Drilling and tapping straight and square... How to?
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  1. #1
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    Drilling and tapping straight and square... How to?

    Hello there,

    I have a proyect going that involves drilling and tapping a lot. I have 8 pieces of 15mm thick steel (flat bar 150mm wide 750mm long) and each needs 8 holes drilled 8,5mm and tapped M10 in them.Thats a total of 64 holes.

    Of course, the more square and precise, the better.

    So far I have done 2 pieces (16 holes) and the results are far from what I would like.

    I am doing it as follows.
    • Measure, scribe and center punch.
    • Pilot drill (not all the way through) with a centering 3mm bit. I am only drilling untill I reach the "shoulder" of the bit (where the countersunking starts), thats like 4mm or so.
    • Then I drill all the way through with an 8,5mm bit.
    • Countersink a bit on both sides.
    • Tap by hand with tapping fluid.


    I have been drilling with a new (to me) substantial drill press, so everything is rigid. Before drilling all the way through I make sure the bit is well aligned with the pilot hole. With the drill running I touch the piece and if the bit wanders (meaning the alignment is not precise) I adjust via dead blow hammer and try again. I may have some holes of the first piece a tad off, but not much.

    Then I start tapping. I had a few sets of 3 taps but I asked and I was told about machine taps. The ones capable of tapping in a single pass. And I bought one.

    I am tapping with a hand held tap turner (?) so the alignment of the tap and the hole goes strictly by eye.

    That said after tapping the 8 holes in the first piece I ended up with a few holes seriously crocked.

    For the second piece, thinking that the single pass tap could be too aggresive, I used my old three pass taps. And the holes ended somewhat better.

    Now my big question is... Is it possible to screw up tapping if the hole is perfectly square to the piece or I just had the holes crocked and the tap just followed it?

    From now on I am going to chuck the tap into the drill press and, somehow, turn it by hand (probably loosening the belt so I don't have to fight the motor). That way I will make sure that not only the bit, but also the following tap is also straight.

    What do you guys think? How do you do it? Any tips I could put to good use?

    Thanks in advance,
    Mikel

  2. #2
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    Re: Drilling and tapping straight and square... How to?

    Try using a spindle tap
    http://www.waltontools.com/products/spndltap.htm

    I had the same problem with crooked holes and they looked bad. They did hold for what I needed them for. If other have better ideas I am intrested also.

  3. #3
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    Re: Drilling and tapping straight and square... How to?

    As you have learned, there is a high liklihood of tapping out of square when doing it by hand.
    You also determined that the solution would be to chuck the tap and wo it with the drill press.
    What I do is drill all the holes on my Bridgeport and mark each hoel on the digital readout. Then, after all holes drilled, I refer back to my readout locations and power tap with the mill.
    If you have access to a tapmatic style tapping head, you will love it!
    Great tool for tapping fast and accurate. They have a clutch inside them that as soon as you lift the quill, it automatically reverses the tap's direction.

    Grant
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  4. #4
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    Re: Drilling and tapping straight and square... How to?

    Quote Originally Posted by Mikel_24 View Post
    Hello there,

    I have a proyect going that involves drilling and tapping a lot. I have 8 pieces of 15mm thick steel (flat bar 150mm wide 750mm long) and each needs 8 holes drilled 8,5mm and tapped M10 in them.Thats a total of 64 holes.

    Of course, the more square and precise, the better.

    So far I have done 2 pieces (16 holes) and the results are far from what I would like.

    I am doing it as follows.
    • Measure, scribe and center punch.
    • Pilot drill (not all the way through) with a centering 3mm bit. I am only drilling untill I reach the "shoulder" of the bit (where the countersunking starts), thats like 4mm or so.
    • Then I drill all the way through with an 8,5mm bit.
    • Countersink a bit on both sides.
    • Tap by hand with tapping fluid.


    I have been drilling with a new (to me) substantial drill press, so everything is rigid. Before drilling all the way through I make sure the bit is well aligned with the pilot hole. With the drill running I touch the piece and if the bit wanders (meaning the alignment is not precise) I adjust via dead blow hammer and try again. I may have some holes of the first piece a tad off, but not much.

