machine shop where one of the guys had a chuck start to unwind, hit reverse in a panic, and the momentum of the chuck slammed it against the register with such force that it jammed *tight*.  He and several other machinists spent about a day trying everything they could to free it.  IIRC, they eventually got it off by cobbling up a parting tool holder behind the chuck, and parting thru the chuck's hub.

As long as return-after-a-threading-pass is the only time you use reverse, everything should be hunky dory.  Just be extra cautious if/when you decide to machine in reverse (or thread in reverse ala Joe Pie).


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## Bob Kelly III

LOL...Will do ! that chuck is too heavy to land on my foot !  or the ways.... which it must have done to put the big dents in the ways where they are....
so it would seam it has spit off the chuck a few times.... though I doubt it was this chuck as it's brand new....but the potential is ever present !
so I will be cautious !
..... yah there isn't much call for reverse..... unless you don't have it ! but when you do it sure is nice to flip the switch and have reverse !
....
I am 99.5% done re making the expanding mandrel for the lathe indexer.... all I have to do is weld a few holes in the pipe I used, and drill a 3/8" hole in the metal part that stuff's into the end of the spindle .... so I can use the chuck key to hold the thing to tighten the nut ! other than that it is done !
....
now I need to find another project ! LOL.....
later all !
Bob.........


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## Bob Kelly III

welp.... got that done fairly fast ! I used a 5/8" end mill in the 5/8" chuck in the tailstock of the Logan and punched a hole through that hard steel like it was butter !  flipped it end for end and did the back side for a completed hole all the way through !
so the expanding mandrel and it's counterpart the bracket that holds the clamp on the saw blade is now all done !
.....
Today I went to see the man I bought the lathe from and gave him a sizeable chunk of the money I owe for the lathe and we got to *******tting about the lathe and he discovered I needed scrap metal and he fixed me up ! I got 3 or 4 pieces of 1/2" thick plate ... something I have been looking for for 4 years !  and a piece big enough to make a steady rest out of !    so I was elated to get my hands on that ! He gave me quite a bit of aluminum plate too.... which I have no doubt I will find a good use for !
...then I went out to the Ranch and scrounge around through the junk and found a piece of 1.5" or 1 3/4"  solid steel axle I have been saving for decades it has 3 more flat pulleys on it too  so I loaded it in the Honda CRV and it just barely fit.... it's probably 7' long lots of turning potential from that steel ! ..... I found some horse shoes too, that we had on our horse when I was just a Kid ! so I brought them home as well hehehehe thinking they might make a good arch for the steady rest..... maybe ....
.....
I am still shocked at how much easier it is to thread by leaving the half nut locked   ..... but I did notice that you need to over-shoot the start area of your threads when threading that way.... so everything gets the slop out of it before the cutter enguages the work.....  1/4" will do that on my machine
....  time wize.. it's about the same I think, as hand cranking and then waiting for the thread dial maybe not , it could be quite a bit faster but I wasn't going for speed ! LOL......it's a heck of alot less nerve wracking though, to me ! 
..... love that reverse switch ! 
.....
later !
Bob..........


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## Choiliefan

There is a discussion on the emcoV10lathe@groups.io  group re loose collars as well as integral pinch locking thread-mount chucks.
Not sure of the legality posting a couple of them here so throwing all caution to the wind:


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## Bob Kelly III

well, there's a good idea !
just machine the chuck adaptor to fit a  locking collar and put a few slices in the chuck adapter so it can flex.... instant locking on !
thanks for the Pic's !  they show all I need to know ! ...
Bob..........


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## Bob Korves

Bob Kelly III said:


> well, there's a good idea !
> just machine the chuck adaptor to fit a  locking collar and put a few slices in the chuck adapter so it can flex.... instant locking on !
> thanks for the Pic's !  they show all I need to know ! ...
> Bob..........


Runout might be poor with that modification.


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## Bob Kelly III

a very good possibility indeed ...perhaps a pinching collar with more than one bolt might help in that regard eh ?
.....
Bob.......


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## rock_breaker

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


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## Bob Kelly III

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.....


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## mmcmdl

Bob Kelly III said:


> , and had to hit it fairly hard with the palm of my hand to pop it loose


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 .


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## Bob Kelly III

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.........


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## Choiliefan

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.


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## matthewsx

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


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## rjs44032

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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## Bob Kelly III

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........


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## Latinrascalrg1

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........



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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## Bob Kelly III

Latinrascalrg1 said:


> 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!


I'm not following your train of thought here....what would hold on the chuck from unscrewing ?
Bob......


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## Bob Kelly III

Winky's workshop (on youtube)  did a really neat thing the other day ...he put a long 1.5" steel bar in the chuck of his logan lathe and then measured the run out...it was horrible ! ...  he put the camera to watching the back of the chuck and then wiggled the bar and it showed the entire back plate flexing on the threads in the back plate....  yet alone the problem of the chuck unscrewing itself, now  it seems all threaded on chucks have this tendency to flex under load.... ( that is my take of it anyway.....) 
 but I guess if you want super precision you shouldn't be using a 68 year old machine right ? LOL..... 
Or one as small as this....  or as Most hobby machinist lathes ....    but I was shocked to see the back plate flexing like that ! i did not expect it at all...
Size does matter ! the bigger the lathe the more solid they are....in every aspect.  so solidifying a not so solid lathe into a solid one is not what I am trying to do here, I'm just trying to come up with a good answer to the chuck unscrewing itself when in use in reverse !
years of practical application on the ranch has taught me that 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 !
.....
Bob.......


