Threading Help

boostin53

boostin53

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I'm attempting to cut some 5/8-24 threads for some dies and have run into a little problem that I cant seem to figure out.

I did my first light pass to check the thread pitch. Its off ever so slightly. Since I was using a scrap piece of O1, I continued to cut them anyways. Because you know, you can never have enough practice. Well I finish the threads and then I use my cheap little thread gauge on them. No match. The first 3-4 teeth on the gauge fit the threads, but anything past that is a no go. They are just ever so slightly off. I compared the gauge to some dies I already have, and it fits.

I'm clearly not seeing what the problem is. Does anybody have anything for me to check? I triple confirmed I have the correct gears and the box set to the correct feed. The Jet 920 I'm using says to use 30 tooth gears and set the gearbox to 7. Those are correct. So I'm lost.
 
boostin53 said:
I'm attempting to cut some 5/8-24 threads for some dies and have run into a little problem that I cant seem to figure out.

I did my first light pass to check the thread pitch. Its off ever so slightly. Since I was using a scrap piece of O1, I continued to cut them anyways. Because you know, you can never have enough practice. Well I finish the threads and then I use my cheap little thread gauge on them. No match. The first 3-4 teeth on the gauge fit the threads, but anything past that is a no go. They are just ever so slightly off. I compared the gauge to some dies I already have, and it fits.

I'm clearly not seeing what the problem is. Does anybody have anything for me to check? I triple confirmed I have the correct gears and the box set to the correct feed. The Jet 920 I'm using says to use 30 tooth gears and set the gearbox to 7. Those are correct. So I'm lost.
Click to expand...

Are you engaging the 120 tooth gear instead of the 127 tooth gear?, If so, you would be cutting a 1mm pitch or 25.4 tpi. The b gear should be near the head stock with the spacer away from the headstock, according to the drawing in the manual.

Bob
 
The A gear is engaging the 120 tooth gear and the B gear is engaging the 127. Let me put it back together and take a pic.
 
Here is the B gear (30 tooth) engaging the 127 tooth gear. And a pic from the side. image.jpgimage.jpg
 
So does the A gear need to go on the other side of the spacerso both the A and B gears engage the 127 tooth gear? I have it removed, but want to make sure before putting it together.

Edit: this is in the manual. It shows the A gear engaging the 120 tooth gear and the B gear engaging the 127 tooth gear. Im lost lolimage.jpg
 
boostin53 said:
So does the A gear need to go on the other side of the spacerso both the A and B gears engage the 127 tooth gear? I have it removed, but want to make sure before putting it together.
Click to expand...

According to the manual, that is correct. Note the positions in the manual for the SAE 24 tpi and the metric 1 mm threads. They both use the 30 tooth a gear and 30 tooth b gear.
 
According to your pictures both the a&b gears should engage the 127.

"Billy G"
 
in all tpi threads both a and b gear engage with the 127
in all metric threads a-gear engages with 127 and b-gear engages with 120
forget about the photo follow the diagram
 
It looks to me like your cutting a 1mm pitch.
According to the diagram, a should drive 127 (30 teeth drive 127), and 127 should drive b (127 drive 30). You have the 120 driving gear b, like shown in figure 22, Figure 22 is a pick of a metric threading set up.

I am pretty sure 24tpi was the last thread I cut on my lathe it the change gear set up looks like this
IMAG0470.jpg
Notice how the 127 tooth gear engages two gears, and the 120 is just used as a spacer.
 
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