Help with chasing threads

[9volt]

Hi, I could use some non-flashlight related help with chasing threads, and was hoping someone here would have some experience they would be willing to share.

I need to fix some messed up threads on the end of a automotive crankshaft where a bolt holds down a belt pulley. I don't think they are messed up too bad and I'm hoping I can chase them and get them cleaned up. I did a little research and read that you should use thread chasers and not taps to do this, but I can't find chasers locally anywhere. Is this info true?

Can I get by with running a tap in there and call it a day?

Is there any advice you can give a newbie to this to help make sure I don't screw things up worse than they are now?

Thanks for any help.

 

[NeonLights]

I had a similar problem a few years ago. I was installing a crankshaft pulley on a Dodge Neon, and didn't get the bolt threaded in far enough on the pulley puller, and it messed up some of the threads towards the end of the crankshaft. I just carefully ran a tap in and used lots of penetrating oil to make sure any metal shavings could come out easily. I sold the car to a guy I know in Michigan, and AFAIK, the car is still running fine today, several years and tens of thousands of miles later. I had the crank bolt out several times after that without any problems.

Things might be a little more critical if the crank pulley on the car you're working on is held on by the crank bolt. On the Neons, the pulley was an interference fit, and the bolt didn't do much. Just take your time with a tap and you should be fine, assuming there are enough good threads to maintain the torque needed on the bolt. Using loctite should help too.

 

[winston]

Helicoils might be an option. I'd take chasers over taps, though. Taps get messy. Sorry I'm not much help. Good luck!
-Winston

 

[9volt]

Any suggestions on where to pick up chasers?

 

[scott.cr]

I too had this happen once. An engine machine shop fixed it for $20, but the crank was already out of the car.

You can get thread chasers from the Snap On truck, or any tool truck. You can make 'em out of a grade 8 (USS) or grade 12.8 (metric) bolt. Just cut relief grooves axially along the threads and remove the burrs. Get LONG bolts, you don't want to bring the head of the bolt right to the crank snout. And use plenty of lube.

Another option... drill the hole out and choose a tap the next size up. Use a bottoming tap.

 

[9volt]

I found the right size and thread chaser locally. What should I use for lube when I'm doing this? Can I use WD40 or motor oil or something like that?

 

[scott.cr]

I found the right size and thread chaser locally. What should I use for lube when I'm doing this? Can I use WD40 or motor oil or something like that?

Engine oil will work fine... the idea when chasing is to LUBE the threads so the chaser moves/reforms the threads more easily, instead of galling or catching due to friction. I wouldn't use WD-40 in this case.

 

[9volt]

If anyone else ends up looking for chasers, Snap-on sells them on their website in alot of different sizes for about $3-4 each