New member looking for advice using a myford super 7

[Robert Johnson 3Participant @robertjohnson3]

[Robert Johnson 3Participant @robertjohnson3]

I have recently obtained a myford super 7, I have experience of using more modern lathes with built in gearboxes. The issue I am having is trying to get a clean cut using the power feed. I think the issue may be the gears are set up for thread cutting. I am unfamiliar with this type of lathe so not sure what gears I should be using or in what order, so any advice would be helpful.

Thanks

Rob.

[roy entwistleParticipant @royentwistle24699]

Rob On the left hand side you will find a compound gear held in place by a latch. This probably needs removing and turning round. It should be shown on the plate on the gearbox to reverse gear on stud A

Roy

[KWILParticipant @kwil]

Rob,

I presume from your words that your S7 just has the standard gear train and not a gear box.?

[Neil WyattModerator @neilwyatt]

Hello Robert,

Welcome to the forum.

Neil

[J HancockParticipant @jhancock95746]

If 'fine feed ' rate is all you want then a 12/25 gear fitted to your tumbler will do it.

If thread cutting is your forte , fit a gearbox before you're driven to madness.

[LambtonParticipant @lambton]

Robert,

Before you do anything else (unless you already have one) get yourself a copy of the relevant Super 7 handbook which contains the answers to most the likely questions. PDF copies are obtainable on the net. Myford Super 7 lathes are rather different to any modern lathes.

Also is helpful to have copy of Ian Bradley's Myford Series 7 Manual which is in print and readily available.

Eric.

[IanTParticipant @iant]

Robert,

Download the manual as suggested, most of it will be relevant whether you have a Mk1 or Mk2 – and set up a high gear ratio for a slow saddle feed. This is the way my S7 is normally set up.

Personally, I do not do enough machine thread cutting to make a gear box an affordable option (I mostly use smaller threads formed with dies) – so I'd suggest you wait and see how much of an inconvenience setting up the odd gear train is before you contemplate buying a gearbox (which won't come cheap). I also cut both imperial & metric threads (using a 127 gear) which is simpler without the fixed ratios of the gearbox I understand – but maybe some else should comment on this, since I don't have one.

Regards,

IanT

[John HaineParticipant @johnhaine32865]

Martin Cleeve in his excellent book on the topic says that a gearbox isn't really a great help – and he earned his living on his machine. I cut a few threads on my S7 using change wheels and it was no hassle at all. And they were metric and I didn't use the 127 tooth wheel which is more trouble than it's worth. Anyway, now it's controlled by CNC so I can do any thread I want without a problem.

As said above, get (download) a copy of the manual, it will tell you which wheels to fit for fine feed.

But it isn't clear what you mean by "getting a clean cut"? Normally any sensible thread set up would give you a clear spiral marked on the material and it would be obvious that you have the wrong gears for fine feed. On the other hand, there are many reasons why you may not be getting a good turned finish even with the right feed – blunt tool, cutting too slow, not taking a big enough cut, taking too big a cut, need coolant, wrong tool height, etc etc. Maybe a photo would help?

[IanTParticipant @iant]

I've had the 127t gear for many years John. I paid about £12 at the time and I think it's probably the only extra gear that I've purchased for the lathe (over what came with it).

There have certainly been many ME articles over the years about alternative gear combinations (that give very close threading approximations for metric threads) and I assume they are quite workable. The only issue with using the 127t (that I've experienced) is that the cover won't shut but that hasn't caused me any particular problems in practice and it's only been used very occasionally.

Regards,

IanT

[Chris Evans 6Participant @chrisevans6]

Robert, welcome along. I am not a Myford user so can not comment. Your location of nearest big town/county could help you if someone is close by.

[BazyleParticipant @bazyle]

Try using a round nose tool. Make sure there is no slop in the saddle gib settings and lock the topslide by nipping up one of the gib crews.

[Howard LewisParticipant @howardlewis46836]

To add to what others have already said. Welcome!

If possible join your local Model Engineering Club. there you will find lots of help and advice, close by.

With regard to your set up, The cutting tool should be sharp, preferably with a small radius on the nose, and adequate clearance (about 5 -10 degrees) at the front and side, and without excessive top rake. The tool should be set on the centreline of the work.

Too high and it will rub rather than cut. Whether too high or too low it fill leave a pip in the centre when you cut across the face of the work.

With regard to feed rate, for a fine finish you need the minimum feed per rev (Tipped tools tend not to like fine feeds, so stick with High Speed Steel until you are more familiar with the machine) For this, in simple terms, the gear on the mandrel needs to be small, and driving through an Idler, or even a Compound Idler, to a large gear on the Leadscrew. (something like 25 : 75/20 : 60) . Also, it maybe that you are trying to cut some unsuitable steel, such as rebar, which is particularly unpleasant stuff. You could do worse that to "learn your trade" on some leaded mild steel, rather than something more exotic such as EN19 or EN32.

Keep us posted as how you get on.

Howard (typos sorted I hope)

Edited By Howard Lewis on 10/04/2018 19:58:32

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