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High tensile steel

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AJW21/11/2018 22:40:43
276 forum posts
117 photos
I need to made the valves for my gas engine.
'High tensile steel' is specified and I have found some 'EN24T' specified by the supplier as high tensile but I would like to know if it would turn ok?

vintage engineer21/11/2018 23:14:13
214 forum posts
1 photos

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

Marcus Bowman21/11/2018 23:17:09
162 forum posts

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.


AJW21/11/2018 23:23:53
276 forum posts
117 photos
Thanks, the high tensile steel was specified by Edgar T Westbury's for his Centaur engine, both inlet and exhaust, unfortunately no grade was specified!
Sounds like you have found it turnable.

John McNamara22/11/2018 03:09:52
1311 forum posts
113 photos

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.


JasonB22/11/2018 07:12:35
16870 forum posts
1815 photos
1 articles

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.

Mark Rand22/11/2018 17:14:26
828 forum posts


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.



Neil Wyatt22/11/2018 17:51:53
16927 forum posts
689 photos
76 articles

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...


JasonB22/11/2018 18:14:54
16870 forum posts
1815 photos
1 articles

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

David Jupp22/11/2018 18:21:48
708 forum posts
17 photos

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.

JohnF22/11/2018 20:38:57
906 forum posts
114 photos

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 ?

Windy22/11/2018 20:52:22
761 forum posts
146 photos

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.

AJW22/11/2018 21:18:58
276 forum posts
117 photos
Thanks for all the info!
I like the idea of using an existing component, I know I have one old exhaust valve in the could be useful box


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