Help. Myford Super 7 threads not equal gearbox chart

FIXED ! I love you guys I wish you were my neighbors! I changed out a 20T with a 24T and BOOM! My chart is now consistent with what the lathe is cutting! Now to order that oil gun off the internet....

If you don't already have a Super 7 manual, it would be worth while getting one from either Myford or Lathes UK.

Matthew, thanks for letting us know we got there!

One final thought to put this one to bed, and that is that it probably wasn't a coincidence that your Dad was playing tunes on the gearbox drive train. It's a well established practice and allows a wide variety of thread pitches not advertised on the gearbox top label to be achieved.

Brian Wood (yes the Brian who corrected my silly error earlier with such tact and poise!) has written a book on the subject. It's title is "Gearing of Lathes for Screwcutting" published by Crowood Metalworking Guides. Amazon have copies, I believe Arc Euro have sold it as well. Quite apart from being an interesting read it's the definitive work on the science behind altering the gear train to make the lathe much more versatile. It majors on the S7 but other makes and models get a mention.

Enjoy!

Simon

Or ask me for a PDF copy. P.M if you need one.

Steve.

I shall find myself a copy. This is a great hobby, but I think it will take me my lifetime to get any good at it. There is so much to learn. I do have a copy of the Super 7 Manual, but it helps beyond measure having a couple guys on the interwebs to help me understand it. I am just getting the terminology down. I chalk this weekend up as a win because I did just run a perfect 18 TPI. ITs a good thing no one is timing me, this is the culmination of about two months of learning. Maybe I will be able to finish the Stuart engine some day

Had you known as much as you do, after this thread, you would have been able to easily sort it yourself.

Yes, it will take a lifetime to learn as much as possible but not to become good at it - after you set up to cut a 100 different threads you will be sufficiently proficient. We (well, most of us) never stop learning.

A ‘win’ because you have gained more experience - that error/mistake/short-coming is now behind you - and you also know about lubrication. Oil will flow to the bearing surfaces easier than grease, won’t block lubrication channels (think here the change gears) and does not leave a deposit which could collect all sorts of abrasive chips/dust (think here, again, of the gear train).

There are always exceptions - I have an engine where the big end plain bearing is greased - but it runs at relatively low speed (300rpm or so?) and was likely greased by the operator just grabbing the greaser cap, on the end of the crank shaft, momentarily while the engine was running!

You are a hobbyist, so timing should not necessarily be a priority. All of us have made and then remade parts because of errors/mistakes/etc. After several practice sessions, your speed will improve. The only timing issue is generally that of the order of cutting the surfaces - careful planning is often required to make the job easier or even possible.

No apprentice would be qualified after only two months of the course - and they would be working/learning full time.

Just remember, there is usually a simple reason and (often) an easy fix to most problems. My advice is to always buy reasonably good quality kit, so you know it is ‘operator fault’ when things don’t work out as expected. The ‘buy cheap, buy twice’ is often demonstrated as a good maxim to adhere to. That ‘few quid extra’ is often repaid after only a short time.

Also you may want to think about joining the Myford Lathes Group https://groups.io/g/myfordlathes

https://groups.io/g/myfordlathes

They have a manual in the groups files

H

Edited By Harry Wilkes on 10/07/2023 08:23:41

As already said, if there vis a problem, start at one end and wsork steadily tghrough from one end to another.

Stating the blindingly nbobvious, the pitch that you cut is detremined byb the ratio between the workp[iece in the chuck and the pitch of the leadscrew.

Normally , with an Imperial Myford one wopuld expect the leadscrew to be 8 tpi (with a pitch of 0.125" )

Brian's book will explain how to set up a gearbox, or train of changewheels to set a ratio which will cut tghe thread pitch that you require, Assuming that in most cases you want an imperial pitch which is a multiple of 8 tpi.

Howard