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Junk Taps?

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  • Junk Taps?

    Where i work we do mostly aluminum work, and we have taps supplied for us for the common sizes we use...

    But lately we've had some steel jobs coming through, and it seems like the taps they give us are good for about one hole in steel and then they feel dull or chipped.

    I don't dare power tap with them, so what i do is put the tap in the drill chuck (without power), and the machine in neutral, and get the tap started so i know it is square. Then i will finish the hole with a tap handle.

    The tap feels sharp at first and the way it should. I turn it no more than a full revolution before backing it off... usually more like a half turn, the na half back. And it seems like as soon as i do that first back turn, the tap must chip a bit and become dull because it feels much harder to turn. Usually last for one hole, without feeling like they are going to break.

    They are 1/4 - 20 Gun taps (i think, i'm not too sure if they are gun taps or not...) with 3 flutes. Is there something i'm doing wrong? Or are some taps just that bad that they're only good for one hole? So far my method is to chuck em after a hole... it seems like a huge waste of taps to me, but it's better than breaking one off.

  • #2
    Are you using cutting oil? What kind of steel are you tapping?
    Try to make a living, not a killing. -- Utah Phillips
    Don't believe everything you know. -- Bumper sticker
    Everybody is ignorant, only on different subjects. -- Will Rogers
    There are lots of people who mistake their imagination for their memory. - Josh Billings
    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
    Don't own anything you have to feed or paint. - Hood River Blackie


    • #3
      Are these taps new or have they been used in something else, like alum. More importantly, are they name brand taps? About the only taps from across the pond that are worth anything are from Poland.


      • #4
        Yes, there are taps out there that bad, that will last just one hole. They usually break before the hole is finished. Whom is suppling the taps? The customer? Are the taps "no-name"? Well, they could be "junk" taps, or it could be low quality "junk" steel, or low carbon steel. Do you know what alloy it is? I will assume you are using some type of cutting lubricant. If not, shame. Contributes to the problem. Did you check a used tap to confirm your "tap must chip" suspicion? If it is chipped it could be: 1) Low quality steel, hard spots. 2) An incorrect tap drill size. 1/4-20 = #7 Drill. Just because a drill is stamped #7, check it. 3) The flutes of the tap are becoming loaded, which could cause the cutting edges to chip or become dull.

        Is there galling of the tap? Do the finished threads appear rough? If so, you probably have a low carbon steel.

        In your case, might I suggest, try using "higher-end" (i.e.Greenfield, OSG) spiral point oxide coated taps. The spiral point drives the chip ahead of the cut, thus reducing or eliminating flute loading. For through holes, IMO, spiral point is the best choice. The oxide coating on the tap has some lubricity, and is to some extent porous which will hold cutting oils at the point of the cut. By doing so it reduces galling of the tap. From what I have learned, oxide coated taps seem to be the best choice for use in metals that tend to gall, low carbon steel is one of them. Yes, more costly than "lower-end" taps, but they seem to last a lot longer. I would think that to toss a tap after one hole would cost more than buying "higher-end" taps in the first place.

        I, like yourself, at work, use mostly aluminum and plastics. Very infrequently anything else. I use, exclusively, "higher-end" TiN coated spiral point taps for everything. Through and blind holes. In blind holes, I just do not bottom them out. Then finish with a bottoming tap.

        [This message has been edited by ERBenoit (edited 05-07-2005).]
        Paying Attention Is Not That Expensive.


        • #5
          You don't say what kind of steel you are tapping. If it's a harder one, that could explain your problems.

          There is definitely a difference in tap quality. If they are buying based on price only they you will have trouble. What ER said about high end taps and spiral point for through holes.

          You mention backing up. That's one technique that helps to clear the chip load on the flutes. Another thing I do with difficult tapping jobs is to completely remove the tap every turn or two and use a brush (tooth brush) to completely clean it and then dip it in cutting fluid. I like Tap Magic but any good one will do. In blind holes I use a can of compressed air with a small tube to direct the air to the bottom of the hole. Stick the tube in to the bottom and give a blast while pulling it out - watch your eyes. It completely clears the chips from the hole so tapping is a lot easier. Works with through holes as well, just aim at the sides instead of the bottom.

          Paul A.
          Paul A.
          SE Texas

          Make it fit.
          You can't win and there IS a penalty for trying!


