Tool hounds will likely prefer to buy the “correct” factory tool to remove the brake caliper piston plug on Norton Commando front brake disc calipers. It works perfectly, of course, but at around $90 it’s a pricey bit of kit – especially if you’re only going to use it once or twice, or at least very occasionally.
Tools and materials used:
Lay the piece of flat steel across the center of the caliper plug and mark the center of each hole as shown. They should end up roughly 13/16-inch apart. Be as accurate as possible but if it’s not exact it won’t matter, as you’ll see. We were installing a new stainless steel caliper plug, so we used it to make our marks.
Using some type of square, mark lines across the flat steel where you made your marks. Next, make perpendicular marks centered through the two lines as shown. The bar stock is 1.5-inch wide, so that means 3/4-inch in. Again, don’t worry if they’re not perfect.
Using a center punch, punch the center point of the intersecting lines. This makes it easier to drill as it gives the drill bit a point to bite so it won’t wander – especially valuable if you drill freehand.
Using a 1/4-inch drill bit, drill the point farthest out on the steel bar. We used a simple drill press with a holding fixture to keep the plate flat and make drilling easier. You can do this by hand with a hand drill, but a shop vise to hold the plate is highly suggested to keep the plate from whipping should the drill bit jam during drilling. Don’t forget to lightly oil the drill bit while drilling to keep the bit cool and lubricated.
Using a 3/8-inch drill bit, drill the second point. The larger hole will aid in the final setting of the tool, as you’ll see.
Lay all the piece out. Clean the flat bar well, using a hand file to remove any raised metal and dress the holes as necessary. We gave our bar a coat of no-rust gray primer, which we should follow up with black enamel if we’re really worried about it rusting; we’re not.
Attach one of the 1/4-inch bolts to the outer hole. Make sure to use one washer under the bolt head and one under the nut. Tighten thoroughly.
Attach the second 1/4-inch bolt and nut, again with washers as before. Center it loosely in the over-sized hole and tighten the nut finger tight only. Check to see if the two 1/4-inch bolts line up properly with your caliper plug holes. If they do, tighten the second bolt and nut securely. If they don’t, adjust the second bolt and nut as necessary to align and then tighten securely. That’s it! You’ve just made your own custom Norton Commando disc brake caliper plug peg spanner! Pretty cool, and you can use the same approach to make other “custom” tools.