    Then I start tapping. I had a few sets of 3 taps but I asked and I was told about machine taps. The ones capable of tapping in a single pass. And I bought one.

    I am tapping with a hand held tap turner (?) so the alignment of the tap and the hole goes strictly by eye.

    That said after tapping the 8 holes in the first piece I ended up with a few holes seriously crocked.

    For the second piece, thinking that the single pass tap could be too aggresive, I used my old three pass taps. And the holes ended somewhat better.

    Now my big question is... Is it possible to screw up tapping if the hole is perfectly square to the piece or I just had the holes crocked and the tap just followed it?

    From now on I am going to chuck the tap into the drill press and, somehow, turn it by hand (probably loosening the belt so I don't have to fight the motor). That way I will make sure that not only the bit, but also the following tap is also straight.

    What do you guys think? How do you do it? Any tips I could put to good use?

    Thanks in advance,
    Mikel
    1-what material and hardness?

    2-what is the thd.? M10 x 1.5?

    3-Check the squareness of the drill to the face of the plate--at 2 right angles
    to ensure that the drill table is not cocked. Presumably, the work is clamped
    well during drilling.

    4-a hand tap with a taper of 7 or so thread leads helps alignment in the hole,
    the less tapered lead, the greater the chance for cocking.
    If you need 8.5 mm of full thread, you can get that by running the long tapered
    hand tap the better part of the way thru the plate--breaking the chips with 1/2 back turn of the tap--before it binds up from the chips.

    How much tapered lead is on the 'machine tap'?
    Short lead=hand tapping problems. In rigid machine tools that hold
    and align the tap--it's not a problem.

    5-hand tapping into a chamfered hole--at least from me, causes cocking problems. I chamfer afterwards, then chase thread burrs with tap

    6-When starting the tap, look at it from 2 right angles

    7-"Now my big question is... Is it possible to screw up tapping if the hole is perfectly square to the piece or I just had the holes crocked and the tap just followed it?"
    Yes--to both.

    8-the spindle tap NRM refers to, looks helpful.
    Blackbird

  5. #5
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    Re: Drilling and tapping straight and square... How to?

    As Jackalope said, invest in a Tap-Matic head for your drill press. It will pay for itself in a very short time.
    Larry
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  6. #6
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    Re: Drilling and tapping straight and square... How to?

    You could make a "tap block" to help align the tap.
    3/4" thick steel block with hole the size of the tap.
    Center hole in block over hole in work and insert tap.
    Holds tap square,I made one years ago with holes for
    taps #4 to 1/2".
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  7. #7
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    Re: Drilling and tapping straight and square... How to?

    are the holes all in alignment on the pieces or in different spots if there in alignment you may be able to make a jig of some sort to hold the tap square to the piece and power with a variable speed drill or t handle like one of these or maybe buy one of these http://www.google.com/url?sa=t&sourc...EcXc1HaLc-oLuA
    350P 30A spool gun cut master 51 syncro 250 other stuff
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  8. #8
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    Re: Drilling and tapping straight and square... How to?

    I do the same thing with my drill press ,start the tap by turning the chuck by hand..Usually the tap starts to slip in the chuck after a few threads (my taps are old though) , so I finish it with the tapwrench at that point..

  9. #9
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    Re: Drilling and tapping straight and square... How to?

