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Drill Bit For Balsa
20 replies to this topic
Posted 10 October 2010 - 10:46 AM
What is the best type of drill bit for drilling holes in balsa?
Posted 10 October 2010 - 12:32 PM
The usual advice is to use Forstner bits.
My guess is that you are having tearing problems. I get the same thing, using light woods. Their is a simple solution, seal your bait before drilling. This binds the fibres together and reduces the tearing. Even applying CA glue locally around your hole locations prior to drilling, dramatically improves the drilling.
Use sharp drill bits. Start off small and increase diameter in stages. This is the way I do it and it works.
PS, I use regular drills, not forstners.
Edited by Vodkaman, 10 October 2010 - 12:34 PM.
Posted 10 October 2010 - 12:35 PM
Ben, I had quite a bit of tear-out using slow speed drill bits on balsa so went to a 15k rpm Dremel with a cylindrical wood shaping bit to drill ballast holes. Since I use a Dremel for most crankbait making tasks, it was a 'natural' for me.
Posted 10 October 2010 - 02:31 PM
I haven't tried drilling any holes in the balsa yet as I was pretty sure it could lead to tear out if not done properly. I've already sealed the balsa, although with a bit of an unconventional technique. I'm out of D2T at the moment, and don't have any propianate pellets to dissolve, so this called for some creative thinking. Had a couple old cranks with cracks in them so I decided to see if they would dissolve in acetone. After sanding off the paint I cut them up into small pieces and placed them into a jar of acetone. Long story short it worked rather well. After numerous dips it formed a hard, slick coating on the balsa. I figured this might help with any tear out problems, but wanted to check with you guys here at TU before I destroyed my lure blank. (there will be plenty of opportunity for that later) I've got some diamond burrs for my Dremel so I'll probably try that first.
Posted 10 October 2010 - 03:10 PM
No matter how bad the tear out, it is always repairable, one could even argue a case for 'desirable' in the case of ballast holes. These holes have to be filled anyway, any tear gives more keying area for the filler. I have read that some builders countersink the holes, to increase this keying area for the filler.
Posted 10 October 2010 - 05:50 PM
If I drill crosswise holes trough wooden blanks to insert rattle casings , I've found , that the Forstner bits would still cause the woodgrain to tear away at the exit of the hole .
I now drill a kinda small pilot hole all the way through , so that the center tip of the Forstner bit can center itself on either side of this small initial bore , the entries of the holes usually won't tear , .....if working accurately , both bores would meet centered , ....I'm talking 'bout rattle casings dia. 5mm and 8mm , pilot hole dia. 2mm .
greetz , diemai
Posted 10 October 2010 - 09:33 PM
I use Brad Point drill bits and dont have any issue with them. Keep them sharp and use higher RPM. They leave a little tear but nothing very noticable. The main issue I have with them is that the wood is not ejected very well sometimes and you need to stop and remove it yourself. I think that is cause my drill cant rotate fast enough. In Aus they come down to 2mm and go up too dont know how big.
Posted 10 October 2010 - 11:16 PM
I use Crown point bits, similar to brad points but much sharper. Spin 'em as quickly as possible, makes a clean, burr free hole. Actually creates a small disc where it exits if properly supported. They're available from just about any woodworking supply....but a mite pricey for the good ones. I've also used the little spot weld removal drills for shallow holes, leave a really clean edge and have a nifty little spring loaded center so it doesn't wander on irregular shaped surfaces.
Posted 11 October 2010 - 03:24 AM
Thanks for all the options everyone. I knew if anyone would know anything about drilling soft woods it would be the good folks here at TU.
thanks to one and all,
Posted 11 October 2010 - 11:48 AM
Ben, if you go with a Dremel wood carving bit, you need to wiggle it a little as you drill or pause and shake out the dust. I haven't had any problems with balsa but if you use a high speed Dremel carving bit on hardwood, it can heat up the wood and cause it to expand, grabbing your bit. You're sitting there with the blank suddenly turning 15,000 rpm - no good outcome with that! - so it requires some finesse. I don't have a drill press so had to learn finesse at the School of Hard Knocks.
