Re: [CAD_CAM_EDM_DRO] Re: Toothed pully design information needed.

Ah, thanks John! I didn't know that. Glad I asked.

Smoke
-----Original Message-----
From: machines@... <machines@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Saturday, November 11, 2000 10:44 AM
Subject: [CAD_CAM_EDM_DRO] Re: Toothed pully design information needed.

>--- In CAD_CAM_EDM_DRO@egroups.com, "Smoke" <Smoke@5...> wrote:
>> Let's see...without even using a book, I would figure the OD of a
>3/8" pitch
>> timing belt pulley having 40 teeth as follows:
>>
>> 40 x .375 / PI = 4.774648....diameter. From this I would simply
>use a
>> cutter made like John mentioned as cut the tooth profiles using a
>dividing
>> head.
>>
>> Does that sound reasonable?
>>
>> Smoke
>
>Not quite, This is where a lot of confusion comes in.
>Funny as it sounds and contary to gear technology the OUTSIDE
>diameter of a timing pulley is Smaller than the PCD.
>Smokes figures are correct for the PCD.
>To get the outside diameter you need to subtract a constant from the
>PCD. In the case of the 3/8" pitch belts, also known as the 'L'
>series this is 0.030" so the OD of Smokes pulley will be 4.775" -
>0.030" = 4.745"
>This constant is the same for all the 'L' series range regardless of
>number of teeth. Other ranges have different constants. I aim to put
>some of this on a page and upload it to the files section when I have
>a minute.
>
>John Stevenson
>Nottingham, England.
>
>
>
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