need advice on turning valve stems

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aonemarine

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I was in the shop yesterday playing around and was trying to turn out a small valve with a .10" stem 3/4" long. The problem i have been running into is the part deflecting and giving me a .005" taper. I could try turning the stems length to size an 1/8" at a time and and then polishing, that would probably get it, but im curious if there are any tips for turning it that would help me out?
 

jasonh

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I've made valves of such dimensions by silver brazing stainless steel onto an appropriately dimensioned drill rod stem and then machining the head to final dimensions. Hence - the need to turn the stem is removed.

That is: In the same manner as myfordboy:

[ame]http://youtu.be/Nofj1CGSCM4[/ame]
 

Gordon

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I have left them about 1/4" too long, center drill the end, use a live center and then cut to within 1/4" of the end and cut off the excess length.
 

aonemarine

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I have left them about 1/4" too long, center drill the end, use a live center and then cut to within 1/4" of the end and cut off the excess length.
Going to give this a try, sounds like a good idea.
 

aonemarine

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Just back up from the lathe, turned a stem 3/4" long polished and measured .00015" taper. Nailed it!!!! That was much easier thanks for the tips guys I need it. :cool:
 

aonemarine

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Yikes!! need to thin down and sharpen my parting off tool, the stem climbed over the tool once cut off and I thought for sure it was going to break, it didnt but I didnt like what it did one bit!
 

gbritnell

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You escaped with luck this time but trying to cut thin material is asking for trouble, even with a very narrow cutoff tool. What I do is just use diagonal cutters and snip it off then make up a split collet and cut to length. To make a quick split collet chuck up a piece of aluminum, in your case it could be .438 diameter by long enough for the valve stem to protrude. Put a mark on the stock where your #1 jaw is on your chuck and drill and ream for the valve stem size. Now remove from the chuck and split the bushing/collet with a bandsaw or slitting saw. Remove burrs and insert the valve. Now put it back in the lathe chuck, the mark you put on it should line back up with the #1 jaw. This is to keep it concentric. Now face off the stem to length. It will be held nice and securely.
I have a box full of these special made bushings. Make sure you mark what diameter the bushing is for future use.
gbritnell
 

MachineTom

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I prefer to part almost all the way through, then stop the lathe, and break off the part, it leaves tha smal pip, then a couple file strokes, or a trip the the belt sander and all good.

If you are very attentive , you will notice tha barely any chips are being made wil turning in the crossfeed, that is the clue the tool is low on center, if its high the force on the handle increases very fast, without chips, stopping instantly when these are noted, is the tough part.
 

aonemarine

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More great advice, I like the split collet idea. My lathe has collets that fit into the headstock and run very true, so I could probably make up a holer to fit inside one of them to hold the valve. the valve stem is too short (I think) to come in from the back side of the collets I have. I think my collets are 3c but south bend calls them 10K collets. Dunno for sure....
 

Herbiev

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Jasonh. Great video. Makes it look nice and easy.
 

Mosey

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More great advice, I like the split collet idea. My lathe has collets that fit into the headstock and run very true, so I could probably make up a holer to fit inside one of them to hold the valve. the valve stem is too short (I think) to come in from the back side of the collets I have. I think my collets are 3c but south bend calls them 10K collets. Dunno for sure....
I think that South Bend made 6K collets to fit the 10K lathe only. 3C are smaller and fit their 9" lathe and others.
Mosey
 

aonemarine

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thanks Mosey, seems like an odd ball collet size....JUST LIKE ME!!!
 

lensman57

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I was in the shop yesterday playing around and was trying to turn out a small valve with a .10" stem 3/4" long. The problem i have been running into is the part deflecting and giving me a .005" taper. I could try turning the stems length to size an 1/8" at a time and and then polishing, that would probably get it, but im curious if there are any tips for turning it that would help me out?
Hi,

I have turned the valves for a Webster engine and they are simillar to yours. I found that it was better to start with a large diameter stock and turn in one pass, you can then use a fine emery cloth to polish the valves or take out a small amount taper . A large diameter stock will witstand a heavier cut better than a thin stock and shallower cuts. Try it if you wish, worked for me.

Regards,

A.G
 
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