Pedal taps
 

Are pedal taps (9/16 20) designed to be threaded all the way through (thread in one side and pull out of the other) or do you stop at a certain point? They appear to be slightly tapered and the further you go in the more material you take off. I imagine this is how they are intended to work. I am using Hozan pedal taps.

Greetings, The main reason to tap crank arm threads is due to cross threading pedals, I put oil on the taps and run them in from the rear of the crank arm. Just thread them in enough to tap the damaged threads and then back it out.
Regards

They are only tapered in the beginning, to aid in starting the tap.

You need to run them in until you hit the straight section of the tap. You will find the effort to turn the tap is reduced when this occurs.

Steve

The safe answer is to run the tap in a bit then remove and check pedal fit. Some taps are tapered and will result in a very loose pedal fit (as me how I know). Additionally bike parts are not like precision parts most of the time. Lot's of pedal threads are far from the text book thread form in reality. Andy.

Yes...you can also ask me why I am asking this question...

So fill us in. Andy

Looking at a pix of the Hozan tap, the shank is smaller than the thread so certainly it can be run on through.
Tap has a taper and partially cuts threads on the first 6-8 threads, but after that the threads are full sized
and no further cutting will occur. The tapered section should be all the way through the crank, though
most pedals have threaded sections that are not as long as the cranks are thick.

Please don't chase out my cranks with your understanding of one brand of taps are and then assumed to be what other taps are. Andy

thread cutting taps work best '1/2' turn ahead and then '1/2 turn back' . clear the cut chips , then repeat.

use cutting oil..

I've always run pedal taps until I get to the "flat" part of the tap (non tapered). That is generally all of the way at the end of the tap, then I back it out the same way I put it in. It should back out very easily (I usually do it by hand with no tool.) I've never had trouble doing this. I have the park tool taps.

And yes, I do the 1/2 (ish) turn forward, then a bit back to clear the chips. Repeat, etc. You can do it by monitoring the pressure you're putting on the tool as well. When it reaches a certain point, turn the tap back a bit, then repeat. (Basically 1/2 forward 1/2 backward isn't a hard and fast rule.)

Are there any 9/16 x 20 pedal taps that are bottoming? I want to rethread a TA crankset from French, but the pedal holes are one-sided and don't go through the crank arms.

Those aren't actually blind holes; they're through-holes with plugs on one end. You should be able to carefully knock out the plug, run your tap through the hole, and then replace the plug.

N.B. You may find that your pedal spindles are too long; those cranks sometimes needed special short-spindle pedals so the pedal spindle didn't push the plug off. You could use washers to effectively shorten the spindle if it is too long.

Thanks John, I wouldn't have figured that out on my own.
Can I use any brand of tap, Park or Hozan? I seem to recall that some warn they are for thread chasing only, not cutting new threads.

English and metric pedal threads are close enough to each other that converting from metric to English is more like chasing than cutting new threads, so it shouldn't matter.

So here's my concern. To properly use a cutting tap, one must start the thing very accurately. One of the reasons you use a tap to chase threads is when someone has run a pedal in at an angle (that is, they've cross threaded the hole).

Chasing threads is a time-honored technique in machine work. But the taps do remove metal. So you end up with a weaker, looser threaded hole. Furthermore, if the person doing the threading is a novice (or even an momentarily inattentive experienced guy) and the tap gets started wrong, you've made the problem worse. Running the tap in from the inboard side is a good idea: the inboard threads probably aren't cross-threaded and can guide a good start.

But here's a question: another type of tap is called a form tap. Instead of having cutting edges, form taps are smooth, and have threads of gradually increasing size. In essence, they form new threads as they are screwed into the hole. There is yet another tap form, called a "chaser", which cuts a bit less metal than a true cutting tap.

Does anyone make chasers or form taps for 9/16 x 20 CEI LH and RH threads?

Taps are typically tapered un less designated a 'Bottoming Tap'. a pedal tap Thru Bike Tool supplitrs , won't be,

If really needing them, You need to go to a Machine Shop Tool supplier for a 9/16 - 20tpi bottoming tap, RH & LH..



BTW, screwing a pedal in from the back side of the crank arm can chase the threads in order to start the pedal threading in , properly..




...

This is the same idea as a form tap. Run the pedal in from the back. Start it carefully, and you should get the threads on straight. Use lubricant. The pros often mention high-sulfer oil, or an old product called moly-dee, but you could use Crisco or gear oil.

9/16-20 taps from McMaster-Carr
https://www.mcmaster.com/#standard-taps/=16jxmjp

No left-hand thread 9/16" x 20tpi taps, though, so only good for the drive side.

WRONG the entire tap has a taper designed into it to assure a snug thread seating. if you run the tap all the way through, the spindle thread will be loose as heck, and the load will be carried only by the face of the spindle shaft, leading to rapid wear of the crank arm.

The Park pedal taps appear to be regular 9/16 - 20TPI LH/RH untapered so I'm guessing this is pretty standard. That is to say, there is a short tapered section at the beginning to get the tap started but the resulting threaded section is not intended to be tapered. As such, starting them from the back side of the crank arm should work fine.

Specialty Bike taps can have a guide ahead of the cutting teeth

As it is all the cutting teeth are not tapered , just the lead in tapers ,, typically..

Present your arguments to the contrary with Pictures SVP.

Scroll down a little bit and there are:
Left-Hand Inch
https://www.mcmaster.com/#2584A907
https://www.mcmaster.com/#2584A908
https://www.mcmaster.com/#2584A909

victornet has them a little cheaper: 9/16-20 High Speed Steel LEFT HAND Plug Tap
The R hand threaded variant also there.

Seems like there is some confusion as to taper on taps, with some posters apparently
feeling the cranks should be tapped like gas and water pipes with a definite taper.
Since pedal threads are not tapered this makes no sense as only the innermost threads
would hold the pedal and it would wobble around in the outer most threads.

OTOH taps are sold in a variety of forms: bottoming, plug and starting. All have a bit of
taper in the initial 2 to 8-9 threads to facilitate starting the tap in the hole for start or plug
taps and with bottom taps the assumption is that the threads are already started, are in
a blind hole and the tap cuts to within 2 threads of the bottom of the hole. Some taps are
sold as re-threading or repair taps, usually these are carbon steel and not HSS and are
meant to repair bunged up threads and are typically plug configuration.

https://en.wikipedia.org/wiki/Tap_and_die

Mcmaster listing of tap types: https://www.mcmaster.com/#standard-taps/=16k1c7g

Whenever removing material the newbies should go slow and use a trial and fit process. Some of us "vets" have not followed this advice and paid for new parts, on our customer's bikes or ours... Partially chasing a pedal thread (start from the back side) AND THEN removing it to be able to check the pedal insertion is so easy to do and doesn't take more then a minute each time. A minute that might save a crank arm and your pride. Andy