Posted 11 October 2010 - 12:39 PM
BobP, I really like the carving bit solution. It would definately solve the tearing problem. I am thinking that starting the hole with the carving bit, then switching to the standard bit, might be the ideal solution, saving unnecessary wear on the carving bit and eliminating the tearing.
Posted 12 October 2010 - 10:51 PM
Dave, I've used both the carving bits with "porcupine" tungsten nibs and the high speed steel Dremel carving bits. The porcupine bits will eventually overheat and lose the nibs on top if you use them as a drill bit and they are expensive, typically $15 ea. The cheaper Dremel cylinder bits are cut so the top of the bit has grooves which will also do the job, just not as aggressively, and it takes some care to hold them (by hand) and get them started without walking - but they last indefinitely. Dremel also sells oblong bits that have deeper grooves on their tops if you don't mind a ballast hole with a domed bottom. I use the tungsten bits for eye sockets and the Dremel bits for ballast holes. I agree the ideal might be to start a ballast hole with the Dremel and finish it with a regular drill bit. Not being a pro woodworker, I don't know the best drill bit type to prevent tear-out on soft woods and I don't own a drill press, so I use a Dremel for everything. Drilling 2" baits with a hand held electric drill seems pretty awkward to me. The other problem with carving bits is they come in a narrow range of diameters, so you can't always find one that is the right size for a particular integrated ballast/belly hanger. I mostly use epoxy putty to glue in ballasts so if the hole is oversize, that isn't really a problem - but that method is inherently less exact than a perfect diameter hole drilled by a drill press.
Posted 13 October 2010 - 01:02 AM
Bob, I tried the combination method and it worked well. I do have a drill press, but I prefer to use a low powered hand held for this job, better visibility. Obviously using the dremel when ever possible, for stability and control. Could do with something between the dremel and the screw driver drill.
The ballast holes that I am working on at the moment are quite small diameter (4.2mm dia). Completing the first 5mm of the hole with the 1/8" dremel router bit was not a chore. Also the 1/8th bit is the right size for barrel twisted eyes. I like the method and it solves all the tearing problems that I was having.
Posted 13 October 2010 - 04:40 AM
Do you get your cylinder bits online or do you have a local source? I've looked online and have only come up with a couple places that had them and then they only had one or two sizes. No doubt I'm not looking in the right place or putting the right terminology into my browser.
Posted 13 October 2010 - 06:26 AM
I just use a sharpened hollow steel punch to start the hole with. They come in all the standard eye sizes you need. Just twist the hole punch and it cuts a perfect circle to prevent tear out. They come in hex end type that you can plug into a battery drill too.
Waste removal after is as easy as lifting the "plug" out along the grain of wood with a light pry or a Dremel.
Posted 13 October 2010 - 01:13 PM
I couldn't get the link to work Dave. I had looked at Dremel, but apparently not in the right place. Will try again. Thanks.
That's a pretty clever way of doing the eyes LaPala. Had never even thought of doing it like that. I've sharpened the end of several different sizes of stainless tubing to use as hole punches in various soft items and think they would do that job nicely. Thanks for the enlightenment.
Posted 13 October 2010 - 01:18 PM
Just Google "dremel router bit", should find lots out there.
I agree, great tool. The kind of thing granddad used to have in his volumous tool box. Yet another tool I will be looking for. Maybe better to make a set.
Posted 13 October 2010 - 02:03 PM
Must be something wrong with Dremel's site. Tried going direct to their site and could never get the page to load. Will try again later.
Edited by RayburnGuy, 13 October 2010 - 02:03 PM.
Posted 13 October 2010 - 10:43 PM
Ben, I buy Dremel bits at my local Home Depot. For tungsten porcupine bits, I order from texaswoodcarvers.com (also a good source for D2T). You're right, the cylinder carving bits for Dremels only come in a few diameters because they aren't really meant for this application.