          • #6
            OSG ASP 21 taps are nice expensive but do you like drilling broken taps out... Its worth the dough to buy a tap at a time of good quality rather than a 40 buck tap set made in china.


            • #7
              As a kid growning up build all sorts of things like go-carts, minibikes and eventually car I used my father's tools. He had both metric and SAE tap an die sets from I believe Hanson and during that entire time I only broke on tap. Now later in life I'm using taps bought at a local machinist supply shop and seem to break taps very frequently. I spoke to my boss about this and we decided to purchase a high quality tap and die set within the next week or so.

              The question I'll add to this converstion is whether or not Hanson's are still made and if so how do they compare on the quality scale these days? What brand is the best? FWIW I use Tap Magic exclusively nowadays whereas years about it was whatever lubricant (typically 3 in 1 oil) I could find. Sometimes I wonder if Tap Magic isn't partly to blame, allowing inferior taps to "bite of more than they can chew".

              -Christian D. Sokolowski


              • #8
                It could be the metal you're tapping too. F'rinstance, the old P-14 and 17 Enfields, you had to start every hole with a fresh tap to even have a prayer of making it to the other side in one piece. Also to consider, what percentage thread are you trying to achieve? If you have at least one diameters' worth of thread engagement, a 50% thread will serve as well as a 75% with alot less tapping stress. If you're shooting a 90% hole things get real sticky, and require the very best tools and techniques for very little gain in strength. I don't know the numbers off the top of my head, but someone out here might. I do remember the difference is smaller than you'd suspect.
                I'm here hoping to advancify my smartitude.


                • #9

                  IMHO, the best taps are made by OSG or Greenfield. I've started buying Cleveland taps because they come in smaller package quantities so far so good. I personally would consider Hanson taps that I have seen more for chasing threads.
                  Jon Bohlander
                  My PM Blog


                  • #10
                    <font face="Verdana, Arial" size="2">Originally posted by moldmonkey:

                    IMHO, the best taps are made by OSG or Greenfield. I've started buying Cleveland taps because they come in smaller package quantities so far so good. I personally would consider Hanson taps that I have seen more for chasing threads.
                    Thanks, Like I said I used Hansons grwoing up and that was 18-25 years ago. Like everything I'm sure the quality has dropped. Our company doesn't have a dedicated machinist, welder or repair person, those duties fall to me but my primary job is sales and R&D so my boss has an interest in providing good tools to make the repair and fabrication part of my job go smoothly. I'm sure I'll have no problem getting a set of OSG or Greenfield out of him.

                    -Christian D. Sokolowski


                    • #11
                      Hello All,

                      My guys tap a few hundred holes a day, and the ONLY taps allowed in my shop are taps made by DORMER.

                      We usually get them from Fastenal I believe, they are not cheap and one hell of a bastard to remove once broken (which in itself is really really rare)

                      If you break one, I promise you, you will invent some new words!

                      Just my .02



                      • #12
                        I had an odd thread to tap, so I looked thru a HF set of taps and dies that somebody gave me. There was one in the set, It was horrible to turn the tap, this was in a low carbon type of steel. I really thought I was going to break it off. So I backed off, went to my local shop supply place and they had one. It was a good brand name, but I can't remember it at the moment, but this new tap cut the threads like a knife through warm butter. I pitched the HF set in the garbage.



                        • #13
                          Back when I was shop foreman I'd interview job applicants. One of the questions I asked each and every one of them was, "Have you ever broken a 1/4-20 tap?"
                          If they answered, "no" I would not hire them because I figured they were either not a machinist or they were a liar and I had no room for either.



                          • #14
                            I haven't broken a tape in 20 or more years, does that count?

                            O.K. I can't remember when I broke the last tap, so I figure late 70s or early 80s.



                            • #15
                              Yes there are poor taps. There also seems to be a belief that all taps need to be backed p to "Break Chips". Not so with a spiral point tap as it forces a chip to curl ahead of it. If you insist on breaking chips in steel with them it is likely yo will also chip the cutting teeth. if you have a gun tap it will have a lead angle ground into the flutes. to see if you have a spiral flute tap look at the flute, if the cutting point is grond at an angel to the akis on the tap it is spiral pointed. If the flute continues straight to the point it can and should be backed up to break chips as they will not clear the flute.
                              Also make sure you lubricate the tap.
                              One last thing, what is the tapdrill size?
                              Remember MD-P (major dia. minus the thread pitch) will get you very far in the tapping world.

                              Hope this is helpful.