Calculate thread pitch and feed rates...

[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.

[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.

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.

[bogstandard]

John,

I know it will be a suck it and see to begin with. So don't worry, I won't run away with it. I am super methodical when I try something new.

I will have to see if someone has a slow count rev counter, or I could lash up a finger counter and a cam.

As I said, I have yet to make my screwcutting tooling. So when I get that done, I can resurrect this post.

Thanks again

John

[John Hill]

John, I tried a lot of ideas for counting the revolutions and finally settled on a rotary switch, but I did have to butcher it so it could go around and around!  I used a laptop to do the actual counting but if you have an old calculator you can make it into a counter!

Just open the calculator and connect up two wires across the '=' key, then close the calculator with the wires connected to your switch. Just press "1 + 1= =" and everytime you close the switch it will increment the count.

Cheers.

[Darren]

I see you've been playing with electronics for a while Mr Hill....what a neat idea 

[Twinsquirrel]

Just open the calculator and connect up two wires across the '=' key, then close the calculator with the wires connected to your switch. Just press "1 + 1= =" and everytime you close the switch it will increment the count.

Love it! seems to sum up the spirit of this site!!

David

[John Hill]

Just open the calculator and connect up two wires across the '=' key, then close the calculator with the wires connected to your switch. Just press "1 + 1= =" and everytime you close the switch it will increment the count.

Love it! seems to sum up the spirit of this site!!

David

It is even better than that David,  say you were cutting a 0.75mm pitch thread and you enter "0++0.75"  it will show you how much thread you have cut!

[Darren]

Now that is very enlightening !!

Somewhere, not that I have a cats chance in finding it, I have a small reed switch....ummm,

You started something now John....

[sbwhart]

OK Chaps

Whats a read switch look like then 

Stew

[Darren]

Stew,

A reed switch is two little strips of contact that are pulled together when a magnet is brought near to them. Usually encapsulated, mine is in a glass tube.
Very cheap and very versatile little switches.

Last time I was using one, some many years ago now, I was winding some transformer cores on a Myford 7 lathe. I used a reed switch to count the turns and a magnet simply stuck on the chuck to activate it with each turn. It was done slowly so no fear of the magnet flying off.

I used a simple 12V counter to do the, erm,,,,counting...

A couple of thousand turns is way beyond the 10 I learnt at school. So was really quite helpful. 

[John Hill]

Reed switches are available for home security systems, they are the little plastic switches that come in two pieces, one bit to fix to the moving window or door and the other piece that has two wires connected to it.  The one with the wires is the switch and the other has a little magnet in it, of course they work with other magnets too.

I am thinking of putting a permanent switch on my spindle, maybe at the 'far end'.

[sbwhart]

Darren/John

Thanks for that, I used a reed (correct spelling this time) when I wired the alarm in my shop just didn't know what it was called.

Cheers
 
Stew