    Make a "Tap Block" as listed above or most taps have a 60 deg center in the end. Get a piece of stock with a 60 deg point that is larger than the hole and will fit in the drill chuck. Run the point down into the hole on your part to locate center and clamp. Raise and use the point in the head of the tap to keep tap aligned.
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    Last edited by jones6780; 06-23-2011 at 08:14 PM. Reason: add photo

  10. #10
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    Re: Drilling and tapping straight and square... How to?

    metric tapping block such as i have linked below
    http://cgi.ebay.com/Red-Metric-Tap-G...391978#vi-desc

    or a tap guide as pictured in the previous post.

    i recommend tap-matic tapping fluid or a thick oil for lubrication if its cold roll or hot roll steel.. if you can deburr the backside of the hole prior to tapping it also helps prolong tap life, the burr caused from drilling a thru hole can be hard on the tap and promote the tap breaking when your retracting the tap, same goes for a burr on the top of the hole.. the tap can drag the burr down into or back up into the hole and break the tap, ive seen this all to often..

    if the holes are in a straight line you could drill all your holes, then countersink (chamfer) all the holes front and back if they arent blind holes.. then put a tap in your drill chuck and hand start the tap in each hole, running the tap in at least for 4 to 6 threads, then go back through all the holes hand tapping them...

    the tap turner you refer to is called a T-handle or tap handle...

    the tapping heads or tapmatic heads people are referring to, i have seen those sell for alot of money so they might be to expensive for you, but if you do alot of tapping they are well worth it, they can also be very dangerous if used incorrectly..

    another tip for tapping is not to get into too big of a hurry, thats when you break taps.. also stop and back out often and dont be too stingy on the lubrication.

    22yr machinist/toolmaker
    Last edited by brucer; 06-23-2011 at 10:26 PM.

  11. #11
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    Re: Drilling and tapping straight and square... How to?

    For your application, on the drill press, I'd use the t-wrench in the quill. Cheap and fairly quick per hole, especially if you don't have to raise or lower the bed. The t-wrenches come in 3 or 4 sizes... I use them all the time. If your doing a lot of holes I'd suggest putting a golf ball on one end of the t-handle... it will save your hand.

    A good HSS tap will work faster and with less effort than the standard hardware store variety. Sure you'll pay 3 or 4 times more per tap... but the tap can last for hundreds of holes. (Oops... I'm using a cheapy in the attached photo )

    I tap a lot of holes. I use a Tapmatic, thread mill, drill-thread mill (very cool, very expensive... it drills, threads and chamfers all in one op), rigid tap, and few other methods. All methods come at a cost in setup time and tooling. There is no one size fits all.

    A Tapmatic for 65 holes is not justified... unless you already own one (I sprang for mine on a 1000+ hole job.)

    A while ago I posted a link the shows the t-wrench method on the drill press:
    http://weldingweb.com/showthread.php?t=56441

    One of my crazier methods is to use my air tap ratchet
    http://weldingweb.com/showthread.php?t=44524
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  12. #12
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    Re: Drilling and tapping straight and square... How to?

    Thanks a lot for all the information. I am not going to quote every post but I will try to answer everything I have been asked.

    The stuff I am dealing with is mild steel. Not hardened by that matter. Thread is 10x1,5 as noted. I checked the squareness of the spindle and seems right to me. I am also placing the piece against the base of the drill (milled, so should be flat and square to the drill head) spacing it with two pieces of 30x30 square tubing (the base doesn't have a hole for the drill to go through and I don't want to ruin it).

    I am not using the swing away table because pieces are somewhat long and heavy and I didn't want to risk chances of having the table rotating on itself or anything.

    Now that you guys mention it... I do remember that the machine tap is very aggresive and has a maybe not so pronounced tapper... Will take pictures and show you. That might be the reason why I was getting better results with the three stage taps than with the machine tap.

    I will try to tap without chamfering first and see what happens. The worst it can happen is that I will need to use the tap again to clean the very first thread.

    I am using a fluid designed for and only for tapping, so it should be good. It is a somewhat thick stuff and you can really feel the difference in using it or not. Half the effort, no binding at all, etc.It is sold in bulk and I don't think the container I have now (a quarter I guess) has any stickers on it but will try to get some more info on it.

    And as NRM and others suggested, I have contacted my usual supplier of machining hardware and inquired about the spindle tap. I hope it is not to expensive!

    In the meantime I will probably drill some more stuff (no tapping this time) I need to put holes into. Just another question. If you had to make through-holes in rectangular tubing... would you just mark/scribe/center-punch on one side and drill through BOTH sides at the same time... or mark/scribe/center-punch on BOTH sides and drill separately?

