Denham Junior Mk2 lathe

[Chuck in E. TN]

Check out this site.

http://www.lathes.co.uk/denham/index.html

Has info on this lathe. May have a manual.

Chuck in E. TN

[yorkie_chris]

He has a manual and parts diagram for £25, but no spares.
Will order a manual.

However would still like to figure it out

Here is a close up of the workings of the reversing lever, it moves between 2 detents 180* apart

I presume the hole is meant to hold some sort of selector fork

[yorkie_chris]

right reckon I've got it fathomed with a bit of help from a mate on another forum who is wise in the ways of science, well center distances and DP's anyway.

The input shaft should drive the 20t gear as it does now.

When you flick it into reverse the top 20t gear should disengage, but having a 30t gear attached to the left side of it, should engage another 30t gear on the bottom shaft which is driven by it's own 20t gear attached.

Clear as mud.

[Pete.]

I think the wide top gear on the right is a sliding gear.

On the shaft below it there should be a pair of gears connected together and free to rotate on the shaft, permanently engaged with the input gear on the lower right. The drilled hole is for a collar to keep this idler in place on the shaft. As you slide the wide gear left and right, it either engages directly with the input gear to the right or with the reversing idler to the left.

The three close-ganged gears on the lower left are the sliding gears for the three speed selector.

[yorkie_chris]

I see what you mean, but I don't think that could work:

That wide sliding one is a 20t, to mesh with one on the shaft below the one below it, the lower one would have to be bigger. The input shaft is on centers with the lower shaft for another 20t, so reversing it would change ratios.

So, I think a 30t pair are needed as the upper and lower shaft are on wider centers than the input to upper/lower distance.

Er, I think. I'm going to get another colchester bantam 30t changewheel the morra so I'll hopefully get it squared away.

[Pete.]

It would work if the missing paired gear were 16 and 25 teeth, 16 to permanently engage with the input gear and 25 to engage with the sliding gear. When engaged this would give a reduction of 5:4 (20:16) then an increase of 4:5 (20:25) keeping the forward and reverse ratios the same which is essential for screwcutting.

[yorkie_chris]

Centers of the 2 shafts are something like 1.875" so with 16DP that would be 30:30 wouldn't it? I bloody hope so because that pair of 30s cost me £20!

If all the pairs have same teeth then ratio is the same without needing to go up then down again.

i.e forward 20:20  1:1
reverse 20:20 (20 welded to the 30) 30:30 is still 1:1

Anyway we see if it works or not. I've got one minor cockup to sort in that there's a keyway in the shaft that the gears must slide past to assemble the 'box and I can't get the key out. (for the idler gears which are/will be free spinning on the lower shaft)

[krv3000]

HI well i hope you have lots of fun with that lathe

[yorkie_chris]

 

It works!
Betcha didn't see that coming!

Now to sort out some tooling.

[Stilldrillin]

It works!
Betcha didn't see that coming!

Now to sort out some tooling.

Don't talk daft, lad..... Of course we saw it coming!  

This is MadModder, you know!  



Blummin well done Chris........    

David D