Worm wanted for lathe

[AJAXParticipant @ajax]

Posted by Pete Rimmer on 08/01/2021 19:32:21:

Well, given that the kind gentleman has pointed you to the correct drawing on the Denford forum:

You now have all the info to produce your worm. Bonus if you can find a lathe which has 5 3/4TPI on the gearbox.

CVA has that pitch on the gearbox as does my Monarch.

The replies on Denford Data and this website have been very useful.

I nipped into work today to borrow a lathe and turn that temporary "feedshaft" so I can test the feed gears with the apron away from the lathe. I noticed their lathe (Harrison ML300) is turning a taper and so presumably the tailstock needs adjusting. Like most equipment there, it doesn't get used. However, I'm not getting involved with that as I have enough jobs to do!

I've finished cleaning up the apron which was thick with an awful paint that had been slapped on top. At least it looks nice.

I will report back in due course.

[AJAXParticipant @ajax]

* Harrison M300

[Anonymous]

Posted by AJAX on 08/01/2021 21:33:47:

* Harrison M300

That's the lathe that will cut an 18DP worm, provided you have the optional 56 tooth gear wheel for the drive train. I bought my gear on Ebay some years ago.

Andrew

[Pete RimmerParticipant @peterimmer30576]

The M300 at your work will cut that worm if you set it to 23TPI (C5SY) and swap the 88 and 44 gears around.

[AJAXParticipant @ajax]

Posted by Pete Rimmer on 08/01/2021 22:00:06:

The M300 at your work will cut that worm if you set it to 23TPI (C5SY) and swap the 88 and 44 gears around.

Still need to swap gears with the full gearbox? I will have to download a manual as I am unfamiliar with the lathe apart from basic tasks.

[AJAXParticipant @ajax]

As promised earlier, here is a bit of an update.

The lathe is currently stripped down so I am unable to test the powered feed under load. However, I have reversed the unevenly worn worm and made a "temporary feedshaft" (turned to size at work and then milled the slot at home) so I can see what is happening. When I did this it was quite obvious the worm was not being lifted sufficiently to engage with the worm wheel.

There is a lever-operated cam at the front of the apron which lifts the worm mechanism via a pin; I have now added a spring behind the pin to make sure that it engages positively. This has greatly improved the action and the lift. Turning the feedshaft over by hand it all appears to work well; the visual signs and "feel" suggest good gear engagement.

I should have the lathe back together and under power to test in a few days time. The temporary feedshaft will make it infinitely easier to get the lathe back together (the temporary will slide out as the real one pushes in) and means I'm quite happy to pull it all apart again when I turn a replacement worm.

Thanks for your interest and advice.

Brian

[Pete RimmerParticipant @peterimmer30576]

Looks like the hole in the lever is much larger than the pin. I would be turning a bush to make it a good sliding fit. Or make a new pin to fit the hole.

[AJAXParticipant @ajax]

Posted by Pete Rimmer on 10/01/2021 17:29:55:

Looks like the hole in the lever is much larger than the pin. I would be turning a bush to make it a good sliding fit. Or make a new pin to fit the hole.

[AJAXParticipant @ajax]

Posted by AJAX on 10/01/2021 18:01:43:

Posted by Pete Rimmer on 10/01/2021 17:29:55:

Looks like the hole in the lever is much larger than the pin. I would be turning a bush to make it a good sliding fit. Or make a new pin to fit the hole.

Pete, it's a good fit. However, I don't rule out the possibility of making a modified pin in the future. Have also considered drilling through and tapping so I can adjust the pressure.

[AJAXParticipant @ajax]

Posted by AJAX on 10/01/2021 18:03:35:

Posted by AJAX on 10/01/2021 18:01:43:

Posted by Pete Rimmer on 10/01/2021 17:29:55:

Looks like the hole in the lever is much larger than the pin. I would be turning a bush to make it a good sliding fit. Or make a new pin to fit the hole.

Pete, it's a good fit. However, I don't rule out the possibility of making a modified pin in the future. Have also considered drilling through and tapping so I can adjust the pressure.

Oh, I think I may have misunderstood. Did you mean the hole in the hand-operated lever or the cradle that holds the worm gear?

[Pete RimmerParticipant @peterimmer30576]

The hole with the spring in it. The pin should be a good fit in there.

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