I Nearly Threaded

It is a bit frustrating, having a weird lathe with no clutch or brake and no lead screw. Or is it feed screw? One of them is not there.

I am trying to figure threading out. I have two sources of instruction. First, my Lathe Learnin’ DVDs from Adrian Pendergast. Second, my rented ATI DVDs featuring Darrell Holland. I haven’t looked at the ATI stuff yet.

Pendergast threads without moving his compound slide. I do not know why you would want to move the compound slide, since I have never been taught that way, but it is my understanding that it’s the standard method. I’m sure I’ll find out about it when I see the ATI disks.

My lathe has a belt drive, a quick change gearbox, half-nuts, a sliding gear (?), a back gear, a VFD, and power feeds. Plus a lead screw direction lever. Since I have that lever, I guess I have a lead screw but no feed screw. Whatever the deal is, there is no screw to disengage when I thread. I’ll put it that way.

Forgot: I also have a selector knob that determines the lead screw speed. It has three positions labeled A, B, and C. And of course, B is the fastest. That makes perfect sense.

To get the thread pitch I want, I have to select the lead screw speed, threading gear, motor direction, and slide gear position. Am I forgetting anything? Maybe.

To make the machine thread, I turn it on, position the tool at the right depth, and engage the feed while watching the threading dial. I’m supposed to do a light scratching pass to see if I have the pitch right.

I have had to figure out which of the controls affect the pitch. Some do, and some don’t. It looks like the back gear isn’t relevant, but I decided to use it anyway. It may be a good idea, because it allows the motor to turn faster.

I looked at the machine’s threading chart today to find the pitch I wanted. I was trying to thread the hammer handle I started working on a while back. I needed 11 threads per inch.

I got everything set up more or less right and took a light pass. The threads were like a 64th of an inch apart. Totally wrong. I started adjusting things. I moved the sliding gear knob. I fooled with the lead screw speed. You name it. Finally, I made a brilliant observation. You can’t thread using the power feed lever. You have to use the half-nut lever. They do exactly the same thing, at different rates. I had them mixed up. I’m not sure why the machine needs two levers that are nearly redundant, but I guess there’s a reason. Maybe it’s impossible to gear it up so the same lever will give feed speeds that are good for both threading and power feeding.

I totally ruined the part while I was doing this experimentation, but I think I finally have it figured out. But because my machine has no clutch, I have to be really alert to keep from running the threading tool into the chuck. I have to hit the half-nut lever instantly, when the tool moves off the area I’m threading. If I just shut off the motor, the tool may keep going for a while.

Now I have to get knurling under control. I watched Darrell Holland do it, and it didn’t make much sense to me. I don’t understand how you get the knurls to go into the same marks over and over as the piece turns. You would think there would have to be a constant integral ratio between the diameters of the knurls and the work, but his knurling looked great. He set his lathe up to move the knurling tool .015″ per turn, to push it down the work. I can’t figure out how how you can make a knurl go sideways without jumping out of the marks it’s making. And how did he know .015″ was the right amount to move the knurling tool on each turn?

I’m sure I’m missing something obvious, because he didn’t worry about any of this stuff.

I think I’m going to take my handy Home Depot Chinese dowel and try to learn knurling on it. It’s cheap metal, so I don’t care what happens to it.

It’s fantastic having a TV and DVD player in the garage. I have the AC running, and I sit out there in a state of total bliss, watching my DVDs.

Maybe I can get that stupid dowel knurled. Then I guess I’ll have to cut some more 304 stainless and try making the hammer handle again.

I have to put all the stuff I’m learning into the instructions I’m writing. The lathe manual is pathetic. It’s not intended for pinheads who play with lathes in their garages. It’s for people who don’t need a manual at all.

If I create anything useful, I will announce it here in big bold type. Don’t hold your breath.