gear cutters

[mike44]

I have 16 DPI gear cutters 14-1/2° pressure angle. I am making a model tractor that the author specifies 48 DPI 14-1/2°pressure angle.
Can I substitute my 16DPI for the 48DPI ? I have only cut gears twice.
mike

 

[guythatbrews]

No can do. Assuming involute form cutter here. You need a cutter of the correct DP, pressure angle, and tooth range.

 

[L Vanice]

Boston Gear sells a large selection of 48 DP brass gears from 40 to 192 teeth. They used to have 32 and 36 tooth gears, but I do not see them today. I have bought a lot of them on Amazon and have noted that the prices of the individual gears are subject to sharp upward and downward changes. I have learned to watch for price reductions and then buy. Today, the 48 tooth gear (only one in stock) is very cheap ($8.75) and the other gears are not, so I bought the 48 tooth gear.

https://www.amazon.com/gp/product/B004N631KI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I have a set of 48 DP cutters and have cut gears with tooth counts that Boston does not have. Each of the 8 cutters is only suited to cut a certain range of tooth count.

DP (diametral pitch) is the measure of tooth size, with 48 DP having teeth about 1/3 the size of 16 DP. So a 48 tooth 48DP gear will be slightly larger in diameter than 1 inch and a 48 tooth 16 DP gear will be slightly larger than 3 inches.

Larry

 

[mike44]

Boston Gear sells a large selection of 48 DP brass gears from 40 to 192 teeth. They used to have 32 and 36 tooth gears, but I do not see them today. I have bought a lot of them on Amazon and have noted that the prices of the individual gears are subject to sharp upward and downward changes. I have learned to watch for price reductions and then buy. Today, the 48 tooth gear (only one in stock) is very cheap ($8.75) and the other gears are not, so I bought the 48 tooth gear.

https://www.amazon.com/gp/product/B004N631KI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I have a set of 48 DP cutters and have cut gears with tooth counts that Boston does not have. Each of the 8 cutters is only suited to cut a certain range of tooth count.

DP (diametral pitch) is the measure of tooth size, with 48 DP having teeth about 1/3 the size of 16 DP. So a 48 tooth 48DP gear will be slightly larger in diameter than 1 inch and a 48 tooth 16 DP gear will be slightly larger than 3 inches.

Larry

Larry, thanks for the information. Now I realize why 48 DPI was specified and why another DPI would not work.The author gave a supplier that he used and each gear needed. I thought I would try making my own gears, probably buy them now.
mike

 

[johnmontrose]

Now I realize why 48 DPI was specified and why another DPI would not work.

This reply is intended more a generalisation of what has gone before than any kind of correction. First, gears are specified in DP (diametral pitch). DPI is normally used to mean 'dots per inch' in printers.

Second, the pressure angle is not important. Any two gears running together require the same pressure angle, but if you buy stock gears off the shelf today, you will struggle to find 14 1/2 degree PA. Much more likely is 20 degree PA.

Third, there are two things in this application that are fixed: the shaft centres and the gear ratio. Any specification of gears (DP or Module) that will satisfy these two conditions will work. Let us say you have a 1:2 ratio and are using 20t and 40t 10DP gears. You could quite easily use 40t and 80t 20DP gears in their place.

 

[L Vanice]

...

Second, the pressure angle is not important. Any two gears running together require the same pressure angle, but if you buy stock gears off the shelf today, you will struggle to find 14 1/2 degree PA. Much more likely is 20 degree PA.
...

The 48 DP Boston gears from Amazon that I linked in post #3 are 14.5 deg. PA. No struggle required, at least in the USA. Maybe they are hard to get in England.

Larry