Drilling large holes?

[Eddy Matthews]

Hi guys,

I'm after some advice - I need to drill a number of 41mm (1 5/8") holes in some 0.8mm plywood.

These holes must by accurately positioned and circular - This is critical!

I've looked at "spade bits" and "hole saws", but neither of those are anywhere near accurate enough in my experience, they both tend to wander away from the centre mark, and don't produce a very accurate round hole. So is there anything else I can use to cut accurate holes at this size?

Any help would be appreciated...

Regards
Eddy

[scotfriend]

Hi Eddy,

i would not recommend a drill because of the thin plywood there is a high risk of damage when drill the hole. I would suggest a kind of grinder it is made of rubber with a pin in the middle to put it on a handdrill and with a ring of grinding paper all around, search the web for the company PFERD.

best regards Hans

[djcf]

Hi Eddy,
Maybe Kim could advise about the possibility of laser cutting?

Clark

[Dinosaursoupman]

Look up Forstner bits. They are far more accurate than spade bits and come in 1-5/8" size. A tad expensive for the decent ones but well worth it. Don't forget to back up the hole your drilling with a solid piece of ply or wood, just an added measure to prevent tearout.
Randy

[Talisman]

Hi Eddy,
Maybe Kim could advise about the possibility of laser cutting?

Clark

Thanks Clark,

The short answer is yes i could do it either laser or jet cut it -
If you have some drawings and material spec i will have a look at it for you - I will be down your way at somepoint next week Eddy so could bring the finished item down with me then.

You can let me know - i will be on skype tomorrow afternoon if you need to chat about it.
Regards,
Kim

[derekwarner_decoy]

Hi PD's....Eddy a "Fly Cutter" ...sorry    "Gasket Cutter" is ideal.. fully adjustable....they are used for cutting gaskets & often have two blades set at the correct radius [ii] & spun in your pedestal drill

They are not expensive......but if you didn't want to purchase one look in your YELLOW pages for gasket manufactures  Derek ...I will find a WEB image

[Eddy Matthews]

Thanks guys, plenty of possible solutions there to look at!

Since Randy mentioned "Forstner bits", I phoned a couple of my woodworking friends, and one of them has a set of Forstner bits that I can try.... So I'll give them a go, and see how accurate they are.

Many thanks to all

Eddy

[steamboatmodel]

If you need accuracy you need to clamp everything down and use a drill press, even with the "Forstner bits".
Regards,
Gerald.