Thanks Dave (and others) for the suggestions,
You make a good point Dave, the factory would have had to match up each fork
to the cross bar if they didn't use the tapered bolt. And then there's
replacements.
Anyway, back to 2001 now, I went hunting at the local engineering supplier
and found a 12grade (even better for drilling out!!:-) 7/16 x 1 1/2inch tap
screw I think it's called (picture a big Allan's key with a head...), which
will be stronger than a bolt. The thread is a very good fit, no side slop
even with the thing almost falling out. So, it's looking good at the moment,
I'll take the three bits to the machinist and see what they can do.
I'll post what happens.
Thanks again
DaveW
'68 Mk1 PI Saloon
----- Original Message -----
From: "David Massey" <105671.471@compuserve.com>
To: "Dave W" <dw_triumph@clear.net.nz>
Cc: "[unknown]" <triumphs@autox.team.net>
Sent: Monday, October 15, 2001 4:53 AM
Subject: re; clutch problems, solved?? (Long)
Message text written by "Dave W"
Dave, the purpose of the tapered bolt is to remove any play that might be
present if the hole were straight. If they used a straight pin through a
straight hole there would have to be zero clearance and the pin would be a
press fit. With the taper pin all you have to do is screw it in intil it
bottoms out.
If the fork and shaft are tapped they must be tapped in place on assembly
so that the threads line up. The factory can't do this since this negates
any possibility of interchangability (in other words the assembler can't go
to the parts bin and grab one of each and have any hope of the parts
fitting together). But the problems with tapping these parts are:
1) Threads come in many varieties. The fork and shaft will, by necessity,
have cut threads and the bolt will have rolled threads. The shapes are
different. Also, I'm not a machinist but machinists I deal with tell me
that threads vary in terms of how deep are the grooves and how high are the
crowns. Loose threads mean there will be play and squirm in the connection
between the shaft and fork. Whether or not this squirm will be a long term
problem is something I do not know, but any additional play is not deisred.
2) The threaded portion of the bolt is the weakest portion. Whether this
makes the bolt not strong enough or not I don't know, but Grade 8 bolts
have a nasty tendency to snap off cleanly when they do break and drilling
out a broken Grade 8 bolt isn't fun.
Welding up the fork isn't such a bad option. You will have to sacrifice
both pieces if you care to remove them but replacements are available for a
little under $100 (I haven't priced these lately so look up the parts
before deciding) but you can overhaul the box with the shaft in place.
About the only thing you can't do is renew the cross shaft bushings.
In my opinion, if you are concerned about the taper pin breaking you should
also be concerned about the Grade 8 bolt breaking as well. Welding is the
best option.
Let me now say that both my TR3 and my TR6 use the taper pins and are
functioning just fine, thank you.
Dave Massey
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