View Full Version : Cutting Curves in Pressure Treated framing lumber
10-06-2007, 06:27 PM
I have been a woodworker for a number of years in doing small furniture projects and a few deck additions on houses. The deck additions up to now have been primarily framing and decking and nothing especially complicated.
Recently, I started working on a gazebo using 2x8 pressure treated joists spanning 8 feet plus a 2-foot cantilever on each end Ö.. 12-foot long lumber. Instead of a simple mitered cut at each end, my wife insisted on a reverse curve .Ö. something like an ogee at each end. She marked out what she wanted on a board and I attempted to cut it with my trusty sabre saw. The first cut went okay Ö.. the second cut overheated my saw. So I made a trip up to Sears to buy their biggest, professional grade, hand held sabre saw and brought it home (assuring my wife that I could do it with new power tools). Unfortunately, I didnít have much better luck with that one either. So I went back to get the longest blades with the fewest number of teeth per inch and tried again. Only marginally better.
I then made a trip down to my local Woodcrafter store to get some information from them. The one guy that I have talked to many times in the past (and who is a professional cabinet guy) told me that you canít cut curves in pressure treated wood (1 Ĺ inch thick) unless you have a regular shop with equipment set up to do that.
I find that statement hard to believe because I see them all over the place (at least my wife points them out to me now that I told her that it canít be done). Most home and garden show exhibits that have a gazebo or arbor set up has fancy cutting on the ends of the joists. I have done that with my band saw for small, easily maneuverable items like a corbel or bracket but handling 12-foot long joists on my band saw doesnít seem to be too practical.
Does anyone out there have any suggestions? How do they do it for all of these craft shows?
10-06-2007, 07:09 PM
Off the top of my head, I would say either a sawzall (reciprocating saw) or a portable bandsaw....
10-06-2007, 07:56 PM
Sounds like you need a MORE aggressive blade, with fewer teeth . . . PT tends to be wet when fresh, compounding the problens trying to 'turn' the blade . . . a fine tooth blade is not what you want for that material.
If your saw takes 'T-shank' blades, you may want to give a pack of these a whirl . . .
It's a 6tpi blade designed specifically for curve cutting . . . and thicker material.
You should be able to get them at Home Depot/Lowes in a five-pack for around $9-$12.
You need to take care to move s-l-o-w to allow the dust to clear while you go.
In my experience, a sawzall is too agreesive to follow a line closely, let alone a curved line.
The only better way to attack this for me would be to rough-cut the ends and finish them with a downcut spiral blade in a router with a template bushing . . . you'll need to make a template for this method, but if you're doing more than 6 or so, it'll go pretty quick once you are set up.
10-06-2007, 08:13 PM
Thanks for the tip. The blade that I tried last is a 6 inch long with 6 teeth per inch. It did better but still choked out on me. It was also wider than the one that you suggested and did not cut the curves as smoothly.
10-06-2007, 08:15 PM
I was kind of thinking about a reciprocating saw but wasn't sure if it would cut the curves very smoothly. I have never used one before.
10-06-2007, 08:20 PM
Wide is a problem if your cut radius is tight, the back of the blade shank is going to rub on the cut surface making for a lot more friction.
If you can't find that Bosch blade, be sure the blade you get has ground teeth, NOT stamped teeth . . . if you can see 'puckering' on the side of the blade shank, chances are, it's stamped steel. As an alternative, both Lenox and DeWalt make good blades as well.
10-07-2007, 05:42 AM
You can make a template out of plywood stock with the finished curve. I allow the PT stock to dry out, and rough cut the curve close to the line, with a Bosch jig saw and a 6 TPI blade. You could also use a down spiral bit in the router. I clamp the template to the PT, and use a 3 1/4 HP Bosch router with a flush trim bit with 2" carbide tipped flute length, either a single or double bearing.
I also use the same router and bits to cut up to 8/4 hardwood stock in a slow pass sometimes without the rough cut.
10-07-2007, 06:35 AM
Thanks for your input Cabinetman,
I have never tried a down spiral bit in my router but one of the other suggestions mentioned that as well. Does it take off much at a time ..... and act like a wood rasp? I wondered how close I should cut to the line with the rough cut. Can I just miter it with my radial arm saw (which is where I am right now) and then trim out the curves with the router bit?
I have about 40 of these to do so making a template makes a lot of sense if I can just get some way to get all of that PT wood cut away to the curve. You mentioned a 3 1/4 HP Bosch router. My hand router is only a Craftsman 1.5 HP ... do you think that is big enough to do the job? I'm thinking if I do a rough cut first and then gradually trim back to the plywood template.
I do have a Porter Cable 2 1/4 HP set up in my router table but that is as big as I have.
10-07-2007, 06:41 AM
I checked my manual and my sabre saw does take either "T" or "U" blades so that is on my list for my next Lowes run. I will give those a try for the rough cut and then check out a down spiral router bit for the finish cut.
