Confused Mom/ Tap and Die Question...

June said:
Can anyone help a single mom figure out how to complete the task of re-tapping a piece of metal? My teenage son has an old moped whose pedal doesn't stay attached to the pedal arm. The opening on the pedal arm where the pedal screws in is stripped. It's an old moped, so finding a replacement part is almost impossible. I don't know how to figure out what size tapping bit to buy or where I would buy it.
I really don't understand "UNC", "NC", "UNF", "STI-UNF", "STI-UNC, "STI-METRIC" etc (and I can't find a source that explains these terms or even a "how-to" guide). All I know is the pedal size is 9/16ths; but how do I figure out how close the threads need to be (is this thread pitch?) Do I just buy a 9/16ths tapping bit? Thank you in advance for "any" help anyone may be able to offer.
Click to expand...
Hi June,
if you have too much difficulty in figuring all this out, i would be happy to do the work for you
if you can somehow get the crank and levers out of the moped
i'll make the arrangements to have the package picked up, repair the parts, and returned to you- all at no charge to you

my email is ulmadoc@gmail.com ,if you are interested
 
If one of the options to purchase a replacement do not work you can remove the crank and take it to a small local weld shop and have them weld the pedal in place. Many small places will do a quick job like that for real cheap while you wait. It looks like the threads on the pedal are also damaged.
To do it right you will also need a new pedal and a thread repair or replacement of the crank.

I am familiar with that break, I have done it a bunch of times. Have your son avoid jumping the bike, it is not made for it and as he gets older / heavier those pedals take a beating when it lands even just riding down a curb is hard on it. It is normal to stand up for bumps putting your full weight on the pedals and then add the impact from landing.
 
June said:
The pedal arm where the pedal screws into is only about 1/2" deep; it's a very hard steel. I'm hoping a 1/2" depth is enough to hold an insert. Yes, the male thread is also damaged. The crank and arm are one piece and it's on the right side. Although this moped is a 1977 Puch Maxi, I thought the thread size would be in inches because my son ordered a replacement pedal a while ago and the size was 9/16ths.
Click to expand...
What was the original problem that required the replacement of the pedal a while ago? There is a possibility that the threads on the replacement pedal were not compatible or were a poor fit. Normally we can feel how good a fit is when screwing the pedal into the crank. A wrench is only required for the last turn to tighten the pedal home.
From the photos I suspect that the replacement pedal might have been incompatible or was cross threaded. It was not fully engaged in the crank arm. If the pedal was installed properly abusive driving by the operator would likely end up with a bent pedal instead of mashed threads.
Your best bet is to get a new crank arm and pedal or to have it fixed by someone qualified. I can vouch for Ulma Doctor, he shoots straight.
 
You must log in or register to reply here.
Back
Top