Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  

Go Back   > >

Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

User Tag List

Thread Tools Search this Thread
Old 07-02-07, 11:23 AM   #1
seņor member
Thread Starter
seaneee's Avatar
Join Date: Jun 2006
Location: yay area
Bikes: Malvern Path Racer, Schwinn LeTour, Follis, Bridgestone 400 (RIP), concord 2sp
Posts: 1,157
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Tapping Steel Cranks

Has anyone ever done this? Will it ruin the cutting tool? Just curious.
seaneee is offline   Reply With Quote
Old 07-02-07, 11:56 PM   #2
Stop reading my posts!
unworthy1's Avatar
Join Date: Sep 2004
Posts: 9,834
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 208 Post(s)
no, taps are harder than the steel they are designed to cut. If you use a generous dose of cutting oil or tap fluid, and go slow (1/4 turn forward, then backward to clear the chips), there will be no damage to the taps.
unworthy1 is offline   Reply With Quote
Old 07-03-07, 11:53 AM   #3
Senior Member
Join Date: May 2007
Posts: 252
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
What exactly is it that you are trying to do?

Generally, in steel, you check the tables (like this one) and pre-drill to the required size. The drill sizes in the table will yield a typical 75% thread, which, for all practical purposes, is almost as strong as a full depth thread, yet much easier to cut. Easier to cut means you are less likely to break the tap off in the hole.

Just recently, I retapped a French threaded (15mm x 1.25?) crank thread to the standard 9/16-20. They are pretty close, yet just far enough apart that modern pedals will not fit. A few drops of cutting oil, five minutes light effort, and the job was done.

Be careful to start the tap square to the work. Back tap (1/4-1/2 turn) every revolution to break the chip.
Staggerwing is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

All times are GMT -6. The time now is 08:17 AM.

  • Ask a Question
    get answers from real people!
Click to start entering your question.