lathe spindle thread ? - Page 2

1. Plastic
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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.

2. Cast Iron
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Originally Posted by dceg
*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

3. Diamond
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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

4. Stainless
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"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"

5. Diamond
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Originally Posted by Ralph_P
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"

6. Diamond
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Originally Posted by dceg
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

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

8. 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.

9. Diamond
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Originally Posted by L Vanice
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.

10. Diamond
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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.

11. Plastic
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Update. The spindle has a diameter of 1.620" on bull gear side and tapers down most likely due to wear. aka. Nominal 1-5/8" x 7 tpi. I have two factory made dog plates that fit the spindle as well as 3 back plates for chucks. I discovered this by making my first thread ever on a lathe. I had a bucket of change gears that I was determined to bring this Ol girl some love. I figured out the nomenclature on Brass tag. SP (spindle) & SC ( screw ie; lead screw ). Turns out I had every gear combo needed. The Brass thread chart shows TPI from 4 to 40. One exception there is no 13 tpi. This explains my 1/2" 9/16" bolt that would"t fit. Yes it has 1/2"-12 tpi bolts. not 13 tpi. I cut a piece of 1.625" from aluminum and began threading after several Youtube videos. IT FIT !!! I can't believe I sat on this project for 20 years, I'm currently working on completing my tool post grinder and replacing the tail stock quill. I realize I made a huge mess explaining this earlier.