Table saw

The blade eats an eighth of an inch

A table saw blade does not divide a board, it removes a slot and leaves two pieces either side of it. That slot is the kerf, and on a full-size saw it is usually an eighth of an inch. Every cut between two pieces costs that much material, permanently, and it is the single most common thing missing from a cut list that does not work out.

Here is the whole problem in one example. A 96" board cut into 12" pieces looks like eight pieces of arithmetic. It is seven.

Which is why a 24" part does not fit twice across a sheet

A sheet of plywood is 48" wide and half of 48 is 24, so two 24" parts across it is the obvious layout. It does not fit — the two parts plus the kerf between them come to 48 1/8", and the sheet is 48". You get one part and an offcut, and the offcut is the piece you needed.

Take a sixteenth off the part and both fit, which doubles what the sheet yields. This is why a cut list is worth laying out before the saw is switched on rather than after.

Every cut goes all the way across

A table saw can only make cuts that run the full width of the piece, splitting one board into two. Those are guillotine cuts, and it is a real constraint rather than a technicality: a layout that interlocks parts like a jigsaw needs a CNC router, and cannot be followed on a table saw at any speed.

It also sets the order of operations. Break a sheet down into strips first, then cut the strips into parts, because that is the only sequence a guillotine cut allows — and it is far easier than trying to wrestle a full sheet across a saw on your own.

A thinner kerf is not free

Thin-kerf blades take about 3/32" instead of 1/8", which sounds like a saving and mostly is — a thirty-second of an inch back on every cut, so five eighths of an inch across twenty of them. The trade is stiffness: a thinner plate deflects more, so it wants a sharp blade, a steady feed and a saw that is set up properly, and it will wander in thick hardwood where a full-kerf blade would not.

Whichever you fit, measure the slot it actually cuts and put that number into the cut list rather than the one on the box. It is the figure everything else is built on.

What this page does not tell you

• —The kerf figures here assume a full-kerf blade at 1/8". Measure yours: make a cut in scrap, then measure the slot with calipers or fit a feeler gauge. Track saws and bandsaws take far less, and a dado stack takes far more.
• —Nothing on this page is a safety instruction, and a table saw is the tool most likely to hurt you in a home shop. Read the manual that came with yours, keep the riving knife or splitter fitted, and never freehand a cut between the blade and the fence.
• —This site does not test tools and does not rank them, so there is no recommendation here about which saw to buy — only about the arithmetic any of them forces on you.