How To Square Up Stock In A CNC Milling Machine

In the CNC work shop one of the first tasks a machinist must learn to do well is how to square up stock in a cnc milling machine. Squared up stock has all sides parallel to their opposite side and all angles perpendicular to adjacent sides.

Using Square stock allows you to create parts that mate well together. It is impossible to repeatedly create parts without starting from squared up stock. Since one of the reasons we use CNC milling machines is to create multiples identical parts, it only makes sense to start with squared up stock.

Begin by marking your rough stock using a Sharpie Marker. Number the sides as shown in the picture, with sides one and four being the largest surfaces. If all sides are equal than just make sure sides 1 & 4 are opposite each other.

The freshly machined side 1 is placed against the fixed jaw of the vise (shown in red).

A piece of round stock is placed in the vise between the movable jaw and the stock. The round stock forces the machined edge flat against the vise jaw.

Flip the stock over so that side 2 is facing down and side 3 is facing up. Side 1 should still be touching the fixed jaw of the vise.

Place the round stock back in the vise between the movable jaw and touching side 4. Tighten the vise.

Machine side 3 flat. Deburr the edges.

You now have two sides parallel to each other. Both sides are perpendicular to side 1.

Leave the stock in the vise. Edge find the edge of side 5. Change tools to an endmill. Machine side 5 flat. Deburr the edges you can easily reach. The other edges can be deburred later.

Place the stock in the vise against the fixed jaw (shown in red) with side 1 facing up. Machine side 1 flat using either a flycutter, facemill or endmill. Only remove enough material to make the surface uniform. Deburr the edges of side one with a file or deburring tool.

With side 2 facing up, machine side two removing as little material as possible while still machining a flat surface. Deburr the edges after machining.

We now have two sides which are machined 90 degrees in relation to (perpendicular) each other.

Clean the inside of the vise. Remove the round stock and place the block in the vise with side 1 facing down. Make sure the block is flat in the vise before machining.

Machine side 4 and then deburr the edges.

Safely move the endmill adjacent to side 6. Machine side 6.

Deburr the edges you haven’t deburred yet.

All six sides are now machined square .