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Tapping Extrusions

Discussion in 'General Talk' started by Ronald4418, Apr 23, 2016.

  1. Ronald4418

    Ronald4418 Well-Known
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    Whoever said tapping and threading these extrusions should be taken out and donkey whipped. I'm to the point of taking all of my extrusions to a machine shop and having them tapped. On top of that, M5 tapps and the necessary clearance drills in Canada at least are about as easy to find as Hen's Teeth.
     
  2. Wiskerstwo

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  3. Ronald4418

    Ronald4418 Well-Known
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    I've used KBC as well as Travers Tool Canada many times though that still doesn't help with the actual tapping issues.

    I've even tried substituting the metric screws with imperial just so that I can get it done and over with. But I'm actually no further ahead, because as I stated before, these V-Rails are a bugger to tap. Mostly due to the small sizes of the taps involved and the fact that my eyesight and hand strength isn't what it use to be.

    Is it just me or does everyone just go ahead and have a machine shop tap their V-Rails for them in lieu of buggering them up themselves?
     
  4. Steve Fox

    Steve Fox Veteran
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    I've tapped around 80 holes, maybe more in V-Slot rail and haven't had a problem.
    I'm still using the original tap that came from Sears & Roebuck 30 years ago.
    Make sure you have the tap perpendicular to the end and use tapping lube.
     
  5. Joe Santarsiero

    Joe Santarsiero OB addict
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    No offense, I believe it must be your technique. With that, using a 4 flute tapered tap will be easiest. If you already are, and still screwing them up then maybe try a tapping die to help keep the tap straight. A tapping die is just a square block with a guide hole. You could make one yourself if you have a drill press.
    It's somewhat important to keep the taps axis inline with the holes mainly to prevent wiping out threads. Aluminum is fairly forgiving of this though. Once you've got them started inline (a few turns with a tapered tap) then turn it two half turns to cut then back it off a quarter to a half turn to break the chips. If it feels to resistive at any point the then adjust to go in less and back off to chip break more often. Eventually you'll know the feel. keep repeating until desired depth is achieved. Follow up with a bottoming tap. Don't forget to use a little tap juice for lube. If you're really tight on budget or time then some spare motor oil, wd40, or even handle wax will suffice as cutting oil. I've been known to use straight dish soap in a bind!

    I'm sure most tap these holes themselves without much problem. It sounds like you just need to refine your technique and get a feel for it.
    I had over 160 holes to tap on my machine. Mostly 10-24 without a problem. 8 of these were #6 and I broke a tap on the first. :/ Luckily It was for a slot. I made sure to go in less and back off more often for the rest. The worst of my problems were my aching wrist and forearm. :D

    You'll get it. Or if you have a shop and you just don't want to try anymore then maybe bring it there to be done. See if they'll let you watch to get your money's worth. If they're good they'll teach you hands on.

    Joe
     
  6. Steve Fox

    Steve Fox Veteran
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    Ronald,

    I just checked my extrusions. The hole is approximately the diameter of a #21 drill bit.
    The recommended bit for a 5mm tap is a #19.
    That makes the hole a little tighter than it needs to be.
    How about if you try drilling out one hole with a #19 bit and see if it makes it easier on you?
     
  7. Ronald4418

    Ronald4418 Well-Known
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    So a 10-24 was sufficient when making all of your connections? I tried using a 10-32 instead of the original M5 x .08 though the available taps have been fine thread instead of coarse threads. Could that be whats causing me the reason for my issues , other than the ability to find machine screw length taps which are generally stronger and less apt to break as easily as standard taps/
     
  8. Joe Santarsiero

    Joe Santarsiero OB addict
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    No. I used a different mechanical system all together. As hinted at by Steve above...you have to have the right size hole for the tap to begin with. If you google tap drill chart you should find a number of charts that'll give you a rough idea of where in metric hole sizes you can tap imperial and what drills are required to move a hole to a tap from one unit of measure to another. I'm sorry. I assumed this was common knowledge. If a hole is too tight or too loose for a given tap the chances of success are low. All of my holes were in range of the tap.

    Joe
     
  9. Ronald4418

    Ronald4418 Well-Known
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    I started by using a combination drill and tap and it worked great for the first few holes. But I ended up hitting a hard spot in one of the holes in the V-Rail of my Z Axis and in my haste to remove it. It snapped in the lower center hole. Mind you the combination drill and tap couldn't be held sufficiently in my cordless drill so I attempted to use it in mmy corded drill. But in my haste I forgot to adjust the speed to a slower rate and the obvious happened. Since then I've been attempting to drill and tap center hole in one end of my X Axis pieces using both the correct clearance drill and tap for 10 -32 NSF. This the closest to M5 x .08 bolt size that I could find. For a country that brags so much about the Metric System, Canada sures as hell doesn't show it with the ability of the necessary tooling. I've got another pair of M5 x .08 Taps on order and will be using them once they arrive and if I can't get through this without any further problems I will definitely be checking out the local machine shops as an option.
     
