[NoMSG]

I'm going to tap extra pedal holes to shorten the crankarms of my kid's bike. Two questions:

1. Is the tap/thread size 9/16-20? (we're talking standard pedals)

2. Where's the best place to get a left-hand thread tap in that size?

Thanks.

 

[Kerry Irons]

What's that tapping?

I'm going to tap extra pedal holes to shorten the crankarms of my kid's bike. Two questions:

1. Is the tap/thread size 9/16-20? (we're talking standard pedals)

2. Where's the best place to get a left-hand thread tap in that size?

1. yes

2. you will need to go to a bike supply source, most likely. I'd ask your LBS to check the QBP catalog. Loose Screws might be a source as well. Try Google.

 

[C-40]

9/16-20

Is the correct thread size. It's considered a special (NS) tap.

Here's one place to get a set: http://www.bikemannetwork.com/biking/p/TL7150

You'll also need an uncommon 33/64" drill bit. A standard 1/2 inch is likely to drill too small.

If you're not experienced in machining setup techniques, you may find it very difficult to get the holes drilled at the correct distance from the crank center and perpendicular to both the crank arm and BB.

 

[MR_GRUMPY]

I could swear that I've seen adjustable crank arns for little kids.

 

[NoMSG]

Awsome. Thanks. What size hole to drill?

Is the correct thread size. It's considered a special (NS) tap.

Here's one place to get a set: http://www.bikemannetwork.com/biking/p/TL7150

You'll also need an uncommon 33/64" drill bit. A standard 1/2 inch is likely to drill too small.

If you're not experienced in machining setup techniques, you may find it very difficult to get the holes drilled at the correct distance from the crank center and perpendicular to both the crank arm and BB.

After my post, I decided to turn on my brain and check Park Tool's website. Sure enough, they have a set similar to the link you gave me. But I'm sure Park's stuff is pricier and I'll have to order it from my LBS.

Yeah, I'm new at this, so there's a significant chance I'm gonna screw everything up. But, hey, it'll be interesting!

[please ignore the last sentence in my title. brain's not fully turned on and I can't edit title.]

 

[dogmeat]

Crank shortner--

http://www.tandemseast.com/parts/cranks.html

My kid's little TREK mtb has a double-tapped crank arm. On out tandem, the kid just wears her funky platform tennis shoes. You can always just duct-tape a 2x4 block on to the pedals- but if you have a milling machine to retap a crank, you could make a pretty nice pedal platform for less than the cost of a left-handed tap. But then, that's not the point if you just gotta machine a part!

'meat

 

[the bull]

Yeah those seem like the way to go, safe and does not ruin a crank.