    I am afraid that if I try to drill all the way through at the same time, by the time I reach the opposite side of the tube (on the inside) not having a center punch in there would make the drill bit wander/walk so the holes will end up missaligned....

    Thanks in advance!
    Mikel

  13. #13
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    Re: Drilling and tapping straight and square... How to?

    Quote Originally Posted by Mikel_24 View Post
    In the meantime I will probably drill some more stuff (no tapping this time) I need to put holes into. Just another question. If you had to make through-holes in rectangular tubing... would you just mark/scribe/center-punch on one side and drill through BOTH sides at the same time... or mark/scribe/center-punch on BOTH sides and drill separately?

    I am afraid that if I try to drill all the way through at the same time, by the time I reach the opposite side of the tube (on the inside) not having a center punch in there would make the drill bit wander/walk so the holes will end up missaligned....
    The length of drill your are using will play a huge part in wander. Most places sell jobber length drills, these will wander easily due to their length and flex. I normally use stub or screw machine length drills when possible. They are about half the length of the same jobber length drill. The shorter the better. Also the material and the angle of the drill will play a roll. Sharp drills run truer than dull ones.

    When doing thin material you don't need a lot of spirals to clear the chips. Cut the drill off short and grind a new tip. Remember the spiral flutes rob a lot of material strength and contribute to the flex.

    Generally, I'd drill straight through the square tube. The first hole will keep the drill steady, especially if the shank is in the hole. You need to ensure your setup is square of course. Check the tram on the bed.

    Try a few test holes on scrap and measure them... if it's acceptable then your golden.

  14. #14
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    Re: Drilling and tapping straight and square... How to?

    I hear what you say Forhire. I am going to get (probably order, I don't think they are going to be readily available) some of those stub drills, which, btw, is what I should be using for pilot drilling instead of one of those bits with two ends (I read somewhere here that those are for making the centering holes in lathe related jobs).

    I am using M10 bolts 100mm long (about 4"). They are not fully threaded (only the last 30mm), so the neck of the bolt is going to be close to 10mm. Since I am not a machinist and I am having the above problems squaring the taps, I am going to drill to 11 or maybe even 11,5mm... that should give me some room for screw ups. The position of the fixed pieces is not criticall as long as it stays stuck and flat to the rectangular tubing.

    I am not sure if I will be able to use one of those stub drills for drilling all the way through because the square tubing is 80mm wide on its widest part. That means I should use, at least, a 75mm drill bit...

    I will make a few holes in a scrap pice and see how it goes.

    I really appreciate when those who do this for a living help out us, mere mortals, with machining related stuff. Thanks a lot!

    Mikel

  15. #15
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    Re: Drilling and tapping straight and square... How to?

    Quote Originally Posted by jpump5 View Post
    You could make a "tap block" to help align the tap.
    3/4" thick steel block with hole the size of the tap.
    Center hole in block over hole in work and insert tap.
    Holds tap square,I made one years ago with holes for
    taps #4 to 1/2".
    X2 Everyone should have one.
    That said I tap a lot by hand but I have done 1000's of tapped holes, the trick is to let the tap find its own way, it wants to cut an equal amount on each side. Forcing it to want you think is square will ruin the hole.
    A drill press can also be used to start the tap, put tap in drill chuck and without turing motor on manually start 2-3 threads. Hand tap from there, drill press spindle will hold tap square.

  16. #16
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    Re: Drilling and tapping straight and square... How to?

    I power tap with the drill press all the time without a tap-matic.

    What I do is use the drill press to drill the hole, then chuck up the tap and loosen the drive belt. Run the tap down to the material and slightly pull down on the drill press handle. The tap will go in about 3-4 threads and the belt will start to slip and the drill head will stop. Shut power off on the drill and loosen chuck, finish the hole by hand.

    There have been a few times I powered all the way threw a hole but I have broke a couple taps trying to do it in one shot so I quit that.

