Single Point Threading on a PM-1030V?

[shooter123456]

It was on the list of options to be purchased with the lathe. The box says “1/2” Threading Kit”. I don’t know what the 1,2 and 3 signify. At machining school, we used 60 degree HSS tool bits.

I might be wrong, but I don't think that is the insert. It looks like you are cutting using the insert seat.

If you have a look at this picture, you can see the silver seat underneath the yellow cutting insert. Your picture showing the insert on center looks like it is very low. The kit you purchased should have 2 external cutting inserts with it.

 

[erikmannie]

I might be wrong, but I don't think that is the insert. It looks like you are cutting using the insert seat.

If you have a look at this picture, you can see the silver seat underneath the yellow cutting insert. Your picture showing the insert on center looks like it is very low. The kit you purchased should have 2 external cutting inserts with it.

I believe that you are correct. I wondered why the 60 degree protrusion didn't extend out very far.

I am so glad that I posted the pictures. I would have spent 40 years cutting with the insert seat!

I am surprised that I could get it so wrong, and even more surprised that I ended up with a serviceable bolt.

I will try it again tomorrow! I was going to try knurling for the first time ever.

 

[shooter123456]

I believe that you are correct. I am so glad that I posted the pictures. I could have spent 40 years cutting with the insert seat!

It looks like it worked just fine and your threads look a lot better than some of the ones I have done using the correct insert... Who knows, maybe the seat is even better and no one knew.

 

[erikmannie]

It looks like it worked just fine and your threads look a lot better than some of the ones I have done using the correct insert... Who knows, maybe the seat is even better and no one knew.

When you use that much cutting oil, I imagine that any 60 degree angle would cut smoothly.

 

[Nigel123]

Glad it worked out for you
As you cut more threads it becomes easier less stress
I maybe wrong but I was taught never part off a piece with it supported by the center
Maybe because it is a long piece and will give before it binds it was okay

 

[erikmannie]

So I have made a cut more threads. I did not take pictures, but I have some points:

(1) I noticed that you can (if needed) turn off power and rotate the chuck by hand. This either backward or forward. This came up for me because I was taking more aggressive cuts (.003") and the insert dug into the work (whereupon I hit the e-stop). If this happened near the end of the pass, I would finish the pass by hand.

(2) I gather that one needs to leave the split nut engaged throughout the entire process for cutting a metric thread. Although I was cutting an Imperial pitch, I previewed this technique. Long story short, I wish that I had made a wider groove near the chuck. With the PM-1030V, you have to power off before switching from forward to reverse. Also, with the PM-1030V you need to start at low RPM (e.g. 50). That being the case, I would want a groove of at least 3/8" wide, primarily for the trip back (i.e. spindle in reverse). Starting at 50 RPM, I needed time to turn up the RPM in order to get enough torque to be able to get back to the starting point, as this is essentially a spring pass with a cutting tool with a negative rake.

(3) Speaking of torque, I was cutting a 1'-8 (1" diameter, 8 TPI) thread in mild steel and the machine could really only handle a .002" DOC. Yes, I had a sharp carbide 60 degree insert and plenty of cutting fluid. That made for a lot of passes.

(4) I found that nailing the major diameter made for a better finished result. I was happy to see that there is a range. Even if you have a taper, you can get all ODs in that range.

(5) I found that having a hardware store bolt of the desired size makes for a good screw thread mike comparison before measuring my work on the machine, or a thread measuring wires comparison for that matter. I found myself using the measured value from the hardware store bolt way more often than the pitch diameter listed in the reference tables.

(6) I found that you can fine tune (with the pitch diameter, of course) how tightly you want the nut to thread on and off. Is this a stud for somebody who wants to thread it on by hand or are you after a tighter fit, for example?

(7) The deep thread in the 1"-8 required me to use the bench grinder to grind a relief in the steel insert seat because the 30 degree insert was not long enough to do the job. One could use a HSS tool bit to avoid this issue.

 

[erikmannie]

On the 1"-8, I had to hit the e-stop about a dozen times. You have to think that is due to overly aggressive cuts.

When the cutting tool dug into the work, the spindle (rotating at between 106 and 180 RPM) would be unable to keep going. I would hit the e-stop button ASAP. I ended up increasing the RPM in an effort to get more torque. One wonders how much more torque is gained from going from 158 to 180 RPM. This is a 1 HP brushless DC motor in low range.

Is it a strategy to engage the thread dial at, say, 180 RPM and then turn up the RPM for the middle of the pass, and then turn the RPM back down for a more controlled stop near the chuck?

One time I did run in too far and the insert holder made contact with a chuck jaw, stopping the rotation of the chuck. E-stop ASAP!
My lathe always starts right back up after this, but I would expect to blow a fuse at some point, overloading the motor like this.

 

[erikmannie]

I had a small amount of 12L14 for one stud, and that machines so easily I felt like I was cheating! I would be inclined to buy some 12L14 hex (which costs about 20% more than mild steel), but I won't roll out the red carpet for myself for practice pieces. I will practice on mild steel and then, if I ever want it to be easy, use 12L14.

 

[erikmannie]

I will also just quickly reiterate that changing the change gears is a snap.

Here are some pics. The 1/2-20 is 12L14. The 1/4-20 and 1"-8 are mild steel. The 1" has chatter because the lass pass was a roughing pass with multiple unlubricated spring passes to clean it up for a pitch diameter measurement. When I measured it, I was there.

 

[erikmannie]

Finally, as much as I dislike all things Shars, I will concede that my Shars 0-1" screw thread mike does the job.