Lathe Chuck Keys-Alloys and Hardening

[jdmosley43]

Hi, I've used the search feature, but cannot find info specific to my application.

We manufacture tail shafts for river boat on The Mississippi, up to 10+ inch OD and around 30 ft long.

I've got some large 4 jaw chucks on very old, but extremely solid lathes, and am having a hard time eating, twisting chuck keys. We are very hard on our chucks, sometimes using 2ft. cheater pipes with all of our strength to get a couple more thou moved without loosening anything and chasing our tail. I realize this is not the best technique by the book, but it's what we choose to in order to get the job done as quickly as possible.

I'm wondering if anyone here also makes their own chuck keys for very large applications, and if you've got any tricks in regards to choosing the correct alloy paired with a proper hardening technique.

I'm also looking for suggestions on material and possible heat treating options for the pull bar. We are using cold roll and always bend it.

What I DO NOT need is something so hard we break, as this could cause serious injury.

Right now we just machined up a couple of 1018 keys, along with a pair from 4140, but I'm fine with ordering more material if there is a better option!

Any all almost all advice would be greatly appreciated!

CHEERS!
-JD

 

[Bill D]

I would rather pay to break a key then a big chuck.
Bill D

 

[jdmosley43]

With our application, I prefer the soft stuff twisting as opposed to anything snapping given the way we have to crank down on these things for that last little bit.

We've snapped a couple with 4140 inserts in the end, and it's EXTREMELY sketchy!!!

 

[MrWhoopee]

Before getting too exotic, try ETD-150 or pre-hardened 4140. Harder and stronger than CRS but nowhere near brittle.

 

[4GSR]

You might try chuck wrenches made by H & R Manufacturing just north of Houston. They are made for larger size chucks like the big hollow spindle chucks we use in the oilfield. I believe theirs are made of 414/45 steel heat treated around 38-42 HRC, equivalent to ETD150. They may even make them out of S-2 Tool Steel heat treated about the same. Ken

 

[eKretz]

The ones I've made out of 4140 Q&T took a pretty similar amount of abuse and still look nearly brand new after 10+ years of daily use. Made the handles and everything out of it. Never broke one, never bent one, never distorted one.

 

[johansen]

2 foot cheater bar on a 4 jaw chuck?! how close do you think you are to fatigue failure of the square threads they use!!


and what would happen if heavy object is turning while failure takes place?

within the last week someone on reddit posted a photo of iirc 20 ton dc motor rotor that fell out of the chuck, destroying the lathe compound, cross slide, etc.

the reason?

damned co-worker thought he knew how to set up and run said work while guy who knew how to do it went on vacation for a day.

substituted flat copper stock for bent copper stock in the chuck teeth. (probably had nothing to do with the copper being bent but rather the amount of torque applied to the chuck key..) (the post also claims they ran it about 50% faster than he would have)

when the lathe shut off.. the acceleration caused the flat copper stock to slip out between the chuck teeth and the shaft, and the whole rotor starts wobbling around. which causes the live center in the tailstock to wear out.. and it slips out.. and the 20 ton rotor drops down on top of the lathe bed....

while the owner of the shop.. who is semi-retired... needs a walker to support him.. is standing in front of the lathe while this happens. .... yes, the tool post manages to contain the event and no harm to anyone was done. lathe needs a new cross slide and compound rest. also possibly new saddle.

i think the post was deleted i'm still looking for it.

anyhow don't be dumb. you should not need to squeeze out more than say 0.001" of runout by elastically deforming the chuck by reefing on the other side of it.

 

[Limy Sami]

Before anyone gets too precious about cheater bars etc on chucks, heavy machining is a whole different ball game.

EG the OP's 10'' dia x 30ft example weighs in excess of 8000 lbs, and ya don't move that sorta weight with a ''silly little chuck key

And while I'm at it, with worn chucks (especially bigguns) ''swinging'' on the key to get the odd thou or two is very common practice.

 

[eKretz]

Yeah big machinery (and heavy work) needs a lot more persuading to move. A 3-foot pipe on a chuck wrench for a 36"+ swing lathe is not abuse, it's necessary. You couldn't hurt jaws that size if you tried. If you've got any brains, when you're running very large machines you learn awful quick to tighten the jaws while they're on top too. Gravity helps. And these size machines use 4-jaw independent chucks pretty much universally, without exception.

As far as a "fuse" goes, the guy turning the wrench is supposed to be the fuse. If your guys aren't very skilled or don't have good judgment about mechanical force and torque/tightening, I can understand why you'd want to use a weak wrench, but that's one of those things that shouldn't have to be done.

 

[jim rozen]

Anybody ever use a rattle-gun on those things?

 

[DDoug]

Anybody ever use a rattle-gun on those things?

54" bullard 4 jaw, used a 1/2" air impact wrench all the time.

 

[eKretz]

Anybody ever use a rattle-gun on those things?

Yes, absolutely, but only for running them up snug. I wanted to feel the torque myself when tightening to make sure they were correctly and securely tightened. Plus you can feel weird things like something that has too much give when it shouldn't, etc.

Never had a job come loose, and for sure wouldn't have wanted to see the aftermath if one did. Almost had one walk out as an apprentice when someone else had set it up for doing some rework on a large center, job was about 30 tons or so.. Job was set in the chuck and on a roller rest so the center could be single-pointed with the compound. Asked the foreman if I should check the setup, he said "Nah, they left a note that said it was ready to cut, just start tooling that center."

I checked that the jaws were tight anyway, and ran an indicator to check if it was dialed in. Part was fully seated in the jaws, etc. Looked good at first glance. Having jogged the machine around a few times, I then ran it for less than a minute, and happened to walk back over the 20 feet or so from the end of the part to the chuck. Glanced at the chuck jaws and saw that the job had walked out a good 1/2" and was just in the jaws by less than that. My eyes about bugged out of my head. Stopped it immediately and started checking, found the problem pretty quick. The guy that set it up didn't have the roller rest set high enough so the job was tilted down toward the tailstock. Last time I ever followed up anybody without a few good checks, regardless of what they told me.

 

[dian]

i have a collection of big 10.9 and 12.9 fasteners for such purposes. not the nicest to machine but they are about the strongest among "ordinary" steels and i know they will not fracture.

 

[Limy Sami]

Anybody ever use a rattle-gun on those things?

W&S even ''built them in to'' (or power wrenches) as an option on their bigger turrets.

 

[jim rozen]

The Okuma LB I used to run had an hydraulic chuck - soft jaws, very accurate, VERY strong.

 

[DDoug]

W&S even ''built them in to'' (or power wrenches) as an option on their bigger turrets.

A wee bit different, it was a very geared down motor, no impact to it.
US2515329A - Power chuck wrench
- Google Patents

 

[4GSR]

W&S even ''built them in to'' (or power wrenches) as an option on their bigger turrets.

I remember dad griping about the "Bubba's" tearing up those power chuck wrenches on those 4A's and 5A's they had in the plant back in the 1960's 70's.