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| mini-lathe leadscrew clutch? |
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| garym:
Hi MetalMuncher, There is an idea for a leadscrew clutch on an old thread on the Model Engineer forum. Unfortunately, there is not much detail so I can't figure out how it works but others probably can. http://www.model-engineer.co.uk/forums/postings.asp?th=57688 Gary |
| MetalMuncher:
This looks like the kind of compact design I was hoping for. But I have no idea how it works either. One issue crossing my mind while thinking about such a modification is that the clutch will also need to prevent any lateral movement of the shaft, which essentially gets divided into 2 pieces when disengaged. I could not think of a way short of incorporating 2 more pillow blocks with a clutch release mechanism between them. So this solution is much more elegant. I will try to reach the member who originally posted that information. Thanks Garym! Rick, some of my brainstorms (complete with lightning! :) ) are also of the Rube Goldberg variety. But they get the job done! Here, there is little room for anything very complex. I did see one assembly turn up in my own interent searching last night which also incorporates an automatic kick out mechanism to stop the leadscrew drive gear mesh when a set point is reached (something I've always wished for since I got this lathe) but it is very complex and another design whose functioning eludes my understanding. Plus the author mentioned it may not work on the standard lathe gearing assembly, and that he had previously modified his lathe gearing with someone else's design for a "threading banjo" (not sure which part he refers to by that term, but I am guessing from context he refers to the forward/reverse gearing device for the spindle?). |
| drmico60:
Hi Metal Muncher, I have redesigned the change gear bracket and replaced this with a more conventional banjo, see http://mikesworkshop.weebly.com/new-threading-banjo.html This new banjo can be easily swung away from the drive gear and this enable the leadscrew handwheel to be turned easily even with the change gears mounted. I have taken this concept a step further and fitted a separate variable speed leadscrew motor to the lathe, see http://mikesworkshop.weebly.com/leadscrew-motor.html The banjo can be swung between the lathe spindle gear (for gear cutting and fine feed) to the variable speed leadscrew motor (for variable speed leadscrew feed). In between these two position the banjo does not engage with either and the handwheel can be used. I also have an autostop coupled to the variable speed motor for cutting to shoulders, see: http://mikesworkshop.weebly.com/autostop.html The autostop can also control the main lathe motor for high speed gear cutting, see: http://mikesworkshop.weebly.com/lathe-motor-control.html It would be easy to modify the banjo so that it could be swung by a lever that passed through a opening in the change gear cover. Mike |
| garym:
--- Quote from: MetalMuncher on April 26, 2014, 10:23:07 AM ---..... I will try to reach the member who originally posted that information......... --- End quote --- The member who posted it "Stub Mandrel" was a pseudonym used by the present editor of MEW, Neil Wyatt before he was the editor and he'll probably reply when he sees the posts. Gary |
| DavidA:
L C Mason, in his book 'Building a small lathe' describes a 'clutch' which is part of the lead screw. It is a simple dog clutch and comprises of a muff coupling that has a slot at one end. This slot engages with a pin that passes through the lead screw. When the muff is moved to one side it disengages from the slot thus knocking the lead screw out of drive. Very handy as it can be set, rather like a milling machine stop, at any point. The device is shown on page 69 of the book. Well worth purchasing even if you don't intend to build the lathe. Mine, like my loco is in a part finished state. Dave |
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