• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
  • PLEASE: Read the FORUM RULES BEFORE registering!

Wear Issues

dirty tools

Active User
Active Member
How do I measure the lead screw for wear?

I don't know if the lead screw has worn of it the gears in the apron are work and need replaced, or both.

it is on my 1916 SB 13 X 5 great machine.
Last edited by a moderator:

Tony Wells

Former Vice President
Staff member
What symptoms are you experiencing? Usually you can take measurements way out near the outboard end where it sees virtually no use and should be as good as new.


Global Moderator
Staff member
H-M Supporter-Premium
With the half nuts engaged with the lead screw, set it for let's say 8 threads per inch. Set you up a 1" travel indicator to indicate carriage travel, mark you a point on the chuck that would be at 12 O'clock position or what ever, so there is a reference point to stop at. Make sure the slack is out of the half nuts and lead screw, mark "zero" on the 1" travel indicator. Rotate the spindle 8 times and stop rotation on the reference point at 12 O-clock position. Take reading on your 1" travel indicator. It should read 1.000" If not, the difference will be the lead error in your lead screw. I would suggest doing this for several inches starting at the headstock and advancing out toward the tailstock for about 12-18" or more. Record each reading to establish a pattern of wear in your leadscrew. A worn gear train will not create lead error, only if the lead screw is worn. Ken


Active User
Active Member
I would try making measurements using the 3-wire method. And using your measurement from the very outboard end (right hand end with the least wear) as your bench mark/reference measurement.

I once bought a Bridgeport feed screw off of fleabay. Seller said it was NOS. When I got it, I noticed wear. Seller said I was mistaken. I proved him incorrect. Using the 3-wire method. Findings proved the center of the feed screw had several thousands wear. He took it back and also paid the return shipping…Dave
Last edited: