Buy 1/4 in. It fits every small and mid-size router sold in the US, and a 12-piece 1/4 in set covers 90% of edge work.
Twelve. Six leaves you short on profiles, fifteen mainly adds sizes you will not use for a year.
Shank diameter, carbide grade, bearing quality, and whether the profiles are distinct. Everything else is packaging.
Carbide for anything you will use more than ten times. HSS only for one-off jobs in softwood.
It changes the cutting geometry, not the profile. Higher angles are for harder material and finer finish; lower angles clear chips faster.
Cobalt (M35, 5% Co). Regular HSS work-hardens stainless and burns out in a few holes.
Wrong blade type or too much speed. Continuous-rim blades at low rpm chip far less than segmented blades at full speed.
Skip no more than one grit at a time: 60, 120, 240, then 400 if you are finishing. Jumping from 60 to 400 wastes paper and leaves scratches.
Usually three things: carbide grade, bearing quality, and whether the case and profiles are actually as described. Sometimes nothing, and you should check.
3-flute for aluminium, 4-flute for steel, 2-flute for plastics and deep slots. Flute count trades chip clearance against finish.
Only for hardened steel above 45 HRC. For mild steel and aluminium, HRC55 cuts better and costs less.
Flute geometry and coating, not the carbide. Aluminium bits have more relief and polished flutes; steel bits have a sharper edge and a heat-resistant coating.
Match your collet. 3.175 mm (1/8 in) for micro and PCB work, 6 mm for general hobby CNC, 8 mm when you take deeper cuts.
M35 (5% cobalt) for most shop work; M42 (8%) only when you drill hard stainless all day and can control speed precisely.
Masonry bits have a carbide tip and a fluted body for brick and block; hammer bits have a stronger shank for SDS rotary hammers; regular bits are for metal and wood only.
Continuous rim for porcelain and clean tile cuts, segmented for concrete and fast rough cuts, turbo for a compromise on hard stone.
Low tooth count for fast rip cuts in softwood, high tooth count for clean crosscuts and fine trim. More teeth = slower feed and smoother finish.
Bi-metal for wood, plastics and thin metal; TCT (tungsten carbide tipped) for brick, block and fibre cement. Neither works well outside its material.
Lower rpm for larger diameter bits. A 50 mm bit at 24,000 rpm is dangerous; the same bit at 12,000 rpm is fine. Small bits can run fast.
The V10 has three regional variants (US, China/Japan, Slim). The filter housing differs, so a US-market V10 needs the US-version filter.
Wash the pre-motor filter monthly and replace every 3-6 months. The post-motor filter is not washable on most models and should be replaced every 6-12 months.
Most Dyson tools share the same clip fitting across V6-V15 and G5, so a 5-piece kit covers the common models. The wand and powered heads are where models differ.
No. 8 mm is 0.315 in and 1/4 in is 6.35 mm; they differ by 1.65 mm and need different collets.
Yes. A 6 mm bit is not a 1/4 in bit; the gap is 0.35 mm, which is enough to ruin a press fit.
118 degrees for wood, plastics and soft steel; 135 degrees split point for stainless and hard alloys because it walks less.
4/6 TPI variable pitch for wood and metal; arbors are sold separately because they set the size range and fit your chuck.
Subtract the pitch from the diameter for a 75% thread. M3x0.5 takes 2.5 mm, M6x1 takes 5.0 mm, M10x1.5 takes 8.5 mm, M12x1.75 takes 10.2 mm.
NPT is the US standard (60 degree, tapered), BSP is British (55 degree). They do not seal against each other.
HRC is the hardness of the workpiece the bit is designed for, not the hardness of the bit. Higher HRC handles harder steel but is more brittle.
Down-cut for a clean top face, up-cut for chip clearance, compression for clean faces on both sides of plywood.
Most US angle grinders use a 7/8 in (22.23 mm) arbor; many imported machines use 20 mm.
They are standard head shapes: A cylinder, C ball, D ball-nose cylinder, E oval, F round-nose tree, G pointed tree, H flame, L taper, M cone, N inverted cone.
If more than two profiles burn, replace the set. Burning is usually wear plus too high an rpm, not a single bad bit.
Replace with cobalt if the material is stainless or hard steel. Snapping is usually too much pressure, wrong rpm, or a bit that was already dull.
Do not force it further. Use a tap extractor or spark-erode it out, then drill oversize and fit a thread insert.
Bi-metal hole saws cannot be sharpened practically. Replace the saw, and check the arbor and pilot bit first.
