Please Read - lathes.co.uk screwcutting software

I did have a copy of these on my PC but they must have been missed when I upgraded my machine. The software sorts through available gears to select the best match for any pitch thread.

Tony had a problem with his web site. He has found NthreadsP but not BoxftrhreadP the version for lathes with a screw cutting gearbox. He is currently appealing for a copy of this one to restore his web site.

If some one has a copy could they send it to him. Contact details are on his web site.

John

-

He should try the 'Wayback Machine' website, it seems to have many, many snapshots of his website.

Neil

Quite right Neil.

**LINK**

The wayback machine often doesn't retain executables but it has in this case. I've let him know via email.

Not the best of programs really for lathes with a screw cutting gearbox but a lot better than nothing. Personally I feel it should work with pitches rather than TPI. All a gearbox does is alter the effective pitch of the lead screw - usually via a couple of gears. On the other hand it's not too difficult to work out the ratio's from the same numbers.

John

-

Hi John,
I use that method with nthreadp.exe. I have made a table of the effective pitch for each gearbox setting and run the program with each value to see which one and which change gears give the best result.

This is the table for my Chester DB10G.

Effective leadscrew pitch against gearbox setting
Actual leadscrew pitch = 2mm Effective pitch at fist idler shaft after 45 to 60 reduction = 1.5mm

Gearbox ratio..... Effective pitch............ Setting

0.4...................... 0.6mm .......................A II
0.5...................... 0.75mm..................... C II
0.7 ......................1.05mm..................... A I
0.875 ..................1.3125mm .................C I
1.0 ......................1.5mm .......................A III (Also B II)
1.25 ....................1.875mm ...................C III
1.75 ....................2.625mm ...................B I
2.5 ......................3.75mm .....................B III

I had to put the rows of full stops instead of spaces as this sites software removed the spaces.

Les.

Edited By Les Jones 1 on 28/05/2015 16:01:26

I did more or less the same thing with my Boxford Les. I started on the basis of wondering why Boxford used a certain size of gear for packing another gear and found that it could give some metric threads that were adequately accurate for many things. I then used that set up to estimate another. This is the result

I did this with a spread sheet but once compound trains are needed that gets tough. Some people use the above fairly regularly but many people insist on having a 127 gear and don't realise that a few microns error doesn't really matter and that lathe screw cutting isn't fantastically accurate anyway. Screws generally aren't anyway which is why nuts are so thin.

I looked for the software again because of an interest in cutting DP and Mod worms. My Boxford came with a fair selection of spare change wheels to use with the gearbox and I suspect who ever bought them had their reasons. The software on lathes co can sort out what they can do pretty rapidly for any pitch I am interested in. One odd fact on worms is that 8TPI is pretty close to 1 Mod, around 0.001 in error. I suspect a bit of lapping would correct the worm rapidly but I could do with a coarser pitch really.

John

-

Edited By John Woodhouse on 28/05/2015 16:42:55

It's not just this particular website that removes spaces - it's part of the HTML standard that ignores more than one space in any text string.

Regards

Phil H

Edited By CotswoldsPhil on 28/05/2015 19:20:35

Thanks Phil,
That's one thing I've learned today. I will have to remember to insert tables converted to a .jpg file as John did.

Les.

I did one some years ago for the Myford screw cutting box.

You just swap the driver gear from 24 to whatever.

That's the standard gearbox with 24 driver gear, again as standard.

Then swap the driver gear and you get modified TPI on top and metric underneath and this one with a 34 shows how many metric pitches are available with just the one gear.

I've written an Excel spreadsheet here that calculates tpi, pitch or lead - metric or imperial using a combination of change gears and/or gearbox (assuming that the gearbox normally has a 1:1 ratio from spindle to gearbox as on the Myford S7). The driver was to find ways of generating the lead for helical gear cutting.

Might be of use,

Rod

I don't think it is quite true to say 'that's why nuts are so thin' - it is because there is no point in having them thicker (heavier, dearer) than needed. Certainly the absolute accuracy is not needed as when a nut is tightened on a bolt the nut is compressed by the load and the bolt is stretched. So even 100% accurate threads become out-of-pitch in use. It helps, though, to have nuts which are too loose in the thread, if anything, and bolts which are too close, if an error in cutting is going to exist.

Allegedly

Cheers, Tim