Locking on a threaded chuck ?

[Bob Kelly III]

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......

 

[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.......

 

[Bob Kelly III]

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......

 

[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

 

[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..........

 

[Latinrascalrg1]

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.

 

[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.......

 

[matthewsx]

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

 

[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.........

 

[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!