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[4]

Wear Issues

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dirty tools

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#1
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.
 
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Tony Wells

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#2
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.
 

4gsr

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#3
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
 

dirty tools

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#4
the hand wheel has to be very lightly held in direction of travel.
The half nuts are adjusted properly
 

chips&more

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#6
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
 
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