Round dial tone thread engagement problem

[Cponzi]

Hi I have a 1942 monarch round dial. I'm trying to set the machine to cut left handed 3/8-24 threads. On the thread selector it says A,B,C,B,C. 24 tpi is under the second "B" column. How do I get the gearbox into that gear selection? Someone told me the center knob will move in or out but it does not move at all. Can someone give me some insight or direction?

 

[Cal Haines]

Hi I have a 1942 monarch round dial. I'm trying to set the machine to cut left handed 3/8-24 threads. On the thread selector it says A,B,C,B,C. 24 tpi is under the second "B" column. How do I get the gearbox into that gear selection? Someone told me the center knob will move in or out but it does not move at all. Can someone give me some insight or direction?

If you look at about 1 O'clock on the dial, you will see that for the outer three rings there is a raised area that says "STUD 48, BOX 24"; for the inner two rings, the area says "STUD 24, BOX 48". What that is telling you is how to configure the end gearing, under the cover on the left end of the headstock. You apparently have your gears set up as "STUD 48, BOX 24". You need to swap the 48 and 24 tooth gears to cut threads on the inner rings.

There are four gears in the end gearing: the "stud" gear is the one at the top, on the output shaft of the headstock; the next two gears are "quadrant" gears and have the same number of teeth (you don't need to remove them); the "box" gear is the one at the bottom, on the input shaft to the quick-change gearbox. You have to adjust the quadrant gears when you swap the box and stud gears. You want a small amount of lash in the gear train, the thickness of a piece of paper (0.004") is about right. When you have the box and stud gears off it's a good time to clean them and brush them down with some way lube.

By the way, you can access the center ring threads (12 to 23 TPI) regardless of how you have the end gears set: if you have "STUD 24, BOX 48", just set the selector to "A" and can cut threads from the center ring.

Cal