French thread cutters? Bonkers

[Canuk]

I bought three thread cutters, for a good price. I reckon they are probably 1950s, they look like VAR but can't be sure. I'll upload photos later but they are very weird sizings. One of them is 35.2mm the other 36.15mm.

This is probably a question for Bikeworkshop, is this normal, to be slightly oversize? I don't know the first thing about bottom bracket tools so any info helpful

 

[novocaine]

Is it from measurements?
A tap is often slightly larger to allow clearance and prevent binding.

 

[Canuk]

No, it's actually etched onto the die

 

[mdvineng]

35.2 is probably for French 35 x 1
36.15 is likely to be Italian 36 x 24f

from Sheldon Brown

 

[juvela]

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t'is common for bottom bracket taps to be intentionally made very slightly oversize for to allow for manufacturing tolerances/variation in cups

back in the early eighties i changed me bottom bracket tap set from VAR to Bicycle Research Products, a California company

was unhappy to discover that cups installed in shells which had been tapped with them wobbled about a bit loosely

visited the head of the company, Don Millberger, and asked about this

he explained that when he visited the Paramount room at the Schwinn factory in Chicago they had a bin of Campag BSC cups which would not fit in shells tapped with Campag BSC taps so he intentionally had made his taps oversize

was not pleased with this so sold me Bicycle Research set and went with Zeus with which have always been content...


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[Canuk]

Ah, I see! How do I know if they are left or right hand cup dies (or does it matter, do they cut both?) I've got really old set of french dies from the 1920s, and they are marked left and right. I'm pretty sure they are VAR on account there were a lot of VAR tools in the same lot

 

[mdvineng]

Look at the helix and the cutting face direction.

 

[bulgie]

French and Italian are both right-hand thread (RH) on both sides. If you have a LH thread BB tap and it's metric, then it's Swiss.

I wonder if your taps are oversized for matching oversized cups. Campy did list 0.5 mm oversized cups as an option, here's a snippet from Catalog 17 (1974):


I assume those were for keeping a frame on the road when its BB threads were wallowed out.
Maybe Var made similar?

 

[juvela]

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oversize Italian cups for repair purposes are very real

purchased in 1971 and all chrome Atala off a bulletin board

wanted it for a part-out of its Campag NR bits

in examining it at seller's home noticed that fixed cup was not Campag

it was an OMG type cup with three doggs

when got cycle home and proceeded to disassemble discovered cup to be marked 36.5 so kept it with frame when sold


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