Would it be criminal to...

[svelocity]

...re-tap the pedal hole of a TA Pro Vis 5 crank to the modern 9/16 x 20 TPI standard?

Just asking...

[Aaron O]

No. Perfectly fine.

[christian]

Logical and fine.

[Louis]

How big is the existing hole?

http://www.accuratescrew.com/TechTips/images/tip8_screw1a.gif

[svelocity]

Thanks everyone for your replies!

Louis - I believe it's the older and smaller French Standard of 14mm x 1.25mm

http://sheldonbrown.com/velos.html#table

[Louis]

OK, so 14 mm = 8.82 / 16 inches

That's pretty close to 9/16

I'm not a machinist, but can one successfully convert a metric threaded hole that's designed for a male thread so close to 9/16 to that size? I'd worry that there wouldn't be enough material left for the new threads.

(again, I haven't tried to do this, others might have)

[svelocity]

OK, so 14 mm = 8.82 / 16 inches

That's pretty close to 9/16

I'm not a machinist, but can one successfully convert a metric threaded hole that's designed for a male thread so close to 9/16 to that size? I'd worry that there wouldn't be enough material left for the new threads.

(again, I haven't tried to do this, others might have)

Good points Louis. I was just going on what Sheldon Brown suggested was possible.

[Louis]

I'll be the last person on earth to contradict Sheldon (RIP), so if if he said it's possible, I'll gladly defer to him. I would assume you don't drill out the hole or anything like that, just use the 9/16 x 20 tap to create a new series of threads through the old ones.

I'd keep a close eye on it for the first few rides to be sure that the pedals are still tight and any sign of problems holding torque would be a red flag that there's something bad happening.

Good Luck :)

[bikinchris]

With all of the great cranksets in the world today, why would you want to deform an antique?
You might be able to trade it as is for something new. There HAS to be a collector somewhere looking for that crankset.

[Louis]

why would you want to deform an antique?


According to the TA web site they're still made today, with both pedal thread types offered ("9/16x20 ou 14x125"), so it isn't necessarily an antique.

I'll leave it to others to decide if something still in production can truly be considered an antique, or maybe a time-proven design.

[Don49]

...re-tap the pedal hole of a TA Pro Vis 5 crank to the modern 9/16 x 20 TPI standard?I too want to re-tap a TA crank to a modern standard. What's holding me back is that the pedal thread doesn't go all the way through the crank arms, it just a one-sided hole.

Anyone know if this could be cleanly re-tapped or would it need to be drilled through first?

[Wilkinson4]

Not criminal, practical. Got some Stronglight 49d with the same treatment.

mIKE

[ceolwulf]

I too want to re-tap a TA crank to a modern standard. What's holding me back is that the pedal thread doesn't go all the way through the crank arms, it just a one-sided hole.

Anyone know if this could be cleanly re-tapped or would it need to be drilled through first?

You can get taps that are made specifically for blind holes.

You might want to drill through anyway, in order to use the allen socket on pedal axles that have such.

[svelocity]

With all of the great cranksets in the world today, why would you want to deform an antique?
You might be able to trade it as is for something new. There HAS to be a collector somewhere looking for that crankset.

I think this is a fair point and a reason I asked the question. I wouldn't call TA cranks from the 70's an antique but it's certainly vintage. I suppose this question is similar to the question as to whether or not one should widen the drop outs from lets say 120mm to 126mm. It's practical and allows you to make your bike more modern but does it lose that vintage appeal?

Anyway I may just leave it alone and use the $45 it would cost for the tap (one time use too) and put it towards some cranks that better fit my needs.

Good discussion and thanks everyone. Cheers!

[CaptStash]

You can get taps that are made specifically for blind holes.

You might want to drill through anyway, in order to use the allen socket on pedal axles that have such.

This is what is known as a "bottom tap", and yes, they tend to be pricey. With that said, I'd bet a local garage will have one and that a six pack of good brew will get the job done!

CaptStash...

PS: I think I have one buried somewhere in a box from some damn ship I took to scrap.

[buldogge]

Remember, you need a pedal tap set (or a 9/16 reverse thread tap in addition to a "normal" 9/16 tap).

Most decent bike shops have the taps…I tapped a set of 14mm Stronglight 106s years ago and had zero issue with them…FWIW.

-Mark in St. Louis