Atlas change-gear problems

[wieking]

I've got a clean 12-24 Atlas Craftsman "deluxe" I've found that some of the manual's directions for change-gear feed ratios and related chart are not consistent. For instance, 96 tpi refers to a 20 tooth gear in the chart and yet 24 tooth gear in the written description. also, same 96 tpi, there is a question "position B" versus "position C".

Does anyone know of "revised" change gear chart/directions that has all of these bugs worked out? All those loose gears and mounting bolts is enough of a workout without having to work out modifications right in the middle of making a part!
Bob
Yes, I know that "some forum" must have covered this but I thought I'd better cut to the chanse.

 

[Tin Falcon]

Ok bob you are welcome here and we do want to help.

I see from the couple of posts you are sincere are serious about model engine building and are here for the right reasons. but please post an introduction in the welcome area tell us a bit about yourself your shop and your interests in model engines. Inquiring minds want to know.

Now for you question
first of all look here

http://vintagemachinery.org/pubs/222/3396.pdf

I do not understand your delema.
are you actually needing /wanting to cut 96 TPI threads with a 12 " swing lathe ??.

I recommend setting up the lathe and try cutting a thread always take a sratch cut and measure pitch before you actuality cut the thread.
I assume the deluxe model means there is a Quick change gear box. to set the thread pitch.

If your lathe uses strictly change gears to set the thread pitch do the math and figure out what gear is supposed to be there.

Any good machine reference or text book should have a few pages on change gears.


Lathe screw constant gear teeth on spindle A x B
-------------------- = ------------------------- = ----------
Threads per inch gear teeth on lead screw C x D

or use an on line calculator like this one

http://littlemachineshop.com/Reference/change_gears.php
Hope this helps.
Tin

FYI the 127 gear if you have one is to cut metric threads 5 x 25.4 = 127

 

[Tin Falcon]

sorry the format changed on the formula

LS/tpi = ST/LST =( A*B) /(C*D )
Tin