  17. #17
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    Re: Drilling and tapping straight and square... How to?

    Here is a tool that may help I found it on another site, it uses a coupling nut.
    also check out this page about half way down it shows a air powered tapping tool
    and an arm to help with straight tapping. All would help for better tapping work.
    http://www.cnccookbook.com/CCTappingArm.htm

    have fun
    Tom
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  18. #18
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    Re: Drilling and tapping straight and square... How to?

    [quote=Mikel_24;524954]I hear what you say Forhire. I am going to get (probably order, I don't think they are going to be readily available) some of those stub drills, which, btw, is what I should be using for pilot drilling instead of one of those bits with two ends (I read somewhere here that those are for making the centering holes in lathe related jobs).

    Center drills are terrible as the center is very fragile. For starting I like to use single flute spot drill. Very rigid. Of course with a shorter drill you may find the spot drill isn't really needed.

    Quote Originally Posted by Mikel_24 View Post
    I am using M10 bolts 100mm long (about 4"). They are not fully threaded (only the last 30mm), so the neck of the bolt is going to be close to 10mm. Since I am not a machinist and I am having the above problems squaring the taps, I am going to drill to 11 or maybe even 11,5mm... that should give me some room for screw ups. The position of the fixed pieces is not critical as long as it stays stuck and flat to the rectangular tubing.

    I am not sure if I will be able to use one of those stub drills for drilling all the way through because the square tubing is 80mm wide on its widest part. That means I should use, at least, a 75mm drill bit...
    For 65 holes, I would make a drill guide that clamps to your stock. The guide would use drill bushings to guide the drill. No center drill required. Clamp it on, drill it, flip it over, drill it from the other side. Provided your guide is accurate then the two holes will be dead on. You can used a bushing of a smaller size for your tap side. I attached an image of the bushing.

    For tubing sometimes I use press in thread inserts called captive nuts which can be faster and longer lasting than threading thin material. It's the second image.
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    Last edited by forhire; 06-24-2011 at 11:29 AM.

  19. #19
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    Re: Drilling and tapping straight and square... How to?

    Some very good advice above!

    I try to avoid hand tapping about as much as house painting or roofing in late July.

    If I'm stuck, then I go long, with either a long tap handle, tap extension or a pulley tap. I like the extension a little better as you can see the tap tilt as well as feel it if the tap tilts a bit on starting (the tap is a bit loose in the extension). I did it this way long before my eyes got wimpy... (doggone censor gave me tap **** for where tilt is subbed above, stupid)

    Drilling... If you are stuck with jobber length or worse yet "automotive length" drills and you are center punching you can move the hole a bit after starting as long as the margin (outside lip) has not yet broken the surface.

    If you set a divider to the hole radius and scribe the hole first a 64th will look like a mile if the bit wanders some. If I am hand drilling sometimes I tilt the drill & move the hole or sometimes "stake the hole". If I am table drilling I'll take a center punch or chisel (if it's bad) and "stake" the side I want to move to. Sometimes this needs to be done twice (if somehow your 1/32" or more off). The drill will remove more material from the gouged side of the hole till the bottom is smooth again or the margin is in. Also for anal drill starting I'll always use 118° drills or even grind slightly more angle to allow more room from the chisel point to the margin. Then I'll usually switch to a 135° or up to 150° depending on material.

    Anyway I threw some junk together and took a pic of weapons for hand tapping, (below);

    Matt

    Oh, & I don't mind using a gun tap (pushes chips ahead) for hand tapping as long as the chips have somewhere to go.
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  20. #20
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    Re: Drilling and tapping straight and square... How to?

    No pictures yet but a little update.

    I grabbed the Machine TAP with the drill chuck and turned it by hand at first while pushing down a bit and then, once the first threads grabbed, turning it all the way down using a screwdriver as a lever through the spindle. Actually through the little slot like openning that is on the spindle for ejecting the morse tapper attachments.

    And yes, all the holes are perfectly aligned now! By my standards, of course...

    Thank you all for so many tips!!!

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