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## Bob Kelly III

rjs44032 said:


> 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



Indeed that is the best solution by far, i have about 1/2 of a collett setup for my lathe and it would completely by pass the threads on my lathe.
but I am missing about $200 dollars worth of pieces to make the collet holder work again... and then the collets ...
so it is not a cheap solution at all for me ! 
I do turn things 4" and 6" in diameter periodically..... in fact I had to reduce the speed on my 3 in 1 to be able to do that.... 
but with the Logan i can just chuck up that big 6" pipe and go to town on it ! 
I shouldn't need to use reverse on it though unless I plan to thread it....   but I would love to be able to thread something that big without the worry of the chuck coming off !   yes I saw Joe Pie's reverse threading videos many times ...going away from the spinning chuck does have it's appeal !
but if your careful you don't have to do it that way .
threading a 6" piece of pipe on the lathe is not something I would consider a beginners task anyway.... <GRIN>

Bob......


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## matthewsx

I bit the bullet and bought a collet set for my Seneca Falls lathe a while back. Unfortunately there are few good alternatives to spending money in this hobby....

The good thing is though when you are ready to upgrade a well tooled hobby size lathe seems to fetch a premium.

Cheers,

john


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## Bob Kelly III

LOL that is very true ! much like aviation.... in any form... it is NOT cheap !
Unfortunately I do not have the money to spend  I only got this lathe because the seller would take payments !  I didn't have $1600.00 in my pocket
nore would I in the next 30 years !    My Hope was that when the Ranch sold I could go buy a 14x70  heavy lathe somewhere and have it shipped to my door.... that didn't work out as the county fathers where the Ranch resides  have made it so expensive to build that the value of bare ground has hit an all time low.... so My "Ship won't come in from that direction anyway !"
 I am into making everything I can for the lathe....simply because I can't afford to buy it. and I really enjoy making things...still
although it would be nice to see what I'm doing and eat food without pain.... living on S.S.I is no picnic.  when you get less than half of what you should be getting...( Medical reasons forced me to take an early retirement, because of that I get $589. a month is all .)
and with that little to work with even finding scrap is a challenge !!!
....
My lathe came with 2 brand new chucks, both Sanyu and very good quality, both have their own back plate, a 6" 3 jaw and a 8" 4 jaw independent.
 and a QCTP with 4 holders a knurling tool and a parting tool and one boring bar tool holder
... I am using the boring bar tool holder for a tool post drill attachment at the moment  but I can quickly take that off it.
and the lathe.... that's it.... that is all he had for the lathe. and it does have a 3 phase Motor with a VFD for 220vac... and I just recently installed a proper forward stop reverse switch.
the lathe was completely restored about 15 years ago and it hasn't been used much sense... 
....it does have some problems, 3 bushings that need to be replaced and I already replaced one problem...  I made an idler gear for it .
which was haphazardly repaired in the past.   and the bull gear has 2 places that have been repaired with a row of screws... I want to fill those with brass and re cut them as soon as I can. other than that the old girl is a good one !  and I am very happy with it !
the seller just wanted someone to use it.... well I will certainly do that !!!!!
Bob..........


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## Latinrascalrg1

Bob Kelly III said:


> I'm not following your train of thought here....what would hold on the chuck from unscrewing ?
> Bob......


The art work is lacking but it should help.  First i am assuming your spindle is similar to the one on my lathe.  On my back plates the last inch or so is not threaded which leaves a gap between the spindle and back plate the width of the threads. In the pictures i Highlighted the area im speaking of to fit the bushing to prevent the tilt you are worried about from using a set screw alone.  My theory is with a soft metal and a tight fit between the spindle and the BP the friction the new bushing adds should be enough to keep the chuck from free spinning if it were to come loose and allow you to add a set screw to lock things down without the sideways kickout being caused from the setscrew sideways pressure being applied, just be sure it doesn't stop the BP from completely threading on to where the Registers (lathe spindle and backplate) solidly seat against each other.

Anyway the highlighted area is my attempt at quickly drawing in what I'll call a friction bushing.


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## Bob Kelly III

Ahhh. ok I see what you are saying  ! thank you for the clarification !  that should actually work !  but it would be a friction lock and not a positive lock
where the chuck can't come off without breaking something.....
no modification of the spindle is needed with your idea though, and that is a big plus !  and the tightness of the bushing you make would reduce the run out.... in fact you could put 3 setscrews in the BP to help true UP the chuck run out as well as clamp down on the chuck.....
that is a very good solution !!!!   
it might be worth doing just to true up a chuck !!!!
great Idea !
.....
Bob.......


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## matthewsx

Use the 4 jaw and true up the part....


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## Bob Kelly III

i've had no real call for the 4 jaw that the 3 jaw couldn't handle it's very accurate right now. but yah the 4 jaw could get a part dead on !
but what I like about the 4 jaw is it's ability to make a crankshaft ! so there are steam engines in the plans in the future when I get more material !
.....
..... boy this is a big bad storm going through right now.... anyone east of me should get ready as I have Blizzard conditions here !.... 
and I'm not going anywhere, i'm staying inside where it's warm !
....
Bob.........


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## Latinrascalrg1

As I read your reply I must say at the point of adding multiple setscrew locations to both secure and some runout adjustment to the BP/Chuck.....I would probably go this amended route which has been previously mentioned and would be easier to accomplish with same results or at least really  close to them.
I would do 4 adjustment setscrew/bolt location 90°apart A-La-4-Jaw style.  I would add a Brass or perhaps even Lead slug to each hole before the fastener of choice. Then Setup an indicator to check the chucks runout an proceed with the adjusting part.

The bad part is in swapping chucks out because you will need to go the the adjustment process again!


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## 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........


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## 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..........


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## stupoty

mmcmdl said:


> 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


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## matthewsx

stupoty said:


> 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


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## Bob Kelly III

stupoty said:


> 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......


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## whitmore

Bob Kelly III said:


> ... 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.


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## 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.......


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## 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......


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