# ? about Lathe Chuck Keys



## Splat (Oct 26, 2013)

I did not receive a 7/16" chuck key for the Bison 3-jaw chuck I got with my Heavy 10. I figure to make my own from a 1/2" drive socket extension but have a question about the actual squared key. My chuck has its key holes squared at the corners, not true 90º corners. Do I need to make the key squared on the edges (don't know the technical term for this) or should I mill it square to 7/16"?  I figure squaring down the corners of the key makes it stronger, no? Thanks.


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## Tony Wells (Oct 26, 2013)

If you mean sharp corners, then the objective is to move the stress point away from the inside corners of the socket. That's where it would be most prone to crack. So if you want, break the edges on your square.


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## Ray C (Oct 26, 2013)

BTW:  The contour you are talking about is called a "Bevel" i.e. beveling the edges is equivalent to "breaking the corners".  In terms of CAD, a bevel is specified by a width -unlike a radiused edge (called a Chamfer) that is specified with a radius dimension.

Side note:  Make the chuck wrench of low or medium hardness material so it does not wear-out the corresponding socket.  Wrenches are cheap, worn out chucks cost money to fix...

Ray


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## Splat (Oct 26, 2013)

Beveling! Yep, forgot about that. Thanks Ray and Tony. I'll bevel them down enough to have the square fit snugly, yet still be able to be removed.


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## Tony Wells (Oct 26, 2013)

Ray, a chamfer is not rounded, but straight. A chamfer is symmetrical whereas a bevel need not be. Normally you will see a bevel called out as a given angle and either a length of the longest side orthogonal to the part axis or in the case of much lathe work, a bevel diameter as it breaks out on a face.


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## Ray C (Oct 26, 2013)

No reason to doubt you and I'll check into why my CAD program seems to enforce the rules that I described...   As I think about it, I agree with you -but took it for granted my CAD program was "all knowing"...  Hmmm, a mystery to resolve...


Ray




Tony Wells said:


> Ray, a chamfer is not rounded, but straight. A chamfer is symmetrical whereas a bevel need not be. Normally you will see a bevel called out as a given angle and either a length of the longest side orthogonal to the part axis or in the case of much lathe work, a bevel diameter as it breaks out on a face.


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## Ray C (Oct 26, 2013)

OK, my bad.  -Sorry...  I had a senior moment.  Fillets are rounded and specified with a radius.  Chamfers are flat and specified with a distance.  My apologies...


Ray




Ray C said:


> No reason to doubt you and I'll check into why my CAD program seems to enforce the rules that I described...   As I think about it, I agree with you -but took it for granted my CAD program was "all knowing"...  Hmmm, a mystery to resolve...
> 
> 
> Ray


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## Tony Wells (Oct 26, 2013)

No problem Ray....it's easy to mix things up. I remember as a young man having a terrible time getting the difference between a bevel and a chamfer, seeing that technically, there are times they are both proper terminology for a particular feature. I've often wondered how the draftsman decides how to call it out. I'm sure there are standards that cover it. I know there is an ANSI drafting standard, but it's been so long that details like that are long gone from this feeble mind.


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## Ray C (Oct 26, 2013)

Thanks for softening the blow but trust me... it was a senior moment -sad that they happen in the early 50's.


-rc



Tony Wells said:


> No problem Ray....it's easy to mix things up. I remember as a young man having a terrible time getting the difference between a bevel and a chamfer, seeing that technically, there are times they are both proper terminology for a particular feature. I've often wondered how the draftsman decides how to call it out. I'm sure there are standards that cover it. I know there is an ANSI drafting standard, but it's been so long that details like that are long gone from this feeble mind.


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## Tony Wells (Oct 26, 2013)

Believe me Ray....I know the exact feeling. I just have this somewhat futile hope that as things in life slow down it gets better, but I really have my doubts. You and I are about the same age, so I know of what you speak and also how it feels to realize that not too many years ago, things that were childsplay mentally now are either totally impossible, or massively difficult.


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## Splat (Oct 26, 2013)

Ray C said:


> Thanks for softening the blow but trust me... it was a senior moment -sad that they happen in the early 50's.



50's?! I think I'm getting them now in my mid 40's! :think1:


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## Ray C (Oct 26, 2013)

What bugs me the most are the aches and pains.  To think that a couple years ago, I was an active wrestler and martial arts instructor and worked PT as a private body guard...  Now, I think a girl scout can kick my butt.  -Sigh...

-rc





Tony Wells said:


> Believe me Ray....I know the exact feeling. I just have this somewhat futile hope that as things in life slow down it gets better, but I really have my doubts. You and I are about the same age, so I know of what you speak and also how it feels to realize that not too many years ago, things that were childsplay mentally now are either totally impossible, or massively difficult.


