If you’re like me when the need arises for a seldom used jig or clamps made from heavy hot rolled steel 1/2“ or thicker, the worst part can be tapping a large number of threads by hand and the tendency is to through drill and deal with holding both ends of the bolt. No, this isn’t in place of accurate tapping on the mill or even drill press.
I was installing some 1/2”t x 4”w x 16” L brackets to support a granite overhang for a kitchen bar top and normally I‘d drill and tap these on the drill press, but the project was a day ahead of schedule and if I could tap them at the client’s house with an old Vermont American tap that was riding in a tool box for a decade and used in a drill to chase rusty threads, it would save 2 hrs of driving to come back the next day. These can’t even be called thread cutting taps - fresh out of the package they are dull, but a few minutes with a diamond pocket knife sharpener to tone down the burs on the cutting edge and off to the races. Turning a dull tap by hand with a 12 point socket and ratchet is insane, so I grabbed a cordless impact driver, the client donated a candle for lubrication and we fully expecting the tap to break. To my surprise it easily made three turns before slowing down. Reverse, one more turn, reverse one more turn, etc - one down, 11 more to go - just kept going until all the holes were done. Wax was smoking off of the tap and after powering through a few hard sections I knew it was probably toast and had chipped teeth all over and threads would be horrible, but the threads were great and the tap was no worse for wear.
I’ve always seen Lisle tap sockets and thought they would be a waste of money, but I have all the sizes now, and a 1/2” square drive cordless impact primarily for automotive, but also to thread holes and tighten up the barrel vice. I’m surprised impact tapping hasn’t brought out a number of products just for it. Since that first experience I’ve tapped 3/4” holes in 1” hot rolled for a couple of action wrenches - with a good quality tap it literally took less than 60 seconds per hole - I started the tap in the drill press chuck and when it went in a few turns and slipped, took it off and finished with the impact.
It’s a piece of cake to make a guide to help square things up on big pieces with a long, smooth, square drive extension and something square for it to slide against. I’m a wood worker so there’s always 3/4” ply scraps and a saw within arms reach. If you cut a 3/8” groove in the middle of two pieces of 3/4” x 4” square ply, wax the drill extension and clamp it lightly with wood screws, there’s a slide with very little slope. Screw that onto a ply L or sideways T bracket and you‘ll be surprised how accurate the hole will be. I’ve even clamped down a couple of stacked 2-3-4 blocks with a scrap v block clamped to the side to get the square drive extension started straight.
I was installing some 1/2”t x 4”w x 16” L brackets to support a granite overhang for a kitchen bar top and normally I‘d drill and tap these on the drill press, but the project was a day ahead of schedule and if I could tap them at the client’s house with an old Vermont American tap that was riding in a tool box for a decade and used in a drill to chase rusty threads, it would save 2 hrs of driving to come back the next day. These can’t even be called thread cutting taps - fresh out of the package they are dull, but a few minutes with a diamond pocket knife sharpener to tone down the burs on the cutting edge and off to the races. Turning a dull tap by hand with a 12 point socket and ratchet is insane, so I grabbed a cordless impact driver, the client donated a candle for lubrication and we fully expecting the tap to break. To my surprise it easily made three turns before slowing down. Reverse, one more turn, reverse one more turn, etc - one down, 11 more to go - just kept going until all the holes were done. Wax was smoking off of the tap and after powering through a few hard sections I knew it was probably toast and had chipped teeth all over and threads would be horrible, but the threads were great and the tap was no worse for wear.
I’ve always seen Lisle tap sockets and thought they would be a waste of money, but I have all the sizes now, and a 1/2” square drive cordless impact primarily for automotive, but also to thread holes and tighten up the barrel vice. I’m surprised impact tapping hasn’t brought out a number of products just for it. Since that first experience I’ve tapped 3/4” holes in 1” hot rolled for a couple of action wrenches - with a good quality tap it literally took less than 60 seconds per hole - I started the tap in the drill press chuck and when it went in a few turns and slipped, took it off and finished with the impact.
It’s a piece of cake to make a guide to help square things up on big pieces with a long, smooth, square drive extension and something square for it to slide against. I’m a wood worker so there’s always 3/4” ply scraps and a saw within arms reach. If you cut a 3/8” groove in the middle of two pieces of 3/4” x 4” square ply, wax the drill extension and clamp it lightly with wood screws, there’s a slide with very little slope. Screw that onto a ply L or sideways T bracket and you‘ll be surprised how accurate the hole will be. I’ve even clamped down a couple of stacked 2-3-4 blocks with a scrap v block clamped to the side to get the square drive extension started straight.
