Treatment to attain Wrench like Surface Toughness?

[xarka]

I am working with a machine shop to fabricate a specialized puller. The puller will see its fair share of hammer blows. I noticed that many of my wrenches, pullers, bearing splitters, etc. show very minor signs of wear, but have been abused for many years. I would like the puller to have the same surface toughness, one that shows very little wear. The base material is 4140 and is sufficient for the puller's function. I just need to specify the treatment of the surface. I have searched the web for such information which I thought would be common knowledge since thousands of retail hand tools have indestructible surfaces...unfortunately, I cannot find.

It would be much appreciated if someone could point me in the right direction or let me know the common practice or process. Thank you

 

[musashi99]

Could be wrong but most wrenches are made from forgings.

 

[swall]

I seem to recall a similar thread on this same subject a while back.

 

[xarka]

Thank you for the reply. I agree..most tools are forged, but heat treated also...I am trying to learn more about this process and how to specify for custom one of a kind tools machined out of steel. A related question would be...how to attain the surface toughness of a forged wrench on a custom tool machined from steel?

 

[xarka]

I searched the archives for wrench surface, tool surface, etc. but no info so far...can't seem to find the right keyword

 

[metengr]

You might want to consider going with 4320 alloy steel and carburize the surface followed by a quench and temper heat treatment to enhance hardness for wear resistance, while still maintaining toughness. The addition of nickel is the key to enhancing toughness with the higher carbon contents.

 

[Kenneth]

Here's the thread I believe swall was thinking of: thread330-126425

 

[xarka]

Thank you for the info. I was trying to start a new thread to find the basic heat treatment for tools, but yes it is technically part of the old thread. I just have not found an answer and continue to research.

Regarding 4320, I will research your recommnedations further...thank you

I thought someone from a tool design background would have a standard heat treat process, whether forged or not. I had a contact at Proto tools but cannot find anymore. In other words, looking for basic process to spec. a new tool...forge tool, then heat treat how? Or for example, an engineer designs a new tool for Snap-On...how would the heat treatment specification read?

 

[JTreglio]

Why not have it titanium nitride coated? You may have to re-heat treat -- processing temperatures are around 450 C. If that's a problem, you can try chromium nitride. CrN can be deposited at lower temperatures without much loss in hardness or increase in residual compressive stress. The coatings will be very thin, 3 to 5 microns is typical, so you shouldn't have a tolerance problem.

Jim Treglio
Molecular Metallurgy, Inc.

 

[xarka]

Jim, I am open to applying hard coatings if the cost for small lots compares to a standard tool (wrench) heat treatment with comparable surface toughness. I am still looking for the standard in tool heat treatment so that I can price and compare. I thought that the spec. would be common knowledge since thousands of tools are on the market.

 

[Flesh]

I don't think surface hardening is the way to go for impact loading. It would seem to me that you may risk the chance of spalling. If you're looking for a tool steel, why not use A2 tool steel? It's a good general purpose grade and is readily available. Good wear and toughness properties. This link provides some background:

http://cartech.ides.com/datasheet.aspx?i=103&e=262&c=techart

You can also find heat treatment recommendations for this grade in ASM's "Heat Treaters Guide".

 

[MikeHalloran]

I have on occasion modified Craftsman wrenches, which are clearly case- hardened. I would estimate the case depth at maybe .015" for a small ignition wrench.



Mike Halloran
Pembroke Pines, FL, USA

 

[xarka]

I am using 4140 with around 45Rc hardness...this combination shows marks from hammer blows.

 

[Metalguy]

The ability to take strong hammer blows seems to be your biggest problem. Why not have a "good" ball peen hammer cut up and examined for material and HT? They seem to have an excellent combo of properties for your app., most likely from induction hardening on the face area. I would stay a few Rc points below what the the striking face hardness is--my father long ago told me never to strike one hammer face with another-probably back around 1950.