What does it mean to "tap" a drain plug thread?

[Bean Counter]

In my continuing saga to fix my perfectly running truck until its broken, I'm coming across the expression of tapping threads. I stripped my transmission drain plug (well, I hope its not the pan) and apparently per the Google machine this is a pretty common booboo. Plug spins freely but wont come out. Obviously since my fingers were spastic enough to strip it in the first place I am thinking of just taking the pan off but there's all that oil in there and I'd probably need to ruin a little kiddie pool to collect it all (it needs a drain and fill anyway). Does tapping it involve just using pliers, a screw driver, or a broken bottle and some proprietary Naval cursewords to get the damn thing out by any means necessary? Or is it something that is ran through the threads/hole after the fact to repair/straighten them? 

[fish vacuum]

Tapping is cutting new threads after the old plug is removed.

[Bean Counter]

thanks. is that easily done without special tools? Does it require a trained hand? A new pan is only $150.

[fish vacuum]

I've never done it. But what I've seen recommended is an oversized, self tapping drain plug.

[fish vacuum]

It used to be that the plug threads were more likely to strip than the pan threads. A new plug would solve that. With the materials used on newer rigs, the pan threads are more likely to strip.

[syoungs]

I'd probably just spend the 150$ on a new pan, but tapping the old one wouldn't be tough, especially if you can finagle that bolt out without taking it off the car somehow, and were able to capture the cutting chips ( run the tap covered In grease would work)

If you drop the pan anyways, a new pan and gasket would make the repair that much easier, and faster, and depending how much meat you've got around the pan to tap, it would probably be a stronger repair you wouldn't have to worry about in the future.

[Woodchuck]

If you aren't 100% sure how to do it, just replace the pan. 

[Fl0und3rz]

Pick and pull or craigslist should get you off pretty cheap and with far less frustration.

[JimmyHoffa]

The tool looks kind of like a drill bit with straight flutes.  It would be slightly larger than the hole, and you twist it in--cutting new threads.  Then you use a bolt that fits the new threads. 
Like mentioned above, you have to clear as many chips as possible.
Depending on orientation of the other bolts on the pan, it might or might not be easier to just swap out a new pan.  Then you have an extra once you tap the hole.

[rtspring]

Tapping a hole is easy, provided you have enough metal left over to tap new threads, and enough room to use tap and tool.  Use alot of lubricating oil,  start it straight!  1 turn forward and then back half of turn to clean out debri.

I would for sure remove pan to drill and or tap existing hole or make larger hole to tap new threads. Some metals are harder, ie stainless, titanium and such.

Go slow!

[rtspring]

Also a wel shop can simply weld up old hole and cut new one and insert a fitting with threads already tapped then weld it in.   Fairly simple task. 

[netcoyote]

If you've already stripped the threads on the existing hole, you will have to go up one size larger on the tap size and that may require re-drilling to the proper tap hole size. There are charts that show tap hole sizes but this sounds like it's getting beyond your skill level. It's not that hard but you should probably consult with someone with some machining experience.

[jackelope]

If you aren't 100% sure how to do it, just replace the pan. 

I agree with this. If for nothing else, the cheap insurance that your makeshift repair won't fail on you in the middle of nowhere. No offense, but if you have to ask the questions you've asked re: what it means to tap threads, what tools, etc... this is not a repair that I would take on. You'll have to remove the pan. You don't want any unwanted metal debris ending up in the pan. You'll need large drill bit, a tap, a new drain plug, and probably a few other things I'm not thinking of at the moment. Then you need to "hope" you drill the hole straight, etc.
Buy the pan.

[Fl0und3rz]

I know what I am doing, and I would rather just replace the pan, simply out of relative ease and surety of the repair.

[Encore 280]

Since it's a pretty common problem the pan threads are usually a harder metal than the plug so hopefully it's just the plug that's stripped and you can go to an auto parts place and get a new plug. Worse comes to worse maybe you can do the HeliCoil (sp) trick. Just my