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Aircraft Drill Bits
7 replies to this topic
Posted 26 July 2010 - 05:49 PM
Aircraft drill bits come in 6" and 12" lengths with diameters in fractions, mm and number gauge. I just ordered a 6" number 55 which is .0520 and 1.3208mm or just a tiny bit larger than 3/64" in diameter.
Has anyone had any experience using these in a drill? a drill press? If so did they drill straight or walk or slop around in 3, 4 or 5" deep holes in lure blanks?
I'd appreciate your experiences and comments.
Posted 26 July 2010 - 06:08 PM
I've not used those particular drill bits, but it's been my experience that drift is most often caused by an improperly sharpened bit or too much pressure being applied while drilling.
Posted 26 July 2010 - 10:21 PM
That is a very small diameter for through drilling. Depending on the grain, it is bound to wander some. RG is correct, I would just add, cut small amounts then clear the swarf, don't try to cut too much at once. Also, cut half way, then drill from the other end (pin location method).
Posted 27 July 2010 - 08:52 AM
If you're drilling wood, a long, thin bit will drift. Wood has grain, and the thin bit will follow the softer wood.
Try starting your hole with a short bit of the same diameter, go slow, with light pressure,and clean your bit often.
That's one of the main reasons I went to bicycle spokes as hinge pins for my swimbaits (thank you CaptSully).
It is much easier to get a straight hole with a larger bit.
And uneven sharpening only exagerates the tendency to drift.
Posted 27 July 2010 - 10:45 AM
Good point about the drill bit following the softer wood.
Posted 27 July 2010 - 06:02 PM
I don't even have such long drillbits , as they are hard to find over here , .......for drilling long holes 1,5mm dia through a lure blank lengthwise centered(to accomodate wire shafts) , I'd first start out with an ordinary short bit , and drill as deep as possible , ......at possibly high rotation speed but low feed and pressure , often cleaning off the chips not to bind the drill , ....just like Mark has already stated .
To substitute a long drill bit I'd utilize a length of 1,5mm dia. stainless steel wire that has it's cutting end beat a little flat and two cutting edges ground onto it(similar to the cutting edge of a real bit).
It has to be inserted into the initial hole PRIOR to switching on the drill or at least run at lowest possible speed ,..... without the guiding function of the pilot hole it might otherwise bend to finally snap off under centrifugal force and hurt you .
Now I drill slowly about halfway through the blank , again at low feed and high speed , ALWAYS switching the drill off before exiting the wire piece from the hole !
After I repeat process from the opposite end of the blank , so both bores would meet in center , .......this way I achieve the exits absolutely centered on either end of the blank and decrease the possible degree of wandering of the bit to about half(calculated on entire blank length) .
Most likely it takes some playing around with the wire drill bit substitute from either end , having it chucked at a length of 3/4 of blank length or even little more(but MUST NOT exit on other end) to finally meet the bore coming from the opposite end , but on 9 out of 10 blanks it works out for me(thanks to my eyeballing abilities) , though it might become neccessary sometimes to grind a point to the wire shaft to easily pass through the transition between the two bores .
If for once it should not work out for the bores to meet , I'd just extend the diameter a bit on one or both sides ,..... sooner or later they'd meet to be able to insert the wire shaft , ......at final assembly in this case I'd just have to fill in some more epoxy glue to fill up the bigger hole .
I most likely do this on lather-turned "Globe" style baits , the blanks I turn down from lighter woods , that do not have a pronounced grain , f. e. abachewood , ......those blanks are up to 6" in length to be drilled through .
Maybe , this helps a bit , .........good luck , .......greetz , diemai
Posted 27 July 2010 - 07:28 PM
I am guessing you dont need them that long? cut them off to the lengths you need with a abrasive wheel.
a trick to using bits that long is drill guides I even use them on my cnc's when we have long tiny holes and have to reach very far down. a drill guide can be something simple or complicated, basically is a predrilled hole that is close to the dia just a tad larger. you can make your own drill bushings.
on wood just peck drill as your flutes will build up fast when using non wood drill bits and seize and snap your drill.
with a small dia hole always center drill your part first.
Posted 28 July 2010 - 02:34 AM
Thanks everyone for great ideas! I really appreciate your help.
Besides the #55 .0520" bit I got a #48 .0760" and a 3/32" which works out to .0938". All are 6" long. The two larger diameter bits give me some flexibility if slop becomes a problem.
The drill bits arrived today and yes Delw, I'ill cut them to fit the length I need. They won't be longer than 4" and maybe I can get by with 3" or maybe on some bugs down to 2 1/2" long. Hopefully using the shortest bit length possible will reduce slop and off center walk.
Possibly I could start drilling with a jobbers length bit, and when it reaches maximum depth, raise the drill press, un-chuck the jobber bit and chuck the cut off aircraft bit and continue drilling. That was my fallback operation but since the bug will be clamped in a jig, I did not want to chance getting off center by un-chucking and then re-chucking. Plus I was hoping to avoid that operation since my production run is usually in the 100-500 range.
Thanks again. Now I'm off to making a hold down jig.