Need some material selection/heat treating help

[unclemoak]

I want to make this wrench so that it can withstand the highest amount of ft lbs of force possible (100+ ft lbs would be a plus) , but I have no idea how to achieve that as I've never attempted to heat treat something before.

The dimensions of the wrench have to remain what they are currently, so I can't simply make it more robust. I was planning on making it out of A2 tool steel. Will the wrench have more strength if I heat treat it? Should I pick something other than A2 tool steel (keep in mind that this needs to be machined from a billet)?

 

[Amitygravel]

A2 can be heat treated for more strength for sure , would take someone with experience to get the results you want. 1095 should work ok too , maybe check with Admiral Steel in Alsip Il. , they are a big supplier. unclemoak , do you have another gunsmithing project up your sleeve ?

 

[unclemoak]

A2 can be heat treated for more strength for sure , would take someone with experience to get the results you want. 1095 should work ok too , maybe check with Admiral Steel in Alsip Il. , they are a big supplier. unclemoak , do you have another gunsmithing project up your sleeve ?

I always have gun-smithing projects up my sleeve

 

[kartracer55]

Why are you remaking it? Did it break in use? or did it just deflect too much?

 

[diesel research]

Will heat treatment cause unwanted "growth" or dimension changes? Will you be able to perform post treatment machining/prep?

Will you need to intentionally makes parts under size/oversize to compensate for growth?

I am thinking back to a set of parallels I made in class. I know they came back from treatment slightly warped, yet oversize in certain areas, and the instructed advised me that a small layer had to be removed to make them less brittle?

 

[diesel research]

After doing some research, I have concluded DO NOT machine any more barrel wrench tools until consulting with your heat treater. In many cases they will want to perform heat treating BEFORE machining.

The less stress risers they have, the happier you will both be.

This is beneficial to both parties. Reduces liabilities on them and required precautions. That means less cost for you, and less risk for them.

It also reduces machining steps since you would only be doing it once instead of pre and post. That means less cost for you and final customer.

 

[OccupantRJ]

Re: Machining after heat treating, other than grinding....Let us know how that works out relative to cost and practicality.

 

[Amitygravel]

RJ is right. Surface grinding is about all you wIll be able to accomplish after heat treatment. Research youur alloys , some may be tough enough to use without treatment.

 

[Jim Johnstone]

Re: Machining after heat treating, other than grinding....Let us know how that works out relative to cost and practicality.

Yeah no kidding, that'll be fun.

A2 is good, but likes to warp on thin sections. Still might be the best bet, contact your heat treater and ask them about expected warping, based on your cross sections.

H-13 is fantastic after heat treat, holds shape well, but you won't want to be doing anything other than grinding and maybe some VERY light finish cuts, with a very rigid machine using solid carbide end mills.

4340 Cromo is also good for this type of stuff, and will through heat treat better than some other grades of Cromo, and most grades of mild steel.

Good luck, let us know what you end up using, and how it worked for you.

Jim

 

[diesel research]

Re: Machining after heat treating, other than grinding....Let us know how that works out relative to cost and practicality.

He has a water jet.

 

[unclemoak]

Why are you remaking it? Did it break in use? or did it just deflect too much?

Basically I made a test wrench out of A2 and tested to see how much force it could withstand. It deflected around 100 ft lbs, which is more than enough. The nut it's tightening only needs to go to 50-55 ft lbs, but I like to have a good margin of safety, that's why I'm looking for suggestions on something that might be a little better choice than A2.

 

[diesel research]

Did you already make a production batch?

As stated earlier, speak with your heat treater of choice. We could specify all the materials in the world, but he has the final say, since he can just as easily decline.

Could you possibly produce a die and broach the future tools?

 

[unclemoak]

Did you already make a production batch?

As stated earlier, speak with your heat treater of choice. We could specify all the materials in the world, but he has the final say, since he can just as easily decline.

