Has anyone modified a French threaded crank set to fit British thread pedals? I have access to a set of 9/16" x 20 left and right hand taps to alter the threads on my Stronglight 49D crank set. Do I have to run a drill through the pedal thread or just go at it with the taps? Thanks and I was not sure if this question was more appropriate in this forum or a mechanical one.

Make sure the crankarms are firmly clamped and be sure the tap is square. Then go at it. I did it the hard way many years ago. I forced a Brit thread into a French thread crank. Tapped them out quite nicely, thank you. Had fun getting the pedals out 20 years later. In fact one is still stuck in the crank arm.

I've used the Park pedal taps to convert a few French Stronglight crank to English threading. No need to drill as your pilot hole is there for you, and since the French diameter is a bit narrower, you have an excellent chance of seating your tap nice and straight. Go slowly, use some sort of lubricant, and back it off every few turns or so.

Neal

I've done lots of them. I think it would be very hard to screw it up. You will be removing a tiny bit of material. I back off a quarter turn every turn.

I did it a few times, using all the wrong tools, and it worked out fine. That's my way of saying it's likely to go fine for you.

Thanks all. I am a retired professional Industrial Mechanic, or Millwright if you will, and I have tapped out hundreds of holes. However, the two holes I am concerned with now are mine and I do not want to screw up the cranks on my 1963 PX10. I will have a go at it and hope for the best. Thanks.

Just one more bit of advice, though being an ex-millwright you undoubtedly already know it. Start the retapping process from the back of the crankarms.

I have the oppersite problem of having not enough 'standard-thread' pedals and lots of spare french threaded pedals

The threads in the cranks are just fine and fit my French pedals no problem. But I want to ride the Peugeot wearing my clip in shoes and cleats assembly. Though I have tried to get used to the Old School cages and leather straps, I just prefer the user friendliness of my modern pedals. And believe me, I gave much thought and trial to this dilemma of form versus function. Function wins, hands down, in this case.

I did try the tap on a junk crank and am a bit concerned about the pedal seeming too easy to thread into the cleaned threads. Perhaps I should just buy a new set of Park taps. I wonder how much they cost?

Probably $35-$40 for a pair.

I paid $30.

Slightly O/T. How long do taps usually last? I've been curious for a while now.
-Gene-

I'd guess a few hundred uses, perhaps more if you're only tapping aluminum (not steel).

If you have a C&V friendly LBS, they may do it for free. Mine did.

Taps will last forever, or close to it if you are careful with them. Careful includes proper storage, ensuring that they do not bang up against one another. Careful includes proper thread cutting fluid and careful includes knowing how to use the tap. Not knowing often results in a broken tap.

That said, if I buy a set for myself, they will outlast me.

As a teenager in the mid-70's, I was so jealous of my non-French threaded brethren. They had so many affordable pedal choices, and my TA cranks were French. Then one day someone told me "You can just drive in new pedals, the pedals will cut new threads." Damn if he wasn't right. I drove in some new $13 Alloy caged Olimpics way back when and have had no problem since. I've even switched that bike to clipless since then and again no problems. Using a tap is obviously the right way to go, but if a ham-fisted teenager such as myself can accomplish the task with nothing but a department store pedal wrench and a cheap pedal, I think it's a pretty safe task for just about anyone to undertake.

Yup, I did that too! But now the pedal is stuck in my Stronglight 49D drive side crank. I think that I will do it the correct way with the hopes that I can remove the pedal should I ever have to.

I have a couple of bikes to pack up for shipping today, but after that, the Peugeot cranks come off of the bike and the taps go in. I hope!!! Better take some pictures of this so that I can write up a short How-To article on it.

I've never tapped pedals, but I have tapped other things often. I am surprised everyone recommends backing off after a full turn or more - I have always backed off a lot more often. Maybe every quarter turn, or every half turn. I thought this was to cut off and remove the shavings that get cut away so they don't clog the threads or the cutting edges...

When I was first taught to tap threads, it was advance 1/4, back 1/2/. I never questioned this, I just do it. Works for me.

My experience has been the smaller the tap the more often you want to back off. Sometimes worth backing out completely to clean the tap and hole helps too on deeper and blind holes. Removing a small broken tap is no fun at all! By the time you get to large taps such as for pedal threads the risk of breakage is minimal, at least in Aluminum with use of a good tapping lubricant.

Reviving an old thread.

What about taking a sacrificial set of pedals (who doesn't have a few mismatched pedals hanging around?) and cutting in channels perpendicular to the threads to mimic a tap? I guess a guy could even put the axle in a lathe and gently taper the end to ease the start.

While you can make a quick and dirty tap this way, for something like this IMO it is important to have some extra length to keep the alignment straight all the way through. Why take a chance on a crooked pedal? Plus it's a highly stressed interface. It might be fine to retap a kids bike or something, but I would splurge on the real tool if retapping a high quality crank like an old TA or Stronglight.

FWIW I like the Hozan taps because they have an extension piece to make sure they cut straight. They are still available and cost ~ $30.

I also have the Hozan taps for this reason but I haven't found a tap handle that fits them. They are also slightly larger than a pedal thread at the fat end so you have to stop about halfway down the tap lest you cut your pedal hole bigger than it ought to be.

I looked in the basement and discovered another Stronglight 93 crankset with ISO threads, albeit with a mismatched Nervar Star NDS arm, but it works perfectly. So instead of tapping, I'll be selling sometime this summer.

As a lifelong mechanic and tech working on cars, bikes and motorcycles, I have chased, rethreaded, reworked and saved many. I have an exstensive rethreading arsenal and make them if I don't have what I need.

I use a mini cut off wheel to make the slots so they have a fairly sharp edge to do the job. I made some out of some old pedal axles that work perfectly.

I also just last evening made one out of a Sugino drive side bottom bracket cup for a frame with the dreaded Italian that seemed to have good threads but wouldn't accept the cups and came with a VO threadless cartridge that was too short as it was for a 1x, had a lot of Loctite and was a mess. I always clean, dress and carefully inspect the threads with a pick tool by hand so I can see exactly what is going on. If I am satisfied they can be saved I proceed with the rethreader. If it seems like it will be much of a fight I use anti-seize and a lot of see-saw during the process.

My success rate is almost 100%, have done it many times at the dragstrip, side of the road, in the driveway, at work, etc. The bottom bracket was barely sketchy so the clean up was done by hand without much ado and a big relief to get a real setup in there. This takes a lot of patience to keep the bad ones from going further south but is worth the effort when it saves a bottom bracket, cv drive axle flange or worse from becoming a nightmare