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Cutting Thick Beams: Which Saw for Crosscuts, Mitres and Rip Cuts?
For thick timber beams, pick the saw according to the cut. A mitre saw or circular saw handles crosscuts and mitres, while a table saw or a circular saw with a guide is the tool for rip cuts. Check the cutting depth first. If the beam is thicker than your saw can manage in one pass, cut from two or more sides or use a saw with a larger blade.
Cutting thick beams goes smoothly when the beam is well supported, the blade suits the cut and you let the saw set the pace.
What will you learn in this article?
- What kinds of cut do you make in a thick beam?
- Which saw should you use for which cut?
- How deep can a circular saw cut?
- How do you cut a thick beam at a mitre?
- How do you rip a thick beam?
- Which blade should you use for thick beams?
- Cutting thick beams by hand
- Why does the saw wander off the line?
- Are cordless saws powerful enough?
- Safety and preparation
- Frequently asked questions about cutting thick beams
- In short: cutting thick beams
What kinds of cut do you make in a thick beam?
There are three basic cuts, and each one asks something different of your saw.
- Crosscut: cutting across the grain to shorten the beam.
- Mitre: cutting at an angle, for example 45 degrees for a corner joint or an angled end on a pergola or veranda.
- Rip cut: cutting along the length, with the grain, to make a beam narrower or thinner.
Crosscuts and mitres are fine with most saws, as long as the cutting depth is enough. Ripping is heavier work: you are cutting a long kerf through a lot of timber, and the saw has to clear the sawdust well.
Which saw should you use for which cut?
| Saw | Crosscut | Mitre | Rip cut | Limit |
|---|---|---|---|---|
| Mitre saw | Very suitable | Very suitable | Not suitable | Maximum beam size given in the saw's specifications |
| Circular saw | Suitable | Suitable, using the bevel setting | Suitable with a guide | Cutting depth per pass |
| Table saw | With a mitre gauge | Limited | Very suitable | Blade height, table length |
| Reciprocating saw | Rough | Rough | Not suitable | Not very accurate |
| Handsaw or Japanese saw | Suitable | Suitable with a jig | Possible, but hard work | Takes time and effort |
Is a jigsaw suitable for thick beams?
A jigsaw can get through thicker timber if you fit a long blade, but it is not a good choice for thick beams. The narrow blade bends in deep timber, so the cut ends up out of square. For a straight, square cut, use a circular saw, mitre saw or handsaw.
How deep can a circular saw cut?
The cutting depth of a circular saw depends on the blade diameter. Many circular saws manage several centimetres at 90 degrees and less on a bevel cut. Check the specifications of your saw for its exact maximum depth at each angle. A beam up to twice as thick as that depth can be cut from two sides. Mark the line accurately all the way round and use the same guide on both sides. A cordless circular saw from the Maxxpack 18V range gives you that freedom on site or in the garden.
If you cut a lot of thick beams, a larger circular saw or a beam saw with extra cutting depth may be worth considering.
How do you cut a thick beam at a mitre?
On a mitre saw, set the angle on the turntable and cut as normal. If the beam does not fit, use a circular saw with a bevel setting.
- Mark the mitre angle on two faces with a sliding bevel or combination square.
- Set the saw to the right angle and check it with a test cut in an offcut.
- Cut the first side using a guide.
- Turn the beam and cut the other side. With a bevel cut, roll the beam over along its length so the angle keeps running the same way.
Mitring from two sides takes precision. Even a small error shows up straight away in the joint.
How do you rip a thick beam?
A table saw works best for ripping. The beam runs along the rip fence and stays straight. With long beams, use roller stands or an extension table on both sides so the beam does not tip or sag.
Without a table saw, you can rip with a circular saw along a clamped straight edge or a guide rail. Cut from two sides if the beam is thicker than the cutting depth.
Points to watch when ripping:
- Use a riving knife or splitter. It stops the kerf closing behind the blade and causing kickback.
- Feed the timber with a push stick, never with your hands close to the blade.
- Do not rush. The saw needs to stay up to speed.
Which blade should you use for thick beams?
| Blade | Use | Result |
|---|---|---|
| Few teeth, large gullets | Ripping, fast cutting | Faster, rougher cut |
| Many teeth | Crosscuts and mitres | Smoother, slower |
| General-purpose blade | Mixed work | A compromise |
A coarse blade clears sawdust better and runs cooler in a long cut. A fine blade gives less splintering at the edges. Sand or plane the cut afterwards if you need a fine finish.
Cutting thick beams by hand
With a handsaw you do not depend on cutting depth or power. It does take time and effort, especially with hardwood.
- A coarse handsaw or panel saw suits ripping and rough crosscutting.
- A Japanese pull saw has a thin blade and fine teeth. It cuts on the pull stroke, which takes less effort and is more accurate.
- Switch sides and turn the beam as you go. That keeps the cut straight and gives your arm a rest.
How long it takes depends very much on the timber and the saw. For a thick hardwood beam, expect several minutes per cut.
Why does the saw wander off the line?
- The blade is blunt or wrong for the cut.
- You are pushing too hard, so the blade starts to flex.
- The beam is not stable and moves.
- You are cutting without a guide or jig.
Replace a blunt blade in good time and let the tool set the pace.
Are cordless saws powerful enough?
Modern cordless saws can cope well with thick beams, provided the battery is charged and the blade is sharp. For a lot of ripping you will need more than one battery. A bonus is that there is no cable to get in the way of the cut. Check the cutting depth and blade speed in your saw's specifications.
Safety and preparation
- Lay the beam on sturdy trestles and clamp it down.
- Support both parts so the kerf does not close up and the offcut does not drop.
- Check reclaimed timber for nails and screws.
- Wear safety glasses, ear defenders and a dust mask.
- Make sure the cutting line is well lit.
- Remove the battery before changing or adjusting the blade.
Frequently asked questions about cutting thick beams
Which saw is best for a 15 cm thick beam?
For crosscuts, a circular saw used from two sides works well, or a mitre saw if the beam is within its capacity. For rip cuts, use a table saw or a circular saw with a guide, again from two sides. Check the cutting depth of your own saw in its specifications.
Can you cut a beam lengthways with a mitre saw?
No. A mitre saw is designed for crosscuts and mitres, not for long cuts along the length. For that, use a table saw or a circular saw with a guide.
What is the difference between a ripping blade and a crosscut blade?
A ripping blade has fewer teeth with larger gullets, so it cuts quickly along the grain and clears the sawdust. A crosscut blade has more teeth for a smooth cut across the grain. A general-purpose blade sits in between.
In short: cutting thick beams
Choose the saw by the cut: a mitre saw or circular saw for crosscuts and mitres, a table saw or guided circular saw for ripping. If the beam is deeper than your saw's cutting depth, cut from two sides with accurate marking all round. Use the right blade, support and clamp the beam, and always fit a riving knife when ripping.