Could you possibly produce a die and broach the future tools?

I didn't make a production batch. I'm holding off until I get this issue resolved.

I might be the person that ends up heat treating them with the heat treat oven I have access to.

But I suppose it would probably be best to pick the brain of a local heat treater so I don't waste a huge chunk of money.

I don't think the features of the wrench aside from the drive square could be broached that easily, then again I have no idea what producing a die or a broach entails.

 

[A_Pmech]

You're making this much more complicated than it needs to be.

Machine it out of 4340HTSR. Yield strength is 120,000 PSI as compared to A2 in the annealed condition which yields at about 60,000 PSI. 4340 HTSR arrives heat treated and stress relieved. It is highly fatigue resistant and machines fine with carbide at appropriate feeds and speeds. A second choice would be 4140HTSR which has a slightly lower yield strength and is not as fatigue resistant but is more readily available.

On the wrench in your photo there's a stepped tool mark due to endmill deflection as a consequence of making two varying depth roughing passes on the "tangs" which engage the nut. Rough the tangs and then make a climbing finish pass of about .02" at full depth to disappear that.

 

[mag409]

My choice for that piece would be S7. S7 gains toughness after heat treat without adding too much brittleness. Depending on where you take the A2 on the hardness scale you could make it too brittle. We use alot of A2 for high wear surfaces and some cutting surfaces. S7 is typically used where the part needs to be tough and still have some give. The other choice would be
O1 tool steel. You can heat treat this at home with a torch and temp stick and a bucket of oil to quench. No draw required on O1. The A2 will need to be drawn back after heat treat to remove some of the brittleness.

 

[unclemoak]

You're making this much more complicated than it needs to be.

Machine it out of 4340HTSR. Yield strength is 120,000 PSI as compared to A2 in the annealed condition which yields at about 60,000 PSI. 4340 HTSR arrives heat treated and stress relieved. It is highly fatigue resistant and machines fine with carbide at appropriate feeds and speeds. A second choice would be 4140HTSR which has a slightly lower yield strength and is not as fatigue resistant but is more readily available.

On the wrench in your photo there's a stepped tool mark due to endmill deflection as a consequence of making two varying depth roughing passes on the "tangs" which engage the nut. Rough the tangs and then make a climbing finish pass of about .02" at full depth to disappear that.

That's what I figured. I'll start searching for a good price on heat treated 4340 or 4140.

On the roughing passes, I'm working on revamping my program to rough all the teeth leaving 0.01" or so on the walls and floor, then come in with a different end mill dedicated to make a finishing pass. I absolutely can't stand steps on walls like on the wrench I pictured. I did it on the profile of the wrench, but didn't on the teeth yet.

 

[unclemoak]

If any of you are interested in reading some background on the project I made a thread over on AR15.com - http://www.ar15.com/forums/topic.html?b=3&f=118&t=482476

 

[coldfusion21]

Neat project and some good info itt.

Also jealous of your machine access.

 

[bburl]

use 4140 or p-20 and machine right to size.After that just salt bath nitride or sometimes called melonite qpq.Google it theres lots of info on this process.We use this on mold parts were strength and toughness is desired.It will not change shape maybe grow a few tenths after heat treat process.The surface hardness will be around 90 rc with about .009 penetration.Its usually pretty low cost as well.

 

[Romey]

4140 heat treat is
Anneal is necessary at1550
ReHeat to 1550F and Oil quench
Temper 350 to 800F for Rockwell hardness of 52RC @350F-40RC @800F
Its a very very simple steel to Heat treat

 

[reznunt]

Basically I made a test wrench out of A2 and tested to see how much force it could withstand. It deflected around 100 ft lbs, which is more than enough. The nut it's tightening only needs to go to 50-55 ft lbs, but I like to have a good margin of safety, that's why I'm looking for suggestions on something that might be a little better choice than A2.

FS of 2 isn't good enough?