4140 Hardening

[stephanfowler]

I got some 1" square 4140 to make a pair of file guides.

Looking for opinions, should I temper and how much....?

I will most likely use them full hard for a while and see what I think, I'm not terribly concerned about them being too brittle being a full 1" square stock.



Chemistry Data from Crucible's site:
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Maxel Tooling Alloy is an AISI 4140 modified chemistry alloy steel heat treated to a medium hardness (26/34 HRC) and ground to tool steel tolerances (+.015 allowance, +0.15/-.000 tolerance).


Typical Chemistry
Carbon 0.42%
Silicon 0.30%
Molybdenum 0.20%
Manganese 1.00%
Chromium 1.00%

Typical Applications
Stripper/Support Plates Filler Blocks
Punch Holders Die Runners
Clamps Base Plates
Short Run Dies Molds
Brake Dies Jigs
Fixtures Tool Holders
Wear Parts Strength Parts




Annealed Hardness: BHN 185/200.

Thermal Treatments.

Annealing: 1550F (840C), hold 2 hours, slow cool 50F(30C)/hr. max. to 1200F (650C), then air or furnace cool. Hardness BHN 185/200.

Stress Relieving:

Annealed Material: 1100-1300F (595-740C), hold 2 hrs, air cool.

Hardened Material: 50-100F (30-55C) below last tempering temperature, hold 2 hrs, air cool.

Straightening: Best done warm 400-800F (205-425C)

Hardening: (Atmosphere or Vacuum Furnace)

Preheat: 1250-1300F (675-705C), equalize

High Heat: 1550-1600F (840-870C), soak 10 to 30 minutes. For vacuum hardening, use the high side of the high heat range and soak times.

Quench: Oil quench to hand warm, 150F (650C). Temper immediately. Water quenching from 1550F (840C) may be used for simple shapes and larger sections. Note vacuum furnaces must have oil quench capability to achieve comparable results.

Temper: Tempering at 400-1200F (205-650C) for 1 hour per inch (25mm) of thickness at temperature is recommended (2 hrs min). Air cool to room temperature.

 

[mete]

I wouldn't worry about preheat for that size. Harden from 1550 F, 10 min. Temper 400 F ,2 hours. If you don't want full hardness just temper higher.

 

[cdent]

Rookie question. Can 4140 get hard enough to resist a typical file? My understanding is that at full hardness it may be below 60 Rc. Just curious if a higher carbon content might work better.

Take care, Craig

 

[jll346]

I think 4140 is a poor choice for a file guide. It can only be brought to 55Rc. I don't think it will last as a file guide. Use some O1 fully hardened.

 

[stephanfowler]

well, I've been using soft 1.2.3 blocks for a little over a year now and they are barely scratched, a lot of it has to do with technique and having done all my work for 3 years without a grinder, JUST file, I'm pretty darn tootin with a file.

the guide is just to help me keep shoulders aligned, the problem i have with using the 1.2.3 blocks is keeping them REALLY aligned, close doesn't cut it.

 

[jll346]

well, I've been using soft 1.2.3 blocks for a little over a year now and they are barely scratched, a lot of it has to do with technique and having done all my work for 3 years without a grinder, JUST file, I'm pretty darn tootin with a file.

the guide is just to help me keep shoulders aligned, the problem i have with using the 1.2.3 blocks is keeping them REALLY aligned, close doesn't cut it.

Even the cheap 1-2-3 blocks are case hardened to 60-62Rc