Flat drill bits vs Forstner for neat holes?

[Tim Brennan]

Yesterday I took a 16mm flat bit and made a hole in some plywood. The result wasn't as neat as I would like. There was a lot of splintering and big chunks kept jamming the spinning bit.

The bit is probably too blunt but instead of sharpening it is it necessary for me to get some forstner bits? Are flat bits really for situations when neatness is not important?

 

[Stone Message]

Yesterday I took a 16mm flat bit and made a hole in some plywood. The result wasn't as neat as I would like. There was a lot of splintering and big chunks kept jamming the spinning bit.

The bit is probably too blunt but instead of sharpening it is it necessary for me to get some forstner bits? Are flat bits really for situations when neatness is not important?

You should only use flat bits where the quality of the finished hole is not an issue. You can neaten up the result by going to a huge amount of effort to clamp sacrificial pieces front and back.

Keep the flat bits for the crap stuff, where you might hit a nail and buy some good quality Forstners. If you are a Festool junkie then the Zobos cannot be beaten but there are a lot of very high quality competitors out there. Once you buy them, look after them and do not make the two fundamental silly mistakes that I made with my Zobos...

I had been experimenting with precision hole production methods and dropped a Zobo on the concrete floor which it hit tip first. I bought a new one and less than a week later hit the remains of a broken screw in what I had thought was a virgin piece of wood. I had one of the Zobos sharpened professionally but it is not quite the same.

Peter

 

[Llap Goch]

Another vote for the Zobo bits. They are fantastic but then they should be as they come at a price but for beautifully clean and accurate holes and almost translucent shavings they are a class act.

I took advantage of the recent Axminster price reduction on the set of Fisch auger bits and they are superb but for general 'rough' hole cutting I use the Bosch flat bits which cut in a more controlled manner than a standard flat bit.

They are aggressive cutters and the screw tip pulls them through the wood but if you want a (relatively) clean exit hole you must use a sacrificial backing. For 'out of sight' (cables or pipes through beams etc) boring they are fast, accurate and cheap to replace should you find a nail or a screw.

Years ago I bought a Rolson Forstner bit set for a few beer tokens expecting them to do the job and then be binned. But those fiendish Chinese machinists did a rather good job and they are still in use and cutting well.

 

[Roseland]

+1 for the Zobo bits.

I like the fact that the centre can be swapped (short point, long point or long pilot drill) or removed (once the hole is started) for a flat bottomed blind hole.

Andrew

 

[junk731]

Yesterday I took a 16mm flat bit and made a hole in some plywood. The result wasn't as neat as I would like. There was a lot of splintering and big chunks kept jamming the spinning bit.

The bit is probably too blunt but instead of sharpening it is it necessary for me to get some forstner bits? Are flat bits really for situations when neatness is not important?

I have a few flat bits from years gone by that gave a respectable neat hole. The main difference was they had a small edge cutting spur that made for a clean cut. If your looking to get a set of forstners now the time. Whether or not you get the Zobo bits or a lower end bit is dependent on the excepted amount of usage and materials you plan to work with.

John

 

[Holmz]

Yesterday I took a 16mm flat bit and made a hole in some plywood. The result wasn't as neat as I would like.
...

There is nothing that beats testing out the various options personally.