I was replacing my water pump when the top most bolt holding it to the engine snapped off flush with the block. I managed to drill it out, but the tap I used to try and remove it broke... now I'm slowly.. and holy crap do I mean slowly.. drilling through the tap to try again. I'm fairly sure I am going to mess this hole up royally getting this sucker out however. So!

What is the thread size and hole size for these? I have a caliper to find the hole size, but I'm not sure about the threads. Turned my 40 minute swap into a day of headaches... please help!

 

I dont know the thread size, but if you have the lower bolt out, just take that to the hardware store and match it. Most have a thread finder hanging nearby. I use ACE or Tractor Supply for that stuff as they seem to have the most selection around here. Never seem to find much anywhere else.

 

Well I'm fairly sure the bolts are 5/16, from what I recall from another post. Maybe I just don't know how re-threaders work. Let me try and rephrase.

I need the size of the drill bit to drill an entirely new hole after refilling the old one, and the size for a thread tap to use. Would it be 5/16 for both since that is the size of the bolt going in?

 

Here is a link to a drill/tap chart.

http://www.lincolnmachine.com/tap_drill_chart.html
Instead of filling the hole, you might want to think about picking up a Helicoil kit.

 

Thanks for the link, and I've heard mixed things about helicoils, but that may just be the easiest way

 

Drilling out a tap is a quick way to ruin a hole. The problem is the tap is harder than your drill bit, so the bit will want to wander off. You're best off with a hammer, punch and picks. You use the hammer and punch to bust the tap into small bits and the pick to work them out of the hole.

Quick question... is the hole a blind hole (not all the way through) or a through hole (self explanatory).

 

Bashing it to pieces does appeal to my current state of frusteration..

And it's a blind hole.

 

I assume none of the busted tap is sticking out... Have you got access to heat?

 

Just a propane torch.. and nope it was way stuck in

 

Bummer. Well... good luck, I know it can be a pain sometimes. Once the tap is out you'll know what direction to go next.

 

Thanks! I'll post back it bashing it to pieces works!

 

Agreed with not trying to drill a tap. You will more than likely do more damage than good. Taps are hardened, so breaking it up is you best bet (but expect it to still be difficult). Assuming there's still enough wall material left, once the tap is removed I would look into the helicoil. They are much stronger than you would think once they are properly installed. In my industry of work, we use them all the time and they work great.

 

Ok so update today. I went and bought some better punches. Bashed the extractor all the way into the back of the hole, since apparently the bolt never even made it to the back wall. So this left me with a hole through a stuck bolt.

Back to the extractors!! (I also picked up a better set of those while I was out.)

Nope.. no luck there. Screw it, ima drill it out all the way. This actually worked now since the broken extractor was bouncing around all the way to the back. I managed to drill it out enough to get the broken piece out but I noticed I had cut through the threads.

Well crap, but at least the bolt came out.

So I suppose helicoil is going to be the only real option now. Live and learn folks.

 

Helicoil should be fine for something like that. It's not like it's holding a head bolt.

 

Helicoils are fine,,,used them many time and had no problems.

In the future you may want to buy a left hand drill bit, or a set, and drill out the bolt as close to the thread size as possible. Many times using the left handed bits they will back out the bolt before you get to thread size. If not, once you get close to thread size you can take a small chisel and tap out the remainder of the bolt.