1/4 Inch by 30 TPI Tap Required



Paul

New Member
Feb 6, 2002
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Hi All. I need to make up some small nuts for old bike brakes, so would anyone have a second taper (intermediate) tap I could beg, borrow or buy? This is a really odd thread (!), not listed anywhere, being a 1/4 inch diameter at 30 teeth per inch. I could have one made to order, but it's a one-off special, and very expensive. I'm hoping someone may have one - it will probably be marked 1/4 30 BSC or CEI .
Thanks.
BSC = British Standard Cycle
CEI = Cycle Engineer's Institute
 

stevek

New Member
Sep 27, 2003
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found 1/4-28 and 1/4-32 sure it is not metric? there is a 6.3mmx1mm tap.
 

Paul

New Member
Feb 6, 2002
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Thanks fellas, for your quick response. Can't use 4 - 40 UNC, but kind of you to offer. I did consider that it could be a metric thread, but no, it's definitely 30 tpi, which would give a metric equivalent pitch of 0.846 m/m, which doesn't exist, 5 x .8 being the closest pitch. Also checked in case it is 1/4 inch by 1 m/m, but no. That would be 25.4 TPI, very close to the 1/4 by 26 BSC. Can't risk any mis-match that may damage the bolts and set screws which can't be replaced. Good point,though - 6.3 m/m is only 2 thou. under 1/4 inch. It does get tricky - found an imperial fastener recently which has a metric equivalent in pitch. Can't recall offhand what it was, might have been 7/32 by 32 tpi, a pitch of 0.79 m/m, again close to 0.8 m/m. When old fasteners are worn, not only are they hard to identify, but almost anything will appear to fit.
My error in my previous post - 1/4 x 30 is not BSC or CEI. I haven't found a listing for it anywhere. Used on Phillips centre-pull brakes, clamps the shoes to the caliper arms. Also on some early side-pull caliper brakes shoes, and some cable clamps. It's not uncommon to find old bikes with these brakes held on with a rusty and bent 1/4 inch COACH bolt! Thanks for your efforts. Cheers.
 

stevek

New Member
Sep 27, 2003
369
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well you can always break down and have a machinist make you one I bet. gonna cost though.
 

Paul

New Member
Feb 6, 2002
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I've found that it is a Raleigh thread. I should have guessed! Who else?