Drill rod and silver steel

[Herbiev]

I am just scouting around for some steel to make a valve seat cutter. I believe what is called drill rod in the US is known as silver steel in the UK and Oz. Any thoughts ?

 

[Parksy]

Check out a seller on eBay called offcuts galore. They sell silver steel/drill rod.

 

[Brian Rupnow]

Drill rod and silver steel are for all intents and purposes the same thing. They are both "through hardening " steels, as opposed to being "case hardening" steels. Case hardening steels generally require a heat treating oven and a supply of hardening salts which are a form of carbon. Case hardening steels remain "soft" inside, but develop a hard outer "casing" when heated in the presence of 'casenite', which is the hardening salts I referred to. For most hobby machinists, a "through hardening " steel is generally sufficient. Through hardening steels come in two main types, O1 which means that it gets hardened by heating to a dull red, then quenching it in oil. For W1 the process is the same, only you quench it in water instead of oil. This process makes the steel very, very hard, but leaves it brittle and unable to handle any kind of shock loading, as it will shatter like glass. To prevent this, through hardening steels are "tempered" after quenching, by soaking them in a high level of heat for a predetermined period of time, which "draws back" the hardness a bit but makes the steel much more shock resistant. For something like the valve seat cutter, you don't have to "temper' it, as it is only used by hand and doesn't see any shock loading. So---Make the tool out of drill rod or silver steel, do all the shaping and sharpening while it is in an unhardened state, then heat the business end to a dull to medium red heat, then plunge it straight down into a small container of 30 weight lubricating oil, twirling it a bit between finger and thumb as you do so. Swish it around a bit in the oil, and then just leave it in the oil for 15 minutes or so to cool off. That's all there is to it. It will come out harder than the devils horn, and needs no further work on it. If you do find out that you need to sharpen it, use a sharpening stone same as you would use to sharpen a knife. I don't think you can get the part hot enough with propane, I use an oxy -acetylene torch. If you only have a propane torch, try it and see what happens.----Brian

 

[Herbiev]

Thanks Parksy and Brian. I managed to score a piece from my local supplier so it's off to the workshop.

 

[bazmak]

which local supplier ? herbie

 

[xpylonracer]

When hardening silver steel I always heat to "carrot red" and keep the heat on for a further short "hold" period before quenching in water, the size of the piece determines the length of the "hold" period.
See the process in this video, check the video at 8:20 on time bar
https://youtu.be/Ev0zllycnHQ
xpylonracer

 

[Herbiev]

Baz. The steel I got is 4140 from Brighton Steel. I got a big tin of Hardite years ago and going to use that to case harden it.

 

[Cogsy]

I've bought drill rod/silver steel from Bohler metals and also Blackwoods if you've got either of those in S.A.

 

[Herbiev]

Thanks Cogsy. We have both here but opposite side of town from me. I'll see how this comes out first and if no good will get some silver steel.