First threads!

[macardoso]

Thanks!

Yes, that's true.

Isn't that true of all thread mics that have changeable anvils? I know Starrett makes thread mics with fixed anvils which require you to buy a full set for all the thread pitches. Each one is over $350.

That's what we would use in the inspection lab at work. Saves money in the long run if your inspection guys aren't wasting a ton of time re-zeroing the equipment between every part. That and a ton of thread gauges. We also had Starrett make us some custom micrometers for doing precision gears.

 

[devils4ever]

That's what we would use in the inspection lab at work. Saves money in the long run if your inspection guys aren't wasting a ton of time re-zeroing the equipment between every part.

That makes sense in a production environment.

 

[Nigel123]

I cut a 3/8"-16 thread on my lathe and had a chance to use my new Shars thread mic. According to the Theoretical Machinist.com's thread calculator, the pitch diameter range for this thread is: 0.3287" to 0.3331". I measured 0.3312" with my Shars thread mic. It fit the matching thread perfectly! I must say the thread mic is definitely easier to use than the wires, but it still requires a little finesse in using.

Also, I confirmed that the 0.75/TPI equation works. In this case, 0.75/16 = 0.0469". I advanced my compound by 0.044". Like previously mentioned, use this equation as a guideline and keep measuring as you get close!

View attachment 321158

Nice looking threads
Still waiting for the thread mic to arrive
The formula is pretty handy to use if set up is right but only good if the parts can be fitted
Funny you cut a 3/8 16 thread the last one I cut about 3 months ago
First pass looked O.K.
Second pass a little rough
Third pass took the points off the thread
Note to self change lathe back to imperial after threading metric

 

[devils4ever]

I found I have to take very light cuts when threading on my mini lathe. The first few passes I can do 2-3 thousandths. After that, I only do 1 thousandth cuts. I sometimes repeat the cut at the same depth to make sure it's clean and not stressing anything. I'm sure a full size lathe can do much deeper.

 

[Nigel123]

I found I have to take very light cuts when threading on my mini lathe. The first few passes I can do 2-3 thousandths. After that, I only do 1 thousandth cuts. I sometimes repeat the cut at the same depth to make sure it's clean and not stressing anything. I'm sure a full size lathe can do much deeper.

If the work is well supported I start at about 8 to 10 thousandths then drop to 5 or so one or two spring passes to clean it up
1 or 2 at the finish to get the fit
Looking forward to try the mic when it comes hope to be able to machine a thread and have
a good fit without test fitting

 

[devils4ever]

You must have bigger lathe than me. If I go too deep, I get into trouble quick!

 

[Nigel123]

You must have bigger lathe than me. If I go too deep, I get into trouble quick!

12 x 37 with 2 hp motor I use HSS tooling with no rake
Trying carbide threading inserts have to change my methods
seem to be cumbersome especially when using the tail stock
and cutting smaller dia threads

 

[SLK001]

You must have bigger lathe than me. If I go too deep, I get into trouble quick!

There is something really wrong if all you can cut is 0.001" each pass. What lathe do you have? Are you using the cross slide, or the compound to feed the cutter?

 

[ErichKeane]

There is something really wrong if all you can cut is 0.001" each pass. What lathe do you have? Are you using the cross slide, or the compound to feed the cutter?

Yeah, that doesn't sound right. I'd make sure the tool is on-center (even more important on a hobby lathe!) and sharp, and your belt tensioned. On the smaller lathes you might find that upping the RPM helps a little as well.

 

[devils4ever]

I have the MicroLux 7X16 mini-lathe from MicroMark. I'm using the compound set to 30 degrees.

I run the lathe at very low speeds to stop the cut in time. Probably in the 30-40 RPM range.

If I take deeper cuts, I'll get chatter and/or the tool with jam into the work piece and jam up everything.