How to chuck up engine valve and turn down stem .010" by grinding...

trackhound · Dec 16, 2019

Im dealing with a set of used rare valves that can be reused IF,,,the stems are turned down slightly, maybe .010-.015" via grinding.
I get chucking up the head but how to support the tip end..?
Either drilling a centering hole or putting it in a "cupped" end I've heard.
I've got a little knowledge on this...only enough to get myself in trouble.
Any ideas on how its really done?
OR...someone whos already providing this service?
Thanks

macchi7 · Jan 1, 2020

I would use a 4 jaw chuck in the headstock of a cylindrical grinder and a female "half centre" in the tailstock to allow access along the full length of the stem. Make sure there is a chamfer on the end so that as you grind the diameter, there is still contact between the stem and centre. Are these valves not available as something close as new and the head and collet groove only modified, which is loads easier. Another way would be sourcing someone who does centreless grinding, but I doubt they will do such a small batch.

TDegenhart · Jan 1, 2020

I don't know this for sure, but I have been told that valve stems are often nitrided for wear. Grind the stem and you will loose that.

Tom

Erstwhile · Jan 1, 2020

For spin grinding I use a a lever made of brass with adjustable weights to change the amount of support on the end of the part

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CalG · Jan 1, 2020

Ideas from the watchers

Other shop-made steady rests for the watchmakers lathe | NAWCC Message Board

Ken hosford · Jan 2, 2020

they can be done on a centerless grinder

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How to chuck up engine valve and turn down stem .010" by grinding...

trackhound

Plastic

macchi7

Aluminum

TDegenhart

Diamond

Erstwhile

Aluminum

CalG

Diamond

Ken hosford

Cast Iron

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