Calculate thread pitch and feed rates...

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John Hill:
Hmmmmm..... it looks like it has a problem doing the calculations, so I am sending you the data file which should load in a couple of seconds.

But if everything fails you can ditch the program (throw it under the bench with some of those other projects) and just look at the data file in your favourite word processor. You wont be able to calculate for new gears but you can look through the possible combinations of what you have, in a 2217 PAGE document. :doh:

bogstandard:
Now you have sent me the data file John, it is cooking with gas.

Some of the results are very interesting.

All I need now is to get my retractable toolpost made, and I will be able to put it thru it's paces.

Many thanks indeed.

John

SPiN Racing:
Ya know... this is one of those threads (No pun intended) that I am soo happy I read through.

I found that when I set my lathe to cut a specific thread.. and I quadruple check the thread... it cuts a thread real nice....

But its not exact.

Over about 2 inches or so it gets off by about 1/4 thread. Granted... if the nut, or thread biting area is 1/2 inch it isnt an issue. But I imagine If I had a 2 Inch long threaded hole.. the cut threads wouldnt match. Hence all the talk here or errors in the gearing... which all makes sense.

And since my lathe is a chinese one without an overly large slew of change gears, I can see how they would be off slightly over larger distances. :doh:

Thanks again all LOL

John Hill:
OK guys! Just a couple of cautions!

I obviously did not turn all those threads and measure them!

What I did was count spindle revolutions (to a resolution of 24 degrees) while the feed screw revolved 10 times, I did this three times and if they were not the same results I did it once more and in every case I got at least 3 out of 4 counts the same. I used electrical contacts and a laptop to do the counting.

However, I did not do this for all 50 combinations of the change levers! I did it for A1 to E1 and for A1 to A5 then I used these to interpolate the other 40 speeds, I did this with a spread sheet.

Accuracy depends on my having done all those steps without error, which is possible but I have no way of really checking them all, and on the accuracy of the feed screw.

John, if you find any errors please let me know. If you have some way of counting spindle revolutions you might like to try setting up for a thread and running for a bit recording carriage movement on your DRO?

I agree SPiNner that the errors are not significant for something like a nut but you would want to know about them if you were trying to turn a feed screw or something. Which lathe do you have? Is the manual online? I might take a look and think about the prospects of a table for you.

John

SPiN Racing:
Actually.... Im not sure if any other companies make a version of this lathe.

http://www.wttool.com/product-exec/product_id/14795/nm/11_x_26_Lathe_With_Stand_WT_Import_

Its labeled the brand of the store I got it from, and its not really a clone of a JET or anything. Its the 11x26 store brand.
THe tolerences were a tad better at the time than the others, as well as the size was a tad larger.

I like it. Dont get me wrong. Love her.
I wish she had one of the selector style gearboxes though.. so I didnt have to spend 30 minutes getting covered in grease changing gears.

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