MOACLW (mother of all cam lock wrenches)

precisionworks

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Like many import lathes mine came with a cam lock wrench that was too short & too soft. Some days see three or four changes in spindle tooling (3-jaw, 4-jaw, 5C, faceplate, etc.) so I went about making a better wrench.

A couple of over size chuck wrenches were purchased on eBay & milled to the correct square size. Too soft. A better wrench was purchased on McMaster but still too soft. Time to build one correctly.

Starting with an 8" long piece of 4140HT (3/4" diameter) the end was turned to .484" diameter, equal to the old chuck wrench (across the edges):
Image-9853934-222909076-2-WebSmall_0_721e52c513a06d8504bc656273e5a9f2_1


Then the flats were milled off until the measurement read .409" across the flats. Finally the last few inches of the bar was heated red & allowed to air cool, producing a HRc reading between 50-55 according to my hardness file testing.

Image-9853934-222907764-2-Web_0_019452c9f76d2d8d5eb205f10ac12e6a_1


Image-9853934-222907759-2-Web_0_124bf30fd18d76e35a86a35f12551f37_1


Image-9853934-222907761-2-WebSmall_0_dea6c68bc241c7d0fbf1e3722ee6061f_1
 

darkzero

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Wow, that's a big key handle, nice!

Thanks for the reminder, I've been wanting to make a cam lock key. So mild steel is too soft huh, assuming it won't last long? I was just going to use 1018 but I do have a piece of 4140 that I could use.

I have been using my automotive tools as the one that came with the lathe sucks. Luckily I had a Snap-On 10mm drain plug socket (well not a socket, it's male) that is the perfect size. The 3/8 drive on an extension/ratchet would work too but is a bit loose. I use both a sliding T handle or a ratchet. My Snap-On sliding T-handle is 8" long & my Snap-On ratchet that I use for this is 12" long. I do like using the longer ratchet better.

Is there documentation online that specifies the recommended torque for all the different size camlocks? Not that I would break out the torque wrench to torque them everytime but just to get an idea of what's recommended. I use to torque down hard on them but now I feel it's not necessary as it may accelerate wear. I just give them a good snug.



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precisionworks

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... So mild steel is too soft huh, assuming it won't last long? I was just going to use 1018 but I do have a piece of 4140 that I could use..
The spindle cams are really hard, showing over 60 HRc with my hardness files, so the drive square needs to be equally as hard or nearly as hard. 4140HT is super easy to harden ...
FLAME-HARDENING - Small surface areas on tools made of 4140HT can be hardened by merely heating with any oxyacetylene torch for a few seconds (long enough to heat the surface to a cherry red color, about 1500°F). No quenching is required. The portion of the steel heated will harden to Rockwell C55/60 because of the rapid cooling produced by the conduction of heat from the small heated spot into the larger adjacent areas which have not been heated. (Source https://www.lindquiststeels.com%2Fdocumentation%2F4140ht.pdf&ei=tW0MVNiBEc-1yAT4pID4BA&usg=AFQjCNGw-zXtDFa-ORjmvNczCntbtD8lig&sig2=v0aT-uRFt4yS6dPr3uV2tA&bvm=bv.74649129,d.aWw&cad=rja
Here you need to be careful. If just the square end is heated red there's a good chance it will snap off at the transition of the square to the round. I've had no failures as long as the tip isn't heated directly by the flame but rather through conduction:
Image-9853934-222998453-2-WebSmall_0_d9694ae53a023606f76395e6ce07d3bc_1

Hold the flame in the area shown above until the square tip is cherry red, the remove the flame & let the part cool in still air.
 

gadget_lover

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I noticed that you used the side of the endmill to provide that nice radius where the flats meet the body of the tool. I'll have to remember that the next time that I'm making a chuck key. I tend to use the end of the mill for that type of thing. 90 degree corners can provide stress risers, and no one wants the tool to snap off as you are snugging it up.


Dan
 

precisionworks

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I noticed that you used the side of the endmill to provide that nice radius where the flats meet the body of the tool.
Actually that transition was made with a 1" diameter end mill having a 1/8" corner radius. I use 1" solid carbide end mills quite a bit as the tool is immensely strong & the corner radius is a nice feature on some jobs. There are some 90° corner end mills in the tooling drawer but not as many.
 
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PEU

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Is that stainless? otherwise hardening a high carbon steel would need a much faster medium than air to harden. Heating to orange and slowly cooling is called normalizing, the process to restore the structure of the steel prior to proper hardening, normalized steel is soft.

What I would do to make it hard (if it is carbon steel) is heat it until its nonmagnetic and then quench it in oil, then heat above the square until a blue color reaches the squared tip, this is called tempering.


Pablo
 

PEU

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Now that I read again I see its not stainless, its 4140.
With this steel you have about two seconds to reach the temperature where the austenite converts to martensite (hardens), otherwise, if you take longer to reach the point of conversion you get trapped inside the "nose" of other cristalline structures, this can be clearly seen with a diagram called TTT:

pnWCpdr.jpg


I highlighted the nose, the temprature where the change happens and the time you have to reach that temperature.

Stainless usually give you about 10 minutes, so you can air harden it without problems.

You may have a mix of austenite+ferrite+cementite (A, F & C in the chart) not the best structure, without much effort you can make a far better heat treat for your tool. [edit] the proper term for the treatment you made I think is case hardening.

Pablo
PS: you learn a lot of metallurgy by making knives :D
 
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