Help idenitifying bolt size

Reply

  #1  
Old 10-31-18, 01:14 PM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 4,105
Received 16 Votes on 11 Posts
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?
 
  #2  
Old 10-31-18, 01:22 PM
V
Member
Join Date: Jan 2010
Location: North East Kingdom of Vermont
Posts: 2,533
Received 1 Vote on 1 Post
Do you have a hardware store nearby that has a metric thread gauge ?
 
  #3  
Old 10-31-18, 01:43 PM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 4,105
Received 16 Votes on 11 Posts
Do you have a hardware store nearby that has a metric thread gauge?
I measured the thread pitch with a gauge and got 1.25MM. Are you talking about the kind you can screw bolts into to check if it threads in properly?
 
  #4  
Old 10-31-18, 01:58 PM
V
Member
Join Date: Jan 2010
Location: North East Kingdom of Vermont
Posts: 2,533
Received 1 Vote on 1 Post
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.
 
  #5  
Old 10-31-18, 02:00 PM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 4,105
Received 16 Votes on 11 Posts
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.
Yes, they have one of those. I'll swing by this weekend. Thanks.
 
  #6  
Old 10-31-18, 03:12 PM
B
Member
Join Date: Oct 2015
Location: Ct.,USA
Posts: 1,982
Received 107 Votes on 94 Posts
1/2- 20 is a standard SAE fine thread.
 
  #7  
Old 11-01-18, 08:09 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 4,105
Received 16 Votes on 11 Posts
1/2- 20 is a standard SAE fine thread.
Hmm, okay. Maybe that's what I have then, because 12.5mm seems way out of acceptable tolerance for a 12mm bolt, don't you agree? Whereas I believe 0.492" is within acceptable tolerance for a 1/2" bolt.
 
  #8  
Old 11-06-18, 10:38 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 4,105
Received 16 Votes on 11 Posts
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
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: