Why is my jigsaw cutting at an angle instead of square?

A jigsaw blade is supported only at the top. Everything below the shoe is cantilevered, so any sideways force bends it — and a bent blade cuts a curve through the thickness of the material even when the line on top looks perfect.

What you'll need

• thicker or wider jigsaw blades
• hex key for the shoe (optional)
• square

Step by step

1. Check the shoe angle.The base plate tilts for bevel cuts and is easily knocked off its zero detent. Set a square against the blade and the shoe and confirm it reads ninety degrees.
2. Check the shoe is locked.The lever or screw must be fully tight. A shoe that shifts during the cut produces a bevel that changes along the length.
3. Look at the blade guide roller.Most jigsaws have a small roller behind the blade that supports it against the feed force. If it is worn, missing or not touching, the blade deflects backwards and twists.
4. Slow the feed rate.Pushing is the biggest single cause. The blade bows backwards, and because the teeth are set, that backward bow becomes a sideways lean.
5. Fit a thicker or wider blade.Narrow scrolling blades are made to turn tight curves, which means they are made to flex. For straight cuts in thick material use the widest, thickest blade that fits.
6. Reduce or switch off the pendulum action.Orbital action makes the saw cut faster and more aggressively, and it increases blade deflection. Turn it off for accurate cuts.
7. Support the material properly.A flexing workpiece and a flexing blade compound each other. Clamp close to the cut.
8. Keep the shoe flat on the surface.Rocking the saw as it goes round a curve or over an uneven surface tilts the blade directly.
9. Accept the tool's limits for thick stock.Beyond about 30 to 40mm, a jigsaw will struggle to hold square whatever you do. A circular saw or a hand saw is the right tool there.

Tips

• Set a square against blade and shoe before any cut that has to be square. It takes ten seconds.
• Turn the pendulum action off for accuracy and back on for speed in rough work.
• If the cut leans consistently in the same direction, it is the shoe. If it varies, it is blade flex.

Common mistakes

• Pushing the saw to make it cut faster — The blade bows backwards under feed pressure, and a bowed blade cuts at an angle through the thickness. The top line stays true, so the error is only visible on the far face.
• Using a narrow scrolling blade for a straight cut — Narrow blades are designed to flex so they can turn. They deflect sideways under any load, which is exactly what you do not want on a straight cut.

If it doesn't work

Questions people ask