Denford Software & Machines

You did have the main spindle and the gearbox drive train running when you were trying out the selector knob didn't you, with the lever on the left hand end of the gearbox in neutral?
I've never done it myself but I understand from reading about the experiences of others on this site, that taking off the front cover and managing to reassemble it again isn't for the faint hearted, so is absolutely the last resort.

Have you put the lever on the left back up to the top position?
Until you do that, the dial selector is locked.

Andy

Hi Again,

I would suggest spraying the gear selector knob with release oil, try to get it down the back to the where the shaft goes into the gearbox.
The lever on the left must be in the fully up position before you do anything else, as stated.
Make sure the gearbox is filled to normal working level with oil, check the sightglass.
Are the gearbox input and output shafts free to turn ?, if so turn them by hand using the drive gears, not motor.
Reassemble it and attempt to wiggle the knob, it might free off, do not use spanners or mole grips on the shaft.
Take things slowly, do not take anything else off !
As has been stated the gearbox is complicated and spares are virtually unobtainable.

Good luck,

Les.T.

Hi Thank you all for your info.
Just spent the last hour in my workshop trying to free it up. Didnt mention it in my earlier post but neither my lead screw or drive shaft is turning in any settings. Looking through from the back of the head stock I can see something try to move when I wiggle the selector dial (with the gear engagement lever in neutral)
Might be going in a bit deep now but do any of you know how the neutral selection works. Is it like the neutral position on a car gearbox

Is the input shaft to the gearbox turning? In other words, are the tumbler gears below the main spindle engaged so the gear train to the gearbox is all turning. You are trying to wiggle the selector knob with the lathe running aren't you? If you've got the left hand lever in neutral, which is where it should be before you try to move the selector knob then no, the leadscrew or feed screw will not turn because the box is in neutral. They will not both turn at the same time, which one turns depends on the position of the right hand lever on top of the gearbox. You should not attempt to move this lever either without the lathe running and a gear selected.

Richard

Hi Richard
Thanks for your reply.
The input shafts to the gearbox is turning via the gear train
With selection lever in neutral and lathe running the dial will not turn. It was turning when I first tried it but was struggling to get feeds working, that was before you explained the stud gears. I tried it again just using the "d" selection. Got the feeds to work, when I tried to reverse the feed by tumbler lever I got no feed, no shafts revolvement and that's when the dial became stuck.

Something not right here. It was working OK before you tried to reverse the feed direction using the tumbler gears which engage to the main shaft?
Then when you tried to reverse, nothing happened? When you reversed, did the gear train still work, did the input shaft to the gearbox still seem to revolve?
There is a shear pin in the drive to the gearbox, and its worth checking that before you even think about trying to take the cover off the gearbox.
You need to undo the screw in the middle of the gearbox input shaft and remove the 2 gears. You may need to remove the quadrant with the other gears in order to do so. The hub the 2 gears fit onto should have a 1/8" dia shear pin securing it to the gearbox input shaft. Shear pins like this are notorious, when sheared, for at times being able to transmit a light load, before slipping again. If the input shaft isn't revolving you will not be able to move the selector dial.
I trust you are having serious conversations with your vendor about all of this?

Hi Richard. Will check the shear pin but all the gear train is moving as should, the input shaft to the gearbox is rotating and the end of the shaft which is flush with the side of the gearbox is rotating (as expected)
I am meeting the vendor tomorrow and will be raising this with him.
Thanks once again

Curiouser and curiouser as Alice said.
I can't see it in your photos, but the big gear you removed was keyed to the input shaft wasn't it? Some of them used the key as the shear device rather than a pin.
I'm getting desperate here, but when I was playing around with my gearbox this evening, I noticed that the lever on top of the gearbox which selects feedscrew or leadscrew has a small mid position in which neither shaft is selected, so results in no output from the gearbox. Might be worth checking the position of that lever.

Apart from that, I regret to say I've no idea.

Richard