# Craftsman/Atlas Commercial lathe gear cutters



## songbird (Mar 30, 2018)

I have a couple of lathes, including a Clausing 5914, a Southbend 13”, a Powercraft/Logan 10” & a 12” Craftsmen/Atlas Commercial lathe. Although I have the metric gears for the Clausing, I’m thinking of setting up the Craftsman lathe to be dedicated to cutting metric threads all the time. I think I want to try cutting these gears myself but need to buy the cutters. Does anybody out there no the correct gear set to buy, (pressure angle ect.)? Is there a gear selector chart for cutting metric threads for the Craftsman lathe? Thanks in advance, JB.


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## vtcnc (Apr 1, 2018)

This may get be helpful in your research, but do not know if this applies specifically to your Craftsman.

Metric Thread Cutting for Atlas Lathes


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## Rob (Apr 2, 2018)

The gears are 16db 14.5 degrees.


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## songbird (Apr 2, 2018)

Rob said:


> The gears are 16db 14.5 degrees.


Thanks Rob.


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## Bi11Hudson (Apr 3, 2018)

Just how "*accurate*" you need the "*precision*" to be is your own call. I can't make *that* decision for you. I have run across several web sites over the years that allow cutting "almost" metric threads on a Craftsman 12" machine. Mine is a 101.27440, a 12 x 36 Atlas built machine dating to the mid 50s, m/l.....

By "almost" metric, I am referring to the *in*accuracy, in most cases a small number in the fourth or fifth decimal place. That would allow a metric nut, for example, to be 12mm thick and run a 6mm threaded rod freehanded. The most accurate I have seen involves using *stock* gears to get an *almost* match.

The article listed above uses this method. There is another determined by a South African fellow that allows a fairly quick swap back and forth. In the 30 second region..... I don't have a link specificaly for this article but I did find a similar one at http://www.conradhoffman.com/metricthreading.htm. Perhaps a little research into Atlas or older Craftsman machines would turn up further conversions.

*True metric conversion* on a machine with an imperial leadscrew will involve a 127 tooth gear. 25.4 x 5 to get the decimal out of the equation. With a 16 DP gear of 127 teeth, we're talking a hefty modification to the back of the headstock. The gear train..... I don't have room on my machine without some heavy modification. In essence, a 1mm pitch equates to 25.4 TPI. If you can get 25.35 TPI or 25.45 TPI, that's pretty close enough for *most *applications. Again, just how close is up to you.

Bill Hudson​


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## rdean (Apr 3, 2018)

A 127 tooth gear with 16dp and 14.5 pressure angle has an outside diameter of 8.06 inches.
That's a fairly large gear to try to fit in the lathe.
Might want to check the space available. 

Ray


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## mickri (Apr 4, 2018)

I did a thread on this.  https://www.hobby-machinist.com/thr...-qcgb-on-a-craftsman-12x36.52915/#post-441419  Another good source of information for odd threads is the QCGB setup manual.  One thread that I am going to need to cut is 1.8mm which happens to be 14.11 tpi.  I could not find 1.8mm anywhere but 14.11 tpi is in the QCGB setup manual.  If you have an odd metric thread and can't find the gearing for it look for it's tpi equivalent.


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## benmychree (May 22, 2018)

The fact is that a 127 tooth gear cannot be cut with an ordinary dividing head, it takes the capability of differential indexing to accomplish; the spindle rotation is transmitted by a gear train to also rotate the index plates while the worm crank is being rotated; having said that, I think the Cincinnati dividing head, when equipped with a special "high number plate" with 127  holes (40 holes on the 127 hole plate) is able to preform the task, this being possible because Cincinnati uses such large diameter dividing plates, the smaller B&S plates don't have enough diameter to drill that many holes.


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## mickri (May 22, 2018)

With google sketchup you can easily divide a circle into any number of equally spaced lines.  You can have an odd or even number of lines.  Here is a circle I divided into 72



and a circle divided into 44



I could do a 127 in about 5 to 10 minutes.  The above circles were drawn 8" in diameter.  You could enlarge or shrink the circle when you print it out.  Changing the size won't affect the equally spaced lines.

Print it out and glue/tape it to one of your dividing plates.  You should be good to go.