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## Hawkeye (Oct 26, 2013)

Guys, wait until you hit 60. Then you'll have ............ what were we talking about?


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## stupoty (Oct 27, 2013)

I made a 1/4 inch (ish)  chuck key from mild steel it was too soft, i hardend it (not very skilled/experienced at hardening) it worked but has sheared off about 3/4 monthes later.

any recomendations for chuck key steel?

Stuart


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## Walt (Oct 27, 2013)

stupoty said:


> I made a 1/4 inch (ish)  chuck key from mild steel it was too soft, i hardend it (not very skilled/experienced at hardening) it worked but has sheared off about 3/4 monthes later.
> 
> any recomendations for chuck key steel?
> 
> Stuart



I have near zero knowledge about this subject, but aren't the tool steels air hardening?

http://www.onlinemetals.com/toolsteelguide.cfm

A2 is.  Here's a link to a temperature vs color chart:

http://www.engineeringtoolbox.com/tempering-colors-steel-d_1530.html

Not cheap stuff, ~$13 for 3' of 3/8" drill rod. It might be cheaper just to buy a key!

Not at Enco:

http://www.use-enco.com/CGI/INPDFF?PMPAGE=512&PARTPG=INLMK3&PMITEM=505-5004

Let me know how this works out for you. I've thought about trying to find a way to make hardened parts without building a furnace.

Walt


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## Ray C (Oct 27, 2013)

Guys,

For simple things like a chuck key it's ok to use simple heat treating procedures but do realize, you won't really know how hard the final product is.  And by no means should you attempt to harden "critical" pieces without the proper equipment and knowledge of the procedures...

For a chuck key (I assume this is a lathe chuck) the square socket on the chuck is made of good material and most certainly hardened to Rockwell 40 or 50 (just guessing).  You want the key to be a little softer so you don't wear-out the socket over time.  I suspect you can get away with just heating-up the last inch or so of the key.

Make the key and use something like 1045 which has enough carbon where you won't have to worry about decarburizing or using a pack hardening compound.  Don't bother using something like A36 construction steel or 1018, 1020 etc.  Next use a couple propane blow torches and set the piece in a vise with the torches aimed at the top inch or so of the tip you want hardened.  Technically speaking, if you have say a 3/8 or 1/2" shaft, it will be hard to heat the metal to the full recommended temperature (but it will be close enough) this way because the remainder of the shaft is conducting-away the heat faster than 2 hand held propane torches can saturate the part with heat.  After 10-15 minutes, you'll probably be able to get it glowing to a medium to bright red color.  Let it stay at that color for at least a few minutes.  Don't do this in a windy area as that only helps conduct heat faster from the unheated shaft part.

Using a pair of tongs or pliers, grab the piece and dunk it in a pot of water and shake it around a lot.  If you're using about a half quart of water in a pan, you can add about 2 good handfuls of baking soda.  This will help raise the boiling point of the water.  Boiling water is not good because the bubbles are super-heated steam which prevents the water from coming into contact and sucking the heat rapidly out of the part.

If you happen to have a piece of 4140 (or similar) follow the above directions and use about a pint of transmission fluid instead of water or brine water.  The amount of liquid you use is important as there needs to be enough volume to absorb all the heat quickly.  Don't do this with just a few ounces of fluid.

Test the piece with a hand file to see if it hardened.  If not, it means you didn't have a 1040 (or similar) material or, you didn't get it hot enough or, the quench water got too hot.  The part ideally needs to go from 1550F to (ideally) 250F during the quench -and it needs to happen within 10-15 seconds.  Anything short of that -and all you're doing is wasting propane.  -Try again, you can do it over until you get it right.

If you got the piece really hard, it's good to temper it.  This will prevent it from cracking and also prevent it from being harder than the socket material.  Warm the part (slowly if you can) in a toaster oven or with a blowtorch to about 500-600 degrees.  For these purposes, just warm it up to this temperature and let it cool.

The very outer edges of the treated area will be soft and crumble away.  The area underneath will be hard.  Since the part is small in diameter, the hardness will go down a good way -but it really depends on the material you used.  In either case (1045 or 4140) it will be more than just a case hardening.

Ray


PS:  Don't use the A or W tool steels.  You can't get them hot enough with a propane torch to do any good (unless you're hardening a very thin rod).  Oxy/Propane or Oxy/Acy, yes.  Pure propane or LNG, no...





Walt said:


> I have near zero knowledge about this subject, but aren't the tool steels air hardening?
> 
> http://www.onlinemetals.com/toolsteelguide.cfm
> 
> ...


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## Ray C (Oct 27, 2013)

One other thing...  While you're heating that part, if you only get the temperature up to 1450 instead of 1550, all you are doing is a strange form of annealing it -which will yield unpredictable outcome.  It might be harder than where you started -or maybe not.

