Robs Howell V4

[gbritnell]

Rob,
Start out by making a tool like the one attached. Lightly cut the seat. This tool will ensure that the seat is concentric with the guide hole. After that put a little lapping compound on the valve and insert it into the head. Attach a small drill chuck or pin vise to the valve stem. Rotate the valve back and forth while every couple of cycles lift it off of the seat to redistribute the lapping compound. It shouldn't take much to lap it in. To test I make up a bushing adapter for my vacuum gauge. The one end will have a diameter a thousand or two larger than the port diameter. Then file a tiny taper on it. You can wring this into the port and attach the vacuum gauge or just a piece of tube and suck on it. Make sure you put a drop of oil on the valve guide to seal it while checking.

 

[RobConway]

Been chasing the runout in the lathe chuck for the machining of the valve seat. Seems my 4-3mm collet has a 0.03mm runout measured on a 4mm carbide shaft, however when I try and tighten it down to 3.175 (valve stem) it goes out to 0.12mm. Purchased another collet today 1/8" (4-3mm) however again a 4mm rod is even better at 0.015 but tighten it down for a 3mm shaft and its actually worse than my original collets >0.15 My 3 jaw chuck provides 0.05 runout on a 3.175 shaft. For comparison also got a 1/2" collet and with a precision silver steel 1/2" rod -its runout was soo good at 0.005

I have the ER32 tapper running at 0.005 now -better than the picture below at 0.015.. I reseated the taper and turned 90 degree.
Looks like I will get another 3-2 collet and squeeze in a 1/8 valve shaft and try again before I setup to machine the seats and make the valve cutting tool, I can feel as the 4-3 collet closes its not compressing evenly around the 1/8 rod. Although thinking I will be lucky to achieve <0.015mm runout and if I can achieve that I will cut 2 valves / seat cutter / lap and pressure test for one cylinder

 

[dsage]

Rob:
Go back one post and make the valve seat cutter George recommends. Works a charm.