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## benmychree (May 22, 2018)

Not having holes, it would be pretty sketchy, and if holes are drilled, they need to be all at nearly exactly the same radius in order for the pin to engage each hole (easily).  Also, sector arms are needed to count holes (or lines); one little error in counting holes or lines means that the project is spoiled.


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## mickri (May 22, 2018)

John you are thinking of my sketch as if it were a dividing plate.  There are no holes to count. no pins to engage or sector arms.  You do need a pointer.  Not having a dividing head and never having used one I don't know if they have a pointer.   To be honest after reading how to use a dividing plate it sounded like a recipe for disaster.

All you do is rotate the sketch from one line to the next as you cut each tooth on the gear.  If you should happen to skip a line or two you can always go back and cut the missed line  The amount of possible error depends on the diameter of the circle. larger is better, and the thickness of the lines, thinner is better.   I did the math based upon an 8" diameter circle and the thinnest line my printer would print.  The maximum possible error was a couple of thousandths on any given tooth. 

 I did not come up with this on my own.  I was researching how to make gears because I need a couple for future projects to be able to cut metric threads.  I found an article or it may have been a you tube video where a guy explained how he made gears with the milling attachment on his lathe.  If I can find it I will post a link.  One of my future projects is to make a simple fixture to cut gears.  Here is a rough sketch of my fixture to show the concept.




The sketch is very rough and doesn't show details like how the gear blank would be attached to the shaft or how I would lock the shaft in place.


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## benmychree (May 22, 2018)

I do not see how the necessary accuracy for gear teeth (spacing) can be accomplished with a piece of paper and a pointer.  On my lathe, when I made my metric transposing gears, the required DP made a gear that was of a diameter that exceeded the swing of the dividing head, which is capable of differential indexing, so I made a smaller gear of a lesser DP that fit the change gears of my automatic gear cutter (antique!), then used it to cut the teeth on the gear required to match the DP of my lathe change gears.  Other change gears are required to accomplish all the common metric pitches; for one, the 127 tooth gear is used in combination with a 120 tooth gear (they are keyed together on the same shaft).
Some time back, I posted a chart of the change gears that were in a article in American Machinist Magazine many years ago (with permission of AM).  The article supposed a lathe with a 4 TPI lead screw, but it also pertains to any other screw pitch with some math being done.


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## mickri (May 22, 2018)

John I am sure that you have forgotten more about machining than I will ever know.  This is a hobby for me and I am very new to it.  I don't use my lathe very much.  If something comes along I try to make it if I can.  I could just buy the gears that I need.  I need 4, maybe 5, gears.  I would rather try to make them.  And I tend to think outside the box.  This sometimes leads to failure.  But more often than not I succeed.

I doubt that I could draw  a circle and divide it into truly equal lines.  I would not even attempt it.  However this is easy for a computer and the printer prints whatever the computer tells it to.  A pixel is .0104 wide from edge to edge.  Make the tip of the pointer .010 and line the edges of the pointer up to the width of the line.  If you are careful how far off will you be? 

I did a quick search and found the article that I referenced in my previous post.  Here is the link.  http://users.tpg.com.au/agnet/cq9325rev7.html  It has numerous pages where he describes in detail how he makes gears.  Here is a picture of his setup.




It seems to work for him.  I will give it a try.


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## benmychree (May 22, 2018)

When I looked on the link, and how the person was making his own cutters using tapered grinding wheels  and burrs, it finally sunk in that he is making SINGLE CURVE gears, not involute; I'd venture to say that the two types would be unlikely to work very well when run, one against the other.  Assume that all gears used on end trains of lathes are going to be made to the involute system, whether module or diametral pitch.


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## mickri (May 22, 2018)

Well John you got me with a single curve gear.  I tried searching for a single curve gear definition verses an involute gear and could not find anything.  Lots of info on involute gears and nothing on single curve gears.

   What I was using the above referenced article for was his method of indexing to cut the correct number of teeth and not the shape of the teeth.  I will buy the correct cutters for gears that I want to make.  I appreciate your feedback.


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## benmychree (May 23, 2018)

I'm thinking that single curve gears are fine for crude gearing run at low speed where efficiency is not a large issue, maybe also for clock gearing, but not for machine tools; I think the issue is having a rolling contact (DP) rather than a rubbing contact (SC)


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