Cincinnati Tray Top Lathe (Thread Chasing Attacment)

I have a Cincinnati tray top lathe and I'm planning on making one and have been looking for pictures of the dial on the thread chasing attachment. Come across pictures of it have an idea of what the attachment looks like just can't come up with good clear photo of the dial. Does anyone own or knows someone with on of these lathes to photograph this attachments dial?

Thankyou;
Travis

all the threading dials I have seen have 1234 spaced at quadrants, with one index line at each. between each is another line with no markings. the dial is flat with the face. The face has a single mark on the top edge closest to the front bed Way. The critical issue is the gear ratio between the dial and the lead screw. Good luck. Jim

I have seen articles on making them and you need the right amount of teeth to work with the thread count on the lead screw I think. I would ask at the Home Shop Machinist or Praticial Machinist forums. On the praticial machinist keep scroling down until you find the antique thread. If you get stuck I could probably find this information if I looked through some of the books I have. E mail me if you need to [email protected]

I bought one on eBay for cheap. They seem pretty universal to me but don't quote me on that . I did have to make a spacer block for mine. I think different brands will work on different lathes. I'm sure there has been a HOME SHOP MACHINIST article on how to make one.

This one is too expensive bit I thought it may be a good picture .
eBay example of dial

A "threading dial" for a lathe having an imperial leadscrew thread is conceptually pretty simple. The gear needs four times the number of teeth as the leadscrew had threads per inch (TPI). Let's say, for example, that the leadscrew has five threads per inch; the threading-dial gear needs four times five = twenty teeth.

The dial is on the same shaft as the gear, so it revolves exactly as the gear does. This means that one full revolution of the gear, and thus of the dial, corresponds to a four-inch movement of the lathe carriage . . . assuming, of course, that the gear is engaging the leadscrew and the leadscrew is stationary.

As Janicholson mentioned earlier, the dial is graduated in increments equivalent to a half-inch of carriage movement relative to the stationary leadscrew, and usually every-other-graduation is numbered (1, 2, 3, 4) to indicate inches of carriage movement.

If cutting an even number of threads per inch, the tool tip and the thread being cut are "in phase" at least once every half inch of carriage movement, allowing the half-nuts to be safely engaged at any dial graduation.

If cutting an odd number of threads per inch, the tool tip and the thread being cut are in phase at every one-inch carriage movement, allowing the half-nuts to be safely engaged at any full inch of carriage movement. Conventional tribal knowledge is that the numbered graduations are at one-inch-of-carriage-travel separations, which makes them the right ones to choose when cutting an odd number of threads per inch. In reality, the UN-numbered graduations are also separated by an inch of carriage movement, and could be used when cutting odd number of threads per inch threads provided the numbered graduations are not used.

By logical extension, the tool tip and a some-whole-number-and-a-half TPI thread being cut are in synch every two inches of carriage travel, while it takes four inches of carriage travel for the tool tip and a some-whole-number-and-a-quarter TPI thread to be back in phase.

Threading dials that work with metric leadscrew threads are a lot more complex, typically having four or more gears, with each gear having a number of teeth that is dependent on the leadscrew pitch. In other words, the threading dial that works with a leadscrew having a 6 millimeter pitch won't work with a leadscrew having an 8 millimeter pitch. If your lathe has a metric leadscrew, buying a threading dial that works with your lathe's leadscrew is a whole lot easier than trying to make one.

Thankyou, for your advice my lead screw on my lathe is 1 1/8 x 8TPI which I think was the common thread count in the day. The only reason I'm looking for close up of the thread chasing attachment dial is to copy. These thread attachment on Cincinnati lathes were different from others that I've seen.

Thankyou;
Travis

You can get by without a dial , by leaving the lead
scew always engaged. Just clear the tool and reverse the
spindle to get back to where you started from then dial the tool back in for next cut
And go again . I had to use this method on a ID thread that ended to a
Shoulder , on that part i put the tool in upside down on center and run the
spindle in reverse when cutting the threads that way no worry of hitting
Shoulder , then leaving lead screw engaged i would by hand turn spindle
Forward making sure tool would clear shoulder go a little past shoulder
Then by hand turn the spindle in reverse until you just clear shoulder
Then set your tool for next cut go again , of course I had the use of
Digital read outs and that helped alot . And where the threads met the
Shoulder I under cut to diameter a little bigger then the threads

Personally I would buy the one on Ebay for $125 before I would make one but that's me. I also understand the satisfaction in making one. Thread dials differ some in operation but on any lathe that I have run you do not need a dial for any even numbered thread, close the half nuts and go. For an odd number thread you will have to close on any number and 1/2 and quarter pitches must close on the same number. If your lathe is inch pattern but has metric threading you must leave the half nuts closed and run the saddle back by running the spindle backwards. Same with a metric pattern lathe that is used to cut inch threads. This is because an exact inch to metric conversion via gears is not possible.

John, you provided the information I would have had to look for for a while to find. Good for you. My only question is can the gear be only 2x lead screw thread as in 8 tpi and a 16 tooth gear? I don't think the gears on my two threading dials are 4x the thread count. (10" Logan, 8 tpi, and 12" Lodge and Shipley 4 tpi I think) Maybe I will go and count, the L&S could be. Yes, the L&S has 4 tpi and 16 teeth, also the dial is numbered to 8 and there is 16 marks. The Logan is * tpi, 16 teeth numbered 1 + 2. and has 4 marks. Interesting. When looking at the info you provide it all makes sense. Pulled out "Screwcutting In The Lathe" by Martin Cleeve and checked it out a bit, he elaborates on what you have said.

4wdtom --

A threading dial having a number of teeth equivalent to two inches of carriage travel won't work when cutting a screw having a whole-number-and-a-quarter number of threads per inch, but will work fine for odd-whole-number, even-whole-number, and whole-number-and-a-half TPIs.

I'll speculate that Logan thought that a smaller, lighter, and less-expensive-to-manufacture threading dial would satisfy the needs of the now-proverbial ninety-nine-and-forth-four-one-hundredths-percent of their customers.

Have yourself a great weekend!

John

Thanks John, makes sense.