[zeoncomp]

I am looking for 20° Pressure Angle Spur Gears and Racks. I understand that these are better than 14 1/2 because multiple reasons. I found this at McMaster .... will this work ?
Thank you.

Spur Gear on Rack

Steel Plain Bore Spur Gears


20 Pitch— 1/2" Face Width

No. of teeth = 20
Pitch Dia. = 1"
Hub dia. = 0.84"
OD = 1.1"
O'all Lg. = 0.94"
Bore = 1/2"


Steel Gear Racks


Length Pitch = 20
Face Wd. = 1/2
O'all Ht = 1/2

[Robin Hewitt]

.... will this work ?

What's not to work? If both are 20DP it will run

20t is not so small that it requires a modified tooth form to engage a rack smoothly, one turn will advance you 3.141592654 etc. inches.

[jcc3inc]

Sir,

We used to buy our rack from Standard Steel Specialties,
www.stdsteel.com/gear.htm

They were a very good supplier. My last price was $23.20 ea in quantities of (2), for 1/2 x 1/2 x 6 ft, 20 DP, 20 degree PA rack. You can find pinions from various sources (Boston Gear). If you use pinions with 18 T or more, there will be no undercutting. We used around 30T pinions so more teeth were in contact with the rack.

You can spring load the pinion into the rack for no backlash. With 20 degree rack, the engaging force required will be [.37 x the max drive force] you expect. For example, if you have 35# drive force max, the spring load will be 35 x .37 = 13#.

For equal forces driving each direction, placing the drive assembly pivot point so that it falls on the rack pitch line will satisfy this situation.

Regards,
Jack C.