[CR]Re: seatpost up-sizing

(Example: Framebuilders:Jack Taylor)

Date: Sat, 04 Dec 2004 09:42:53 -0800
From: "alan" <worthy2@earthlink.net>
To: classicrendezvous@bikelist.org
References: <MONKEYFOOD31yeUsTsa000013bc@monkeyfood.nt.phred.org>
Subject: [CR]Re: seatpost up-sizing

>I've used the shim method on seat posts, but as you move the seat post the
>shim seems to squirm around and get out of position, it gets to be a hassle.
>An old machinist's trick to give some purchase on a too lose shaft is to
>take a center punch or a carpenter's nail set and ping a couple dimples
>around the shaft. A little edge of metal gets pushed up around the dent
>that will hold the shaft in place until you tighten the set screw or
>whatever. Too tight and just file down the erupted metal. It may not be
>prudent to put slight dents on a good post's shaft, even below the visible
>part, but it is one way to enlarge the diameter slightly. I have done this
>on solid shafts, never on a tube. I'd approach it delicately to avoid
>distortion, do a little test down at the bottom first.
>Dennis Young
>Hotaka, Japan
> The expanded machinist's technique is to knurl the thing. This
> "expands" the metal by raising the surface around the entire
> circumference of the tube, and there are hand operated knurling tools
> that you can use to control the depth and put the knurling exactly
> where you want it. Only caveat: the tools are a little pricey if
> you're only using it once, and it might be overkill. A sympathetic
> machinist or frame builder should be able to do it for you and do the
> right amount for correct fit.

Alan Goldsworthy
San Francisco, CA