Thanks for your input.
10-07-2007, 06:59 AM
It might be worthwhile to take the router out of the table and slap a base on it. No sense trying to overwork the smaller router. The rough cut only has to be 1/4" to 3/8" from the final line. As long as what you are ultimately routing off to the template is less than the diameter of the bit it will cut smoothly. The flush trim bits with the long cutting flutes are 1/2" shanks. If your router is variable or multi speed, run it full speed.
With that many to cut, you'll find out after the first few the best sequence. Make sure your template has a good edge. Check it frequently for any dents, or voids. You can use the spiral bit, or even a straight faced cutter for the rough cut, and the bearing bit for the final cut.
10-07-2007, 09:08 AM
Ken: I like Cabinetmans suggestions. Just a thought about roughing in the cut. You could use a circular saw on the outside radius and make multiple straight cuts to rough it in. On the inside radius make straight cuts perpendicular to the line and cut with jig saw. You should be able to get close enough to use a template and a router to finish. FWIW
10-08-2007, 11:51 AM
If the Curved ends are not going to be structural at all (no weight on them) you could just cut off a small section, cut them out on your band saw and glue the back on. Expecially good if your going to paint. If you are doing a clear finish, you may see the joint.
10-08-2007, 06:19 PM
Thanks for the input Fred,
I am still trying to talk my wife into letting me just miter the ends or do something with a straight cut that I can do on my radial arm saw. I have about 40 of these to do and, though your suggestion sounds like it would work pretty good, it seems time consuming to me .... especially for that many.
I am thinking now that I might pursue the idea that Wood Mangler and Cody suggested and get a hand-held bandsaw. I haven't priced them yet but maybe the rental idea that Cody suggested might work. That seems to me like it would be a one pass deal with a little touch up with a hand-held sanding drum ..... probably an oversimplification.
10-08-2007, 06:54 PM
Ken, I think what you're seeing is lack of stroke on the sabre saw. With the power off, push the blade "into" the shoe as far as it'll go. That represents the top of the stroke. Wrap masking tape around it, or mark it with a Sharpie, or otherwise make some indication of where the blade exits the shoe.
Now pull the blade "out of" the shoe as far as it'll go. You may need to bump the trigger to get it to go (fingers AWAY). Now measure between the shoe and the mark you made.
If the measurement is less than 1-1/2", that's your problem. That blade MUST have at least a 1-1/2" stroke to get the job done - otherwise, the sawdust from the underside of the board never gets cleared at the top of the stroke, and just gets rolled up & down inside the kerf.
If the measurement is at least 1-1/2", you're golden. I'm betting it's less, though... in which case you've gotta' go with other tools - bandsaw (handheld or stationary), or reciprocating saw (depending on how tight a curve you want, you may be able to find a slim enough blade to make the curve... or you may have to make several passes to get it to work), or router.
A coping saw would do the job, but I suspect you'd rather get it done this year. :)
-- Tim --
Things are bad...
Last night my fantasy girlfriend
For an imaginary guy...
10-08-2007, 10:20 PM
Ken: That bndsaw that Cody shows might do the job. I have used quite a few of them on rebar and they worked fine. As far as using them on a 2x6 you might have a problem with the saw frame getting in the way. They cost in the $300 range so be sure it will cut the profile that you want. The only thing I have used them for is cutting metal.
10-09-2007, 07:16 AM
That makes good sense. I never really gave much thought to the stroke not being enough to clean the sawdust out of the cut. Added to that, it is PT wood that is wet and sappy and that pretty much explains why my saw choked out in it. I got the longer 6" blade with the 6 tpi but I guess if the stroke is not long enough, that length of the blade doesn't help much.
That give me the support that I needed to get new toys for my workshop. :-)
10-09-2007, 08:24 AM
Out of my largest jig saws, Bosch, Milwaukee, and a big old Craftsman scroller that refuses to die, the longest stroke is 1". Smaller jig saws have only 5/8" - 3/4" stroke. IIRC 1" is just about the max on most all jig saws.
10-09-2007, 10:49 AM
That's about what I figured... :)
EDIT: BTW, I've never had squat for success at cutting 2x material with a sabre saw. It's terrific for material 3/4" thick & thinner, though... :)
-- Tim --
Things are bad...
Last night my fantasy girlfriend
For an imaginary guy...
10-09-2007, 12:13 PM
Whats the diameter of the arc? Maybe you can find the right size hole saw?
10-09-2007, 10:09 PM
I have read all the previous posts and my opinion is go with Dbriski. Use Titebond III and clean up the joint with a sander. Even with a clear finish or none at all no one will ever notice and how much easier it will be.
06-02-2010, 09:04 AM
I believe a hand-held band saw is the best tool to use here. You can even rent it.
He is no fool who gives up what he cannot keep for that which he cannot lose.
09-07-2010, 03:34 PM
This is what you need.......you can cut any radius with these....all the way down to about 1"