Hardening of Screws Required?

Hi Guys,

I am coming to the end of a mauser 98 sporter build. I need to make a couple of new screws for the action/trigger guard without the keeper screw recesses. In the past when I have made screws for such purposes I havn't bothered to harden them, but is it better practice to harden lathe turned screws?

Cheers

I made a pile of screws from 8620 and had them case hardened. Without the heat treat its almost impossible to get them tight without the screw driver marking the head. I don't know what's typical for a screw, hardware store screws sure aren't very hard. It will be interesting to see what other people say. Maybe use 4140 HT?

I have made screws for a noted builder out of stress proof, fatigue proof, and heat treated 416 (26 to 32RC. All of these will deform a little if proper screw drivers are not used. On my last project I made the screws from W1 tool steel and am quite happy with the results. W1 machines nicer than O1 if you are worried about warping you can always oil quench small screws (less than 1/2 inch) instead of water quenching. I polished these before final tempering then heated them in an oven till the oxide colors were molted, sorta imitating color case. A little hotter and a nice blue can be had. W1 is close to spring steel in carbon and alloy content. On this last project I had to screw them in and out a hundred times at least with and had no screw driver damage.
If you want hard stainless screws you could heat treat 416 and quench in oil instead of air. I did this with some annealed bars and tempered them at 300 degrees. These bars will still machine with just a little difficulty, but they give a nice finish and are 40+RC.

The 2 screws on the left are original Krag that were butchered by someone else. The 2 middle ones are the W1 replacements and the 2 on the right are W1 for the forward pillar. The colors look better in person.

It is best if they are a little hard, but you sure don't want them hard enough to be brittle. W1, stressproof (1144), 4140, or mild steel casehardened are all suitable.

Here, in the U.S. you can just buy some screws ready made:

Forster Trigger Guard Screws Mauser 96 98 Non-Locking Pack of 2

And there is no need to harden the screws you make if you can't just buy some that suit.

on screws I make I torch blue them which supplies some heat treatment and color.

Claude Wright said:

on screws I make I torch blue them which supplies some heat treatment and color.

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The only "heat treatment" that would be "supplied" would be softening. Hardening steel requires heating to the austenitic stage which would be approx 1400 degrees F. followed by a rapid quench.

tdmidget said:

The only "heat treatment" that would be "supplied" would be softening. Hardening steel requires heating to the austenitic stage which would be approx 1400 degrees F. followed by a rapid quench.

Click to expand...

A few months ago I would have agreed with you 100%. Now I do not know.

http://www.practicalmachinist.com/vb/general/heat-treatment-w1-321103/index2.html

Why that happens with W1 I do not know.
Does it happen with other steels?
Does the hardness change or just the resistance to bending?
What is the actual change going on in W1 when so quenched?
Would this treatment do any thing on 1018?
If I had more time I could do more experiments and probably have more questions to answer.

Funny thing the customer in that thread got the advice to do this from a heat treater, how did the heat treater know that would help when there is no published info on this phenomenon that can be found?

Back to the original poster's question, I do not know if trigger guard screws need to be heat treated, I have always used heat treated stock or done a most machining hardening. What is the worst that can happen if it does not work, you will need to make them over. I prefer to over do it the first time and not do it again, but I do not learn as much that way.

Don’t.

Screws are the cheap replaceables, the tapped parts are the ones that stay, generally, and cost much more. That is the reason why the tapped part should be harder than the screw. Choose a tougher screw, not a hard. And employ a screwdriver that fits the screw face. Watchmakers grind their drivers to exactly match the screw.

Mechanola said:

Don’t.

Screws are the cheap replaceables, the tapped parts are the ones that stay, generally, and cost much more. That is the reason why the tapped part should be harder than the screw. Choose a tougher screw, not a hard. And employ a screwdriver that fits the screw face. Watchmakers grind their drivers to exactly match the screw.

Click to expand...

I worked in a tool and die shop for a while. Die sections are hardened to 55+RC and much harder than the standard grade 8 (and Allen) screws. It was standard practice to counterbore screw holes, so the first thread would not pull out. With the screw softer than the threaded material the screw stretches when tightened and the force is concentrated on the first thread of the die blocks. Too soft a screw could cause other problems as well, perhaps galling in the hole or breaking off in the hole if it is too soft, be careful there.
Good point on proper fit on the screw drivers.

Since I make screws from 01 tool steel , torch bluing does hardened the screws.
I heat the screw red , quench in oil and then burn off the oil on the screw with the torch and then allow it to cool.

Mechanola said:

Don’t.

Screws are the cheap replaceables, the tapped parts are the ones that stay, generally, and cost much more. That is the reason why the tapped part should be harder than the screw. Choose a tougher screw, not a hard. And employ a screwdriver that fits the screw face. Watchmakers grind their drivers to exactly match the screw.

Click to expand...

I hollow grind my screw drivers ends so the part in the screw is straight sided, not tapered. Also have taken a scrapped Yankey spindle with chuck, cut off the chuck shaft at 6" and added a brass T handle.
That gives very good push pressure and I can use the handle end as a light tapper hammer.

I think a screw should be 45/48 or harder..

Consider precipitation hardening stainless. 17-4? perhaps. Hardens at lower temp than typical quench from red heat.