- Oct 28, 2014
The drain hole in the fork leg has stripped the threads. Is there enough material to tap for 1/4 - 28? Otherwise I will need to buy a helicoil kit to do the job. Any idea what the existing thread is?
as said by Kommando it is BSW thread
IMHO there is plenty of diameter for a helicoil but not enough depth and even if you get the helicoil in, you'll probably have trouble getting a seal. If you have a machine shop willing, you could make a flat spot and use a 5/16 x 18 button head or hex head. The metal is very thin there - if I remember right only about 2.5 to 3 threads.It sounds like there is plenty of room to helicoil for 1/4 - 20 then.
The damper unit is a solid at the point of contact if the drain bolt was too long, the cavity starts above, BSA used drain bolts with an extension which engaged a slot in their damper body to stop it spinning on tightening or loosening the bottom damper body retaining bolt. I have added the same slot to Norton damper bodies and used a pin up the drain hole when tightening the bottom bolt.Just remember at the end of the hole is the damper unit, If you were to drill on location and to far you might alter the compression damping ?.
As it happens, I have both my Mk III lower sliders in my solvent cleaning tank at the moment. To those who say simply tap it out to 5/16", no can do. The counter-bore for the screw head is only .375". You would have no room for the screw head to seal. No big deal IF you have a Bridgeport mill.Anybody with a spare fork slider, can you measure the depth of the hole? I know the screw is very short. Right now the screw is in place and holding oil but barely. I will leave it in until more info comes in.