Heat that part up to a good medium/bright red and hold it for at least 5 minutes.

PS:  Again, these are procedures for quicky parts...  Not critical stuff.

Ray


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## FanMan (Oct 28, 2013)

Ray C said:


> BTW:  The contour you are talking about is called a "Bevel" i.e. beveling the edges is equivalent to "breaking the corners".  In terms of CAD, a bevel is specified by a width -unlike a radiused edge (called a Chamfer) that is specified with a radius dimension.



Huh?  Not any place I've worked.  A chamfer is an angled corner, most often but not always 45°.  A radiused corner in CAD (at least the ones I've used) is a "fillet".


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## GK1918 (Oct 28, 2013)

Hawkeye said:


> Guys, wait until you hit 60. Then you'll have ............ what were we talking about?



MAN am I in trouble since I caught CRS diease...  I have a wonderful IDEA  lets all have a chuck key makin day huh!

All my lathes, have different S.O.B.en  keys.  Problem is I never can find them, when I do, its when I retire for the day
go home and sit on the stupid thing (or me).    A string with key painted flouresent orange still doesnt work. And then its the
old same old, go to the stock shelves, put key down get stock, return to lathe "wheres the key"??  
What about those clap ya hand thingys that beep??  
Do I lose the keys to the shop?  NO they stay on the door all day,  so there they are at closing time.    UUGG


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## Ray C (Oct 28, 2013)

Please see posts 5-7 where I acknowledge my mistake.

It's also a common mistake to read and comment on a post but and not read subsequent posts...



Ray



FanMan said:


> Huh?  Not any place I've worked.  A chamfer is an angled corner, most often but not always 45°.  A radiused corner in CAD (at least the ones I've used) is a "fillet".


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## 4GSR (Oct 28, 2013)

GK1918 said:


> .......All my lathes, have different S.O.B.en  keys.......  .    UUGG



GK,

They do make double ended chuck keys,  one size on one end and another size on the other. They are common around hollow spindle lathes where you have both outboard chucks and inboard chucks on the spindle.  These chuck wrenches were not small, were rather big, with 24"-30" handles, 3/4"-7/8"-1" square/hexes on them.  I don't miss them one bit!

In our world, I have a four jaw that uses a 1/2" square wrench and a 3-jaw that uses a 9/16" square.  I though about making one wrench head that would have both sizes on it.  Get around to it one of these days...


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## FanMan (Oct 28, 2013)

Ray C said:


> Please see posts 5-7 where I acknowledge my mistake.
> 
> It's also a common mistake to read and comment on a post but and not read subsequent posts...



Sorry, I do usually look for that and avoid repeating what somebody else already said, not sure how I missed it.  Chalk it up to bouncing between my tablet and my laptop over the weekend, I guess.


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## Splat (Oct 29, 2013)

So let me see if I got this right before I spend more time making a key. I have both impact socket drivers and chromed, what I guess is more hardened, socket drivers laying around I could use. An impact socket driver would be preferred over a chrome hardened driver for a lathe chuck key?


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## Ray C (Oct 29, 2013)

Too hard to say and either will do as long as it fits properly.  If it's too loose or sloppy fit, it will wear things out prematurely.  A "comfortable" fit will last many, many years.

Ray



Splat said:


> So let me see if I got this right before I spend more time making a key. I have both impact socket drivers and chromed, what I guess is more hardened, socket drivers laying around I could use. An impact socket driver would be preferred over a chrome hardened driver for a lathe chuck key?


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## Splat (Oct 29, 2013)

Ray C said:


> Too hard to say and either will do as long as it fits properly.  If it's too loose or sloppy fit, it will wear things out prematurely.  A "comfortable" fit will last many, many years.



Gotcha. Thanks Ray.


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## Walt (Oct 29, 2013)

Ray C said:


> Guys,
> 
> For simple things like a chuck key it's ok to use simple heat treating procedures but do realize, you won't really know how hard the final product is.  And by no means should you attempt to harden "critical" pieces without the proper equipment and knowledge of the procedures...
> 
> ...



Thanks much for the simple process rundown Ray. FWIW, I do have an oxy/acetylene torch, but working at lower temps would be much easier.

Walt


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## Ray C (Oct 29, 2013)

Torches work OK for small parts and I use one a lot if I'm just making a quick punch or something similar.  For larger or longer pieces, as soon as you move the flame to a different spot, the other area cools off by a couple hundred degrees almost instantly.  A combination of a propane torch and O/A can help overcome that.


Ray




Walt said:


> Thanks much for the simple process rundown Ray. FWIW, I do have an oxy/acetylene torch, but working at lower temps would be much easier.
> 
> Walt


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