Re: [CAD_CAM_EDM_DRO] Re: cutter or tooth profile for XL series timing belts/pulleys?

Hi,

To answer your first point on tooth spacing, this measurement does not need
to be calculated as it is freely available from any catalogue selling
pulleys i.e.. SDI or HPC Gears. Just look up the table for the belt pitch
and look down the list for the diameter with the correct number of teeth.
Another way of doing it if you have any sized pulley for you belt is to work
out the circumference using pi x D and divide it by the number of teeth on
the pulley. Take this number and multiply by the number of teeth you want.
Not as accurate as looking up the sizes at it relies on your micrometer and
you measuring to tenths.

Your second point is a little more difficult to explain. What you appear to
refer to is the pressure angle which would be between 40 to 50 degrees
depending on the belt requirements, a 0.2" pitch belt has a 50 degree angle
where as a 3/8" has 40 degrees. What I couldn't get right was the small
radius at the top and bottom of the tooth profile. My pulleys made the belt
ride out of the teeth without lots of tension on the belts but they never
jumped a tooth and it has been working on my tool and cutter grinder motor
to spindle for about ten years without wearing out.

Regards,

Terry


| Thanks guys,
|
| I did get a spreadsheet from one of the members that helped out a
| lot.
|
| There is a very tight relationship between the tooth spacing and the
| diameter of the pulley. In order for 'X' amount of teeth to fit
| on 'Y' diameter pulley, the ratio has to be exact. In other words,
| a pulley with 20 teeth MUST be exactly 'Y' diameter.
|
| There is another aspect similar to gears too, it has to do with the
| angle on the sides of each "tooth" so that the teeth on the belt can
| enter and exit the "tooth slots" in the pulley without rubbing. So,
| again, the angle on the sides of the "tooth slot" are important.
| Sorry for the funny terms, gearing and pulleys are not my "cup of
| tea".
|
| Chris
|
|
|
|
|
|
| --- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...>
| wrote:
| > Blue,
| >
| > Thats how I see it too. machine pockets in the gear for the teeth
| of the belt to ride in. The pitch diameter and resulting blank
| diameter would be calculated from the center point of the radius of
| each belt tooth. the diamter of the pulley has little effect on the
| shape of the belt teeth.
| >
| > Ron
| >
| > Blue <jo001k1132@b...> wrote:
| > Hi,
| >
| > First of all I have not tried this but I have cut a lot of gears
| using a
| > home made hob. I did try using a single point cutter and dividing
| head many
| > years ago with some success but it wasn't perfect because I didn't
| get the
| > radius's right. It did work and is still going strong but it was
| for a motor
| > drive and no precision was necessary
| >
| > Wouldn't the pulleys be treated the same as for involute gears
| just with a
| > different pressure angle, I think it would be 50 degrees if memory
| serves.
| >
| > The hob acts in the same way as a rack cutter and will cut any
| size of
| > wheel. Making the hob is an easy turning/milling job.
| >
| > Regards,
| >
| > Terry
| >
| >
| > | > Does anyone have a drawing of a cutter or tooth profile for XL
| series
| > | > timing belts/pulleys? I am hoping to mill up some pulleys in
| the
| > | > comming weeks. I have a pulley and a belt in my hands, but if
| someone
| > | > has already made up a cutter drawing, it sure would save some
| work!
| > | >
| > | > Thanks
| > | >
| > | > Chris
| > |
| > | We discussed this a few months ago.
| > |
| > | it is not the exact form unless you have one gear.
| > |
| > | Each gear tooth will be different on each gear as the total
| number of
| > | teeth changes.
| > |
| > |
| > | That said, check the files section.
| > |
| > | Alan has a program in a folder
| > | Timing Belt Pulley - Program to generate Gcode to mill timing
| belt pulleys
| > |
| > | Dave