Helical gears tend to be the default choice in applications that are ideal for spur gears but have nonparallel shafts. They are also utilized in applications that require high speeds or high loading. And regardless of the load or swiftness, they generally provide smoother, quieter operation than spur gears.
Rack and pinion is useful to convert rotational motion to linear movement. A rack is directly the teeth cut into one surface of rectangular or cylindrical rod formed material, and a pinion is a small cylindrical equipment meshing with the rack. There are many ways to categorize gears. If the relative placement of the gear shaft can be used, a rack and pinion belongs to the parallel shaft type.
I have a question regarding “pressuring” the Pinion into the Rack to lessen backlash. I’ve read that the bigger the diameter of the pinion equipment, the less likely it is going to “jam” or “stick in to the rack, but the trade off may be the gear ratio enhance. Also, the 20 degree pressure rack is better than the 14.5 level pressure rack for this use. Nevertheless, I can’t find any information on “Helical Gear Rack pressuring “helical racks.
Originally, and mostly due to the weight of our gantry, we had decided on larger 34 frame motors, spinning in 25:1 gear boxes, with a 18T / 1.50” diameter “Helical Gear” pinion riding upon a 26mm (1.02”) face width rack as supplied by Atlanta Drive. For the record, the motor plate is bolted to two THK Linear rails with dual vehicles on each rail (yes, I understand….overkill). I what after that planning on pushing through to the electric motor plate with either an Air flow ram or a gas shock.
Do / should / may we still “pressure drive” the pinion up right into a Helical rack to further decrease the Backlash, and in doing this, what will be a good beginning force pressure.
Would the use of a gas pressure shock(s) are efficiently as an Air flow ram? I like the thought of two smaller push gas shocks that equal the total power required as a redundant back-up system. I would rather not operate the surroundings lines, and pressure regulators.
If the idea of pressuring the rack is not acceptable, would a “version” of a turn buckle type device that might be machined to the same size and form of the gas shock/air ram work to change the pinion placement in to the rack (still using the slides)?
However the inclined angle of one’s teeth also causes sliding contact between the teeth, which creates axial forces and heat, decreasing efficiency. These axial forces perform a significant function in bearing selection for helical gears. Because the bearings have to endure both radial and axial forces, helical gears require thrust or roller bearings, which are usually larger (and more expensive) compared to the simple bearings used in combination with spur gears. The axial forces vary compared to the magnitude of the tangent of the helix angle. Although larger helix angles offer higher velocity and smoother movement, the helix angle is typically limited to 45 degrees due to the production of axial forces.
The axial loads made by helical gears can be countered by using double helical or herringbone gears. These arrangements have the appearance of two helical gears with opposing hands mounted back-to-back again, although in reality they are machined from the same gear. (The difference between the two designs is that double helical gears possess a groove in the middle, between the teeth, whereas herringbone gears usually do not.) This set 
up cancels out the axial forces on each group of teeth, so larger helix angles may be used. It also eliminates the necessity for thrust bearings.
Besides smoother motion, higher speed ability, and less sound, another benefit that helical gears provide over spur gears may be the ability to be used with either parallel or nonparallel (crossed) shafts. Helical gears with parallel shafts require the same helix position, but reverse hands (i.e. right-handed teeth vs. left-handed teeth).
When crossed helical gears are used, they may be of either the same or opposite hands. If the gears have got the same hands, the sum of the helix angles should equal the angle between the shafts. The most common example of this are crossed helical gears with perpendicular (i.e. 90 level) shafts. Both gears possess the same hand, and the sum of their helix angles equals 90 degrees. For configurations with reverse hands, the difference between helix angles should equivalent the angle between the shafts. Crossed helical gears offer flexibility in design, but the contact between the teeth is closer to point contact than line contact, so they have lower drive features than parallel shaft designs.