Question about valves

[Adaware]

I tried to make some intake valves just to see if i could do it and i turned out much better than expected, i got the tolerance down to +- 0.005mm on a 4mm shaft 50mm long in stainless (free end machining) and i'm quite happy with that, the only problem is that i think the surface is too rough because i can't get more than 3000rpm on the lathe. I belive i need to grind them to get a proper finish but i need some ideas on how i can do it.
I have a 3-axis mill available where the spindle goes up to 12.000rpm, if i make a rotating fixture of some sort i can mount on the machine table i think i can do it in some crazy way. Anyone that have suggestions?

I want to do everything with machines because i need a lot of valves.

[One of Many]

You could cut them a tad big and hand sand in the spindle using 220-320grit wet/dry or emery to improve the surface finish and size them perfectly to a polished shaft before parting them off. Works fine for me!

How many valves? Large production runs might pay off to leave .15-.30mm, have them sent out and centerless ground.

DC

[stevehuckss396]

I also turn the stems to .005 thou bigger then polish with 600 and then 1000 grit. It takes only a few minutes if you dont leave more than the .005.

[One of Many]

Originally Posted by stevehuckss396 I also turn the stems to .005 thou bigger then polish with 600 and then 1000 grit. It takes only a few minutes if you dont leave more than the .005.

.005 seems a bit much for hand sanding and keeping the stem parallel. I usually only do .001-.002", but it does depend on the surface finish condition on the final cut. A poorer finish will take more to clean up. I have used a broad backer board behind the abrasive to support it enough to avoid a subtly waved surface from removing more in one area than another.

When the tolerances get really tight, I have fab'd up an external lapping clam shell clamp and use various grits of lapping paste. Fussy, but it works. I was surpized to see the honing process show how uneven the surface was after rough hand sanding the first .006.

By the size of the valves, that is a grand size model engine if it has a lot of them.



DC

[tstom]

You don't need a lot of rpm I believe the grinder spindle motor on my valve grinder only turns 3450 and the valve chuck motor is much slower...probably only a few hundred rpm

You could search for a used automotive valve grinder some of them go pretty cheap, just make sure the collet will close small enough for your valves

the finish on the face needs to be smooth but not mirror like definitely not polished ...the stem is smooth but with enough "roughness" to retain some oil

[Adaware]

The grinder wheel on the valve griner machine is pretty big so you can get more m/min with less rpm on the spindle?
I used a CNC lathe to make the valves so i can't go in there and hand sand to get a better finish, the old manual lathe is really stressed when it hits about 1500rpm and it's alittle unstable. What if i mount a live toolholder in the CNC lathe (se picture1) and mount a 125mm grinding disk (picture2) on it and spin it up to 2000rpm and i set the speed of the lathe spindle to 3000rpm. Than i can get a cutting rate alittle over 800 m/min, is that a sufficient speed on a grinding disk to make a smooth enough surface?
It would be similar to a valve grinder just a tad more complicated...


It's "huge engine", 300cc DOHC V8, that means 32 valves :P

Pic1


Pic2

[stevehuckss396]

Originally Posted by One of Many .005 seems a bit much for hand sanding and keeping the stem parallel.

You are right! I meant .0005. Didn't put enough zeros.