[CR]5/8" v. 16 mm; the truth can now be told...


Date: Fri, 31 Aug 2007 19:06:34 -0700 (PDT)
From: Fred Rednor <fred_rednor@yahoo.com>
To: hsachs@alumni.rice.edu, classicrendezvous@bikelist.org
In-Reply-To: <46D8B920.9000303@verizon.net>
Subject: [CR]5/8" v. 16 mm; the truth can now be told...

Friends,

I went to my basement and measured 5/8" and 16mm tools. I have an assortment of 6 point wrenches and sockets from Craftsman, Snap-On and Stahlwillie (German made), as well as a Park 16mm "peanut butter" wrench. I have a really accurate set of metric calipers with which to perform my measurements. To my amazement (and chagrin) the 5/8" tools were all closer to 16mm than any of the 16mm tools. We're not talking about big differences here - something like .05mm. But it was illuminating. The Park "16mm" wrench was the furthest from a true 16mm - it was actually something like 16.3mm.

I'm now convinced that tool manufacturers (even Snap-On) use the same pieces for both 5/8" and 16mm - they simply mark them differently. I'll probably never use that Park 16mm wrench, since I can get a tighter fit with a Snap-On 5/8" socket. But I'm keeping it as a collector's item. By the way, Park no longer makes 15mm and 16mm "peanut butter" wrenches. Luckily, you can still find them at those bike shops which still have a supply of older, unsold parts and tools.

This reminds me that when I'm working on 8mm or 13mm nuts/bolts, I always first try 5/16" and 1/2" wrenches, for the tighter fit. If the wrench is just too tight, then I revert to the proper metric size. Conversely, for 5/16" Allen screws, I first try the slightly larger 8mm hex key, and revert to 5/16" when the 8mm key is just too big. The only Allen head bolts I've encountered that were truly too accurate for this sort of substitution were the original Phil Wood axle bolts. Those were devious. The shaft was something like 8mm with 1mm threads, but the heads would only accept a 5/16" hex key.

There also seem to be a few 6mm fasteners that are actually either 1/4" or 7/32". It's a wild world sometimes... Cheers, Fred "sono eguale" Rednor - Arlington, Virginia (USA)

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