Fuel tap fix.

[Tony saccParticipant @tonysacc93877]

The brass inlet spigots on one of the fuel tap bodies pulled out when I disconnected the fuel hose, the other seemed a little loose also. To fix, I removed the spigots from both tap bodies, reamed the holes, turned up two new brass spigots 0.08mm oversize and pressed them into place.

I’ve done lots of pressed spigots for various things and discovered if the brass spigot is polished the tolerance can be increased up to .30mm.

On this job I stuck with .08mm as the tap casing is very thin and I didn’t want to break it.  The casing around the spigot hole is a lot thicker of course.

[Clive FosterParticipant @clivefoster55965]

Very nice job.

I wouldn’t have had the nerve to try pushing a parallel interference fit into the soft casting alloy of the tap body. Too much chance of reaming out the hole if things got a touch out of line.

Unfortunately a bit small for my favourite, and much safer, self gauging taper method. The male and female parts being made with tapers on each side equal to the interference fit desired and sized so they freely side together until engaged half way. Much harder to mis-align things and forces are much reduced as things don’t come up to a full interference fit until fully home. I guess a taper D-bit could be used for the hole in true old line Model Engineering fashion.

The one I did donkeys years ago got threaded and Loctited. Never again! Too much hassle for the relatively minor saving over buying a new tap. But it was a “fix on Sunday ride to work Monday” thing.

Clive

[Tony saccParticipant @tonysacc93877]

I’ve done dozens and dozens of press fits in cast aluminium, 6061 and other stuff.  If the edge is round and the spigot polished they press together easy peasy.  It takes practice.

 

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