question on gear rack

[wired]

Hey guys, I'm looking for gear rack in lengths longer than 6'. Perhaps 10'
, 16 pitch, .500" wide, .500" thick. Any suggestions where to get it. Thanks. John.

[Al_The_Man]

Boston gear have 16 pitch .75x.75 in 20deg or 16 pitch in .5x.375 in 14 1/2 deg pressure angle. I think you may have a problem getting 10ft lengths. it is easy to join if that is what concerns you. The 20deg pitch takes a bit more load. Another source I use is Sterling Instruments Stock drive products. machined ends, but more expensive.
Al

[wired]

Thanks for the info Al, John

[fz1]

The plasma machines I used to make for one company sometimes had tables up to 50 feet long. Thew were driven by rack gears and joining them together is real easy. The ends have to be machined so that when they are put end to end it looks like there is no difference in the tooth profile. Then when mounting the racks on your machine use a scrap piece of rack and clamp it over the two pieces of rack mounted to the machine. This will alow you to make longer racks with no problems of proper mesh.

[Al_The_Man]

Originally Posted by fz1 Thew were driven by rack gears and joining them together is real easy. The ends have to be machined so that when they are put end to end it looks like there is no difference in the tooth profile. Then when mounting the racks on your machine use a scrap piece of rack and clamp it over the two pieces of rack mounted to the machine. This will alow you to make longer racks with no problems of proper mesh.

Usually the machined ends means that you do not have to do any matching, but if they are non machined you do not neccessarily have to butt them up close, what you do is cut or machine the ends so the cuts are just short of the bottom of the valley, (the gear does not contact this point). and if you do this to both ends you end up with a very small gap, and as long as you mount them using the method you outlined it will be OK.
Al

[fz1]

Also this might help some. The motor and drive gearbox was mounted on a hindged plate. This was spring loaded to keep the mesh of the pinion tight against the rack. It kept backlash down to a minimum.

[wired]

Great tip! thanks for help!
John

[Al_The_Man]

Here is a previous forum link on exactly that It was a gantry I retrofitted last year.
http://www.cnczone.com/forums/showth...15&page=3&pp=5
Al