Mark VII gear rack

[Darkehorse1]

Looking to replace the gear racking on both of my old Mark vii. Anyone know where I can purchase them? Thanks

[JPG]

They appeared on E-Bay a while back.

[chapmanruss]

There is currently one person on ebay (houseofrust) selling 3D printed replacement racks. They also have a 3D printed replacement Speed Control Cam for sale. In the past there was a different seller making 3D printed racks.

Actual OEM racks would have to be found used and may not be in any better condition than yours.

[SteveMaryland]

Expensive, but I would replace a plastic rack with new steel or aT least aluminum. Beats having something that soon breaks.

I think a used plastic rack would by this time be brittle. I would not trust a printed part for the same reason.

Reid and Stock Drive still sell small gear components including racks in various materials. Small sizes. Asian companies are also in that market.

I see Grainger also sells them. Might have to buy a new compatible pinion also.

Somebody somewhere sells most anything, including rack gears that could be adapted to a Mark VII.

REID SUPPLY - RACK GEARS.JPG (85.62 KiB) Viewed 34437 times

[edma194]

I see Grainger also sells them. Might have to buy a new compatible pinion also.

I agree steel or aluminum is preferable to any plastic.

Do you know the pitch and height for the Mark VII?

[SteveMaryland]

No, I don't know the specs on the Mark VII rack gear (and I dont own a Mark VII). But if both the rack and the pinion were replaced as a set, we would not need to know, just know the center distance between pinion and rack, and shim up the rack accordingly.

I don't even know if the original rack was radiused to fit the way tube or not. No doubt a COTS rack + pinion would need some machining.

Now that would be a good reason to do a 3D printed part + a COTS rack: design the printed part to interface with the way tube and also provide the shim-up to make the center distance. You would then have a steel rack mounted on a plastic base that in turn interfaces well with pinion and way tube.

[JPG]

The OEM racks had a radius interfacing with the way tube.

[Darkehorse1]

Thank you for the info! Greatly appreciated.

[miken]

I see Grainger also sells them. Might have to buy a new compatible pinion also.

I agree steel or aluminum is preferable to any plastic.

Do you know the pitch and height for the Mark VII?

I measure my MVII rack at 4tpi.
As best I could measure the gear is 12 tooth, 1.165" OD.

Mike -