Myford gearbox question

Gents,

I have a novice question and I feel almost reluctant to ask it but here goes.

Our lathe (Super 7) has been fitted with an original Myford late model gearbox (leadscrew passes through the ‘box). We have just installed and levelled it and started playing with the gearbox. We found that the powerfeed only works with the top selector in B. In order to use either A or C I need to move the tumbler selector.

Is this normal?

Apologies again but we are beginners and are still summoning up the courage to start on our Stuart No. 1 sometime this month.

Thanks for any info,

Mark

Edited By Mark Gould 1 on 05/05/2018 17:12:56

Mark not sure what you mean by the tumbler selector, are you referring to the reversible gear cluster inside the change wheel cover ? This changes from feed to screwcutting , or do you mean the tumble reverse lever?

You should be able to select any of the TPI or feed rates on the top plate by moving the lever A B C and the train selector on the front of the gearbox 1 to 8 plus of course selecting feeds or threads with the revesable gear cluster

Hope this helps John

Are you sure the drive dogs are engaging correctly when you select positions A and C with the top selector lever?

Hi Mark,

Have you looked at this gearbox manual?

Thor

John,

I mean the Tumbler Reverse Lever (or Carriage Reverse Lever). Before we had the gearbox fitted, I only used this lever to change power feed direction to headstock to tailstock and for using power crossfeed to feed INTO the work (away from the user).

But now we have the gearbox fitted and with this Tumble Reverse Lever in the lowest hole, we seem only able to get the leadscrew turning if the gearbox selector is in B. If we try either A or C the leadscrew stops turning.

I must sound like a complete fool, apologies.

Mark

PROBLEM SOLVED.

Apparently, the selector on top of the lathe is best moved while the machine is running. The leadscrew now turns in A, B and C,

Thanks for all the handy tips guys.

@Thor, I have that manual, thanks. It deals in great detail how to install the 'box but not so much in how to use it. Thanks anyway mate.

@Rick I think they are best engaged while the machine is running or so the advice was from the guy that built it. it runs perfectly now, thanks.

You would have had to take the top off the gearbox to fit it. On the underside of the gearbox ABC lever there is a quadrant, a bronze slipper fits onto this, the oblong part engages in a slot in a sliding gear. It sounds as if the slipper is either not engaged with the sliding gear of it has fallen off. It needs to be supported with a finger and guided into position when refitting the top of the gearbox.

Mark, your post crossed with mine, glad you sorted the problem. I've had leadscrew handwheels on all my lathes, I turn the leadscrew by hand whilst moving the gearbox levers, probably kinder to the machine than trying to engage the gears while it's running.

Ok Dave thanks for the tip!

Yes it's fine to have the gearbox running whilst selecting ratios A, B and C. This ensures the drive dogs engage correctly. It's also ok to engage the selector whilst using fine feeds but, not advisable to engage the selector whilst in the high (screwcutting pitch) range as the gears may be subject to wear or damage. Better to rotate manually to engage the selected pitch. Glad you got the problem sorted.