Can a Gear Rack Be Made on a Bridgeport CNC?

[Cartierusm]

I need a small gear rack, Mcmaster has them but they are $32 for a 48 Pitch 20 Degree Pressure Angle for 2 feet of this, this seems expensive to me. Is it possible to make a gear rack on a Bridgeport CNC? If so how? I would probably like to keep it at 20 degree pressure angle and the same pitch so I can just buy the pinon gear as I don't have a 4th axis right now. Oh and it only needs to be 8" long.

[Mcgyver]

Originally Posted by Cartierusm I need a small gear rack, Mcmaster has them but they are $32 for a 48 Pitch 20 Degree Pressure Angle for 2 feet of this, this seems expensive to me. Is it possible to make a gear rack on a Bridgeport CNC? If so how? I would probably like to keep it at 20 degree pressure angle and the same pitch so I can just buy the pinon gear as I don't have a 4th axis right now. Oh and it only needs to be 8" long.

sounds cheap to me, you'd need to gash it out first then with an end mill at the right angle or accurately tilt the head, cut one side then other....48 is small, so allow for a bunch of busted end mils and a lot time....yup, $32 seems pretty cheap

2' of rack actually is not trivial to make. the problem is what machine gives you 2' of travel parallel to the spindle axis so you can do it with a proper gear cutter instead of an end mill

[Cartierusm]

I only need 8", but as you said a PITA to make without a horzontal mill.

[Les A W Harris]

SPI has 18" for $58.76!!

Berg has 11.055" long (one has to register for pricing).

Looks like you have located a good source allready!

Cheers,

[HuFlungDung]

I don't think you can beat the price of the purchased rack, either.

It is a lot of trouble on a manual mill as well, because indexing the teeth is difficult to automate (like with a dividing head). However, I think you're supposed to gear up a universal dividing head to drive the X axis screw with an indexing sequence of some sort: the indexer gears drive the table, making it easier to accomplish the spacing. You'd need a right angle head on the vertical, in order that you could cut with motion of the Y axis, and index with the X, in this method (for long racks).

You might want a right angle head in any case, since the arbor support gets in the way when milling long racks on a horizontal spindle.

You could do the indexing accurately if the mill had an accurate linear scale on it, and work out a table of positions for each tooth location. This would help eliminate the backlash and feed screw wear problems. However, the tooth spacing does not work out in whole number increments, so you'd need to watch every tenth, and compensate for rounding errors by calculating the position from tooth zero to every other tooth.

[Cartierusm]

Thanks for the input I just went ahead and bought the rack, just seems so expensive for a little item.