Using a Forstner Bit

[glenpen]

I am trying to make a hole 40mm Dia. by 7cm long. When I reach about 4 to 5 cm long the wood and bit gets hot of even on a low speed of 500 rev.
It struggles to carry on drilling, I keep removing the bit to clear the waste wood but within seconds it struggles again. I am wondering if I need a better Forstner Bit. Ideas please
Glen

 

[Bigblackdog]

what bit are you currently using? It it a through hole or a blind hole?

 

[glenpen]

what bit are you currently using? It it a through hole or a blind hole?

I need to hold a bottle in it which is 7cm long so I am using a blind hole

 

[Bigblackdog]

A decent forstner should do the job.

 

[rayf6604]

A turner once y of showed me when using a forstner bit, to have one of those small garden hand sprayers handy and keep spraying water onto the bit when you withdraw it to keep it cool.

 

[Grump]

Keep it sharp and take the screw off the end when you have a pilot.
Don't worry about speed these things will rip into it when sharp.

 

[glenpen]

A decent forstner should do the job.

Any recommendation of a decent forstner

 

[Woody]

As brian said sharp take a small diamond stone to it

 

[Doug]

If you are drilling into end grain I prefer a sawtooth bit such as these Planet Forstner Bits in Planet Plus

 

[Walter]

Heat is caused by friction. Friction is caused by too much speed or pressure or a blunt bit.

Solution = sharp tools, correct speed and pressure.

I also agree with Doug re: saw tooth bits.

Or if you can justify the cost:

FAMAG 1622.040 40mm Bormax Forstner

or these:

Colt Sawtooth Forstner Bit - John Davis Woodturning Centre

or even:

FAMAG 1663.040 Bormax3 Carbide Tipped Forstner Bit 40mm

 

[rayf6604]

Turner Retreat have a selection of saw tooth forstners on clearence but you may have to phone them. They are in imperial sizes and are only about £3 each. They bring them out every time they have one of their open weekends. I have a few of them and they have been fine so far but I don't use them very much. If you only have the odd job you need them for they might be worth a call

 

[Penpal]

So far using Forstner bits this a style classification time marches on and real success depends on quality bits the advice given by Walter has governed my success with them, as Ray says also every trade show I have seen they trot out some interesting looking bits some of these I have bought and they tend to skid rather than cut, hope you find your best and share that with us.

Peter.

 

[wm460]

I bought a set of forstners, the best chinese workmanship Very good for balsa wood, OK on pine, Mulga forget it.

 

[monophoto]

1. Sharp bits are critical. Forstner bits can be 'tuned up' using a diamond hone in mere seconds.
2. Lube is helpful. Brendan Stemp is a commercial pepper mill and flute maker in Australia whose work involves drilling lots of deep holes. He favors using linseed oil as a lubricant. Obviously, this is not a good idea if you intend eventually to glue something into hole.

 

[Penpal]

Thanks for the hint Mono et Manu.

Peter.

 

[glenpen]

So far using Forstner bits this a style classification time marches on and real success depends on quality bits the advice given by Walter has governed my success with them, as Ray says also every trade show I have seen they trot out some interesting looking bits some of these I have bought and they tend to skid rather than cut, hope you find your best and share that with us.

Peter.

Finally succeeded by doing what Doug said, I bought a Planet Sawtooth Forstner Bit and as Monophoto said I used Linseed oil.

 

[Doug]

Glad to hear you've got it sorted Glen

 

[Penpal]

Thanks for the resulting success mate.

Peter.

 

[Phil Dart]

Don't blame the tool, blame the method. I put it to you that your new bit succeeded because it is brand new and therefore factory sharp. Use it a few times, sharpen it a few times, then try the same job again to see if it still does the job so easily.

40mm by 7cm is a big ask. You are much better off reaching full depth with a narrower bit in the first place, say 25mm, then repeating with the 40mm bit. By removing the core with a narrower bit to start with, you are lessening the work required of the larger bit by a vast amount, and your original one would probably have done the job.