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  10. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Drill out with a 3/16" bit and let the screws form their own threads. So much easier (it takes just seconds) and you'll find the threads have a very good, very tight grip. Note: not for use in thin (3mm or 1/8") plates. Those still need to be tapped, preferably with a forming tap rather than a cutting tap. Threadforming | OpenBuilds
     
  11. Jonathon Duerig

    Jonathon Duerig Veteran
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    My personal strategy for tapping extrusion usually involves designing a way to avoid it entirely. The very first extrusion build I did was a kit using a design that somebody else cooked up. After hand tapping ten holes or so, I swore it off. Now I use plates and brackets in all my designs instead. You can often get a more sturdy connection that way as well.

    If I find myself absolutely needing to screw into the end of extrusion again at some point, I think I'll try out Rick's threadforming suggestion.

    -D
     
  12. Joe Santarsiero

    Joe Santarsiero OB addict
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    Note: forming taps have their own tap drill size which can change based on material.

    Good luck.
     
  13. Ronald4418

    Ronald4418 Well-Known
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    Finally broke down and ordered a pair of the taps available in the OpenBuilds Store only to have a surprise in the mail today. I had ordered a tapered and bottoming tap on Ebay previously. I got a surprise when I opened the package, they didn't send me one pair. They sent me 5 pair of taps. I also found a new 11/64's inch drill bit to try using as a clearance bit.
     
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  14. Metalguru

    Metalguru Master
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    Ronald4418 | OpenBuilds I share your displeasure with the Canadian metric issue. We've officially been metric for what, almost 40 years? But 9 times out of 10 I have to order metric screws and taps out of the US, because they are scarcer than hens teeth here. I use McMaster Carr a lot. I do have a set of taps/dies from Canadian Tire that has a decent metric selection, but woe is me if I break one...

    I have to agree that the roll thread forming taps or Ricks method of using the screw itself to roll threads is good. Roll your own! As always, when penetrating a tight hole, use a good lube. ;)

    Spaenaur is probably your best bet for fasteners in Canada. www.spaenaur.com. They have fluteless polygon taps which are roll forming types. Spaenaur is pretty good, but they have minimum order quantities and you can only get full boxes. They do accept credit cards.

    Have you tried the self tapping screws in the parts store? They work pretty well, once, but would not survive many assembly-disassembly cycles... There are also self tapping metal screws, they are like mini disposable taps. I often use one of these to tap the hole, then put in the real screw after. Use a hex head so you can get some torque on it. When it wears out, throw it away and use another one.

    [​IMG]
     
    #14 Metalguru, Apr 27, 2016
    Last edited: Apr 27, 2016
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  15. Metalguru

    Metalguru Master
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    I think I finally have the answer for tapping extrusions.

    I had a bunch of holes to tap and I didn't get my roll forming taps yet, so I was using a standard tap. After doing a couple of holes, with much cussing and fuming, I stumbled on a product that works so well I can't believe it. It's called Stick-Kut, and its a cutting lube made with bees wax.

    David the Swarfer recommended a similar product to me for cutting aluminum plates, he says he just wipes it onto the surface of the plate before cutting and it stays put and lubes the bit. The jury is still out on this application, but it works like a hot **** for tapping.

    First step is to drill out the hole with a #19 drill bit, or 4.2mm if you have one. Holes in the extrusions are not that close tolerance. Then, take a countersink bit, preferably one of the diagonal hole types, and put a small chamfer on each hole to be tapped. Makes starting the tap much easier, and you don't get the ridge around the edge of the hole.

    Now, dip the end of the tap in this stuff, maybe put a little on the end of your finger and push it into the hole. Start tapping as normal. The tap now goes in like buttah! I even used an electric drill on low speed, and it taps like crazy. You can go half a dozen turns without reversing to break chips, and then just a twist or two in reverse gets you going good again. It seems to make the tap break the chips into much smaller pieces, which keeps them from jamming up the tap. I tapped a dozen 25mm deep holes in about 10 min. Just clean out the tap grooves on a paper towel after the hole is done, then dip it in the Stick-Kut again, and away you go.


    20160521_200231.jpg
     
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