[morqthana]

Hi, forum and routing newbie here...

I am looking into the idea of using scaffold boards for garden fencing, dropped into slotted posts (concrete or galvanised).

Grade B boards work out about less per sq m than a decent fence panel, and then factoring in a 3.6m/12’ span results in a 50% reduction in posts and concrete, and less labour (I’ll be paying someone to erect it), so it becomes quite a cheap system.

But they are square edged, so I thought I’d T&G them.

I’ve got a ½” 1850W router (Elu MOF 177/02) in a table. So a few questions:

Cutting the groove down the centre of the board should be straightforward enough, but for the tongue does anybody know if I’ll find a bit that will cope with 38mm (1½”) stock, or will I have to do 2 passes with a rabetting cutter?

What sort of feed rate should I plan to get, allowing for cooling intervals (the cutter, not me)? Boards are softwood - typically spruce or pine.

And cutter life? I’d have 500-odd metres of boards to do.

 

[DesertRatTom]

1.5 inches wide. I think you could do T&G on a router table if the boards are straight, not warped at all. You could use a half inch cutter that cuts a flat bottom, and cut the groove first. Then reset the bit to trim away half an inch from the edge and pass the board through twice. That would create the tongue. Half inch shank would be a good choice. No way would I attempt this with a freehand router.

You should not try to cut in one pass. To have a half inch overlap, you should probably make a minimum of three passes. Do a batch, then do a second pass, then again doing all at once, make the final cut. You want the tongue just a little under half an inch thick so it can slip. If the wood is not fully dried, you will need to clean the bit several times because it will pick up pitch and that will cause overheating. Buy two bits of the same type because 500 meters is a lot for one bit, because you will need to make three passes, for 3 cuts per board, so you are routing a total of 1500 meters, for 4,500 passes through your router. This is why they charge more for T&G material.

If you have a table saw, and the boards are straight enough, I'd use a dado set. Much more robust. You can bury the stack in the fence and only expose the amount you want to trim off each side of the tongue edge. Then you can run it centered to cut the groove. That's three cuts, times three cuts per board. A dado stack will do a much better job--if the boards are straight.

If you do it with a table saw, get a couple of featherboards to hold the boards to the fence so the groove is nice and straight. Tongue again should be slightly smaller than the groove.

Also, after you cut the first one, whichever method you choose, dry fit it to make sure your measurements are right. If the groove isn't centered, the boards will be offset and will put strain on the tongue when nailed in place..

 

[jw2170]

Welcome to the forum @morqthana .

Tom has made some great suggestions.

It really depends on how straight those scaffold boards are, and if they are rough finished...

 

[DesertRatTom]

Do let us know what you decide to do. If you don't have a table saw, this would be a great excuse to get one. A table saw is such a basic tool, you'll be using it for decades. Make sure the saw you get, used or new, will take a dado stack that's at least half an inch wide. A 10 inch saw would be my choice, but make sure it has a solid fence. You can use an 8inch dado set.

 

[old55]

Welcome to the forum @morqthana

 

[morqthana]

Thanks Tom - food for thought. Dado blades an interesting idea. Totally precise alignment isn't hugely important - the boards aren't going to be nailed to anything - they'll just sit on top of each other like this:

I might need a helper, though - with supports for the overhangs I'm confident I could keep the boards lying flat as I run them past a router, or doing the tongue with a dado saw. On edge for the groove with the table saw, not so sure. They are 13' x 9" wide, x 1½" thick, and weigh about 42lb.

Maybe a hybrid approach - dado blades for the tongue, router for the groove.

 

[morqthana]

Ha! - I wrote that post (#6) yesterday, but for some reason for which I can't think of an excuse, didn't click post.

And now I've posted it when I shouldn't, as I actually came here with an update.

Maybe I should have a lie-down instead.

 

[morqthana]

It really depends on how straight those scaffold boards are, and if they are rough finished...

Well, they certainly aren't cabinet making quality

Scaffolding boards, unplaned, just sawn. Probably not very dimensionally consistent either. A photo from one supplier I've found:

And he says "some may be slightly warped"

I think a good plan, before ordering all 130-or-so boards would be to get an initial few, and see how I get on. Even if I end up dropping the idea, I'll find a use for the boards.

Do let us know what you decide to do. If you don't have a table saw, this would be a great excuse to get one. A table saw is such a basic tool, you'll be using it for decades.

Spoiler: Contains content some readers may find upsetting

I'm not really much of a woodworker, so I probably wouldn't make much use of one. I'd not be averse to buying one on eBay, using it for this, and then selling it, but I'd have to factor in the cost, and too much of that leads to "why don't I just buy fence panels".

Make sure the saw you get, used or new, will take a dado stack that's at least half an inch wide. A 10 inch saw would be my choice, but make sure it has a solid fence. You can use an 8inch dado set.

And now we arrive at the update I came here with. I suddenly realised that I won't be able to use dado blades. My "table saw" is actually a multi-function work table under which you clamp a hand-held circular saw (or router, or jigsaw). It does what I need for doing stuff with wood for DIY purposes, but you can't get a dado stack into a hand-held circular saw....

So it's back to using the router...

 

[DesertRatTom]

OK, given that new bit of information, I want to suggest you not o tongue and groove. I think you want an overlap for privacy. Instead of T&G, you might consider a ship lap joint..

Change the dimensions in the drawing to C = 1.5 inch E = 3/8ths inch. D and E can be slightly narrower to allow for some warping. and easier fit. A little warping should not be a problem with this simple joint.

