A Forstner bit is the best way to bore high-quality holes that are accurately sized, accurately located, and with a cleanly cut rim. Today, the bits come in a variety of designs. To find out which ones are best, I tested 18 brands judging them by several criteria: Size, chip-clearing, temperature, and drilling ability.

Size –  In general, I tested 1/2-in.-dia. and 1-in.-dia. bits but a 5/8-in.-dia. bit was the smallest bit size in the MLCS set so I used that one in our tests. I measured the diameter of each bit to see how close it was to the specified size, and then I measured the diameter of the hole itself. Most holes were slightly larger than the bit that drilled them, indicating slight runout. For the MLCS bits, the 5/8-in.-dia. bit was 0.617-in.-dia.and the 1-in.-dia. bit was 0.996-in.-dia. The bits drilled holes that were 0.622-in.-dia. and 1.000-in.-dia. respectively.

Chip Clearing – Bits choked with chips don’t cut well and may increase friction and burning. Many of the 1/2-in.-dia. bits became badly plugged when the head went below the wood’s surface. The 5/8-in.-dia. MLCS bit plugged. The 1-in.-dia.-bit plugged as well if it drilled more than 3/4-in. deep.

Temperature – To test the longevity of the bits, I mounted each 1-in.-dia. bit in a drill press. I chose the larger bits for this test because there is a greater area in contact with the wood, and therefore more friction. I set the speed to 480 rpm and drilled 100 holes 1 in. deep in hickory, a wood known for its ability to dull a sharp cutter. I used a digital infrared thermometer to check each bit’s temperature every 10 bores. An increase in temperature could signal a dulling cutting edge. While the temperatures ranged from 134ºF to 268ºF, the MLCS bit measured an average of 186°F. In general, bits that made cleaner cuts generated less heat.

Drilling Ability – No other type of bit can match the quality of a Forstner for the cut around the rim and sides of a hole. The MLCS bit left a bore rim with very good quality.

I also tested to see how the 1/2-in. bit cut overlapping holes and holes drilled at an angle. The rim design in Forstner bits allow you to drill clean overlapping holes, as when excavating a mortise. The MLCS bits scored an “good” in their ability to bore overlapping holes. The Forstner bit’s sharp rim also makes it easy to start the bit in a steeply angled workpiece, as when cutting pocket holes in a table apron. The MLCS bits received a good score when tested for this.

If a truly flat-bottomed hole is the deciding factor in picking Forstner bits, the MLCS bits with the removable center spur are the ones to buy. Overall, however, I picked Famag bits as the best overall in the tests. Grizzly gets the nod for best value.

The MLCS bits are available from www.mlcswoodworking.com.

Fine Woodworking Recommended Products

Festool DF 500 Q-Set Domino Joiner

This joinery machine revolutionized woodworking for so many. There is no easier way to get mortise and tenon joints—but it comes at a cost.

Buy at Amazon

Fein Turbo II HEPA Wet/Dry Dust Extractor

Among the most powerful HEPA-rated shop vacs on the market, Fein’s Turbo II is quieter, more compact, and nimbler than the rest.

Buy at Amazon

Bosch 12V Trim Router

Trim routers are easier to handle when you cut the cord, and the Bosch’s compact, curvy shape and unique base give it unmatched control.

Buy at Amazon