When the cut gets slow, the flutes look polished, or it starts smearing instead of cutting. Replace with a fresh single or double cut burr of the same shape code.
Usually the wrong shank size, a worn collet, or a dirty bore. An 8 mm bit in a 1/4 in collet will always slip.
Straight carbide bits with 2 flutes. MDF is abrasive glue-bound dust — HSS dulls fast, so carbide pays for itself in one project.
Chip-out comes from the cut geometry, not the rpm. Use a down-cut or compression bit, and score the cut line if the edge must be perfect.
Slow the feed at the exit corner, use a down-cut bit on the visible face, and take a light climb cut on the last pass.
A hobby shop gets 2-3 years from a carbide set. A production shop running daily gets 3-9 months from the same set. Heat is what kills them, not hours.
For softwood and occasional use, yes. For hardwood, MDF, or anything you sell, no — the bearings and the carbide grade are where the money went.
Wooden case, stood upright, with a silica pack. Never let bits touch each other — carbide chips against carbide.
Step drill for holes up to about 35 mm in sheet under 4 mm thick. Hole saw above that, or for thicker plate.
Forstner. It cuts a flat bottom and a clean rim; a hole saw leaves a plug and a rougher edge.
Match the arbor thread to the saw: 1/2-20 for most small saws, 5/8-18 for larger ones. The pilot drill diameter matters too.
Yes, at low rpm with constant cutting fluid and light pressure — but expect one or two holes per saw, not fifty.
M35 cobalt with a 135-degree split point, run at about a third of the speed you would use in mild steel, with cutting fluid.
Brad-point for clean holes with a precise entry, auger for deep holes, Forstner for flat bottoms. Standard twist bits wander on hardwood.
Carbide-tipped masonry bit at low rpm with no hammer action, or a diamond hole saw with water. Never use hammer mode on tile.
Drill a pilot in the head, use a left-hand extractor, turn counter-clockwise with steady pressure. Heat helps if there is threadlocker.
For internal threads, yes if there is enough material left — use the same size tap to clean up, or go oversize and fit an insert. For external threads, a die can usually be run back over.
Measure across ten threads and divide by ten, or match against a known bolt. Pitch is the distance between crests, not the diameter.
Hand taps come in taper, plug and bottoming sets and are meant to be turned by hand with a wrench. Machine taps cut in one pass in a machine, and snap if used by hand.
A die stock holds round split dies for cutting external threads. A die wrench (or die handle) is the older two-handle version. Both do the same job; the stock is easier to keep square.
Single cut with a coarse tooth, run slower than you would in steel, with a wax or oil lubricant to stop the aluminium welding to the flutes.
It depends on head diameter and material. A 6 mm head runs about 25,000 rpm in aluminium and 12,000 in stainless. Bigger head, slower.
Start at 18,000 rpm with a 6 mm bit, 2,000-3,000 mm/min feed, 3 mm depth of cut. Then adjust by chip size, not by sound.
Yes on most bits with a bearing. The bearing is a standard size; measure the bore and the outer diameter and buy a sealed replacement.
For light work in tight spaces, yes. They cannot take the torque of a hole saw or a large bit, and the cheap ones strip their gears quickly.
Round or hex shanks up to 10 mm (3/8 in). A 1/2 in chuck takes up to 13 mm. Hex shanks up to 1/4 in fit both.
Soak the bit in oven cleaner or a dedicated bit cleaner for 10-15 minutes, then scrub with a brass brush. Never use a file or sandpaper on the carbide.
Yes on a bench grinder with a gauge, for bits 3 mm and up. A hand-sharpened bit is fine for wood and mild steel but will not hold in stainless.
Almost always one of three things: the shank is not seated past the jaws, the shank is scored, or the chuck jaws are worn. Check them in that order.
A keyed chuck holds tighter and does not loosen under load, which is why drill presses still use one. Keyless is faster for small bits and hand drilling.
Mount a known-good bit, spin the spindle by hand, and read a dial indicator on the shank just below the collet: under 0.05 mm (0.002 in) is healthy, over 0.1 mm explains chatter and burnt edges.
Hex shanks for impact drivers and quick-change holders, round shanks for three-jaw chucks and drill presses. A round shank in an impact driver spins in the jaws.
SDS Plus for hammers up to about 1 in drilling capacity, SDS Max for 1-1/2 in and above. The shanks are different sizes and are not interchangeable.
Use a quick-change extension with a hex-shank bit for clearance holes, or an aircraft-length bit when the hole has to be accurate. Extensions add runout, so never use them for a precision fit.
