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Building Tips and technical articles. => Building techniques => Topic started by: david beazley on July 16, 2012, 03:31:00 PM
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Well, at least I hope not! #^ I am looking for a way to bore or core clean holes in balsa. I use the tried and true sharpened K&S brass tube, but I am looking for something I can use in a drill press. I have seen in the past something called Gaskins Softbore tools, out of England but a google search turned up nothing on this side of the pond. What do people use when they want to make a lot of clean holes with no breakout on the back side of balsa? Short of soldering tube to a home made mandrel what options are out there? Has laser cutting and ARFs killed the market?
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You can use a new endmill. I've do that and it works well, but it has to be new and sharp.
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Might look for Forestner Bits (spelling)?? They have several different sizes..
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Might look for Forestner Bits (spelling)?? They have several different sizes..
yep - Forstner bits are the way to go. drill from one side until the point shows through -then flip it over and bore from other side - that way it wont break out
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How clean & how big?
Forstner bits work well, but to get them smaller than 5/8" or so you need to go to Fleabay.
Brad-point bits work OK, but they tend to like harder wood -- contest balsa may not be the best for 'em.
I've had good but mixed success with making "sorta Forstners" out of regular twist drill bits -- basically I grind them hollow, so that the edge of the bit is slicing through the balsa. You need good bearings on your drill press, though -- without the Forstner's centering brad they really want to wander. And they don't self-clean the hole at all -- you need to peck, then blow them off, then peck, then blow, maybe going 1/32 of an inch each time.
None of these make a hole that's knife-edge straight on the backside, but all of them do way better than twist drills. The Forstner bits do best, and the sorta-Forstners come in second when they're sharp and I'm not impatient.
Here's a picture showing what I mean, with a 3/16" sorta-Forstner and the back sides of two holes that I drilled with it. The one that's a bit torn up is the one that I did first, and re-learned the meaning of "slow enough" -- I got impatient on the last peck and went too far. The bit could use sharpening, too -- from all accounts balsa is incredibly abrasive for being as soft as it is, and I certainly know that I need to sharpen my tools a lot when I'm not just using disposable blades.
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Thanks for the replies. I have some Forstener bits and some brad point bits(admittedly old and dull) and they work OK when I flip the work over like Bootlegger suggests. But they both are designed for harder woods. Ideally I would like to find some steel tubing with similar wall thickness to the K&S brass tubing. Something that will hold an edge. I'm looking to make holes from around 5/8"-1" range.
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Thanks for the replies. I have some Forstener bits and some brad point bits(admittedly old and dull) and they work OK when I flip the work over like Bootlegger suggests. But they both are designed for harder woods. Ideally I would like to find some steel tubing with similar wall thickness to the K&S brass tubing. Something that will hold an edge. I'm looking to make holes from around 5/8"-1" range.
if thats what you want to do - get the dremel diamond ege cutters - they do just what you are looking for and go right down in size
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Thanks for the replies. I have some Forstener bits and some brad point bits(admittedly old and dull) and they work OK when I flip the work over like Bootlegger suggests. But they both are designed for harder woods. Ideally I would like to find some steel tubing with similar wall thickness to the K&S brass tubing. Something that will hold an edge. I'm looking to make holes from around 5/8"-1" range.
Hi David,
Try some old steel golf club shafts. They will give you holes in the 5/8" and a touch bigger. Easy to sharpen and will hold an edge for quite a while.
BIG Bear
RNMM/AMM
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Try applying masking tape to the backside of the mterial in which you are drilling this has worked for me in the past.
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I made these holes with common drill bits for the 1/2" and a hole saw for the 3/4".
I flip it over as mentioned above and place a block of wood under the piece.
I roll sandpaper and finish sanding.
The 1.125" holes, in the last photo, were drilled with a hole saw after the fuselage was framed. Just don't push hard.
Charles
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Thanks for the replies. I have some Forstener bits and some brad point bits(admittedly old and dull) and they work OK when I flip the work over like Bootlegger suggests. But they both are designed for harder woods. Ideally I would like to find some steel tubing with similar wall thickness to the K&S brass tubing. Something that will hold an edge. I'm looking to make holes from around 5/8"-1" range.
If you are going that big with the holes, go get new Forstner bits. Yes they are expensive. I myself being a cheap skate, still use brass tubing and keep sharpening the edges. H^^
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I have seen special so called "knife edged" hole cutters (they are expensive). They have a serrated edge somewhat like a steak knife. You could make your own with a thin walled steel tube and a chainsaw sharpening Dremel bit. Just work you way around the cutting edge grinding little scallops (at about 45 degree angle) in the tubing.
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Try some old steel golf club shafts. They will give you holes in the 5/8" and a touch bigger. Easy to sharpen and will hold an edge for quite a while.
I love that idea! It will give me a great deal of satisfaction cutting up my old clubs! Now, if I can just straighten them out... ;D
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I love that idea! It will give me a great deal of satisfaction cutting up my old clubs! Now, if I can just straighten them out... ;D
To get a really fancy tool, leave the grip on the shaft to help you turn it. A small slot ground into the side of the shaft will allow a piece of music wire to punch out the discs that may build up in the shaft.
Bill