I blow out with compressed air; if gunk is stuck in there, I have some old gun cleaning brass brushes I chuck into a drill and run that in the hole, and then again, compressed air. If there's no thread damage, I wouldn't run a tap in it, although thread chasers can help as long as you have the right size. You can clean bolts with brake cleaner, won't always work, just keep it away from the bike. I have a grinder with a wire brush on one side, use that to clean gunky bolts, just don't get carried away, will eventually remove metal, too (and throw your bolt across the room if you're not real careful). I replace bolts with any damage or pitting, unless they're big, expensive ones, and then it's a judgement call. Look at the threads on a bolt; if they have a flat side, or noticeably more angle on side, it's been over torqued badly, and then it might be a good idea to run a tap in the hole, since those treads probably got stretched, too. Think about that the next time you want to crank a bolt down without a torque wrench. You'll probably only get away with repairing threads once.

If I don't know the bolt size, and feel too lazy to dig the thread gage out, I press the tap against the bolt; you can tell if the threads match, and compare widths. If it's really tight and doesn't want to go in, drop a size. If it goes in and wiggles, up a size. Just never force the tap. If you do use a tap, keep it lubricated (motor oil works), and don't force the tap; break one off, and you'll probably have a shop get it out, if they can. When/if it gets tight (like a bolt getting tight), back it out, clean the shavings, oil again, and go back in just a little farther, and repeat. You can "nibble" with more success than just playing gorilla with it. I've taken over an hour to clean out a bore in hard metal, making over a dozen "nibbles" for each turn. When you're working with something that costs tens of thousands of dollars, the time doesn't matter. If it costs way less, but it's yours, it's worth it, too.

 

+1 that this is the way to go! Sears has an SAE and metric set, both chaser taps and dies, for $50.00.

Here is an excellent article about this very subject...

http://harleytechtalk.org/htt/index.php?topic=44321.0

With a regular tap & die you risk cutting metal that you don't want to lose!

Steve

 

If you decide to use the tap set be careful not to bottom the tap out and break it. Or worse yet rethread the holes. Bolt with slots works and the price is right

 

I use a brass or plastic brush and parts cleaning solvent. Be careful using compressed air as it will blow stuff back at you.
I have used the slotted bolt method for chasing threads that were filled with paint. Usually it doesn't take much to clean the little bit of gunk out of threads unless the hole was open in very dirty conditions.

 

I'm with iclick on this.

I wouldn't go trying to re-tap anything unless I had known damaged threads. The issue is gunk. I typically use naphtha. Better known as lighter fluid. It cleans as well as brake cleaner without the fumes of brake cleaner which are bound to set off every smoke detector in your house.

Naphtha is almost odorless and very effective. Compressed air, brush, tethered the clean bolts in and out and clean again.

Did you ever by mistake go to tap something and realize you grabbed the wrong tap?

 

I agree.
There's no need to chase the holes with a tap unless there is some old Loctite in the threads.

 

Don't tap perfectly good threads, I use a wire brush, works for me.

 

Not yet.

I don't use regular taps to clean threads either. I have two thread chaser tap sets, one for fine threads and one for course threads. Jims sells the course thread set for about 50 bucks, but you can find the same thing from Jegs for about 15 bucks.

 

+1 ... Yep! ... We have a winner! "Lakerat" is 100% correct! ..... NEVER use a tap to clean out undamaged threaded holes .... a thread chaser is designed to clean out the hole and the threads without removing any metal!

 

Use the Craftsman thread chaser kit, SAE fine and coarse, metric, tap and die. Will not cut any metal, just clean up the threads.