PM-1660TL

[Downunder Bob]

I tried a 1/4-20 thread tonight, and on the scratch pass I crashed the 60° HSS cutter into the work very near the chuck. The 60° form tool went past my safety groove (the length where I intended to disengage the half nut lever) and into the round stock that I had sticking out (which I never intended on getting into). This broke my HSS threading tool (see photo).

This happened because I somehow failed to disengage the half nut lever. I guess I wasn’t used to the feel of this particular lever.

Once the machine was turned off (I used the foot brake), the 60° tool was jammed against the chuck jaws, and I wasn’t able to disengage the half nut lever. I was a little concerned that I wouldn’t be able to get the machine going again because the half nut lever was stuck engaged and the form tool was very tight up against the chuck jaws.

The carriage was also flush up against my micrometer stop. I had to move that back out of the way and loosen the QCTP to make room to slide the tool holder back toward me.

Even then, I had to allow the still engaged half nut/leadscrew coupling to continue a little toward the headstock until I could disengage the half nut lever. This all makes the case for practicing the threading maneuvers out where there is room to do so.

View attachment 344193

Get on the internet and find Joe Pyzinskie videos. He ha s a sure fire method of screw cutting both internal and external, guaranteed you will never crash the tool into the chuck, you will always get good result This method also allows you to run at higher speeds which will improve finish. It's bulletproof.

 

[erikmannie]

The pm-1660 description implies that the adapter fits into the internal taper of the spindle. Have you tried that?


Spindle:

• Spindle Mount D1-6 Camlock Quick Change
• Internal taper of Spindle (With included reducing sleeve) MT 4
• Spindle bore 2.55” in. diameter (will pass a 2.500″ piece)

No, I have never tried that. I always had a 3 or 4 jaw chuck mounted up while trying to insert a dead center. Now that I realize how it is supposed to work, I can see why I had such difficulty.

So apparently chucks, face plates and the like do not have a taper in the center hole.

The thing that threw me off was the dimension for the maximum diameter of an MT6 taper (2.4940”). Reading that my lathe can pass a 2.5” bar, it sounded like I would be able to slide an MT6 dead center all the way through. I still don’t understand how something with a 2.55” diameter can have a 6MT if the max diameter of a 6MT is 2.4940”.

Apparently this all gets sorted out at the spindle nose. I will be very interested to get a nice close look at the spindle nose when I install the face plate.

Note: Alan B. helped me install 4 jaw chucks (in person!) on both of my lathes last weekend.

 

[davidpbest]

If the bore of your spindle is 2.5”, the only Morse Taper that the spindle nose could have is MT7. Every other MT taper is smaller at both ends than the ID of your spindle. An MT7 taper is 2.75” at the small end. An M6 is 2.116” at the small end which would constrain the spindle bore to less than 2.5”.

 

[erikmannie]

If the bore of your spindle is 2.5”, the only Morse Taper that the spindle nose could have is MT7. Every other MT taper is smaller at both ends than the ID of your spindle. An MT7 taper is 2.75” at the small end. An M6 is 2.116” at the small end which would constrain the spindle bore to less than 2.5”.

This is the mystery! I have an email in to PM tech, and I will post on here the contents of their reply.

How horrifying would it be if I found out that I had no taper in the spindle nose?

My machine has a D1-6 camlock, so the question is: what are the dimensions and angle of the internal taper of a D1-6 camlock spindle nose?

That question is not answered here:

Lathe Spindle Nose Mounting Identification Chart

Lathe Spindle Nose Mounting Identification Chart

www.smalltools.com

 

[erikmannie]

Get on the internet and find Joe Pyzinskie videos. He ha s a sure fire method of screw cutting both internal and external, guaranteed you will never crash the tool into the chuck, you will always get good result This method also allows you to run at higher speeds which will improve finish. It's bulletproof.

I have watched most of Joe Pie’s videos several times. He is amazing! As I recall, I was reluctant to try the “threading away from the headstock” because I think he turned his threading tool upside down. Until I get more experience, I want to keep those forces pushing down on the carriage. I’m sure it’s fine to pull up, however.

 

[davidpbest]

This is the mystery! I have an email in to PM tech, and I will post on here the contents of their reply.

How horrifying would it be if I found out that I had no taper in the spindle nose?

Oh, it would be so horrifying that you should machine an MT7 taper into the spindle nose yourself. What a great opportunity to learn how to cut tapers! I’m sure Joe Pie will teach you how.

 

[Ianagos]

Oh, it would be so horrifying that you should machine an MT7 taper into the spindle nose yourself. What a great opportunity to learn how to cut tapers! I’m sure Joe Pie will teach you how.

I don’t think I’d try that just yet


Hopefully I can clarify a few things for you.

You don’t need any chucks mounted to use a center in the headstock.

The spindle nose refers to the small outside taper and mounting flange that is d1-6 on your lathe

The inside of the front of the spindle is very likely to be tapered. I haven’t seen a lathe where it’s not. But the tapers vary. Your lathe should have come with a tapered reducing sleeve. It may have just looked like a ground cylinder with a hole in it.

Once you find this or order one from pm you need to remove your chuck and then clean the first few inch of the spindle bore very well. Then also clean the adaptor inside and out.

Most likely the adaptor fits the same size centers as your tailstock although that’s not always the case. Therefore I’d say it’s probably an mt4. Clean and mt4 center and slide it in it should seat just like in your tailstock.

Then lastly you can add a faceplate if you want. Or a chuck. Old school would be to use a face driver plate but not many people have one.

 

[AlanB]

Erik, I wonder why you are looking for some other taper in the spindle. They only claim MT4 with the included adapter. So I suspect the spindle taper is not a standard one, and only the adapter supplied matches the custom taper in the spindle bore. One task would be to document that taper so you could make other items that would directly fit into it.

The fact that they didn't use a standard taper in the spindle suggests some reason for not doing so. Perhaps PM will reply soon and shed some light on the issue.

The pm-1660 description implies that the adapter fits into the internal taper of the spindle. Have you tried that?

Spindle:

• Spindle Mount D1-6 Camlock Quick Change
• Internal taper of Spindle (With included reducing sleeve) MT 4
• Spindle bore 2.55” in. diameter (will pass a 2.500″ piece)

 

[Just for fun]

Erik, I just read through this thread. That sounds like a really nice setup you have. I don't even have a lathe yet, but I sure enjoy learning.

 

[erikmannie]

It will be interesting to see if the reducing sleeve has the same angle as a #7 Morse taper (1.4894°).