drummond round bed screw cutting question

drummond round bed screw cutting question

This topic has 7 replies, 3 voices, and was last updated 11 November 2015 at 23:22 by keith wedgwood.

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11 November 2015 at 19:35 #211610
keith wedgwood
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@keithwedgwood19516
hi all i have acquired a nice Drummond round bed lathe and i wish to venture into screw cutting so i have managed to get a manual for it which gives the gearing in t.p.i.

now my problem is that for 12 t.p.i. the first stud and the 2nd stud are idle but the mandrel 25 tooth gear and the lead screw 30 tooth gear are too far apart to mesh. am i missing something
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11 November 2015 at 19:35 #7864
keith wedgwood
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@keithwedgwood19516
11 November 2015 at 20:42 #211624
nigel jones 5
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@nigeljones5
probably! there is another nut which when slack allows the gears to slide in and out and thus mesh. I hope yours has better headstock bearings than mine, but then it is over 100 years old!
11 November 2015 at 20:45 #211626
nigel jones 5
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@nigeljones5
11 November 2015 at 21:23 #211630
Michael Gilligan
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@michaelgilligan61133
Posted by keith wedgwood on 11/11/2015 19:35:45:

hi all i have acquired a nice Drummond round bed lathe and i wish to venture into screw cutting so i have managed to get a manual for it which gives the gearing in t.p.i.

now my problem is that for 12 t.p.i. the first stud and the 2nd stud are idle but the mandrel 25 tooth gear and the lead screw 30 tooth gear are too far apart to mesh. am i missing something

.

Keith,

For "idle" … read "carrying an idler gear"

does that help ?

MichaelG.
11 November 2015 at 21:37 #211633
keith wedgwood
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@keithwedgwood19516
thanks Michael

it helps a bit does it mean i just use just 1 gear with the amount of teeth being irrelevant
11 November 2015 at 21:48 #211635
Michael Gilligan
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@michaelgilligan61133
Posted by keith wedgwood on 11/11/2015 21:37:29:

thanks Michael

it helps a bit does it mean i just use just 1 gear with the amount of teeth being irrelevant

.

Keith,

Yes … an idler gear [or any number of them in series] makes no difference to the overall ratio … but each one reverses the direction of rotation.

Have a play with some gears on the banjo and you will soon get the idea.

MichaelG.

.

Edit: The animation on this page might help.

Edited By Michael Gilligan on 11/11/2015 21:52:57
11 November 2015 at 23:22 #211651
keith wedgwood
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@keithwedgwood19516
many thanks for the info
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