Thread: Deep boring with a forstner bit

G'day jacko
You would be better off with a saw tooth bit for deeper holes. You still get a nice clean hole but the saw teeth clear the waste quicker and keep the bit cooler. They can still over heat on deep holes so you have to take it steady. Don't go too deep before clearing the rubbish out and make sure the bit is sharp. The saw tooth bits look just like a forstner but with teeth instead of a full ring around the outer edge. Hope this helps. You could also try a spde bit they aren't as clean or as accurate. Also, don't spin too fast.
happy drilling
Shaun

When I use Forstner bits for normal drilling, as soon as they warm up, wipe some candle wax on the outside of the bit. This cuts down on friction and stops the wood and bit getting too hot. For what you're doing, you'll probably have to do it several times for each hole.

cheers,
Alex

try an auger wood bit it will be clean and will remove waste a lot faster these bits work best at low low speeds years ago thats all carpenters had to bore holes with
good luck

kenny

Gooday.

Have to agree with Kenny on this one.

Make sure that the auger you use is suitable for power drilling. If it has the screw thread end, grind it to a point.

It also helps if you can do it on a drill press, but there aren't many around that can drill more than 75 mm deep.



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Ian () Robertson
"We do good turns every day"

Might find the best and most acurate of all is a shell auger. However it might not be the easiest to find. They look a bit like a woodturning gouge and cut quickly, cleanly and acurately through end grain.

Unfortunately I have no idea where you might be able to get one.

With both the forstner and sawtooth bits it is imperative that they are really sharp. You will probably find that the cheaper ones you buy in a set from Carba Tec and others will not stand up to too much deep end grain boring. However the Stubi and other top shelf ones will probably make reasonably short work of the job.

Just my 2 bobs worth.

Cheers - Neil

As Neil says the shell auger is the way to go, but another way is to start the hole with the size forstner you need , to a depth of about 10mm. Then with the largest twist drill you have , drill almost to the depth you need. Then bore with forstner bit . Also if you have compressed air in your shop , use this while cutting , to remove waste and cool the cutter. Forstner bits are great for cutting across the grain but into end grain , they are not too efficient.

Jacko
I've made a few vases about 8 to 10 inches deep and 3" at the top. I drill to the bottom with a 3/8 inch bit and then hollow the vase with a ring tool attached to the end of a 1/2 inch bar. I believe I could go deeper if I put it on a 3/4 inch bar or made the opening bigger so I could get the tool rest partially inside. John L

Thanks folks, I appreciate the input.

Jacko