High tensile steel

It machines fine with tip tools but I'm not sure if it is suitable for exhaust valves.

EN24T turns to a nice finish, using conventional tooling. I use tipped tools. The T stands for 'tempered'. So this is a relatively strong steel which can be hardened if necessary. I have made some parts which are subject to considerable stress in a full size hydraulic tube expander, from EN24T. They were hardened afterwards (not by me) and have outlasted the original parts.

Marcus

Hi
I don't know what size the valves are?

When I only want a small quantity of a tough steel I sometimes use a high tensile Unbrako cap screw or bolt from the scrap bin. Or maybe a stainless steel bolt if corrosion is a problem?

I am sure one of the learned forum members will know the properties and if they are applicable to your use.

Even if you have to buy one it will probably cost less than buying from a metal wholesaler they often have a minimum charge.

Regards
John

All my open crank engines and 4-stroke aero engines have 303 stainless valves and that is what tends to be specified on less ancient engine plans. Easy to turn and easy to get hold of.

[PEDANT MODE]

The T in EN24T, EN16T etc. doesn't stand for 'tempered' it stands for the specific temper condition. There are quite a number of different tempers available, but you'll normally only manage to get the other conditions if you are ordering quite a few tons of the steel at a time.

In the case of EN24T, it works out at about 34hRC. It actually machines better than when in the fully annealed condition. which is rather grabby and tear prone.

[/PEDANT MODE]

The T actually indicates the mechanical properties, specifically the range of tensile strengths the steel must fall in. T is 850 - 100 MPa.

Oddly the letters seem to be consistently applied to both EN numbered steels and BS 970 numbered steels.

EN24T is actually two designation systems behind the curve, MEW editor Harold Hall was fastidious about referring to 230M07 instead of EN1a, but actually since 1991 he should have been quoting BS En 11SMn30.

All my local stockholders sell EN1a...

Neil

I think you want another 0 one the end of that Neil. 850-1000

Neil, the first BS970 used the (old, British) EN numbers, only in early 1970's versions of BS970 were the 'new' designations brought in. So not really a surprise that the 'condition' letters were used across issues.

Many years ago a customer of mine who worked at an Unbrako manufacturing plant brought me a quantity of bar ends from auto screw making machines 4"-5" long, he told me they were EN24. The material turned beautifully and was indeed extremely tough when heat treated as you would EN24 from the old ESC spec book.

It would be interesting if anyone can confirm the material spec for Unbrako screws & bolts ?

Any Thoughts ?

What about using a full size vale and machining to the size you require.

My flash steamer valve is a Rover K series exhaust valve and can machine with sharp HSS tools.

Make sure its valve with a non welded head also check material some pattern valves are not that good.

En 21-4N is good genuine old 650 Triumph exhaust valves were made of that cheaper types would tulip or worse.