Cutting patterns on the tails of raffters or perlins

[Donald Grudeski]

I have a job to build a Pergola and have to cut the tails of the rafters in a decorative pattern. I am thinking of using my router with a pattern cutting bit and a template , should I cut the bulk with a jig saw or just cut the pattern with the pattern cutting bit? Or should I use a downward cutting spiral bit and a template guide? The material is 2X cypress or cedar and if my life sucks pressure treated not sure yet. Or do you have another way that will do this job fast a accurately. Thank you for you help.

[cc]

rough cut with jig, finish with pattern

[toolman946 via CraftKB.com]

I second that.

When you waste away most of the wood with a jigsaw you lower the stresses on the router and bit.. and avoid overheating the bit.

It's good to always wear a dust mask... imperative for your health when working with pressure treated wood.

[Robert Allison]

I have always used a jigsaw only. I have a very good jigsaw (Bosch) and I use a finer tooth blade. I am aiming for precision, so the slower cutting speed helps with that. Plus the finer tooth leaves a smoother cut. I just touch it up with a piece of sandpaper and a file.

The only time that I had to change my method was when I was cutting details on a 6x12. For that I used a hand held portable band saw. Now those had to be sanded a bit.

[SonomaProducts.com]

You really do need to cut it away to near finish and trim with the router. Even more so on a 2x. Would pretty much be impossible otherwise. I would be intrigued to see if using a good, corded jig saw, you could maybe follow a pattern and not route at all.

Spiral bit with bearing will give the cleanest cut but trust me a spiral really gets some bite. It should ONLY be trimming a fairly close cut next to the template shape if you go that route (pun). I have had some real hairy situations gouging, throwing pieces, having them yanked from the template holder and even broken those suckers. I am still amazed how I didn't end up with part of a spiral in my gut, seeing how deeply it was embedded in the wall, just to the right of my torso.

[montyhp]

Don,

That is what I did. I made a pattern from masonite and attached stops so the pattern is "self aligning" to the wood. Then I used the pattern to mark a line on the board, cut to line with jugsaw, then clamped the pattern to the board and cleaned up with a top bearing bit. Went pretty fast on 48 joists.

Montyhp

[J. Clarke]

I'm curious--have you used a downcut spiral bit for template routing? Seems to me that it would address several of these problems--the up thrust would tend to tilt the bit out of the work instead of into it and avoid the gouging, and the up thrust would also if the bit slips in the collet tend to force it deeper instead of pulling it out (note--learned the hard way--_always_ clean the collet and bit with a non-lubricating solvent such as lacquer thinner before use when working with spiral bits and still don't trust the things to stay put). Should also eliminate tearout at the top edge.

Seems to me that the ideal would be a compression bit--no tearout at either end and no thrust to speak of. Only one I can find that would do 2" stock in a single pass though is an Onsrud that's over a hundred bucks--Ekstrom-Carlson may have some in steel for less but I can't find prices--might be worth giving them a call.

I think I'd arrange things so that the stock was between me and the bit working with a chunk of exposed carbide that big.

Not going to be a guided bit in that kind of length--need to use a guide bushing and cut the template a little undersized to match.

[Swingman]

"Donald Grudeski" wrote

Those around here who do if for a living generally just use a good jigsaw. If "fast" is indeed required, practice cutting your pattern on some cut-offs and you might find that is all that is necessary.

IME, cypress is not the wood it used to be in most places. Western Red Cedar, an excellent choice for outdoors, will likely be many times the price of pressure treated stock.

--

Last update: 12/14/07 KarlC@ (the obvious)

[Bonehenge (B A R R Y)]

I've done several pergolas and benches in red cedar. Decorative ends are done by rough cutting to a hardboard pattern and finishing with a

1/2" x 2" pattern routing bit. I carpet tape the pattern in place and remove the pattern with a 4" drywall knife. Inside corners that the bit can't reach are finished with a shoulder plane. Final smoothing is done with 80 grit glued to a scrap block.

Some guys can just jigsaw them out, and have them look nice. I've never had the results I want, with my cut ending up not square to the faces. The router guarantees a 90 edge to the faces.

The pattern process sounds a lot slower than it is in actual practice, once the tools are laid out.

[DT]

Norm did this a number of years ago, but on rather thick wood, 4" or 6" so a handheld jig saw wouldn't work. I thought his method was innovative. He placed the piece up on stands so it was as high as his bandsaw. But then he left the wood stationary, and wheeled the bandsaw around on its casters like a giant jigsaw - perfect ogee cuts!

[J. Clarke]

Now _that_'s genius. One of those things that is _so_ obvious once you see it but that I'd have never in a million years thought to do.

[DT]

Yep, I've been waiting for years for an excuse to use that trick!

[Donald Grudeski]

[Robert Allison]

That is exactly what I did. A portable band saw held in my hands. I set in on a slick piece of masonite and just moved it around the cut with my hands. Still needed a lot of cleaning up, probably due to the band saw being the cheapest one I could find for this one job. I wish that I had known about that caster trick at the time, I could have done that with my good band saw.

New trick noted and stored for future reference.