MadModder
The Shop => Tools => Topic started by: yorkie_chris on December 16, 2012, 03:26:13 PM
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So on with the very steady improvement of my old denham lathe, it uses changewheels for screwcutting. I've got some of the wheels but not the full set.
At the moment it's a bit of a bodgerama, I didn't get any sort of shaft or anything to hold the gears on the segment arm.
The gears have a 3/4" bore with keyway, the slot on the segment arm is 5/8".
Can anyone recommend a clever solution for this? I haven't seen any old lathes with this setup to copy but there must be plenty on here.
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So you need to turn up a short stub, with a 5/8 diameter and 5/8 thread at one end, a plain 3/4" section at the other with probably a reduced diameter part on the end threaded 5/8". The stub is retained onto the quadrant with a 5/8 nut on the 'far' side of the quadrant, the gear slips onto the 3/4 plain section, with a fat washer followed by a 5/8" nut.
You will also probably want to make up one with a double length 3/4 plain section for pairs of gears pinned together, though sometimes a sleeve is used with a keyway to fix two gears together
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I've just done the same thing with my lathe after getting a gear set that had different bore diameters.
It's just a matter of turning up a set of adapters.
Very satisfying when it is all done.
Dave.
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Do you just run the gears on plain steel journals or make a brass sleeve?
Do you drill the gears on a common PCD to dowel/bolt them together when running a pair and not use the keyway?
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If you turn up a stub at 3/4" diameter with a 5/8" or smaller thread on the end then file or mill flats in the 3/4" bit so it fits in the 5/8" quadrant slot you won't have trouble holding it when tightening the nut that will hold the stub to the quadrant or the retaining nuts for the changegears.
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Being cast iron my gears are happy to run on the steel shafts.
Dave
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Yorkie Chris wrote:
Do you just run the gears on plain steel journals or make a brass sleeve?
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Mine has just the one cast-iron stud gear, but it's on a keyed steel carrier sleeve[1] that runs on a pair of caged needle-rollers...
First time I took it apart I thought "Ooh, POSH!" and then "Oh..."[2]
Dave H. (the other one)
[1] To allow for compound gear pairs *if required*
[2] Cos the stud shaft was in a right state!
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Where the gears are just running as idlers I let them run straight on the steel shafts.
Where they are keyed I have made a couple of split 'shells' that fit the shafts and slip past the keys. I filed a matching keyway into the gear to alllow it to drive.
I will have to make up some further spacers to get some sort of standardisation. But for the threads I need at the moment it works well.
Dave.
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An alternative to keyways is to pin the gears
(http://www.flickr.com/photos/27950278@N04/8291965343/)
These are a bit smaller and from my Exe 2-1/2" lathe. They are 18DP with a 7/16" bore. The pin is press fitted into the gear and engages with a clearance hole in the gear it is coupled to.
A similar system was used on Drummond lathes I believe.
Ray
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An alternative to keyways is to pin the gears
(http://www.flickr.com/photos/27950278@N04/8291965343/)
These are a bit smaller and from my Exe 2-1/2" lathe. They are 18DP with a 7/16" bore. The pin is press fitted into the gear and engages with a clearance hole in the gear it is coupled to.
A similar system was used on Drummond lathes I believe.
Ray
Infact rather like the suggestion in the first reply :doh:
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Pinning them together face-to-face is fine, my gearset came with such an arrangment. But won't you still have to key them to the leadscrew on occasion ?
Dave.
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The output from the headstock and input to the screwcutting/power feed gearbox are both keyed.
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Just make a keyed blank gear with pin-holes so you can chop and change the gears on those shafts as you like.