Wolverine is probably everyone's favorite X-Men character because of his anti-hero attitude and cool mutant powers. Seeing someone dressed up as this comics character at Halloween costume parties or sci-fi and comics conventions wouldn't likely be too surprising for fellow fans. But what can really make an impression is if the costume were equipped with real-looking retractable Wolverine claws.
1. Manufacture the claws from aluminum plates.
The actual length of the claws would depend on the length of your forearm. An aluminum flat bar with 1" x 1/8" dimensions would give the right thickness. Draw the actual shape of the claws on paper to be traced out on the aluminum plate. You can design it using graphics software and print it out to be more accurate. Once the claws have been traced out on the aluminum plate, you can cut it out using a band saw, and smooth the rough edges with a belt sander. To give an 'adamantium' finish, you can run each claw on a wire brush wheel.
2. Make a retractable housing.
Ball-bearing tracks such as those found in a sliding keyboard tray would be perfect for this. You will need 6 tracks, one for each claw. Shorten the slider on each track so that it attaches to only the short end of the claw. Fasten slider and claw together with a bolt. You may need to drill matching holes in each one. Fashion three tracks together to form one retractable housing set for one hand. Use long bolts, washers and locking nuts to space them apart appropriately and to attach them securely with each other. Again you may need to drill matching holes in each tracker. Put screws on the inside bottom edge at each end of each tracker. These will function as stoppers so that the claws and sliders don't fly out and accidentally injure somebody.
3. Sew the retractable housing to a cloth harness.
Use any fabric thick enough that it won't rip from the housing's weight. Cut the cloth in such a shape that when it covers your forearm it will fit tightly. Put snap on buttons on the edges for closing it over your forearm. Drill small holes on each side of the housing where you can run the sewing thread. Nylon strings of an appropriate gauge would be strong enough to attach the housing to the harness.
This harness can be worn to enhance a Wolverine costume. Just make sure that there are correctly positioned holes in the gloves where the claws would come out.