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  1. #21
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    It may just be the camera/photos, but to me it doesn't look there is any relief.

    Measure a tooth width at the leading edge, and then again at the trailing edge,
    it should be narrower.

    Then toss it in a V-block and check to see if its relieved radially.

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  3. #22
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    Quote Originally Posted by J.Hainen View Post
    Attachment 306371Attachment 306372Attachment 306373Attachment 306374Attachment 306375

    Hi all

    I have attached pictures of one of the broken taps. There is a small piece missing, did a disappearing act somewhere on the shop floor! Unfortunately I have no pictures of the old taps, as they have all been disposed of prior to now.

    The company making this tap specialise in this type of work. The rep that i spoke to seemed to have some concerns about getting a tap of this format to work properly, but as stated here, we used taps from a different supplier without issue for several years.
    Uh oh...a "Rep" is in the middle of things.

    if you can't speak with the manuf directly, shove the broken tap in the "Reps" face, and with your other hand, shove him to the wall, and demand the they FIX THE PROBLEM.....NOW

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  5. #23
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    I think the needed fix is simple:

    Find another vendor. These are the worst examples of custom "taps" I've ever seen.

    Not exaggerating. Not one bit. If this was a conventional thread, you'd be better off filing a few slots into a bolt and using it.

    If you can't find a good vendor in your area, ask around here. I'm sure we can find someone a few thousand times better than who you're using now.

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  7. #24
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    To expand, everything is wrong. The thread form, reliefs, grind, geometry, material, heat treating...

    EVERYTHING!

    However, if you didn't have an existing good tap, or a specced drawing, it's not just the vendor's fault. Do you have a proper drawing for the tap?

  8. #25
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    That is a fairly gnarly looking tap, looks like brittle fracture, torque induced so the thing stood it for a while before failing, somthing caused the tension to increase beyond capacity, clearance, profile or whatever, I’ve seen a toolmaker making a better one off in HSS on a tool and cutter grinder, I couldn’t but I know it’s doable,
    Mark

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    Thanks all for your input and advice, it has been very helpful.

    I will speak to the company dealing with the taps today, raise all of the points made here and see what comes of it. We were never able to supply them with a full tap from the previous supplier. However, they received part of a broken tap, as well as full drawings for the male and female parts related to it, and old drawings for the original taps too.

    In the meantime, any recommendations for specialist tap manufacturers, both in Europe or the US would be greatly appreciated.

    Thanks again,

    Joe

  10. #27
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    Regal is a premier cutting tool manufacturer:

    Special Taps | Custom Made Taps | Regal Cutting Tools

    As is GWS:

    Special Taps - North American Tool | A GWS Tool Group Company

    Both are US companies, a search for "custom high speed steel taps" in your country or Continental Europe should give other options.

    In fairness, your tap form is on the extreme end of "special tap", so it may be outside the range of even these companies. And it may take a couple iterations of design to get an optimal form, as the previous tap geometry isn't available either from drawing or example.

    And expect to pay a $$$ (€€€) price for the taps. But if they work correctly, they'll be worth it.

    Make sure the tap supplier understands all the cutting conditions in your situation - the machines used, tap holding method, cutting oils used, the specific steel alloy, way that you drill the minor diameter and tolerance, whether the hole in the piece is through or blind, speeds you want to run at, desired tap life, coatings as options for better life and cut quality, etc.

    If you don't have a company engineer who's experienced in cutting tool design and execution, you'll be leaning heavily on the expertise of the tap manufacturer. Make sure you supply them with every bit of information they need (I'm sure I'm forgetting things in my above comments, hopefully any missing details will be brought up).

    Good luck, and let us know who you find and how the final taps work for you. A successful tap will look very different from what's in the pictures you provided.

  11. #28
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    Oh, and pay the successful company to generate a fully specified drawing for your records of the final tap geometry. This sort of information should be controlled by your engineering department, so if the new vendor goes bust at some point you're not back in your current predicament.

    Some vendors will not want to do this, but if you put the requirement in your original request for quote you shouldn't have a problem.

  12. #29
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    My last thought: Don't bother with the current vendor, you're wasting your time. It's harsh, but the pictures you posted make clear they're not anywhere near competent to supply a properly designed tap for your needs.

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  14. #30
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    This sounds like a serious problem and some kind of solution is probably needed fast.

    You ask about a serial tap set and that may be a good idea but I am not thinking about the taper, plug, bottoming taps that are common in the US. Instead, you might try a style of tap set where all three taps have the same taper at the tip, but each one only cuts a percentage of the full thread height. The first tap cuts only about 50% of the thread, the second one 75%, and only the final tap cuts the full 100%. They are made in much the same way as a plug taper tap but then 50% of the thread's height is ground off the first one and 25% is ground off for the second. All three taps must be used to create a usable thread.

    I have a set of metric taps that are made this way and they greatly reduce the amount of torque needed at each stage of the process. You could take several of the taps that you have and mount them in a spindle at a grinding wheel to reduce the height of the threads on two of them. This may get you by until you can obtain taps of the same quality as the original supplier provided.



    Quote Originally Posted by J.Hainen View Post
    Thanks for all the responses.

    The tap should be set up to push the chips forward, as the component being tapped is effectively a tube which connects two drive-line components together. We haven't been able to observe whether this is happening because the tap breaks so quickly, before any substantial cutting is done.

    Unfortunately we have none of the old taps from previous supplier. All were broken, and the piece that was saved was lost by the new supplier when it was sent to them for reference. The taps are coated.

    I think a form tap would likely struggle because of how coarse the thread is, and the shape of the thread - simply too much material to deform.

    Would it be worth considering a serial tap set to try and reduce loading.

    I will try to get a photo of one of the broken taps today.

