Large Forstner bits (55mm plus)

[DirkM]

Hi there,
I am looking for a quality forstner bit with a 70mm diameter. I know Fisch do them, but i cannot find any company in the uk that supplies that size. Anyone out there know where I could get this, without going into Europe.
obviously I could use a smaller bit and then hollow out the rest, but I need to go about 250mm deep.
Thanks, Dirk

 

[marcros]

What are you making?

70m plus is a large volume of wood to remove. It isn't something that I have needed to do, but the 25mm one that I have used to drill to a similar depth produces a lot of shavings. Personally I think that I would probably look at some form of hollowing/boring setup.

 

[LJM]

Try Toolite in Mitcheldean. I know they stock such things and can do mail i order. Don’t be put off by the rubbish website or apparent chaos in the shop; they’re knowledgeable and helpful, and are happy to price match.

 

[Phil Pascoe]

You're going to need a hefty lathe even for a top class forstner that size.

 

[Cabinetman]

Wine bottle storage? I personally haven’t come across a Forstner bit that size, I think you will struggle to get one drills that deep, unless you have some form of extension but it will wander I think. Ian

 

[Lazurus]

Hollowing rig?

 

[bp122]

Why not use a fly cutter and then use a router to clear the middle?

 

[LJM]

The ones stocked by Toolite are deep. I was looking at them myself when considering how I might tackle a project of mine.

 

[Spectric]

Hi

I do not know what it is you are doing, but I had to cut some flat bottomed recesses that were 76mm diameter for a job. What I did was to make a template from ply using a fly cutter in my pillar drill, and attaching this to the workpiece. Now using a 1/4 bosch router with plunge base and guide bush fitted with 20mm Wealdon cutter just set a depth and remove the material, reset depth and remove more material until you reach your final depth. Making several shallow cuts is easier and more controllable than trying to plough out deep cuts.

This hole cutter is good because you can set it up to an exact size to allow for the router guide bush. Armeg AHC40-200 Adjustable Hole Cutter With 40mm - 203mm cutting diameter - Discount Electrical

This is a cheaper version

Erbauer Adjustable Holesaw with Cowl 29cm 9 Piece Set

These cutters are good for a flat bottomed hole Bottom Trim

 

[Richard_C]

I got a set of large forstners from Amazon, and later a one off 65mm. Not exactly high quality but work OK. Lots on there, I think they are called 'sourcing map' but who knows what that is. I took care to get hex shank ones.

I have used the 65 a few times on the lathe, on elm and beech spindles. The feed speed suggested in the blurb is a joke, I think its in metres per second. I drilled a pilot (4mm or similar) to get it started, pilot was a bit deeper than the sides of the bit and I reckoned once the bit was fully in it would look after itself which it did. Slowest speed, mines belt drive and 360 rpm, Lots of backing out and I did some other things at intervals while it cooled.

65 was a bit bigger than the OD of my chuck, so could go in the full travel of the tailstock without bother.

I'm sure a boring set up would be better but for occasional jobs a forstner can work - with patience.

Why 65? A standard 330ml beer or coke can is a shade under 65. A 3 inch spindle centred and rounded carefully will give you 76 ish, so you can create a very thin walled aluminium lined box.

 

[Cabinetman]

Hi

I do not know what it is you are doing, but I had to cut some flat bottomed recesses that were 76mm diameter for a job. What I did was to make a template from ply using a fly cutter in my pillar drill, and attaching this to the workpiece. Now using a 1/4 bosch router with plunge base and guide bush fitted with 20mm Wealdon cutter just set a depth and remove the material, reset depth and remove more material until you reach your final depth. Making several shallow cuts is easier and more controllable than trying to plough out deep cuts.

This hole cutter is good because you can set it up to an exact size to allow for the router guide bush. Armeg AHC40-200 Adjustable Hole Cutter With 40mm - 203mm cutting diameter - Discount Electrical

This is a cheaper version

Erbauer Adjustable Holesaw with Cowl 29cm 9 Piece Set

These cutters are good for a flat bottomed hole Bottom Trim

Not quite sure how you would use a router to dig a hole 250 mm deep though Spectric!

 

[Spectric]

I read that as 25mm ! Not good getting old.

 

[Adam Pinson]

You're going to need a hefty lathe even for a top class forstner that size.

I usually work up to that kind of size with smaller ones....also for me nothing beats carbide tipped forstner bits

 

[owen]

What about a hole saw?

 

[Cabinetman]

I usually work up to that kind of size with smaller ones....also for me nothing beats carbide tipped forstner bits

Welcome to be proved wrong as I would love to know how, but I thought it wasn’t possible to use a Forster bit on a pre-drilled smaller hole. Ian

 

[Phil Pascoe]

If the workpiece and the bit are held securely, there's no reason why not. It's relevant only for the first few millimetres, anyway.

 

[marcros]

Welcome to be proved wrong as I would love to know how, but I thought it wasn’t possible to use a Forster bit on a pre-drilled smaller hole. Ian

Generally speaking I think you are correct, but on a lathe the setup seems rigid enough to allow it to work.

I would always do the largest holes first, but the items I have made using multiple bits have the widest hole being shallowest and step down as they go deeper. Otherwise I suppose that it is not a stepped hole!

On a very large Forsner bit, I wonder how many holes you could get before it needs sharpening. It is removing a lot of waste.

 

[Adam Pinson]

Welcome to be proved wrong as I would love to know how, but I thought it wasn’t possible to use a Forster bit on a pre-drilled smaller hole. Ian

On my lathe it's possible, also my main reason for doing that is because my bits are somewhat blunt, new bits are in the mail

 

[Cabinetman]

Generally speaking I think you are correct, but on a lathe the setup seems rigid enough to allow it to work.

I would always do the largest holes first, but the items I have made using multiple bits have the widest hole being shallowest and step down as they go deeper. Otherwise I suppose that it is not a stepped hole!

On a very large Forsner bit, I wonder how many holes you could get before it needs sharpening. It is removing a lot of waste.

Yes thank you I hadn’t thought about using one on the lathe, I suppose the other way would be to use one on a morticing machine but it would need to be a beast to have the power – as you say that’s a lot of waste to remove.

 

[Adam Pinson]

What about a hole saw?

Hole saws are limited by their depth, mine all tend to smoke a lot too... Need new ones