How to set the gearbox to drive the leadscrew ?

Sounds silly, but I've only just got this Super 7 with Q/C gearbox, and the
gearbox manual is decidedly sketchy and not much help to someone unfamiliar
with the gearbox.
As received, my lathe was obviously last used set for ordinary
(non-screwcutting) work. The leadscrew is quite free to be turned by a
spanner on the Simmonds nut (no handwheel is fitted).
But I can't see (or learn from the manual) how to set things so that the
leadscrew is driven by the gearbox.
I seem to have tried all combinations of lever settings, without success.
What am I missing ?
Jim Hawkins
Reply to
Jim Hawkins
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tumbler reverse lever?
c
Reply to
Charles Ping
Quadrant/gears fitted between tumbler reverse and the gearbox input shaft?
Regards, Tony
Reply to
Tony Jeffree
I have tried reversing the tumbler reverse gear (smaller gear inwards) and find that the gears then turn freely, but they are still not driving the leadscrew.
Jim Hawkins
Reply to
Jim Hawkins
Its possible to set the gearbox in neutral by carefull setting of the lever on top of the box - in fact this makes up for the lack of a dog clutch. Might be that this lever is not properly adjusted to engage the gears.
Regards, Tony
Reply to
Tony Jeffree
Doesn't make any difference whichever position that lever is in. Does this mean there is something adrift/broken/loose inside the box ? If so, is there any problem removing the top cover to see ?
Jim Hawkins
Reply to
Jim Hawkins
Could be. Worth having a look - taking the top off is straightforward (small number of cap screws - 4 or so) & you sould then have a better idea of what is/is not working. It is certainly possible to re-fit the lid so the lever doesn't properly engage with the range changing gears.
Regards, Tony
Reply to
Tony Jeffree
Just to check the blindingly, bleedin' obvious. When you turn the mandrel does the input shaft to the gearbox turn? The collar on the right hand side nearest the front should also turn. If either the top or front adjustment lever are not engaged propoerly then the collar nearest the headstock on the righthand side of the gearbox will not turn and neither will the leadscrew. Turning the leadscrew however should turn this collar.
Removing the top should make it obvious where the drive train is disconnected. If you need a scan of a manual then let me know via this NG.
Good Luck
Bob
Reply to
Bob Minchin
Have you released the "Bull wheel lock & engaged the back gear" & made sure the "Tumbler gear is engaged"
Reply to
Salamanda
I am assuming that you wish to cut a thread.
Reply to
Salamanda
I've already downloaded a copy of the gearbox manual from the MyMyford group website, thanks Bob, though to be honest it seems to be intended more as a guide to installing the gearbox rather than a simple 'how-it-works' for ignoramuses like me. You ask about the mandrel - which bit is that ? Sorry to be so higgerant but there isn't a bit called that on the parts list ! At the moment, with the drive from the countershaft disengaged and the reversible cluster in the screwcutting position, the gears turn very freely, but the leadscrew is unaffected. Conversely, the leadscrew can easily be turned by hand, but this has no effect on the gears. At present the lathe is lying on my garage floor and difficult to work on, but tomorrow it's going to be lifted onto its stand in the workshop. Once in there I'll have the gearbox top cover off and see what's going on and report what I find.
Jim Hawkins
Reply to
Jim Hawkins
My two pennyworth,
I am not conversant with Myfords but I understand that some lathes have a sort of fusible link (shear pin?) in the leadscrew drive. It might be worth looking closely at any collars near where the leadscrew exits the gearbox.
Ian
Reply to
Ian
Which version of the gearbox do you have the early or late model.
Reply to
Salamanda
I'm not trying to drive the lathe yet Salamanda, just trying to find out how the gearbox works while I've got the motor removed.
Where do these instructions come from ? Is there a user's guide I wot not of ?
Jim Hawkins
Reply to
Jim Hawkins
Hi Jim, the mandrel is the main lathe spindle - the one with the chuck on the end! I was just asking to make sure that you had a continuous drive chain through the gears to the gearbox.
I have a note on a yellow post it on my manual giving the names of Malcolm Townsend and Colin parker as two people who have been helpful to me at Myford in the past. Not saying the other staff are not helpful or indeed if Malcolm and Colin are still there.
Good Luck
Bob
Reply to
Bob Minchin
The information is from the Myford series 7 manual by Ian Bradley.
Reply to
Salamanda
Hi Jim, Might I add a thought to your problem, you say you are playing with your Myford on the floor. If this is so, you might not have noticed that the gear selector has to not only sit in a slot but also has to have its peg locked in its hole at the bottom of its travel. If it is not at full travel the gear is in a false neutral. Once the pin is in the hole, then you can move the lever on the top of the box till it also engages the relevant range. Hope this makes sense, always easier to show than to tell. T.W.
Reply to
the wizard
Success!!! After taking the gearbox top off, I was surprised to see that the leadscrew just goes straight through the gearbox and out the other side! No pinions on it at all! It was obvious that it must pick up drive from the gearbox output shaft outside the gearbox - behind the quadrant in fact. Removing the gears and then the quadrant revealed the problem: the pinion on the end of the leadscrew was loose on the shaft, and had slipped down the shaft so far that it had slipped out of mesh with the gearbox output shaft pinion. No great difficulty fixing that. Pleased to find how easy it is to disassemble everything. Must give all the bits a good wash in white spirit before re-assembling. Next problem is to sort out how the clutch works, but I don't anticipate any trouble now the beast is up on its stand in a well-lit workshop. Sorry it's taken so long to reply, but the 'heavy gang' didn't arrive to do the lift untill 3:30 this afternoon - dark already. here by then. Lastly, my sincere thanks to everyone who's helped with suggestions and explanations. Groups are one of the best things about the www.
Jim Hawkins
Reply to
Jim Hawkins
Jim, There is a very useful modification you can easily make to the gearbox. This adds two detent positions interspersed between the three positions of the top lever. This fixes the leadscrew drive in neutral quickly and safely. There is a screw beside the top lever with a spring and ball under it. I think it is 1/4 bsf. Make a threaded bush to match this thread or use a short bolt. drill a hole about 1/8"mm diam right through the bush/bolt. Remove the screw, spring and the ball-ended cup using a small magnetised screwdriver. With the lathe switched off, move the lever into the first neutral postition taking care to put the lever in the middle of the travel betwen the two adjacent engaged positions. Insert the bush/bolt to just trap the control lever. Use the drill to make a dimple through the bush. Repeat for the other neutral position. Remove the bush and use the magnetised screw driver to remove most of the swarf. A little left behind wont do any serious harm. Replace the ball-ended cup, spring and screw. Test the detent action, deepening the dimples if needed to get a positive action. Almost takes longer to write it than do it but a well worthwhile modification IMHO.
Good Luck
Bob
Reply to
Bob Minchin
Jim if you go to pilotltd.net You can download a copy of the Super7 Manual. Have you got the cone clutch or the expanding ring type. Both are straightforward units to adjust. Best Regards Ron.
Reply to
Salamanda

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