If it stands proud, grip it and turn it back out; if it is below the surface, drill around it with a smaller solid-carbide bit or burn it out. Never hammer a punch into a hardened bit.
Yes in aluminium workpieces only: a saturated alum solution held at about 50 C eats an HSS tap over one to three days and leaves the aluminium alone.
Sulphurised tapping fluid for steel, kerosene or light oil for aluminium, and nothing at all for cast iron. The wrong fluid is worse than none in aluminium.
For aluminium and light drilling, yes. For steel it evaporates before it does any work, and holes burn and work-harden.
Carbide, 1/2 in shank for anything deeper than 6 mm, and lighter passes. Hickory is hard enough to chip a 1/4 in shank on a deep cut.
Pine burns from feeding too slowly, not from rpm being too high. Keep the bit moving at a steady rate and take one full-depth pass where the cutter allows it.
Carbide only, pilot every screw hole, and count on replacing cutters sooner. Ipe is dense and abrasive enough that a plain HSS bit will not survive one deck.
Black oxide for general shop work, TiN only for repetitive drilling in steel. Once you sharpen either, the coating is gone and you are back to the base HSS.
They are the same coating written two ways. What matters is whether the tool runs hot and dry, which is what AlTiN is for, versus wet and cool, where TiN or uncoated is fine.
Only for carbon fiber, fiberglass and other abrasive composites. On wood the coating adds nothing, and a coated bit cannot be resharpened.
Morse taper (MT2, MT3) mates the arbor to the machine spindle. Jacobs taper (JT33, JT6) mates the chuck to the arbor. You need both numbers to order a chuck that fits.
R8 is the spindle interface on many mills; ER20 or ER25 hold the cutter. If your mill is R8, you run an R8-to-ER adapter, so the answer is both, not either.
Feeding in the direction of cutter rotation, taking too deep a cut, or letting the bit grab a corner. Every edge cut should feed against the rotation.
Fence locked, bit tight, guard and featherboards in place, workpiece clear of the bit at start-up, and push sticks within reach. Thirty seconds of checks prevents most table injuries.
Yes for MDF, particleboard and any production work. The dust is a health hazard and it also packs the cut, which overheats the bit and burns the edge.
Carbide grade, bearing quality and shank tolerance — not piece count. Two 12-piece sets can differ by five times in price and look identical in the box.
One good bit if you know the exact profile you need. A set if you are still building furniture and need options — but below three profiles, single bits are cheaper.
Buy the one that matches the fasteners you actually handle. SAE for US machinery, plumbing fittings and older equipment; metric for anything imported after the 1990s.
2-1/8 in (54 mm) for the knob bore through the face, and 1 in (25 mm) for the latch bore from the door edge. Drill the latch hole first.
3/4 in for one or two cables, 1 in if you may pull more later. Keep the hole at least 1-1/4 in from the stud face, or cover it with a nail plate.
Measure the outside diameter, not the nominal size: 1-1/2 in PVC is 1.900 in OD, so a 2 in hole saw gives a working clearance fit.
A power auger with a bit 2 in wider than the post for concrete, or 1 in wider for gravel. Call 811 before the first hole, every time.
Yes. Standard European concealed hinges take a 35 mm cup bore, 11-13 mm deep, set 3-5 mm in from the door edge.
8 degrees for drawer sides, fine furniture and hardwood. 14 degrees for half-blind joints, softwood and jigs that need a stronger wedge. The bit must match the jig template angle.
Set it on scrap, cut, measure the result with a caliper, and adjust in 0.1 mm steps. Never set depth by eye on the finished workpiece.
Only as a light finishing pass of 0.5 mm or less, and only with the work held against a fence or in a jig. Never climb cut hand-held with a large cutter.
Several light passes are faster overall in hardwood: three passes at 3 mm beat one at 9 mm because the bit stays sharp, the motor does not bog, and you skip the cleanup of a burnt edge.
A dull bit or a feed that is too slow for the rpm. The edge rubs instead of slicing, and the friction scorches the surface in under a second.
Measure the shelf stock with calipers, not the nominal size. Plywood sold as 3/4 in is usually 0.70-0.72 in, so a 3/4 in bit cuts a loose dado and the shelf rocks.
Four jobs cover a standard cabinet install: 35 mm hinge cup, 5 mm shelf pin, pilot holes for screws, and a flush-trim bit for filler strips.
Rout it with a straight bit and a template, then square the corners with a chisel. Set the depth to the hinge leaf thickness plus 0.5 mm, not deeper.
