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Counter-sink problems
I guess I thought machine counter sinking with a cage and appropriate bit was a no brainer. My first attempt using these tools (other than a few practice holes) was on the rear spar of the horizontal stabilizer (RV-9). I never got two holes in a row to be the same. I had to clean off the bit about every 3rd hole or the tool wouldn't remove any material from the next hole. So is my problem: (a) technique, (b) dull or bad bit, (c) bad cage, or something else. The tools are the ones sold by Avery and I was using them in my small air drill with the spar clamped to my workbench.
A half dozen or so of the holes are much deeper than I wanted them to be. Do I need to trash my spar? Thanks for any help!! |
I recommend you ditch the air drill (when machine countersinking) and try a cordless battery drill. Use medium pressure with full RPM of the battery drill (usually about 600 RPM).
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Countersinking
Also be careful around the corners. If the cage does not sit squarely on material on top/bottom/left and right, you can get a deeper hole than intended. I find that just a slight wiggle of the cage as you finish the CS helps with the consistancy of the depth. I am going to guess that you have it set too deep because if it is set to the proper depth, and you are not on a corner, there should be no way to get it to drill too deep a hole no matter what you do to it. Find some thick scrap or go to home depot and buy a cheep piece of aluminum angle and practice a bunch of holes until you are comfortable. Not really much to it, but if you have never used one before it does take some getting used to.
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Practice on some scrap, sneak up on the proper depth....
As the CS cage heats up, you might need to make some tweaks to the setting. I also use the wiggle technique to get that last little bit of depth. Keep the bit clear of chips, keep the area under the cage clear of chips. This is just part of the process..... Can we see a pic with the rivets in the countersink? Quote:
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-The base of the cage might not have been flat against the material (this can be difficult on a narrow spar flange). Rock the cage a bit back and forth to make sure it's sitting flat, then hold it down firmly while drilling. - Shavings stuck in the cage might prevent the bit from extending fully. I'd clean the bit on every hole (or at least shake out the majority of the shavings). - Shavings on the work might prevent the cage from sitting flush on the material. Brush them all off before starting each hole. On your calibration countersink, try redoing it after cleaning out all shavings from the bit and the work. If you see any additional shavings, your first countersink did not achieve full depth. Good luck, Boris |
Turn it really slow, low speed on a cordless drill slow. You can't go too slow. Even at 100 rpm it will take the same amount of time to countersink it, and wont chatter. The flutes on these countersinks are tiny and wont hold much swarf so cleaning it out every hole or 2 is normal.
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whatever you do...Don't try to use the cage in the drill press. Bad idea...ask me why I know.:D
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Countersink
From all the advice above, (all very good by the way), I've found the best way for me to get decent results is to use the electric drill, drill slowly, wiggle the cage, and keep a rivet the size you are countersinking for and test the hole as you go. You can't go too slow, and after a few tests, you get the hang of it and only test on every third or forth countersink.
I am the epitome of KLUTZ and have made my share of screw ups, and then some, and this method works for me. Flyer68 |
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