Turnscrew Heat Treat

[Bill Haumann]

I just finished shaping the tips of a mongrel group of turnscrews I cobbled together over the past year, so I expect they are made of different steels.

It seems to me that it couldn't hurt to heat treat the tips, which I think I should be able to accomplish with a propane torch without removing the handles.

I was thinking to heat to red, quench in oil, and temper to indigo/blue.

Should that work for all the varieties of steel ordinarily encountered with vintage turnscrews?

[David Barnett]

I was thinking to heat to red, quench in oil, and temper to indigo/blue.

Purple. For screwdrivers, turnscrews, cold chisels for cutting metal, stop at purple, which should be around 525° F, whereas indigo/dark blue comes in around 570° and on the soft side, especially for smaller turnscrews such as gunsmiths use.

Unless your turnscrews are fairly long and robust, you may want to use a heat sink, shield/barrier gel or both if you intend to leave the handles in place. Bench jewelers use barrier gels to protect gems—welders for heat treat and so on.

[george wilson]

You apparently do not know what kind of steels you have used for your screw drivers. It is necessary to use known hardenable tool steels. Basically,there are 3 types of steel: Air hardening,oil hardening,and water hardening. There are many other steels that have too little a carbon content to harden. Indeed,if you have used a random low carbon steel,heating them red hot and quenching them might make them softer.

You can easily buy drill rod in either oil or water hardening. I suggest oil hardening because it is a bit tougher than the simpler chemistry water hardening steels.

If you have bought water hardening,heat it to an orange color and quench it in water. Then,polish the steel so you can see the bright surface and heat slowly to purple. Use vegetable oil or automatic transmission fluid to quench oil hardening,and temper it to purple. Never use used motor oil for a quench. You will coat the steel with a very hard black crust,which is a bear to get off.

[Winton Applegate]

As a last ditch, if the ones you have do not harden, you could use this stuff. Nothing to loose. A pardner in a shop i used to share had it around. I never tried it.
http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/color-case-hardening/surface-hardening-compound-prod27119.aspx

[David Barnett]

As a last ditch, if the ones you have do not harden, you could use this stuff. Nothing to loose. A pardner in a shop i used to share had it around. I never tried it.

It works but it's a very shallow case much more suited to resisting abrasion than torquing a challenging screw, but for small, thin parts it's worth a try. I've used it on smallish vintage files and rasps after resharpening. Neat, special use product.

[george wilson]

No,I'm afraid the steel needs to be properly hardened clear through,and the temper drawn. Those case hardening products don't penetrate very deep. Usually just several thou at most under normal use. The soft core of the screwdriver will still bend.

They took the GOOD STUFF,Kasenit off the market because it contained a bit of cyanide,IIRC. Everyone had used it for EONS without trouble. I haven't tried this new Brownell's stuff,but the thin penetration I referred to was what Kasenite would do. Most of the new stuff is watered down due to liability. It's too bad we have to bend over backwards to protect those who will use a product wrong,get it in their eyes,etc.. I grew up using the good old paint stripper that would eat your skin. The cure: KEEP it off your skin!!:)

[David Barnett]

They took the GOOD STUFF, Kasenit off the market because it contained a bit of cyanide, IIRC. Everyone had used it for EONS without trouble.

Absolutely right, George, Kasenit is no more. Sodium ferrocyanide (yellow prussiate of soda) sounds far worse than it is and because the cyanides are so strongly bound to the sodium, is not even particularly toxic, having long been used for anticaking in salt and other products intended for human consumption.


I grew up using the good old paint stripper that would eat your skin. The cure: KEEP it off your skin!! :)

Reminds me of the Churchill anecdote—

Young MP: "At Eton, Sir Winston, they taught us to wash our hands after using the lavatory."

Sir Winston: "At Harrow they taught us not to piss on our hands."

[Winton Applegate]

soft core of the screwdriver will still bend.

I was afraid of that. The screw drivers on my Swiss Army knives could use a bit of the toughening up. They bend as well. Maybe because they are thinner than a regular screw driver.

The case hardening stuff seems more in the line of gun dudes. He was a gun dude.

[george wilson]

Swiss Army knives are made of a stainless steel that is not the hardest metal for screwdrivers. Whatever type it is,it is very light and silvery in color. 440C is a type of stainless that will get pretty hard(60 RC),but even it has low carbon(.40). It relies on other alloys for its hardening. I don't know if any stainless would make a good screwdriver,however. My Leatherman is made of 420 stainless,a lesser alloy than 440C,which is called "surgical stainless". The screwdrivers in my Leatherman have been o.k.,though I haven't torqued them terribly hard. My little eyeglass screwdriver in the Leatherman was easily filed down smaller to fit eyeglass screws. Too easily. Most of the time,modern things being what they are,I have used the Phillips screwdriver in it without trouble. The little eyeglass screwdriver can bend rather easily if I try using it on a somewhat larger screw. I wish my Leatherman was 440C,but it isn't. It has still served me quite well. I have even gotten battery cables loose with it in a pinch.

[Winton Applegate]

What the heck lets take this down a nice rat hole.
See you guys in a minute.
I just bought this knife because it has the pliers in it, even with a small wire cutter. The pliers are like killer precise as far as edge alignment and surface detail and finish.

http://www.amazon.com/gp/product/B0007QCORY/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

At the same time I ordered a second set of these Snap On pliers, to have a set at home.

http://buy1.snapon.com/catalog/item.asp?item_ID=636952&group_ID=680940

Or so I don't have to have my home set at work; how ever you want to look at it. I found myself hauling them back and forth with me which is ridiculous. Nobody else I have found makes a 4-1/2" pliers.
I was on a pliers thing, what can I say ?
Well the new ones were so poorly made I took them back and got a second pair which were only marginally better and no where near as nice as my ten year old first set.
For five or ten dollars more Victorinox can make better pliers and throw in a nice pocket knife.

PS: on the Snap Ons it wasn't a day or two and I was peening the pivot bolt so the nut would stop unscrewing even though they do this stamped imprinting on the nut to act like a nylock. After ten years they are still doing this misguided stamping and NO body seems to have noticed it aint workin".

The Victorinox pliers just look on with amusement and a nice pivot that is free of play and can not loosen and literally fall apart as I have had the Snap Ons do.