Triangular to Square Tap Adapter

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About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Earlier I did an Instructable on a thread Tapping Fixture for a Drill Press. The tap too easily slipped in the 3-jaw chuck on the drill press. I could buy commercially produced adapters, but they seem a little expensive. This Instructable will show a way to make your own.

Materials

  • 1/2 inch steel rod

Tools

  • Hacksaw
  • Grinder
  • Drill press and twist drills
  • Miniature file (triangular)

The photo shows the adapter I made. It has a square socket for the end of my 1/4 x 20 tap. It also has three flats to fit the 1/2 inch chuck on my drill press.

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Step 1: Saw the Steel Rod to Length

I cut about 1 inch from a piece of 1/2 inch steel rod. That is enough to catch and hold the square end of the tap and to keep the tap in alignment when being used in the drill chuck.

Step 2: Mark for the Three Flats

I put the piece of rod I cut into the drill chuck and made marks with a felt tip pen that align with the three chuck wrench holes.

Step 3: Grind Flats

I placed the marked piece of rod into my vise and used a hand-held grinder to grind a flat where each mark is. I ground just a little and checked to be sure my ground flat was centered on the mark as much as possible. I also tried to watch that the ground flat has parallel sides, not keystoned sides.

Step 4: Set the Hole Depth

This tap is a strong 1/4 inch in diameter. I had to use a twist drill that is a few thousandths of an inch over 1/4 inch in order for the tap to slide into the hole drilled up the center of the rod for it. I used masking tape to mark the desired depth, but it moved while I was drilling. A collar with a setscrew would be better.

Step 5: Drilling

I drilled up from the bottom of the rod to pass the round shank of the tap, but stopped to leave an amount equal to the square end's length. Then I changed twist drills and used a smaller one equal in diameter to the thickness between two flats on the tap's square end.

Step 6: File to Fit

I used a miniature triangular file to file the smaller hole so it makes a square socket for the square end of the tap. It is just a matter for a little filing by hand followed by checking the fit. It takes a little time and care, but works out pretty well.

Step 7: Use the Tap Adapter

Now I can put my tap and adapter into the drill press chuck. I can add the handle I made for turning the chuck. See the earlier Instructable. The tap will not slip in the chuck now. (See the link to that Instructable in the Introduction to this Instructable.)

At the present my tap can fall out of the adapter. I can use some tape to hold it. Also, 1/4 x 20 threads are the most common I make, but I will need to make a new adapter for any other tap sizes I want to use. If the socket hole is too small to receive a file, I may have to use a setscrew to keep the tap from slipping.

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    17 Discussions

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    CPUDOCTHE1.

    19 days ago

    I am thinking that the tap slipping in the chuck is good when you hit a hard spot, fill the tap with chips, or something else happens. With small taps, I take the belt off of the drill press and turn it by hand. With larger taps, we power tap in the mill or drill press.

    3 replies
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    Phil BCPUDOCTHE1.

    Reply 19 days ago

    In my experience the tap slipped in the chuck on the drill press before any useful threads could be cut. Whenever I have tried tapping under any kind of motor power I broke things.

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    nic.bryan.73Phil B

    Reply 18 days ago

    I have the same issue, it's worn down the teeth in my drill's chuck enough that it can't grip small round drillbits anymore.

    And your last comment about maybe adding a set-screw. Do it. I've never found that a set-screw makes things harder. Although, I would recommend a double set-screw, one on either side.

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    Phil Bnic.bryan.73

    Reply 18 days ago

    The mention of a set-screw was a consideration in the event I could not get a small enough file to make a square opening. Yesterday I did make a second adapter, but for #10 taps (10-32 and 10-24). One of my miniature files worked very well.

