Gallery, Projects and General > The Design Shop

Leadscrew Clutch Options?

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BillTodd:
There's not a lot of space to play with, is there?

Improving the general fit and hardness of the parts will, I'm  sure,  improve it.

Pay attention to any part that forces another to  i.e. are the dogs exactly 90 degrees apart ? (if you remake it, i suggest two dogs 180 apart would be easier ) does the slide lever try to push the dog to one side (causing it to jam) .?

I have a very similar mechanism on my Haughton Cadets they can get stiff but are usually ok under normal threading loads.

Btw. The dogclutch is not usually much use when threading as there is not  normally a simple relationship between the clutch engagement points and the screwpitch. For instance the Cadet's 10tpi lead screw and four tooth clutch, means that is is only useful on 0.025" pitch (40 tpi - where is can be engaged at any point) .

You may find it easier to fit an electrical stop (and reverse ) or thread backwards away from the shoulder (there's an explanation somewhere on the forum of this) .

Bill

velocette:
Hi Sparky
The pictures tell the story not a lot of room to play around in is there.
Bill Todds suggestion that two points of contact to separate the clutch will help.

Eric

velocette:
Hi Again
Pondering on this over breakfast Came up with this to get two points to operate the dog clutch
Bore the bottom of the gearcase and fabricate two shafts with a yoke on the outside of the gearcase.
Attached a rough sketch

Eric

sparky961:
Thanks for your thoughtful input so far. I shouldn't have mentioned threading in relation to the dog clutch. I don't use it for threading. In fact, I thread very rarely with this lathe because it takes way too long to set up.

It brings to light an important omission on my part though. I have been using the dog clutch instead of the half nut because a number of years ago I installed a fixed full nut. This was due to a lot of backlash from wear. It wasn't simple at the time to fix the half nut.

Now that I'm looking at the bigger picture, it seems using the half nut would work better. I may have even advanced enough since then rhat I can correct the backlash to a minimum.

chipenter:
Case hardening the exsisting my be the quickest and cheepest option for you .

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