Some advice please.

I have made two multi tooth gear cutters in boron steel of about 60 mm diameter, 1 inch bore and 6 mm in section thickness; the next stage is to harden the cutting teeth.

I want to restict the risk of scaling in the bore and location faces next to the bore and as I don't have suitable grinding facilities to finish those they are machined to size.

Can anyone recommend an effective coating that will do this for me please?

Many thanks

Brian

Gentlemen,

Thank you for your suggestions

Michael. I'll see what the guvner can provide in the way of soaps to try out.

Jason. I tried your suggestion as I have Tippex in the house. Testing was done on a small sample of the steel used for the cutters, painted on one side and open on the other. At red heat I could see scale forming on the unprotected side and after quenching the painted side was a lot cleaner, not spotless it must be said. Out of interest I took a sample up to gas welding temperatures, here the Tippex failed as you would expect in a severe test like that.

Niko. Duffy Condursal is probably excellent but buying and shipping from Illinois for a small job like mine is completely unrealitic; if the job is a disaster it is easier to make new parts and try again. If I was doing it every day that might be a different matter.

On balance I might try a combination approach with soap and Tippex, the Tippex is visible which helps a lot in monitoring the effects

Thank you all again

Brian.

Hello Niko,

I looked the product up and was taken straight to the Duffy page in the USA. I would need to look for it from a UK stockist in Yorkshire, next move if the other methods fail me.

Thank you again for you interest

Brian

Hello Neil,

I have seen whiting (what ever that is) mixed with meths as a recommendation. Checking out French chalk I find it is actually ground talc and that of course is talcum powder, so I will experiment with that as well. At least the perfume will inprove the smell of the job! Another experiment would be to mix plaster powder (gypsum—calcium sulphate) with meths.

Just for reference, my wife laughed when I asked about soft soap—–unobtainable she tells me. It is based on potassium stearate rather than the much cheaper sodium stearate, the basis of ordinary soap, and that difference is where the 'soft' bit comes from. Today those more gentle soaps have all been replaced by pump action oil based creations, probably completely unsuitable for this purpose.

Regards

Brian

Hello John,

I've used Black lead as grate polish in the past, just never considered it for this application. The last time I used it the formulation had given it an almost silvery appearance, certainly not black as it had been. I think in the end I used to add graphite to shoe polish and use that instead.

In your case scaling would be very bad news and the sealed plugs are perhaps doing much of the work, but there will be residual oxygen in the barrels before you seal them.

I will mull over all the contributions and choose a path, at the moment shields and plugs sealed with Pyruma is my favourite

Jack Hobson

I don't have the facilities for heat treatment salts but I do have a small muffle oven, so it will have to be the more traditional methods of heating and soaking at temperature followed by water quenching. My experiments on small samples of this boron steel so far leave them hard enough after quenching, but I have yet to try the effects of stress relief. Local industrial advice was to use a domestic oven at 180 Centigrade

Brian

Hello John Ockleshaw and Vic,

I have spoken to a local heat treatnent business, they even know the boron steel I am using, but they don't have, or don't bother with small scale facilities for one and two off's as these will be. The neat way would be to induction harden the rim with the teeth, but that is not available with these people.

I suspect I would have to travel to Gateshead of even further afield to get professional help of that kind and for the few gears these are to make the effort and cost of it all would be self defeating.

Vic. I don't know where stainless steel foil can be acquired either, for this job I will make compatible shields and clamp them in position, using Black Lead, powders in meths or Pyruma as sealants depending on the results of trials on test sections.

Thank you though for the interest and suggestions

Brian

Edited By Brian Wood on 21/08/2014 09:41:43