is there such a thing?

[vqdriver]

as a one inch threadless rigid 29er fork?

[pitcrew]

Not unless you want to call a 1" threadless 700c road fork a 29" fork (and use a road brake caliper with it, and a skinny tire)....

You have a 29er frame with a 1" headtube, or are you building some type of franken-bike?

[vqdriver]

frankenbike to make use of an old frame
need big clearance

[PacNW2Ford]

There is if you call Christopher Igleheart, Steve Potts... maybe there's others

[Ken Robb]

I think Rivendell might have some to sell.

[xjoex]

The Kona project 2 700c 1" threadless fork might work, but you'd probably be limited by tire size.

-Joe

[Bob Loblaw]

Any 1" cyclocross or touring fork with canti posts will do. You won't be putting a 2.2 inch tire on it though.

Salsa makes a 29er called the Fargo which comes with a rigid, disc brake fork. Not sure if it's 1 inch.

BL