# Chuck Key



## Hukshawn (Jan 3, 2017)

So, the chuck key to that new 6" 4 jaw chuck broke the other day. The square tip snapped right off... piece of crap...
So, that particular store is annoyingly far away and closes at 5pm. Thinking about just making another, cause... why not? 
Is there a way I could harden the tip? Good evening project.


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## Uglydog (Jan 3, 2017)

Leave it soft.
No reason to harden it.
If something has to be sacrificed it cheaper and easier to make a new key than purchase a new lathe chuck!
Certainly possible that there was a flaw in the key.
However, sorry-gotta ask, how tight were you trying to get her?

Daryl
MN


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## RJSakowski (Jan 3, 2017)

A tool usually breaks due to being too hard.  Soft tools deform.  It is possible that there was a defect in the key whuch caused the break.  If that is the case, you can usually see evidence of an old fracture  as a slightly different color.


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## Hukshawn (Jan 3, 2017)

Totally had to be defective. I was centring a piece of aluminum in the 4 jaw and did my final snug on the first of the two snugging jaws, and *clink*, just snapped off like nothing. Don't kid yourself, entirely cheap Chinese crap. The chuck is the same... 
aaand, it'll give me a chance to try milling something on the lathe. Was thinking of putting it in my 5/8" boring bar qctp holder and just mill the square tip then lathe out the rest of the handle and just use a rounded off long bolt as the handle.


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## Hukshawn (Jan 3, 2017)

On closer inspection, it's cast...


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## Uglydog (Jan 3, 2017)

Sounds great!
As a temporary, can you use the existing T handle and mill a square end? 
Just a little shorter.

Daryl
MN;


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## Hukshawn (Jan 3, 2017)

Nuts to that... this handle was brand new, it's ****** me off now. If I was humanly capable of throwing a piece of steel away, it would be a goner! 
Already got a new one turned down. Tomorrow I'll set it up and mill the square.

Edit. This is a 5/16" handle for the 4 jaw. My 3 jaw is a 3/8". So for now I'm using the 3 jaw.


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## bfd (Jan 4, 2017)

what  is the square size I have made them out of socket set extensions using a t handle just depends on the size otherwise  make  your own its easy. bill


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## Catcam (Jan 4, 2017)

As it is cast and there does not appear to be any old fractures from the picture it would be a waste of time machining a new square in the end of the existing shaft. From my experience any steel shaft would do.
Don't make the square end too close a fit and round off the corners so it slips on and off easily


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## Hukshawn (Jan 4, 2017)

bfd said:


> what is the square size



5/16"


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## AGCB97 (Jan 4, 2017)

Having made several myself, I think the end needs to be hardened and tempered. Lots of leverage on that tiny end to deform it!


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## Hukshawn (Jan 4, 2017)

AGCB97 said:


> Having made several myself, I think the end needs to be hardened and tempered. Lots of leverage on that tiny end to deform it!


I've never hardened anything before, can you give a bit of a walk through?


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## AGCB97 (Jan 4, 2017)

Heat it red with a torch or whatever else you may have then quench in water. Then heat slowly till it just gets steel blue and let cool naturally in air. Just the end 1 or 1  1/2" would be good


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## jpfabricator (Jan 4, 2017)

Heat until a magnet won't stick to it, water quench. put it in a 400* oven for 1 hour for every inch thickness, turn the oven off and let cool overnight.

Sent from somwhere in east Texas by Jake!


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## Hukshawn (Jan 4, 2017)

Sounds easy enough.


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## TakeDeadAim (Jan 4, 2017)

I made mine from 17-4 stainless tool stock and it has lasted over 10 years. I do have access to  small heat treat furnace so I did take the material to H900 spec hardness, which is simply 900 degrees F for 1 hours then air cooled. The material really needs to be strong more than it needs to be hard and i suspect the Rockwell C35 as purchased condition would work well.  If you are using cold rolled steel round 1018 etc. you wont get much "hardness" as the steel has too low a carbon content.  Easy to obtain tool steels like 4140 pre heat treated and S7 drill rod would work well as purchased.  Your steel supplier should be able to provide at least rough heat treat guidelines should you desire. In the modern era a google search would most likely locate the information as well.


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## mikey (Jan 4, 2017)

I agree with the above - the key needs to be tough instead of hard. Commonly available 1144 Stressproof is what I use. Put it in a collet block and mill the 4 sides. Turn off the corners slightly on the lathe and radius the nose with a file. Drill for the handle and you're done.


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## Hukshawn (Jan 4, 2017)

I'm gonna try this one out first since I already started. And playing around with the heat treating should be educational at the least. 
I'm going to have to figure out a reasonably local supplier for things like drill rod. Otherwise my local steel supplier has lots of stuff. A fairly wide selection of shaft stock too.


