I have two mid-century engineer's books, giving info on gearing. Fowler's Mechanics' and Machinists' Pocket Book (43rd annual ed., 1951) has tables of data for cycloidal and involute gears but only 15 degree pressure angle. It mentions Grant's Treasise on Gears, describing an odontograph and mentions the 15 degree standard. Applied Mechanics by David Allan Low (15th ed., 1940) mentions the "common tangent to the pitch circles" (aka the "line of action") being usually 14-1/2 to 15-1/2 degrees. So, whilst looking backwards to some degree, these suggest that 14-1/2 may not have been univesral, or that 20 degree PA was being used in the UK up to and during WW2.
3:25 And the 0.25 value for sin 14.5 degrees is what I was taught 50-odd years ago, as the 19th century's easy to use value before calculators and perhaps log tables and slide rules. Also the drill point of 118 degrees gives a length from tip to full diameter of 0.3 of the drill's diameter, the amount the drill must go through a piece of work to produce a clear hole. I was a planning engineer, so useful knowledge. We had automatic (not CNC) Warner-Swasey lathes. By the 1960s, standard industrial gearing was 20 degree pressure angle.
Bill, Thanks for watching, your comments and references. 15 degrees was definitely European and 14.5 degrees was predominately in the US in the early years. The sought after text "MAAG Gear Book" (Zurich Switzerland) 1963 references 15 degree gears. www.patreon.com/posts/maag-gear-book-98346358?Link& 20 degrees is definitely the more often practiced pressure angle now. Andrew
Martin, thanks for sharing your knowledge and watching. Do you know when their first standard regarding gearing and the pressure angle was published? I would like to add that to the description in the video or make another.
@@EvolventDesign The earliest I can find is BS 436 Specification for machine cut gears, dating from 1932, which was updated in 1940 and withdrawn in 1967 when BS436 was split to become BS436-1 though to BS436-5 those being replaced in 1996 by BS ISO 6336. The last update of 6336 was in 2019.
@@MartinE63 What a thorough review, thank you so much. The AGMA standards are similar with many revisions over the years. You are well versed in the British Standards and I really appreciate you adding to our overall knowledge base, I will add this to the description. Cheers Andrew Prestridge
Very true, DIN 867 defines a 20 degree pressure angle. Prior to 867 (in Germany at least) the standard was 15 degrees-very close to 14.5. Not sure when DIN first published 867, but it was after 1917 and before 1936. Regardless, it was long after the 1841 work of Willis.
I love the history of our technology culture. Thanks ! --------Doozer
I have two mid-century engineer's books, giving info on gearing. Fowler's Mechanics' and Machinists' Pocket Book (43rd annual ed., 1951) has tables of data for cycloidal and involute gears but only 15 degree pressure angle. It mentions Grant's Treasise on Gears, describing an odontograph and mentions the 15 degree standard. Applied Mechanics by David Allan Low (15th ed., 1940) mentions the "common tangent to the pitch circles" (aka the "line of action") being usually 14-1/2 to 15-1/2 degrees. So, whilst looking backwards to some degree, these suggest that 14-1/2 may not have been univesral, or that 20 degree PA was being used in the UK up to and during WW2.
3:25 And the 0.25 value for sin 14.5 degrees is what I was taught 50-odd years ago, as the 19th century's easy to use value before calculators and perhaps log tables and slide rules. Also the drill point of 118 degrees gives a length from tip to full diameter of 0.3 of the drill's diameter, the amount the drill must go through a piece of work to produce a clear hole. I was a planning engineer, so useful knowledge. We had automatic (not CNC) Warner-Swasey lathes. By the 1960s, standard industrial gearing was 20 degree pressure angle.
Bill,
Thanks for watching, your comments and references. 15 degrees was definitely European and 14.5 degrees was predominately in the US in the early years. The sought after text "MAAG Gear Book" (Zurich Switzerland) 1963 references 15 degree gears.
www.patreon.com/posts/maag-gear-book-98346358?Link&
20 degrees is definitely the more often practiced pressure angle now.
Andrew
Nice job
Awesome information! Great video!!!
Thanks Danny- you are awesome and have been along for the ride since the very start. I appreciate your kind comments.
@@EvolventDesign My pleasure Sir!! I always enjoy watching and learning from you!!!
Great video!
The British Standards Institute precedes all the others mentioned - it was founded in 1901 as the Engineering Standards Committee
Martin, thanks for sharing your knowledge and watching. Do you know when their first standard regarding gearing and the pressure angle was published? I would like to add that to the description in the video or make another.
Makes a lot of sense since so much of the Industrial Revolution started in GB which also generated many original patents.
@@EvolventDesign The earliest I can find is BS 436 Specification for machine cut gears, dating from 1932, which was updated in 1940 and withdrawn in 1967 when BS436 was split to become BS436-1 though to BS436-5 those being replaced in 1996 by BS ISO 6336. The last update of 6336 was in 2019.
@@MartinE63 What a thorough review, thank you so much. The AGMA standards are similar with many revisions over the years. You are well versed in the British Standards and I really appreciate you adding to our overall knowledge base, I will add this to the description. Cheers
Andrew Prestridge
Hey Martin does the BS 436 Specification for machine cut gears, dating from 1932 indicate 14.5°, 15.0° or 20° Pressure Angle?
Gear heads for sure
20 Deg for Metric
Very true, DIN 867 defines a 20 degree pressure angle. Prior to 867 (in Germany at least) the standard was 15 degrees-very close to 14.5. Not sure when DIN first published 867, but it was after 1917 and before 1936. Regardless, it was long after the 1841 work of Willis.
Thanks for your comment and watching the video
Did some more digging and the DIN 867 earliest publication I can find is from July of 1927. Added the date to the description of the video.