Making an auto-reversing tapping head - sort of

Have you guys seen the auto-reversing tapping head for drill presses?

They get all kids of great reviews but are usually $200 to $400 and I was thinking of ways to make one. That got me thinking of how often I see people using drill motors to do manually but fear that the movement of switching to reverse would/could break the tap. So I was thinking of modifying an old 15V drill with an external button for reversing direction.

A tapping guide will help keep the tap and drill motor straight.

Any thoughts on the idea?

I’ve never heard of tapmatics changing direction breaking a tap. Is this commonly a problem?

Love these things. After WWII, the San Diego surplus lots had tons of these for about 10 bucks. We had two, one ended up with my brother and I have no idea where the other one went. Many times I’ve wished I’d kept track of the other one.

I went to buy one and the sticker shock got me then and now…

I was told that they were gear driven, no springs except to make the clutch work… I never did take one apart…


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I was referring to the fact I don’t have a tapmatic so using a tap in a drill motor is going be tricky throwing the Reverse button without putting torque on the tap and breaking it.

Thinking about it further, my first test should be just putting a reversing button on it which is easy to engage with the hand/fingers already on the drill. Even the old corded Craftsman I had with a lever above the trigger is cumbersome enough to make it tough to hold the drill in perfect alignment while throwing the lever.

Oh, I see! I’ve done a lot of hand-drill M3 tapping aluminum with a spiral flute tap, using dewalt cordless drills which have what I find a convenient button. I haven’t broken a tap yet. But also those times that I’ve done this in openbuilds extrusion, I’ve recently used 3d printed tap guides that clip into place.

I can only imagine!

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My Makita, Royobi and Craftsman cordless drills all have a push-thru button for Forward/Reverse and it takes a bit of force to push in from either side. Maybe those bits are tough and threads won’t get cut too poorly if the angle of the tap shifts. Surely not as smooth as the auto-reverse mechanism of those golden tapping heads.

I’ll be tapping some 2mm and 3mm aluminum to make some of the Russ Spec lightweight laser heads for the K40 so not lots of material to bite hence my thoughts on keeping that tap straight at all times. I will be using a metal tapping guide but probably just holding it in place with my left hand while my right does the drill motor tapping.

You know, I think part of the complexity of the tapmatic is that it allows for radial as well as axial float. You don’t need radial float for a freehand power tapping auto-reverse. The only need you have for axial float is to disengage the dog clutch to switch direction!

You don’t want to over-torque here anyway. It’s not impossible that you could make an auto-reversing mostly 3D-printed freehand tapping head with a body that clamps to your drill body somehow. It sounds like a fun design challenge.

But honestly, for tapping 2mm/3mm aluminum, a handheld tap guide and reversing the drill should be fine. I’d be surprised if you broke a tap; activating the direction button is probably less sideways force than just using a hand tap, and I’ve successfully hand-tapped M2.5 in ¼" aluminum with a straight flute tap. For 2mm/3mm aluminum, I’d hand-hold the metal down to the table while tapping and just let off pressure on the metal while engaging the reverse trigger on the drill.

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Back in the day I worked with 256 taps and screws. I had to be careful because they definitely would snap if you were too aggressive.

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When I was a kid, my dad put the tap in a drill press and we just used our hand to run it in and out. Ensuring a square tap. I do that today, when required…

Much better than one of the T handles for taps.

Taps need to be hard to be functional. The harder the more brittle… Most of us have snapped a tool in a lathe also… too big a bite :crazy_face:



Oh, I’ve boiled aluminum in alum for hours to partially disolve a snapped tap, don’t get me wrong! And about a week ago I finally had my first crash on my lathe, which fortunately only took out the carbide insert. :grimacing: