That old timer at the local NAPA changed my mind about using tap and die sets on rusted bolts

Last Tuesday I was at the NAPA on 12th Street getting wiper blades and this retired mechanic in his 70s overheard me complaining about a snapped exhaust manifold bolt on my F-150. He told me I was wasting time with the cheap spiral flute taps from the hardware store and handed me a set of straight flute bottoming taps. I figured he was just blowing smoke but he walked me through it. After using his method with cutting oil and backing out every quarter turn, I got that bolt out clean in under 20 minutes. Three years of snapping bolts and this one trick from a stranger saved me 150 bucks on a shop visit. Anybody else ever have a random guy at the parts counter save your bacon?

2 comments

2 Comments

hugo_ellis17d ago

Hold on, you're mixing up tap types a bit. He didn't give you a straight flute bottoming tap for a rusted bolt. That's for cutting threads in a blind hole, not for removing a broken bolt. What you really needed was a spiral point tap or, better yet, a left hand drill bit and an extractor. The real trick he taught you wasn't the tap style, it was the "quarter turn and back out" method with plenty of cutting oil. That's what clears the chips and keeps the tap from snapping. Straight flutes are actually worse for rusted out junk because they don't push the chips up and out of the hole. I've used that same backing out technique for years, and it's the single best thing you can do for any stuck fastener.

paige87017d ago

Gotta push back on that a little, @hugo_ellis. In my experience, a straight flute tap can work fine on rusted junk if you just keep the hole packed with oil and back out every quarter turn like clockwork. Spiral points are great for clearing chips, but they can also snap easier if you're not careful with the feed.