You are really making two rabbets along the length of the board. On on the bottom, the second on top. They need not be much deeper than 3/8ths, just enough to overlap and give you privacy.

You can create a shadow line between boards by making D a little longer on one side. The extra length will create a shadow line on one side.

You could cut these with a big rabbeting bit on your router, or by cutting with a conventional blade in your table saw. It will probably be slightly faster to use the saw, even though you're making twice as many passes. You just set the blade height and fence spacing to cut to rabbet. It doesn't have to be perfect and once set, almost anyone could do the cutting.

 

[TenGees]

Myself, I wouldn't dream of cutting all that on a router. I like Tom's ship-lap idea, cut on a table saw with a rip blade. You'll be making a lot less sawdust too. And maybe you could use the off cuts as tomato stakes. ;-)

 

[DesertRatTom]

If you line up several boards vertically, then clamp them together, you could cut the ship lap with a circular saw. I've seen experienced carpenters do this freehand, but for me, I need to support the saw so it doesn't wobble or wander.

That takes care of the vertical cut, for the horizontal cut, you don't need the extra support. You might be able to find an inexpensive edge guide for your saw which would make a nice, reliable cut. Here's a picture

It's the wide side of the of the saw base that needs support so the narrow side is always on the side of the board that's being cut off. Get a decent rip blade 30 or so teeth. They're made for cuts like this. See, got you down to bare minimum cost. I see why you want to use the planks. That's going to be a forever fence.

 

[morqthana]

OK, given that new bit of information, I want to suggest you not o tongue and groove. I think you want an overlap for privacy. Instead of T&G, you might consider a ship lap joint..

Actually the thinking behind T&G was to resist movement, but shiplap would do that too.

You can create a shadow line between boards by making D a little longer on one side. The extra length will create a shadow line on one side.

And shadow gaps look good.

You could cut these with a big rabbeting bit on your router, or by cutting with a conventional blade in your table saw. It will probably be slightly faster to use the saw, even though you're making twice as many passes. You just set the blade height and fence spacing to cut to rabbet. It doesn't have to be perfect and once set, almost anyone could do the cutting.

Yup - and it would be worth the effort to make a tall fence to use when the boards are on edge.

Myself, I wouldn't dream of cutting all that on a router. I like Tom's ship-lap idea, cut on a table saw with a rip blade. You'll be making a lot less sawdust too. And maybe you could use the off cuts as tomato stakes. ;-)

Yes - shiplap is a good idea. If I was determined to cut T&G, then unless I buy a table saw which can take a dado stack I would have to use a router, but I was always unsure how realistic that would be, hence creating this topic.

If you line up several boards vertically, then clamp them together, you could cut the ship lap with a circular saw. I've seen experienced carpenters do this freehand, but for me, I need to support the saw so it doesn't wobble or wander.

Sorry, Tom - I'm trying to picture that, and failing. I've got to remove material as shown:

and I can't see how to stack and cut multiple boards....

That takes care of the vertical cut, for the horizontal cut, you don't need the extra support. You might be able to find an inexpensive edge guide for your saw which would make a nice, reliable cut. Here's a picture
View attachment 401529

Yup - I've got one of those, (although I always prefer, if I can, to clamp a guide to the work). Or I can mount the saw under that table I have.

 

[mlerchenmuller]

Silly question. Why do you need to tongue and groove? The pieces will sit edge-to-edge. The boards are 1-1/2” thick. I cannot imagine they would bow out.

 

[DesertRatTom]

Making the vertical cut with a circular saw, the issue is having a wide enough base for the saw to ride on. By clamping four boards together, you create a fairly wide base support. Just an easy way to steady the saw so it doesn't tilt or wander. Stack them up so the ends look like books on a shelf. Four boards will give you a six inch wide surface for the saw to ride on.

You won't be making much sawdust that way compared to a router. With a full kerf blade, the cut out pieces will be 1/4 by 5/8 ths. Perhaps usable for gardening.

 

[morqthana]

OK - gotcha.

I think if I am going to do this I'd look at knocking up a tall fence so I could easily run a single board through.

Though mlerchenmuller asks a good question - do I need to bother with any of this? The idea came to life because I am keen on using boards like this for a fence, and I have a tendency to over-engineer, so when I thought about stacking boards on edge I thought "it would be better if they were locked together in some way". T&G seemed a good way, I know you can get matched pairs of router bits, and we were away.

But I've probably got better things to spend my time on. Just thinking (gut feel) about pushing the work through, imagining a steady rate that's not going to start a fire, it's got to be at around 10-20 seconds per foot, 4 cuts per board, so say 40-80s per foot, and boom, 20-40 hours just cutting. Plus humping about 2½ tons of wood from one pile to another. 4 times, given 4 saw settings if I want a shadow gap. Or 3 if I cheat with the vertical cuts.

Plus I don't have a workshop with enough space to pass 13' boards through a saw, so I'd have to work partly or wholly outdoors which means set-up and tear-down time. Could so easily be a 2-week job.



It's the sort of activity, when thought about at the normal scale I do for DIY round the house and garden, seems a goer, but when scaled up to about ⅓ of a mile of boards causes a bit of an "ah... hmm..." moment.


I've just talked myself out of doing it.

So thanks to all of you for all your help, suggestions and interest, and I'm sorry it didn't result in a plan. I should have thought about the logistics sooner.

I'll stick to not setting up a commercial-scale wood machining operation in future.