Catnap 

I recently acquired one of these stems, and it was short one of the bolts for the sliding clamp piece. I have a lot of spare bolts on hand in my shop but none of them fit, in either diameter or threading. Anyone know what kind of bolt these stems use?

Alternatively, I have one of the bolts I need, so how do I figure out the key data (threading, diameter) from it so I can find a match?

juvela

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Catnap 

It’s this model of stem:

juvela

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thank you for the photo

here is the catalogue page -

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oneclick 

I have one of the ones pictured - the Regolabile - and it's not the one in the photo. It has a triangular bottom section that rides in a V-groove in the quill. It's several bikes deep, but I think the bolt that clamps the bar-clamp to the stem has a cylindrical section that rides in whichever groove is chosen. This arrangement gives only a limited number of discrete adjustment positions, but is less likely to rotate under maximum power (which is a Bad Thing). For the infinitely-adjustable round version it looks as though any stem-clamp-bolt would do, given a pitch and diameter match. You say you have one that matches, almost certainly it is a metric thread, and similarly a normal- or fine- version is probably correct. Measure the diameter over the threaded section, if metric it will be a small amount smaller than a unit mm measure; then you only have two choices.

Catnap 

quick update here: the issue was the bolt diameter. I measured it with my calipers and it was 6.8mm diameter. so, roughly 7mm. All of the bolts I had measured to either 5.8mm or 7.8mm diameter, which translate to M6 or M8 bolts. I guess 7mm is fairly uncommon. Ultimately I was able to find a matching 7mm and it worked well. case closed!

oneclick 

7mm is not often found - at least in the cycle world. The first time I met it was on the clamp-bolts for the triple-tree of a Gitane Testi (look it up, 50cc, 6 gears, disc brake, glass-fibre bodywork. Yes, lots of noise, lots of fun.).

The carbon-steel ones had seized in the aluminium clamps, drilled them out and bought a die and made new ones.

T-Mar

No surprise here, as it's from the company that orignally used the atypical 7mm Allen key recess on their expander bolts. I'm sure lots of members can tell you stories of how frustrated they were trying to find said key for their 3TTT stem.