Tricky hole problem

[geejay]

I have just completed a picnic table project and have a 1 1/4" square hole at a central junction which I want to enlarge to about 1 3/4" diameter. The problem is that the hole is 5" deep formed by a cross joint of 4 timbers 1 1/4" x 5" any suggestions would be welcome.

Thanks

[mrgrimsdale]

Depends what kit you've got but it might be easiest to fill the hole nice and solidly (folding wedges, glue etc) and then drill it anew.
Or a tapered wooden mandrel with 60 grit paper round it?

[davyowen]

You could also attach a batten to the underside of the table and then drill it out using a hole-saw - you need the batten to accept the pilot bit otherwise it'll just skid all over the place. Considering the depth, you'll probably need to attach a roughly sized block to the batten as well to allow the pilot to get going before the main part hits the tabletop.

Another option is to cut a template from MDF and then use a router and flush-trim bit (Wealden do a 3/4" cutter that has a 75mm cutting depth Code=T8042B-1/2).

Or do one of the above options just so that you have a pilot hole and then you can use a forstner bit to finish it off.

[thatsnotafestool]

You could also attach a batten to the underside of the table and then drill it out using a hole-saw - you need the batten to accept the pilot bit otherwise it'll just skid all over the place. Considering the depth, you'll probably need to attach a roughly sized block to the batten as well to allow the pilot to get going before the main part hits the tabletop.

Another option is to cut a template from MDF and then use a router and flush-trim bit (Wealden do a 3/4" cutter that has a 75mm cutting depth Code=T8042B-1/2).

Or do one of the above options just so that you have a pilot hole and then you can use a forstner bit to finish it off.

But it's 5" deep.

[bigdanny]

http://www.diytools.co.uk/diy/Main/sp-2 ... bi-met.asp

As aid previous. Holesaw. when you get to depth of holesaw just chip the core out with a chisel then start again with the holesaw until you get all the way throu. You may need an extension to the holesaw. The other option is an auger but very pricey for a one off.
http://www.woodsmithstore.co.uk/shop/Pr ... Eye+Auger/

Happy boring
D

[geejay]

Thanks for the advice guys. I can see now that I need to plug the hole but can I get a fostner bit or a hole saw that will go to a depth of 5"? Even if I keep cleaning out the core with a chisel I still need to be able to reach to the bottom of the hole at 5"deep. Maybe plug the hole and try a spade bit?

[mtr1]

You could fill the hole, then pilot all the way through. I know you can get long bits for this, then drill your larger hole from both sides perhaps, it would only be 2.5 inchs each way.

[thatsnotafestool]

Trouble with that, Brian, is that apart from Forster bits, AFAIK all drills require something to register their central spike of the bit into. Otherwise as you drill, the bit bounces around..at least in the initial stages ..leaving a non-round hole....ah, just thought, you could make a guide by drilling through a block of wood and clamping it over where you want to drill.

EDIT: Another way would be to fill in the hole as Grim suggests. Start the new hole with a Forstner bit which will give you a clean hole (we are assuming it's a round hole but maybe it's square in which case back to the drawing board), go as deep as you can and then swap over to an auger bit which can be got long enough to drill 5" and then some.

[davyowen]

Even forstner bits need some wood at the centre of the hole to get started, so either way, it will require a guide (as I said originally, a batten attached to the underside of the table) or for the hole to be filled in completely. I think filling the hole is a lot of unnecessary work though - having to faff about with folding wedges and glue etc, when a bit of mdf screwed to the undersides would do the job just as well.

[geejay]

Having considered all the suggestions I'm going to try a forstner bit with a guide at the top of the hole. I think once the forstner gets started it should be well enough supported. The mdf at the bottom of the hole won't work because it's 5" away from where I'm starting the hole! I've discovered I can buy Forstner bit extensions so if it gets a good start I should be OK. I'll try a test piece first as soon as I can get hold of an extension. Thanks for all your help. I'll let you know how I get on.