19TPI on South Bend Lathe

This topic has 11 replies, 7 voices, and was last updated 20 November 2014 at 10:45 by Brian Wood.

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11 October 2014 at 03:24 #7331
Doug Bauld
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@dougbauld76775
I would apreciat any guidance in accumplishing this task
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11 October 2014 at 03:24 #166247
Doug Bauld
Participant
@dougbauld76775
My lathe is a SBL with a quick change box, it will do 18 and 20TPI nothing listed for 19TPI. I do have transposing gears. The closest Metric equivalent is 1.30mm. Not good enough for the project at hand. All helpful hints and idears much appreciated. Thank's Doug in Canada.
11 October 2014 at 14:22 #166272
Bazyle
Participant
@bazyle
Have you seen the variable lead method. You can adapt any sliding tool holder you might have such as a quick retract thread cutting aid, a slotting attachment, a scale engraving slide etc. There are several threads on the site covering the same topic.

Since you mention transposing gears does this mean you have a metric leadscrew? What other gears do you have? You will need a 38 (2×19) since 19 is a prime. If it is a one off you can make do with a rough cut plastic gear with triangular teeth.
11 October 2014 at 16:40 #166283
Brian Wood
Participant
@brianwood45127
Hello Doug,

If you have a 42t gear, put that on as the stud gear and use 56t as the screw gear. Set the gearbox for 40tpi and you will cut a thread of 0.0525 inch pitch with a leadsscrew of 0.125 inch, which is 19.048 tpi, probably close enough.

Regards Brian
11 October 2014 at 20:01 #166296
John Burridge
Participant
@johnburridge26484
The other way would be to set up to cut 38TPI then have it with on e of the driven gears
12 October 2014 at 11:30 #166345
Brian Wood
Participant
@brianwood45127
Sorry John, the South Bend lathe gearbox doesn't provide 38 tpi either, or for that matter any of the multiples of 19 so your approach is a non starter..

56T is a standard supply gear for the imperial box so 42T is a minimal addition to give Doug what he wants. If a 38T gear is used in the drive, then the gear driving the gearbox (the screw gear) will also need changing, making another purchase necessary.

Regards Brian
12 October 2014 at 17:27 #166385
John Stevenson 1
Participant
@johnstevenson1
Brian's answer will be the simplest and cheapest way to achieve what the OP wants.
12 October 2014 at 18:51 #166388
Doug Bauld
Participant
@dougbauld76775
Thank you Gentleman, I am enjoying the interest and input to my project. I would prefer to achieve the job by using change gears. I do also have another SBL9 without the quick change gear box, in pieces at the moment as it is in dire need of serious service. This is probably the machine that I should be setting up to do the job. I have came across this 19 TPI several times more recently with Chinese manufactured products. It is not common in North America and seems to appear first in the English system of manufacturing. My lathes are all Imperial with 8TPI lead screw. Thanks to all Doug in Canada
12 October 2014 at 19:07 #166391
Speedy Builder5
Participant
@speedybuilder5
3/8 BSP 19tpi
12 October 2014 at 20:25 #166395
Anonymous
….not only but also……1/4" BSP.

Andrew
13 October 2014 at 10:34 #166424
Brian Wood
Participant
@brianwood45127
Doug,

I've sent you a PM

Regards Brian
20 November 2014 at 10:45 #170143
Brian Wood
Participant
@brianwood45127
Hello Doug,

I have sent you a PM, contact may well be in your favour now that you are snowed in

Please get in touch directly if you prefer wood_y[at]btinternet[dot]com all lower case, no spaces and note the underscore—-not a dash

Regards

Brian
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