I want to try something with a rack.

[DesertRunner]

I have made a bunch of gears and was intending on driving from one to the next (see attached link) but I am concerned about the compound load so I since decided to give using a rack a try as the method of drive.  I am fully aware that at this time there is no method to cut the rack using this program.  Were my head is at is that if I can work out the shape of the gear in terms of side profile then I could use CamBam 3d to cut them using a endmill and cleaned up with a ball nose cutter.

So what I need to know is for module 5 gear what is the spacing the teeth need to be apart on the rack and were would I go to find the correct side profile.  My logic is I can draw the rack in Alibre export it in STL to CamBam and then cut the final rack.  It may not be perfect but It will be better then nothing.

All suggestio n greatly appricate d.
Tony

http://gearotic.com/ESW/FavIcons/index.php?topic=565.0

[ArtF]

Tony:

   I havent yet done it for my project but I need to soon, so this is off the top of my head..

  Again, this is off of the top of my head so till I do it I cant be sure Im clear on the math.. I always have to check such things in reality..

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  Kinda as in the above.. the angle of the lines is 20degrees ( the PA ) and the dot distance is as a described ..

Art

[John S]

Spacing between the teeth on a rack is equal to the Circular pitch of the gear.
In the case of Mod gears this is Pi x Mod, so 5 mod has a spacing of 15.708 mm.

John S.

[ArtF]

>>Spacing between the teeth on a rack is equal to the Circular pitch of the gear.
In the case of Mod gears this is Pi x Mod, so 5 mod has a spacing of 15.708 mm.

lol.. I cut some of my reply so I could fit the dots and forgot to paste it back in to explain it.. Thx John..her e's the missing text

  A module 5 gear with 20 teeth has a diameter to 100 at the pitch line. ( nTeeth times MOD ). A diamter of 100 has a circumfer ace of 100 * PI = 314.15926 , so each tooth is 314.15926 / 20 = 15.708mm or as John pointed out it devolves down to PI * mod since the tooth count cancels out.   The pressure angle is 20 degrees. SO a series of dots placed 15.708mm apart, with slanting lines as I showed above at 20 degrees can be joined at the top at dedendum hight and at the bottom at addendeum depth to create a rack from the placed dots.. ( if you can picture it as above.. so make some dots, slant some 20 degree lines centered on them, join them top and bottom and you shoudl have a rack that works.. Sorry for this missing paragraph ..

Art

[DesertRunner]

Thanks guy I appricte the info, a guy on the CamBam form suggested cutting the buy using side profile, which is a good suggestio n, my only issue is that as I remember it would need a 6mm cutter and my teeth/rack is 60mm wide.  The other suggestio n was make a end mill with the gear profile which is a bit more of a issue given its a steel rack.
Tony

[ArtF]

Tony:

 There is no gear tooth profile on the rack, while the gear is an involute shape, the rack is just straight lines slanted at pressure angle..
A Vtooth cutter would cut a rack ..

Art

[DesertRunner]

Sorry if its a dumb question but how deep or how wide across the top of the tooth?  Give what you said Art I may try tlt the head of the mill to 20 degrees cut one side then turn the rack and cut the other side.
Tony