wats the different between a tap and die and a rethreader kit. which is better, or is it good to own both?

 

A tap puts threads in a hole, a die puts threads on a rod.
You would use a tap to make a nut basically, and a die to make a bolt.
A re-threader kit probably has some of each, maybe a thread file, thread gauge, maybe some other stuff?

I'd buy a basic tap and die set, in metric and imperial. That should come with the taps and dies for all of the coarse threads, and a thread gauge. If you want the fine threads you can buy a more complete set, but I doubt you'll use 'em much.

 

a tap and die set will be made of better steel to cut threads and will be made to be sued with a tap wrench or die handle. a rethread kit would also contain "taps and dies" but not be hardened or designed to cut threads. the rethreader kit would also be made to use a wrench or socket instead of a special handle. i own both and use both but as a rule when i want to clean threads i use a wire wheel on a grinder and gun brushes in a cordless drill.

 

I've found I use taps way more than I've ever used dies. I could count on one hand how many times I've ever needed a die. I usually just buy another bolt instead. I agree with ede about using a bench grinder with a wire wheel to clean bolt threads. Works great! I never thought about using a drill with gun brushes for bolt holes. That's a great idea! Another good way to clean threads in bolt holes is to buy a set of thread chasing taps. They don't actually cut like a tap does, just clean the existing threads. I used to use regular taps to clean the bolt holes when assembling an engine until I read that regular taps can actually weaken the threads by re-cutting them. Make sure to blow out the holes with compressed air after cleaning the threads to remove any debris left. You can pick up a set of thread chasing taps from Summit or Jegs for about 12 bucks in either fine or coarse thread. If you pick up a good tap and die set and a set of thread chasers, you should be good to go for most situations.

 

For cleaning up existing holes, a roll-form tap works great, without over-threading the holes and weakening.

 

Huh, learn something new all the time. Never heard of a roll-form tap before. Are they pretty easy to come by, or are they only sold by specialty companies?

 

They're sold under various descriptions/names, but it you Google "roll form tap" you should get a few hits. They've been around for decades.