Locking on a threaded chuck ?

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
Click to expand...
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.......
 
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!)
Click to expand...

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........
 
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!
 
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........
 
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 !
Click to expand...
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).
 
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.........
 
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..........
 
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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