Gun Drills

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Gun Drills

Post  Bob Salter on Thu Jun 09, 2011 4:28 pm

Well I finally bit the bullet and ordered my first gun drill. I thought I would order one for concert pitch but at the last minute I decided to get one for narrow bore. I can drill CP without much difficulty, but getting narrow bore to drill well without twisting has proved near impossible. I always seem to get a twist in the last few cm of the bore and it ruins it for the reamers. All you other gun drill users, what type of fitting do I need for attaching the drill to the air supply? I cant tell from the order details although it does mention a 1/4 bsp thread.

Bob
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Re: Gun Drills

Post  Bob Salter on Fri Jul 01, 2011 2:44 pm

It finally arrived. To my surprise it appears to be a parrot nose d bit drill with a hole up the middle. I was expecting something a little more, well, hi-tec. I went up and got the fitting to hook it to the compressor today and am going to have a gentle test run tomorrow. I am hopeful that I can FINALLY make these narrow bore d and flat UP chanters with a completely straight bore. We shall see.

Bob
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Re: Gun Drills

Post  Stu on Sat Jul 02, 2011 10:59 am

They are only a D bit drill with a coolant hole. But MY how they cut. I have a dozen different sizes, wonderful things if only for the time saved boring, one minute and I'm through a two foot chunk of sugar maple with a perfectly straight and polished bore!
Just don't put too much pressure on them (especially the small diametre ones) or you will change the course of the bit and have a wonky hole.
Also, wear a glove unless you like wood dust embedding itself in your hand as it exits the bore at a hundred miles an hour. Well, it does not usually pierce the skin, but it does feel like you just stuck your hand in a sand blaster

Stu
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Re: Gun Drills

Post  Stu on Sat Jul 02, 2011 11:01 am

Oh yeah, I usually run my compressor at 90psi for this as I've had some trouble with binding at less than 60psi. Not sure why, lots of guesses from the bit heating up and binding to the dust not clearing the bit and binding, but not really sure why.
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Re: Gun Drills

Post  Bob Salter on Sat Jul 02, 2011 2:53 pm

Thanks for that. I ll try it tomorrow.

Bob
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Re: Gun Drills

Post  Bob Salter on Mon Jul 04, 2011 12:09 pm

Well I would have to say, WHEN CAN I GET MORE OF THESE? Very Happy The bore of a flat chanter would take me up to 45 mins to do and more often than not was curved and also involved burnt fingers and HUGE amounts of swearing. I prepared the blank, stuck it in the lathe and 72 SECONDS later had a perfectly straight bore which came out about a mm off centre at the far end. A little bit of a change. Wow.

Bob

ps Time for a wood order methinks Smile
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Re: Gun Drills

Post  Stu on Mon Jul 04, 2011 5:34 pm

You gotta love the things. I hated d-bit boring and it reeked havoc on my poor old back, bore one day, flat on back the next. Gundrills are boring tools of the gods!
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Re: Gun Drills

Post  Yuri on Thu Aug 11, 2011 8:03 pm

Hi guys. I've been off the site for a while, won't bore you with the details of just why. By the way, thanks, Seth and Bob for getting me back here.
Anyway, as I remarked on the yahoo sister site, I am genuienly puzzled by the D-bit thingy. I mean, 45 minutes? What's wrong? I never used a gundrill in my life, so cannot comment on that one, but drilled probably thousands of pilot holes for all sort of woodwinds by now, using nothing more sophisticated than a couple of home-made D-bits. (one shorter, about 250mm, suffices for a lot of needs, and one longer, maybe some 400, probably less, that follows up the shorter bore if it needs to be extended.)Well, I have to say a 300mm bore takes me about 5 minutes. True, not quite 72 seconds, but fairly close, and certainly NOT 45 minutes. I just genuinely cannot understand what's going wrong with others' D-bits. Very occasionally I have a trouble with some curving, but just about in all cases it's either some timber that I never used before (usually the softer kinds), or I'm getting impatient, and of course making it a much longer process by doing just that. I mean not clearing the shaving (or wooddust, whatever you prefer to call it) often enough, so it builds up, and pushes the bit off to one side.
In case anyone wishes to try out a D-bit, homemade, here's a tip: grind down the tip to EXACTLY half of its diameter, otherwise it WILL cut a curve. If the grind is not quite reaching the middle, it will cut "upwards", if it overshot, it will be "downwards", when you hold the flat surface of the bit facing up. Also, another thing I do is to relieve most of the shaft, very low-tech, just running it over a sander, twirling it all the while, so a drill, say 4mm, is only 4 mm in the first inch or so, and perhaps 3.5 mm for the rest, on average. The purpose of course is to have as little friction as possible.
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Re: Gun Drills

Post  Stu on Thu Aug 11, 2011 11:15 pm

Fraid I'm one of those who has never managed to get a dbit to cut a bore in anything less than 5 minutes. This is why I love my gun drills.
Never had a problem with the dbits going off centre, just cutting extremely slowly and labouriously.

Stu
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