Calibration tools: calipers, gauges and what you actually need

Most printer tuning is measurement. Without a way to measure, you are adjusting settings and hoping — and the difference between a printer that produces parts which fit and one that produces parts which nearly fit is almost entirely down to owning a set of calipers.

Digital calipers: buy these first

If you own one measuring tool, own these. They cost very little and they are the instrument for:

• E-steps / extrusion multiplier calibration — mark 120 mm of filament, extrude 100 mm, measure what is left. This one procedure fixes a startling proportion of quality complaints.
• Wall thickness checks — print a test cube, measure the walls against what the slicer intended, adjust flow.
• Dimensional accuracy — measuring a printed 20 mm cube tells you whether your steps-per-mm and shrinkage compensation are right.
• Filament diameter — spot-checking a spool that prints badly. Good filament holds close to 1.75 mm; measure in several places and at right angles for ovality.
• Designing parts that fit real objects. Arguably the biggest use.

Cheap digital calipers are fine for this work. Their weaknesses are battery life and drifting zero — press the zero button before each measurement and they are perfectly adequate. Stainless steel jaws are worth the small premium over plastic.

Feeler gauges

A set of feeler gauges gives a repeatable nozzle-to-bed gap instead of the traditional sheet of paper, whose thickness varies with the paper. Useful if you level manually and want the same starting point every time. If your printer has an automatic probe, this is optional.

Worth noting: the paper method is not wrong, it is just imprecise. Both are only a starting point — final Z offset is set by looking at a printed first layer, as described in first layer calibration.

Other things worth owning

• A small square — for checking the frame is actually square, which is the sort of thing nobody verifies until prints come out as parallelograms.
• Cleaning needles sized to your nozzle, for clearing partial blockages.
• Hex keys that fit properly. The set that came with the printer is usually soft and will round off your grub screws. This is a genuinely worthwhile upgrade — see belts and tensioners.
• A cheap infrared thermometer if you suspect the bed is not reaching the temperature it reports.

What you do not need

Micrometers, dial indicators and precision gauge blocks are lovely and almost never necessary for FDM printing, where layer height and nozzle width set the real limits on accuracy. Spend the money on filament instead.