Back gear and tumbler reverse

Hi again,

the back gear and tumbler reverse selectees I’m a little confused with.

what exactly do they do and what position would I have them in for general turning.

it says the tumbler is either in forward neutral or reverse, which holes are which.

also would I only select back gear if I was screw cutting.

thanks

chris m….

Download the Myford ML7 User Manual that is available free all over the net. It tells you how to use all the controls on your new lathe. You can't hope to get by without it.

Tumbler reverse affects the lead screw direction only.

Back gear affects spindle and lead screw speed.

You might also need back gear for cutting large dimeter work.

There is a Myford Lathe group on groups.io that has the manual in its "Files" section too.

The principle is common to most lathes.

'

Back-gear is a low-speed range for screw-cutting and turning large diameters and often, awkwardly-shaped or interrupted-cut work-pieces.

VItal: To use the back-gear the main drive from pulley to spindle must be disengaged; and on the ML7 (certainly my edition) this is by slacking (not removing!) a small socket-head screw on the face of the spindle pinion at the chuck end, moving it outwards and re-tightening it. It disengages a simple dog-clutch within the gear.

Access is restricted and needs an Allen-key with its short end, cut further short.

NB: Never use back-gear as a brake for removing a tighly-fitting chuck by impact. That is a recipe for broken gear-teeth or other damage.

'

As Dave says, the tumbler-gear controls the direction of rotation of the lead-screw, for cutting left- as well as right-hand threads.

Neutral - central pin-hole, so when you are not using the change-wheels and leadscrew, they are not dragged round unnecessarily. It reduces power-consumption and wear.

You also put it in neutral if you operate the lead-screw from a hand-wheel (an optional extra).

I would not like to say which of the two engaged position gives the normal, fine-feeds and right-hand thread position (cutting towards the chuck) because I have fitted a gearbox to my lathe; but it is simple to establish.

My approach without gear-box: Set up the required change-wheels; ensure the tool, saddle etc. are safely clear of the work and chuck; set the lowest speed pulley and back-gear; engage the tumbler. Then engage the clasp-nut and watch which way the saddle moves during a few chuck revolutions.

This is my habit especially on the Harrison lathe, as that has additional gears that also affect the direction!

I would not worry too much about screw-cutting at this stage. It is not especially difficult, but it does need general turning experience and familiarity with the particular lathe, first.

Chris,

It is good that yoiu are asking questions about the lathe.

Some, probably many, will be answered if you buy and read Ian Bradley's "Myford Series 7 Manual"

You must become familiar with the machine before using it, otherwise you might well damage it.

At this stage, I would not worry about setting up the changewheels for screwcutting or fine feeds. Wait until you have gained more experience.

If you engage Back Gear, you MUST slacken, or remove m(To prevent loss ) the grubscrew located in the bottom of the groove in the driven pulley.

If you do not do this, everything will lock up, since you are trying to drive the lathe with two different gear ratios engaged at the same time.

Maybe I should PM you.

Howard

" If you engage Back Gear, you MUST slacken, or remove (To prevent loss ) the grubscrew located in the bottom of the groove in the driven pulley. "

CAREFULL!

You need know the finer details of the specific machine.

That screw in the pulley may well apply on some versions of this lathe, but not all !

My ML7 uses a simple dog-clutch in the spindle pinion. Hence my qualifier above.

I can fully concur with Nigel above. The myford does not have a grubscrew at the bottom of the groove.

Roy

CHris. there is a copy of Bradleys book for sale on the home workshop site, super cheap.

Edited By bernard towers on 02/06/2022 22:40:52

Edited By bernard towers on 02/06/2022 22:41:19

Quite right folks

After 20 years the memory fails. My ML7 had a dog, secured by a capscrew, on the chuck side of the pulley to lock the pulley to the spindle. This needed to be disengaged when Back Gear was engaged..

My present lathe has a spring loaded peg, which can be locked out, in the second driven gear to perform the same function.

Howard