Safety valve seat by drill, not D bit.

[Another JohnSParticipant @anotherjohns]

So, it's a cold clear day here, high was -14c, and yours truly decided to make a "D" bit in the basement workshop, with oil hardening silver steel. On the floor, with a fire brick or two, a plumbers propane torch, and the tub of oil. No workshop shed outside, no garage, just snow and my large torches packed away for the winter.

Fortunately the wife was at work; and the smoke detectors did not go off, but the hardening was not good enough. Had the doors open for a few hours getting (hopefully) enough of the smell of the oil quench out of the house – now letting it warm up…

Short of mail-ordering in a 9/32 dis HSS blank and grinding it, is it "ok" to make the valve ball chamber with a drill bit, not a "D" bit? The angle that the ball sits in will not quite be as sharp as with a D bit, but does that matter?

It won't be warm enough to do the hardening outside for a good few months yet…

John.

[Another JohnSParticipant @anotherjohns]

[DMBParticipant @dmb]

John,
whole idea of a D-bit is to make 90* angle between reamed hole under the ball and a flat surface giving a sharp corner for the ball to sit on. The reamed hole under the ball ensures the seat is round to match the ball. Careful attention to forming the valve seat should ensure satisfactory seating of the ball and therefore, a tight seal.
(Another) John.

[Mike ClarkeParticipant @mikeclarke87958]

Hi John,

When I made my safety valves I drilled most of the metal away and completed the profile with a slot drill mounted in the tailstock chuck (it was only taking the smallest amount off the diameter and squaring the bottom of the hole).

Regards,

Mike.

[Neil WyattModerator @neilwyatt]

Grind one on the end of an old drill. Won't be as hard as the other end, but good enough for brass or bronze.

Neil

[nigel jones 5Participant @nigeljones5]

The easy solution is to make the valve in two parts so that you machine the ball platform in the lathe, drill and ream the hole then screw the body on afterwards. This is how I do it as Im hopeless at making d-reams and the like!

[BazyleParticipant @bazyle]

There was no need to use oil instead of water for a low performance item like a d-bit. It might be argued that the excessive speed of cooling of a water quench is going to cause microcracks but so what in a low stress application like this. Also distortion isn't going to matter in the unlikely event of it happening unless you are trying to bore deeply.

Just do it again in water and don't even bother to temper if you are cutting brass.

[Russell EberhardtParticipant @russelleberhardt48058]

Make sure it is hot enough before quenching. "Cooked carrot red" is a better guide than "Cherry red".

Russell.

[Another JohnSParticipant @anotherjohns]

All good thoughts – now to plan the counter attack to ensure success…

Thanks – John.

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