Boring and broaching in a keyway is something only a machine shop can do normally. Also going to 1" is going to weaken the coupler quite a bit.

Okay you got the L075 style couplers. The ones you need are the L095 ones. But you need make sure you have the side clearance for 2.1" Diameter plus some wiggle room.

The 7/8" one uses a 3/16 " key and the 1" uses a 1/4" key. Prices are for reference only and are USA prices.

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