Match the saw to the knockout, not to the conduit trade size. Half-inch EMT needs a 7/8 in (22 mm) hole, three-quarter needs 1-1/8 in (28.6 mm), one inch needs 1-3/8 in.
Keep holes in the middle third of the joist depth, no larger than one third of the depth, and at least 50 mm from the top and bottom edges. Never notch the bottom edge.
A 1/2 in radius round-over for a soft nosing, or a bullnose bit when the nose has to be fully rounded. Large radius bits belong on a 1/2 in shank at reduced rpm.
Groove first with a straight bit at one third of the board thickness, then cut the tongue to fit that groove. Making the tongue first leaves you with a joint that does not close.
Brad-point bits from 2 to 6 mm for clean holes, and 3 mm shank router bits for edges. Anything under 3 mm needs high rpm and light feed, or it snaps.
Soak in a chelating rust remover or citric acid solution, then scrub the shank with a brass brush. Keep abrasive away from the flutes and never touch the cutting edge.
Chemical stripper plus a card scraper, not a sander and never a router or burr. Power tools cut through softened paint and into the timber in one pass.
Pare the chip clean, then fill with a sliver of matching veneer or a wax stick. If the chip is longer than 25 mm, rout a shallow rebate and inlay a strip instead.
Yes, if you can afford to lose 3-5 mm of width. Clamp a straight edge, run a flush-trim or pattern bit along it, and the damaged edge becomes a clean reference.
Only after you have swept it for metal. One embedded nail chips a carbide edge, and a carbide bit that has chipped will not cut cleanly again until it is re-ground.
Drill it clean to the next size up, glue in a hardwood dowel, then drill a fresh pilot. Filling with glue and toothpicks fails the second time the joint takes load.
Usually yes. Rust on the shank and body is cosmetic; rust or chipping on the cutting teeth is not. Clean it, inspect the teeth under a light, and retire any tap with a chipped edge.
Chuck a straight rod, bring the table up, and sweep a dial indicator around a 150 mm circle. More than 0.1 mm difference across the circle means the table needs shimming.
A caliper depth rod, measured at two points 90 degrees apart, and read against the surface the hole was drilled from. Tape on the bit is a guide, not a measurement.
Measure with the internal jaws of a caliper at two points 90 degrees apart. A twist drill typically cuts 0.05-0.15 mm oversize, so a nominal 10 mm hole measures about 10.1 mm.
Run the matching bolt or a thread gauge into the finished hole before you assemble anything. A bolt that goes in by hand for its full length with no wobble is the pass test.
Yes. Measure the shank with a micrometer at three points. A 1/4 in shank should read 6.35 mm; under about 6.30 mm it will slip under load.
Use an offcut of the new flooring plus underlay as a gauge, and add 3 mm for the door to swing. If the total is more than the existing gap, the door has to come off and be trimmed.
Cut a test piece and measure its width at both ends. A taper of more than 0.2 mm over 200 mm means the fence is not parallel to the bit.
Cut the template from 6 mm MDF or 8 mm acrylic, file the edge to the line, and use a pattern bit with the bearing on the template. A template that is 0.3 mm out makes 50 parts that are all 0.3 mm out.
Set the quill depth stop, add a fence and a hard stop on the table, and drill without moving the workpiece clamp. Repeatability of 0.1 mm comes from the stops, not from skill.
Yes in wood and plastics up to about 30 mm total, using a template on top and a clamped stack. In metal, stack drilling works but heat and chip clearance limit it to two or three plates.
Never with fingers near the bit. Use a carrier board with stops, a handscrew, toggle clamps, or double-sided tape, and keep the bit opening in the fence as small as the cut allows.
Yes. Number your bits, rotate every 50-100 parts, and log which bit cut which batch. Rotating spreads wear and tells you when a bit is about to fail instead of finding out mid-run.
Several smaller sets usually win, because you buy the sizes you use and skip the ones you never touch. One large set is better when you need every size immediately and want one case to find them in.
Buy if the bit costs less than about three rentals, or if you can name a second job for it. Rent if it is a large cutter that needs a machine you do not own anyway.
Yes, at least one spare pilot drill per common size and one spare arbor. The pilot drill snaps far more often than the saw wears out, and a saw with no arbor is unusable.
Buy per project until you can name three future jobs for a size. Stockpiling feels efficient and usually ends with a drawer of sizes that have never been out of the case.
Yes if you work across M3 to M12 regularly, because a single tap costs a large fraction of the whole set. No if you only ever cut two sizes, where one good tap each is better steel for the same money.