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  1. #21
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    *If you don't know how to wire check let us know what size (3) wires you have and we can give you the measure size it should be.

    I have no idea what your talking about. Wire check? I'm getting a thread checker to start with. maybe a nut. Sorry for this correction. still navigating this forum.

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    Quote Originally Posted by dceg View Post
    *If you don't know how to wire check let us know what size (3) wires you have and we can give you the measure size it should be.

    I have no idea what your talking about. Wire check? I'm getting a thread checker to start with. maybe a nut. Sorry for this correction. still navigating this forum.
    The intent of the three-wire measurement of an outside thread is to measure the pitch diameter.

    Machinist's Calculator - Measure threads across 3 wires

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    Thread wire sets can be had from 10 bucks to about 40 bucks and with 3 wires are used to measure across a thread at the places it will touch or come close to the mating surfaces at near the middle of the V or sides, with measuring over the wires. This is perhaps the least expensive accurate way to measure a thread. The nut or thread gauge test would require a go and no-go nut or gauge for every thread so would be a very expensive way to test multiple/many threads. Yes, there are many other ways to check a thread.
    Still trying a 1 1/2 -8 with an inexpensive nut is an Ok way to check your thread, after you are reasonable sure /thinking it is 8 threads per inch.
    A 1 1/2-8 thread would measure 1.5249 to 1.5176 over 3 .0722 wires.
    A simple formula can be used to check that thread with using 3 wires wires near the size of .070

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    Quote
    "The OD appears to be tapered. maybe due to age use. Beginning starting threads OD 1.520" last thread is 1.620"

    Looks like 1-5/8"

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    Quote Originally Posted by Ralph_P View Post
    Quote
    "The OD appears to be tapered. maybe due to age use. Beginning starting threads OD 1.520" last thread is 1.620"

    Looks like 1-5/8"
    Unified Screw Threads, Standard Series

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    Quote Originally Posted by dceg View Post
    The lathe is a Sheppard. very old I'm thinking 1920's. I've owned for nearly 20 years and made new spindle bearings from brass shortly after buying. Chuck is tight and she cuts pretty good up to .025" close to chuck. I'm pretty sure it is a 8 TPI. I recently replaced the cross feed screw so I was getting acme thread mixed up with spindle threads. The OD appears to be tapered. maybe due to age use. Beginning starting threads OD 1.520" last thread is 1.620" Good idea on buying a 1.5" x 8 nut. The ol girl probable wont make threads again as I dont trust the very worn lead screw on carriage. I have a bad feeling because other bolts found on this lathe have odd thread size. 9/16" or 14mm course is very close but wont fit correctly. I'm new to this site and very impressed with multiple responses. I live in Des Moines so yes if any one is looking to assist please do.
    If the pitch is 8 TPI and the OD is a little more than 1.5, I would consider taking the spindle out and getting it machined to a true 1.5 inch x 8 TPI, perhaps using a new chuck, adapter plate or faceplate with that standard thread as a gage. Then you can use commonly available tooling for South Bend or other lathes.

    Such lathes normally have a 3 MT bore and they work fine with that size bore. If your spindle has something larger than 3 MT, consider whether the smaller thread would weaken the end of the spindle.

    Larry

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    Instead of taking the spindle out, machine it in place, using the lathe. It will be concentric to everything that way.

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    Given the that this thread began with a good deal of confusion about how to measure and describe threads , are you sure you're getting an accurate reading with the calipers?

    Is there an un-threaded portion of the spindle nose that you can measure to get the nominal diameter? It will usually be a few thou below the fractional dimension to allow for thread root clearance.

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    Quote Originally Posted by L Vanice View Post
    If the pitch is 8 TPI and the OD is a little more than 1.5, I would consider taking the spindle out and getting it machined to a true 1.5 inch x 8 TPI, perhaps using a new chuck, adapter plate or faceplate with that standard thread as a gage. Then you can use commonly available tooling for South Bend or other lathes.

    Such lathes normally have a 3 MT bore and they work fine with that size bore. If your spindle has something larger than 3 MT, consider whether the smaller thread would weaken the end of the spindle.

    Larry
    Along with that thinking if the spindle nose is not hard the machine might cut the 1 1/2-8 thread. With being mild-hard a carbide tool but might be considered. A quick file check would tell. Perhaps a center could be put in the head stock and a slug turned between centers to test the gearing for an 8 TPI if the Op is worried about the machines ability.

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    QT OP: [I have no idea what your talking about. Wire check? I'm getting a thread checker to start with. maybe a nut. Sorry for this correction. still navigating this forum.]

    I wonder if there is a PM guy close to dceg in Iowa to go have a look at this problem spindle nose.


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