Bastard Cut Flat File with Handle

A flat bastard file is the workshop's deburring-and-fitting tool. The bastard-cut tooth pattern (between coarse and fine) is aggressive enough to take a hacksaw burr off in a few passes, fine enough that the surface it leaves doesn't need a separate finishing step. For a freshly cut steerer, the same file knocks the burr off the cut edge so the part seats squarely in the headset.

The 763HB-US is 200 mm long, 20 mm wide, 5 mm thick; the file body sized for bench work, with a wooden handle pre-fitted (the "-HB" suffix in the part number) so the file doesn't bite into a palm under load. The bastard cut runs the full length of the working faces.

The two jobs a flat file does well

• Deburring a cut steerer or seatpost. The hacksaw leaves a burr around the cut perimeter. The flat file knocks the burr off in two or three passes per edge. The result is a clean edge that seats against the headset or the frame's seat tube without binding.
• Removing material from a bolt that's a hair too long. Spec is spec, and a bolt that protrudes past the threaded part it's threaded into needs to be shortened. Clamp the bolt in the vise, mark the cut line, hacksaw to length, then flat-file the cut end flat.

For curved cuts, see the half-round file (flat face on one side, half-round on the other) or the round file for small holes.

Specs

• 200 mm long
• 20 mm wide
• 5 mm thick
• Bastard cut
• Premium hard plus carbon steel
• Wooden handle pre-fitted, hanging hole
• Article number: 763HB-US

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The 763HB-US is one of three file profiles Unior catalogs for the bike-shop trade (flat, half-round, round); same carbon-steel stock, same heat-treatment, three working geometries. A working shop owns all three because each handles a job the others can't.

Pro tip from our mechanics

The file is meant to cut on the push stroke and lift on the return. Dragging the file back across the workpiece dulls the teeth and packs the gullets with material. Lift on the return, file again on the push. Same rule applies whether you're deburring a steerer or squaring a cut bolt end. Our workshop hand tools guide covers files and the rest of the workshop hand-tool layer in more depth: Workshop hand tools every bike shop needs →