Help idenitifying bolt size
#1
10-31-18, 01:14 PM
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,706
Help idenitifying bolt size
I need to determine the size of a particular bolt in order to purchase the proper tap. I thought it was a 12MM bolt, but I am measuring 12.5MM with my caliper. Thread pitch is 1.25MM. Is 12.5MM outside the acceptable tolerance for the nominal diameter of this size bolt? 12MM is close to 1/2" and 1.25MM thread pitch is about 20/inch, but 1/2-20 is not a standard size. This is off a child's bicycle, most definitely made in China, so maybe it's some odd ball size?
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#3
10-31-18, 01:43 PM
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,706
Do you have a hardware store nearby that has a metric thread gauge?
#5
10-31-18, 02:00 PM
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,706
Yes . . . . full service hardware stores will often have exposed metric nut and bolt threads for most popular sizes and pitches for their Customers to use before finalizing a sale.
#7
11-01-18, 08:09 AM
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,706
1/2- 20 is a standard SAE fine thread.
#8
11-06-18, 10:38 AM
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,706
It's a 1/2-20 as suggested. I was able to clean up the threads on the bike pedals using a 1/2-20 RH and LH nut and purchased 1/2-20 LH and RH taps to clean up the threads on the bike. All is good now 
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