Gear Rack and Pinion Gears

[Rypper]

Hello,

I want to upgrade my older cable driven cnc machine to rack and pinion.
So I am in need of the name of suppliers of gear rack and matching pinion gears.

My current rails are 120" for the x axis and 72" for the y axis so if possible I would like to get 10 foot sections or shorter lengths that can be joined nicely together.

Thank you,
Tom

[RICHARD ZASTROW]

Rypper, Martin sprocket & gear, Arlington TX 3-24 pitch; 2,4,6 ft lengths. 14 1/2 deg. pa 20 deg. pa matching pinions different lengths, material etc.

[Al_The_Man]

Boston Gear also sell a range fairly well priced.
If you don't buy the machined end type, the un-machined is cheaper and all you need do is use a short section to mesh the mating lengths for alignment, but first cut or machine the ends so that it is just short of the bottom of what will be the tooth depth, this allows a slight gap which is no problem as the gear should not bottom out.
Al.

[jcc3inc]

Sir,

A good source of gear rack is Standard Steel Specialty Co. They stock 6 foot lengths of 20dp, 20 degree PA, and may have 24dp, 20 degree PA. A quote on 22 Feb. this year was at $23.20 each/2-24 pcs. 20 degree Pinions are available from Bearing distributors and others. I would opt for the 6 foot sections as they are easy to join, and 6 feet is a standard length, easy to ship by UPS, I believe
.
I would setup the drive gearbox/motor so that the unit is pivoted or hinged with spring loading into the gear rack. Place the pivot line/hinge axis so that it lies ON the pitch line of the gear rack. This ensures that driving forces, forward and back, do not tend to add or subtract to the engaging force.
With 20 degree gearing (preferred for smoothness of operation), the separation force due to the pressure angle is Tan(pressure angle). Thus if you need 50 # of driving force, the spring load of the pinion INTO the rack should be 50 x TAN(20 degrees) = 18#.

You can contact me if you have further questions. jccinc-at-owc-dot-net

Regards,
Jack C.

[Rypper]

Thanks to all for the info.

Jack, thanks for your offer I will contact you once I start the conversion.

Just so I order the proper materials. My gear rack should be 20dp, 20 degree PA and the pinion also 20 degree, but how many teeth on the gear.

Tom

[Al_The_Man]

For that size table I use 16 & 12dp depending on the weight of the table, once you come down to 20dp you are often limited to .5" face width, which is a bit light for a heavy table, I use a pitch dia of 2" to 2.5" for the spur gear.
Al.

[jcc3inc]

Rypper,
The min number of teeth for no undercutting for 20 degree PA is 18 teeth and for 14 1/2 degree it is 32 teeth.
One likes to have several teeth in contact at a time, so more than 18 teeth is desireable; HOWEVER, you have to take into account the gear reduction from your drive motor.
JCC

[project5k]

more teeth means more top speed, but also means you need more torque to turn it and less accuracy per step of the motor...