The most practical steel for my application

Hi Guys,

If I buy EN8 or EN24 steel how easy is it for the man in the shed to harden and if necessary temper these metals. If for example EN8 comes as normalised can it be machined then hardened easily without expensive equipment. I have tried to find the answer to this but all I find is can be hardened by flame or induction process and tempered at approx 600 to 700 degrees C for a period dependent on size. My thoughts would be holding such a temperature would be quite an accomplishment for a period without an oven.

I fully understand you can get variants of these steels but some basic pointers would be helpful. my aim is to look at the best substitute to silver steel should I wish to. Are the steels I stated more practical to use for a one off pinion on a clock than EN1A which is readily machinable though not as strong.

Chris

Hi Chris,

I just use silver steel for anything that needs hardening. I've had good success with case hardening powders on other metals.

As links are being removed, search ebay for "case hardening powder"

Jim

What size clock is it and what size pinion. Why don't you not want to use silver steel. A picture may help as well.

David

Use EN24T and leave it as it is. French clocks were hardened, English clocks were not. If you harden you must polish.

regards Martin

Just out of curiosity how do you go with distortion during the hardening process?

Spin (rotate) whilst heating and lower into a quench. Can be done in the drilling machine. Assures even heating and quenching.

regards Martin

Hi David, at the moment just accessing alternatives / possibilities.

Chris

Hi Martin,

Can you clarify whether you are recommending the use of EN24T over the use of Silver Steel and if so why. I am becoming a convert as both silver steel and EN24T are reputedly not the easiest steels to machine but EN24T as you say can be left once machined without further heat treatment. Or have I got this wrong?

Chris

Hi Chris

I am suggesting it because you seem to want an alternative to silver steel.

Quoting (loosely) from J Malcolm Wild (Wheel and Pinion Cutting in Horology) silver steel used to be available in free machining form which had 0.2% selenium to increase the machinability (KEA108). Selenium is no longer permitted as an addative for steel so Wild quotes alternatives as EN24T EN8DM and silver steel.

EN24T actually machines quite well with a good finish and is supplied hardened and tempered. Readily available it needs no further heat treatment. It is specified for gearing being resonably tough.

EN8DM machines more easily than EN24T. It can only be hardened by induction or flame hardening (or presumably case hardening).

And then there is Silver Steel which according to Wild can vary considerably in machinability. As far as I can gather the reason for this is the manufacturing process where the smaller sizes can have a work hardened skin due to cold drawing which in the smaller sizes may be quite deep and not removed by the centreless ginding to finished size. George Thomas stated that machinability in Silver Steel benifits from annealing which get round this issue. Alternatively machining a larger diameter rod down to size may help. Other better informed Metallergists on the forum may add to the above or put me right if I'm off track.

English clocks generally use higher module pinions than French clocks. For small diameter (Low Module pinions) hardening and polishing becomes more desireable or for 30 day or month going clocks where low friction is important.

Hope that answers your question

regards Martin

Just a quick practical update on using EN24T for clock pinions.

Just cut 2 off 0.6module 7 leaf pinions in EN24T using a new cutter and a part worn cutter, both PP Thornton.

Both cutters had no problems machining the teeth and a very good finish was achieved. Blank was initially machined in the lathe to produce a 0.350 " stock with a 0.206" length on the end for the pinion. Transferred to the dividing head on the Myford VMC mill to machine the leaves. Tipped cutter for turning and neatcut cutting oil added with a small brush for both operations. It is worth clearing the cutter of swarf after each pass to avoid recutting chips. Teeth were cut at 270 RPM with slow hand feed.

regards Martin

That should obviously read 0.206" dia length on the end

regards martin