Best drill bits for forbon

[Zhangliqun]

Starting to fabricate my own Tele bridge parts for some no-baseplate designs, plus I sometimes need to widen the holes on existing flatwork to accommodate larger diameter mag. Regular bits (3/16" and larger) seem to just squish the forbon out to the side and get bogged down instead of cutting through it. Brad point bits work a bit better but maybe something with a longer point would work? Your thoughts, gentlemen...

[DrStrangelove]

For soft woods, my carpenter friend recommends a brad point bit.
It looks like a bit with four flutes extended so that the hole's edge cuts first.

I'm guessing you would want to feed the bit slowly in a press since it looks like it will grab hard.

Wikipedia says it is also called a "lip and spur" bit or a dowling bit.
http://en.wikipedia.org/wiki/Drill_bit


HTH

-drh

[Joe Gwinn]

Starting to fabricate my own Tele bridge parts for some no-baseplate designs, plus I sometimes need to widen the holes on existing flatwork to accommodate larger diameter mag. Regular bits (3/16" and larger) seem to just squish the forbon out to the side and get bogged down instead of cutting through it. Brad point bits work a bit better but maybe something with a longer point would work? Your thoughts, gentlemen...

Use a nice sharp brad-point bit turning as fast as the drill can, and feed slowly.

For wood and fiber, faster is better, with feed rate adjusted to keep the drill point from annealing itself (thus becoming soft and dull) or the workpiece from burning.

Drill presses intended for wood will have much higher max rpm than those intended for metal, and so some drill presses will not be able to turn fast enough to make clean holes in wood or fiber.

[dpm]

The Italian CMT brad point bits are fantastic. Get the best bits you can find, they're more than worth it - quality tools are the first step to quality work. Everything Joe said above is absolutely correct. You may want to experiment with different speeds and feed rate on a piece of scrap to get the feel of it.

For enlarging holes you might want to try a semi-fluted tapered reamer, though they are pricey.

[Zhangliqun]

I have some brad point bits and as I said, they do work better. Apparently this mini-drill press just needs to turn a lot faster. Guess I'll just open the top and move that belt.

[jonson]

Hi guys. Pokin me nose in again but as I been a boreing things(including people) for a long time I thought I'd chuck in my pennyworth.
Quickly took some pics of what can be done to a drill and this is only a small part of what is achievable. Shop bought brad point, lip and spur point dowel drills whatever you care to name them are great for carpenters but always need to my mind a bit more refinement for drilling other materials. The drill bit on the left in the first pic is a shop bought and will probably snatch a bit when going through the other side which will not happen with the other four.
It takes a bit of practice but none of those bits started off life as brad points and I do them on the right hand edge of the grinder. Start grinding a point then roll the bit forward and to the right and with not to much practice you can start putting real sharp points and wings on these boys. The game is not to get to long a point but keep it just ahead of the wings. If the back of the wings are rolled well off then snatching is elliminated but the cut is super clean. If you play about till you get the grind right what will happen is as you drill through the drill will suddenly stop cutting so when you back the drill out you will find a perfectly cut circle of material stuck on the drill point and that spinning with the drill has stopped the cutting. Your base board underneath should just have a centre dot and a scribed circle in there. The only time I use a drill like this to enlargen an existing hole is if I run it on a false centre other wise it will not run true as can be seen from the drill on the right where the tip has overheated. In the second pic there is a standard drill on the left and then one I have ground with a much steeper angle and this will cause the drill to follow the existing hole and centre itself plus if used for plastics because the drill point takes longer to pass through it will also elliminate snatch. It will still cause a fluffy top face so is much more suitable for hard materials. The last pair on the right are forstner pattern bits and will cut clean holes in forbon and some thin plastics but can bind and overheat on stuff like perspex acrylic sheet. I agree with Dpm about using a reamer to open the holes up but would go for an onsize reamer with the tip ground back a little or you will end up with tapered holes and your fit could be a bit loose.
If you are stuck for an onsize drill and want the holes a bit bigger then grind one cutting edge of the drill a bit longer than the other to throw the point off centre and the drill will wobble slightly and do the trick but needs a bit of experimentation to get it right size. All of this is capable with a small stone mounted in a drill as well as a bench grinder but keep the wheel dressed with a piece of carborundum stone or a wheel dresser(hedgehog.) Probably now bored the shit out of you experianced guys but this maybe some help for any newbies.

[NightWinder]

Jonson, great thread. Many here appreciate a thorough explaination and another point of view, its not really a debate topic, more educational. ie: less time debating, more time learning!! Many probably prefer that method ( learning, not debating)....but while we are here, its sure to come.
Considering the cost on the onsrud stuff, I may appt for this myself and compare. I'll still grab a few from them....considering they are on their make business wise. Real thorough....You don't bullshit.....

[jonson]

Thanks Nightwinder just hope to do my bit for all the info I get back from you guys. By the way your bits are in the air.

[David Schwab]

Shop bought brad point, lip and spur point dowel drills whatever you care to name them

The two on the right in the right most photo are known as Forstner bits. These are some of the best bits for drilling clean holes. I'm not sure of the smallest size available, but I've never seen them smaller than 1/4". If you need smaller than that, brad points are the way to go.

[Spence]

He wants to widen the existing holes. You can use a step drill for that.

[David Schwab]

He wants to widen the existing holes. You can use a step drill for that.

Good idea!

[Zhangliqun]

Looks like step bits are the way to go, thanks Spence!

[NightWinder]

I;ll tell you what, I just got some hss bit from a buddy. Man, what a difference higher quality makes.....When this one gos, I'll have to get more, but its like night and day....Holy shit I can't believe it. I'm drilling through steel,N/s, forbon, and wood.....like butter. I only have one,LOL so I come back and let you know how long it lasted. Don't forget your saftyglasses!!