    Thanks again all.

    Joe

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    Quote Originally Posted by EPAIII View Post
    I have a set of metric taps that are made this way and they greatly reduce the amount of torque needed at each stage of the process. You could take several of the taps that you have and mount them in a spindle at a grinding wheel to reduce the height of the threads on two of them. This may get you by until you can obtain taps of the same quality as the original supplier provided.
    I get your point, but in this case I can't agree with trying to use the current "taps".

    1) Your method leaves a cylinder on the OD, there's no radial relief. Now, it's likely there's none on the current taps too, but it's still not right.

    2) There's no cutting face/hook. It's a straight cut, and likely not even an angular clearance.

    3) Improper thread lead in.

    4) Crap material and heat treat. Look at picture 3 in post #21 - the "cutting edges" have crumbled! Ugh, you'd be better off grabbing a hunk of oak and whittling a tap-shaped-object from it!

    5) Lastly, the previous taps (that worked) seemed to be one-shot. I would try to avoid multiple passes if possible, and would encourage the OP to find a vendor who can make that work. It's not an easy thread, but it's not crazy either.

    I hate to beat up this unknown vendor, but they were totally in over their head with this attempt at a tap. Do not waste another moment on these, find a new vendor with proper capacity and engineering expertise.

    For the OP, read this page to get a better handle on the parameters involved in tap design:

    Geometry Features of Taps | Threading Tap Geometry | Regal Cutting Tools

    It's a little rudimentary, but it presents most of the requirements a tap needs.

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  17. #32
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    Quote Originally Posted by EPAIII View Post
    This sounds like a serious problem and some kind of solution is probably needed fast.

    You ask about a serial tap set and that may be a good idea but I am not thinking about the taper, plug, bottoming taps that are common in the US. Instead, you might try a style of tap set where all three taps have the same taper at the tip, but each one only cuts a percentage of the full thread height. The first tap cuts only about 50% of the thread, the second one 75%, and only the final tap cuts the full 100%. They are made in much the same way as a plug taper tap but then 50% of the thread's height is ground off the first one and 25% is ground off for the second. All three taps must be used to create a usable thread.

    I have a set of metric taps that are made this way and they greatly reduce the amount of torque needed at each stage of the process. You could take several of the taps that you have and mount them in a spindle at a grinding wheel to reduce the height of the threads on two of them. This may get you by until you can obtain taps of the same quality as the original supplier provided.
    dont forget these "series taps" are hand taps with straight flutes, at least the ones i have come accross so far (i have a box full of them).

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    From the photos it looks like there are not very many lead in (reduced diameter)teeth. With more the torque needed would be less.

    The flute face does not seem to have a good surface finish.

    The radial rake attitude seems not very positive.

    Many taps have a gash at the lead that gives a bit of positive axial rake to the first few teeth.

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  20. #34
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    Quote Originally Posted by michiganbuck View Post
    From the photos it looks like there are not very many lead in teeth. With more the torque needed would be less.
    Look at pic 3 from post 21. You could have infinite lead and it wouldn't matter.

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    Quote Originally Posted by Milland View Post
    I get your point, but in this case I can't agree with trying to use the current "taps".

    1) Your method leaves a cylinder on the OD, there's no radial relief. Now, it's likely there's none on the current taps too, but it's still not right.

    2) There's no cutting face/hook. It's a straight cut, and likely not even an angular clearance.

    3) Improper thread lead in.

    4) Crap material and heat treat. Look at picture 3 in post #21 - the "cutting edges" have crumbled! Ugh, you'd be better off grabbing a hunk of oak and whittling a tap-shaped-object from it!

    5) Lastly, the previous taps (that worked) seemed to be one-shot. I would try to avoid multiple passes if possible, and would encourage the OP to find a vendor who can make that work. It's not an easy thread, but it's not crazy either.

    I hate to beat up this unknown vendor, but they were totally in over their head with this attempt at a tap. Do not waste another moment on these, find a new vendor with proper capacity and engineering expertise.

    For the OP, read this page to get a better handle on the parameters involved in tap design:

    Geometry Features of Taps | Threading Tap Geometry | Regal Cutting Tools

    It's a little rudimentary, but it presents most of the requirements a tap needs.

    id fully agree with what is said above. the tap has what looks to have no cutting angle and looks to be a 90 degree face to the edge of the flutes, torque would be through the roof and the tap wouldnt ever handle it as its not cutting, its more like trying to broach a tap hole with that flat face.

    and look at the shear line, it got twisted off, and the tap thread tooth behind it is already chipped, makes me wonder about chip evacuation which looks to have no way to do it.

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    Quote Originally Posted by Milland View Post
    Look at pic 3 from post 21. You could have infinite lead and it wouldn't matter.
    Agree, with more lead and perhaps having two roughers at lead taper of a few thousandths, off set the rougher notch, better geometry, made of HSS likely it might go 3x the number of holes and so pay for the changes.

    less tool changes, less scrap parts also a plus.

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    Quote Originally Posted by Milland View Post
    Look at pic 3 from post 21. You could have infinite lead and it wouldn't matter.
    Huh, did someone remove a post? Well, the pics I mention are now in post #20, not #21.

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    Quote Originally Posted by Milland View Post
    Huh, did someone remove a post? Well, the pics I mention are now in post #20, not #21.
    Yes I saw that and went to #20

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    It would be interesting to know what the op pays for each tap,
    Perhaps a guy with tap making gear could bid a price to make a dozen or so.

    I have made taps but don't have the proper gear now.

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    I'm going to walk-back a little bit on my comment of teeth crumbling in pic 3, post 20. I was so focused on one area that I didn't fairly assess the actual teeth. But my overall view stands that these are not worth any more effort, and a better vendor is needed.

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