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

Hi Alan R, list,

The cutter should look like a tooth profile. Remember that the teeth roll
against each other, not rub.

Cut a tooth profile on the end of a tool bit. Add proper relief after
getting the profile correct. A mandrel to hold the cutter (square, not
angled to the shaft) much like a flycutter is used to mill the teeth. XL
profiles can be laid out and ground by hand, if you are careful. Check the
profile against a fresh pulley.

Determine or calculate the diameter of the blank for the desired number of
teeth from pulley info tables. Some calculations will give you the depth
you must cut in from the diameter of the blank.

Cut a single tooth "recess" (tooth slot?) at a time making passes across the
face of the timing belt pulley with the "flycutter". Use the appropriate #
of passes (proper depth of cut per pass). Rotate blank to next position,
and repeat.

A good fitting pulley will closely fit a belt wrapped around it. There
should be no gaps between the teeth faces. There might be the slightest bit
of a gap at the bottom of a tooth recess in the pulley. Examine a similarly
sized commercial pulley and belt to observe this.

Check a Gates or other belt catalog for dimensions (most) of the belt and
pulleys.

Alan KM6VV

> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Alan Rothenbush
> Sent: Friday, September 16, 2005 1:44 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: cutter or tooth profile for XL series
> timing belts/pulleys?
>
> On Monday 29 August 2005 14:22, lcdpublishing wrote:
>
> > 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.
>
> It seems to me that all of the motion is transmitted by the sides of the
> "teeth" on the pulley and belt (for XL series anyway).
>
> Therefore, a person could cut properly angled teeth in two passes, with
> the
> blank first angled clockwise and offset left just the right amount to cut
> the
> left of the tooth (and all the way round to cut the left side of all the
> teeth) and then angled CCW and offset right an appropriate amount to cut
> the
> right side of all the teeth.
>
> The area between the teeth would look a bit like a "W", and a skinny
> cutter is
> clearly called for, but so long as the tip of the W is lower than the
> tooth
> on the belt (or a third pass taken to clean this up), this would seem to
> work .. with no fancy cutter required .. just a 1/8" dia. or so endmill.
>
> Am I missing something ?
>
>
> Alan
>
> --
> Alan Rothenbush
> Academic Computing Services
> Simon Fraser University
> Burnaby, B.C., Canada
>
>
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