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    gadjetramjet

    Tip 19 days ago on Step 7

    I actually, cut the female end off of a 3" ; 3/8" extension and welded it to the top shaft, just above the pulley on my drill press, (removed pully first etc. then slide the pulley back over when done) Drilled a hole through the cover, for access. This was to be able to use the crank down handle of the drill press without the motor on, and using a drill press vise, was able to use my other hand to turn the tap, that was contained in the drill press chuck, with a standard 3/8 ratchet wrench. this enabled me to have a perpendicular tap. and so I can turn or back up when needed to clear debris.
    Honestly though, it only works well for "small" tap jobs or one offs, etc. It is quite cumbersome if you have to do a whole bunch at once, and very slow! Accurite, but slow

    I went and bought a set of "tap holders" that adapt to a 3/8" drive, they work well. There are various types. I needed to tap 1/2 x 13 in 3/8" steel ... over 200 times! I ended up using two of the tap holders with a 3/8" to 1/2" impact adapter and a impact. It worked well, but not great, you still had to be careful with binding. So you go in a bit, back out a bit, go back in etc. and lots of cutting fluid. I went through two taps, and two "holders" as the impact eventually exploded the 3/8" end. ...and one "el cheapo" impact. But it was a heck of a lot quicker and easier than by hand!

    1 reply
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    Phil Bgadjetramjet

    Reply 19 days ago

    Did you look at my earlier Instructable linked in the Introduction to this Instructable? It shows a collar I made for the lower part of the chuck. A handle on that collar allows me to turn the quill both directions while adding downward pressure on the quill. Your solution sounds similar in its end effect. This tap adapter goes in a pair with that earlier Instructable.

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    Bill Barker

    19 days ago

    You could probably use a small, powerful magnet instead of a setscrew; might be less effort.

    1 reply
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    Phil BBill Barker

    Reply 19 days ago

    When I improvised my drill press for holding a tap, I did not expect to need this adapter. Experience showed I needed it. I will experiment to see if I need to make other changes, like a magnet. Thank you.

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    Phil BIvanK57

    Reply 19 days ago

    Something breaks when I try to tap threads with any kind of added power other than my own hands. I just do not do it.

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    knife141

    22 days ago

    Nice work, Phil. I took a similar approach to make a wrench to unlock some sliding panel doors at our church. The doors used a wrench that had a 3/8 inch square hole. One day the original wrench disappeared, and I made a new one out of some scrap steel I had using pretty much the same approach. I always appreciate your instructables!

    2 replies
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    Phil Bknife141

    Reply 19 days ago

    This morning I made another adapter, but for #10 screw threads. I have two #10 taps. One is for 24 tpi and the other is for 32 tpi. These two adapters will cover the bulk of the threads I will tap. Fortunately, my files were small enough that no welding was necessary to make the square socket.

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    Phil Bknife141

    Reply 22 days ago

    Thank you. It is good to hear from you again. Instructables changed something a few years ago and encountering people you regularly saw has become very hit and miss. Congratulations on the wrench. I need one of these adapters for #10 taps, but the square socket will likely be too small for a file. I am thinking about cutting a 3-sided box in a flat piece of steel and welding that onto the end of a round with flats I prepared.

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    TimF10

    19 days ago on Step 7

    While I understand the concept, I would be wary of this. It appears that the OP is attempting to his his drill press to power tap holes. Depending on the materials, this may be fine. The problem is if you are tapping the wrong materials or hit a hard spot in the materials, it can easily snap your tap and you then either have to spend time removing the broken tap or scrapping your work.

    They do make power tapping bits to be used in milling machines for this exact purpose. If you are going to do this, please ensure that you are wearing all of your PPE including safety glasses and some kind of face shield.

    3 replies
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    FamilyF4TimF10

    Reply 19 days ago

    Tim, if you had followed Phil's link @ the start, you would see that he was hand tapping, using the quill for alignment only. The idea of just filing the adapter you need is something for us to keep in mind.

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    TimF10FamilyF4

    Reply 19 days ago

    Most taps have an indent in the back side just for that. All you need is to take a section of rod, and to blunt the point to fit that little indent. Then use the rod in your drill press to center and tap a straight hole. This seems like way more work than the 30 seconds it would take with a steel rod and a bench grinder.

    How do you even put a tap wrench on the tap after you have attached this "adapter"? The only use for this adapter is to be able to use a drill to power tap a hole. I wouldn't want to have the resistance of my drill press drive train fighting against me while I was trying to hand tap a hole by hand.

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    Phil BTimF10

    Reply 19 days ago

    My tap simply slides in and out of my adapter. It does not permanently attach to the adapter. And, FamilyF4 is correct. The drill press quill is used without power from the motor. It only holds the tap for better alignment. The tap is just as available and just as functional in a standard tap wrench after use with my adapter.