Drill dead straight into oak end grain

[hudster]

I am about to erect something very similar to this:

The bottom of the oak legs will sit on a stainless steel pin, which is concreted into the ground, with about 10cm sticking up. There will be a 1cm or so gap between ground and timber to keep the legs from standing in water.

I'm wondering how I can drill the hole for the pin in the bottom of the legs. It's obviously not possible to get them into a position for a pillar drill, and I'm worried my hand drill with an auger or forstner bit will wander when trying to get it dead straight. Any ideas?

 

[chappers]

do you have a router or there are devices that fit to a drill that make it work like a drill press, like these or drill over sized slightly and fix with resin, or even make a guide from something that you can get under a drill press if you have one.

 

[hudster]

I do have a router, not a fancy one but it has been fine on oak before.

I've never used it to get that depth though (about 9cm) - fit extensions?

 

[Kevin Adams]

You could buy a vintage horizontal drill stand for less than a tenner, like this:

http://www.ebay.co.uk/itm/BLACK-DEC...684294?hash=item2efb2f6a86:g:Gt0AAOSwopRYb46p

make a quick jig, job done

PS. Might be worth drilling a pilot hole first, then slowly increasing the size of the hole, waste won't clear too well when drilling end grain.

 

[bernardgreen]

The bottom of the oak legs will sit on a stainless steel pin, which is concreted into the ground,

How will this cope with shrinkage of the frame ? ( assuming you are building with green oak or other timber liable to move as it's moisture content varies over time )

Provided the junction at the top of each post has enough diagonal bracing to ensure the post remains vertical then the base of the post can stand on a pad of lead, The soft lead presses into the end grain to prevent moisture entering the timber. The pad will shape itself to the contour of the concrete and thus not slide easily across the concrete and thus keep the post in place. But being soft it will remain flexibe enough to allow for any slight and slow movement as the frame shrinks.

If the lead pad is 10 mm thick then it will keep the post above any rain water that lands on the slabs. The pad has to be no larger than the post to prevent rain resting on the top of the pad.

 

[rsgaz]

http://www.wolfcraft.com/en/products/p/drill_guides/1_accumobil_mobile_drilling_aid/s/p/index.html

If you read the reviews on amazon, you'll see that they made the tolerances a bit too big on this item, but it does work well with an oversize drill bit. So, for example, the '6mm' guide bush can fit a 6.3mm drill bit into it and then there's no play and it will drill straight for you, but as chappers says, if you have access to a drill press, then just make one of these.

Gaz

 

[Chud]

Take a look at Paul Sellers on YouTube - he does a video for a 'Poor Mans Beading Tool' - as part of that he creates a simple jig to drill a hole square into the tool - the bit you want starts about 2 minutes in - just scale it up.

 

[hudster]

How will this cope with shrinkage of the frame ? ( assuming you are building with green oak or other timber liable to move as it's moisture content varies over time )

Provided the junction at the top of each post has enough diagonal bracing to ensure the post remains vertical then the base of the post can stand on a pad of lead, The soft lead presses into the end grain to prevent moisture entering the timber. The pad will shape itself to the contour of the concrete and thus not slide easily across the concrete and thus keep the post in place. But being soft it will remain flexibe enough to allow for any slight and slow movement as the frame shrinks.

If the lead pad is 10 mm thick then it will keep the post above any rain water that lands on the slabs. The pad has to be no larger than the post to prevent rain resting on the top of the pad.

Interesting idea. I went with the pins option because the oak supplier recommended it, and because it will provide some slight stability whilst we are building it. The pins are 20mm so if I made the holes 25mm or so, it would presumably remove this risk and also mean it's less essential I get a perfectly straight hole?

 

[Roger928]

Seal the end grain well with 2 or 3 coats of exterior grade varnish.
If it just sits on those I'd be expecting to find the entire structure in the next doors neighbours garden upside down after heavy wind.

 

[hudster]

Seal the end grain well with 2 or 3 coats of exterior grade varnish.
If it just sits on those I'd be expecting to find the entire structure in the next doors neighbours garden upside down after heavy wind.

It's 1.6 ton! And actually mine is a pergola so is the same as the photo but without the pitched roof

 

[Roger928]

Pergola sounds like a nice name. But seems to be just 4 posts with a flat top.
It will take off like a kite.

That image looks stunning. I'd like that in my garden but would make the house look like crap.

 

[hudster]

Pergola sounds like a nice name. But seems to be just 4 posts with a flat top.
It will take off like a kite.

That image looks stunning. I'd like that in my garden but would make the house look like crap.

This is the actual one we're building - I didn't use this photo because it isn't mounted on pins. There is no chance of this blowing anywhere - the cross sections are 110kg each alone. That said, having it on pins will mean it can't shift to the side as the oak weathers

 

[hudster]

You could buy a vintage horizontal drill stand for less than a tenner, like this:

http://www.ebay.co.uk/itm/BLACK-DEC...684294?hash=item2efb2f6a86:g:Gt0AAOSwopRYb46p

make a quick jig, job done

PS. Might be worth drilling a pilot hole first, then slowly increasing the size of the hole, waste won't clear too well when drilling end grain.

Genius! I didn't know these existed. This one looks even easier if it is rigid enough, would you agree?

 

[Roger928]

I have the wolfcraft guide ...
http://www.wolfcraft.co.uk/en/products/p/drill_guides/s/c/index.html

The tenons on the arch braces of the OTS framing look to be draw bored and pegged. And left sticking out as a feature.
Will you follow that superior joinery method?
Their tenons look to be about 75mm long.
£3833ex vat for that last one you posted.

 

[hudster]

Yes I like the pegs sticking out, but each to their own. It is a good kit - they test assemble at the yard, then number the joints, dismantle and deliver.

I am in no way affiliated