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## Hukshawn (Jan 4, 2017)

I can't use too hard of steel cause my limited selection of end mills aren't great. If I can't mill it, I'd have to grind it, and that's no fun.


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## Charles Spencer (Jan 4, 2017)

Hukshawn said:


> If I can't mill it, I'd have to grind it, and that's no fun.



I've had to grind down several lathe chuck keys for various reasons.  I never even considered milling them.  It was much quicker and easily accurate enough to grind them.  I just used a check gauge and usually get the job done in 10 - 15 minutes.


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## Hukshawn (Jan 4, 2017)

Actually turns out this piece of steel is pretty hard. A file on its edge bites a bit but flat it skates over. No idea what this steel is... 
Ehh, ikl grind it, heat treat it like described here. If it works, great.


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## Eddyde (Jan 4, 2017)

I made one using a piece of  O-1 drill rod, didn't harden it, no need in my opinion. 
Here is a couple of photos:




I subsequently added ball ends to the handle, no pics though...


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## 4GSR (Jan 4, 2017)

Don't wast your time trying to heat treat the material.  Especially if you don't know what you have.  Get a piece of 4130-4142 steel that is already Q & T to 28 36 HRC.  That's a common grade and hardness for heat treated steel out that you can buy.  OR use a piece of drill rod that is not rock hard.  Like a piece of W1 or O1, in the soft condition it is in the 25-36 HRC range. It has enough toughness to last a long time.  Ken


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## Hukshawn (Jan 4, 2017)

No idea what this steel is... it was some kind if a shaft. Had threads on one end, and this on the other... it ground like tool steel. But was soft enough to smooth over with the wire wheel. 
Pretty happy with this... I think I may leave it and see how long it lasts. There's enough left on the cut off to make another if this one breaks. And, I don't have to unnecessary run the oven for an hour.


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## Hukshawn (Jan 4, 2017)

Eddyde said:


> I made one using a piece of  O-1 drill rod, didn't harden it, no need in my opinion.
> Here is a couple of photos:
> 
> View attachment 143057
> ...


How do you like that little dividing head? There's one at a local machining store for not a huge amount of money. How versatile do you find them? I ask cause they seem small and limited... doesn't really look like you could do a whole range of gears or something like that.


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## Eddyde (Jan 4, 2017)

Hukshawn said:


> How do you like that little dividing head? There's one at a local machining store for not a huge amount of money. How versatile do you find them? I ask cause they seem small and limited... doesn't really look like you could do a whole range of gears or something like that.


It's called a spindexer, yeah, not the best for gears but great for basic dividing in 1 degree increments, so 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36, 40, 45, 60, 72, 90, 120, 180 & 360 divisions. I like it especially since I only paid $40 for it.


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## bfd (Jan 4, 2017)

yes sorry I saw the size after I posted a reply my bad you can take a 3/8" extension  and grind or mill it to 5/16 grind down the ball if required then use a sliding t handle type breaker bar quick to get you running again bill


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## Hukshawn (Jan 5, 2017)

http://www.sears.com/grey-pneumatic...=JB Tool Sales&prdNo=4&blockNo=4&blockType=G4

I have two spark plug T handle wrenches I use for electrical services. this wrench is for my 4 jaw. I had just used the 3 jaw till I made this up. And, there was just enough meat on the old one to turn the jaws still. But still, broken won't do. 

And I'm looking for all the little lathe projects i can do to hone my skill. I still have ideas for an er32 collect chuck and making a milling attachment for my cross slide.


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## Mikesal (Jan 5, 2017)

I bought my lathe at an auction & the chuck key was missing.  I had an "old" T handled wrench laying around that I cut the socket off the end & forged the end into the square.......2 day later I was visiting the model T ford club website & found out that I had just destroyed a lug wrench for the '26 / '27 cars that had wire wheels.....it was worth more as an antique wrench than what a new chuck key would have cost......what a dope.....


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## Highsider (Feb 2, 2017)

Hukshawn said:


> On closer inspection, it's cast...


That's not cast, it's hardenable steel from China, where they seldom bother to draw the temper after hardening a tool.   You'll find that the broken end is not fileable and is too hard to machine.  You could grind a new square lug onto the end of it, if that doesn't result in it being too short.    Once ground to size, it will be bare metal bright.  Draw the temper yourself by heating about halfway up the shank and watching the color change at the square lug as the heat soaks down to it.   It will start straw colored, then brownish and then blue.   Don't let the blue reach the lug, quench the key in water the moment the brownish color reaches the lug.  Try the file test again.  It should be  fileable now, but if not, apply more hear the same way 'til the lug is just a bit darker and quench again.  When it just becomes fileable you've reached the ideal compromise between hard and strong.  Many Chinese junk tools are as brittle as glass, but they don't care because they're being sold in the US.


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