Brad point drill bits: what they are, sizes, and speeds
A brad point drill bit is a twist drill reground for wood. In place of the twist drill's straight chisel edge it has a sharp center spur that fixes the bit exactly on the mark, and two raised outer spurs that score the hole rim before the cutting lips plane away the waste [1] [5]. The same bit is sold under the names lip and spur drill bit and dowel (dowelling) drill bit [1] [3]. This page covers the anatomy, what the bit can and cannot be used on, the size chart with overall and flute lengths, and the RPM to run each diameter at. It stays on brad point territory: for choosing between spade bits, Forstner bits, and hole saws at larger diameters, see wood boring bits compared, and for bit materials and coatings see drill bits by material.
The one-minute answer
Three facts cover most of what people ask. First, the center spur is what stops the walking: it pushes into the wood first and holds the bit in line, which is why a brad point bit starts exactly where you marked, even at an angle [1] [5]. Second, the spurs are why the hole is clean: they sever the wood fibers at the periphery before the inside of the hole is removed, so fibers are cut rather than pulled messily out of the timber, on both entry and exit faces [1] [2]. Third, it is a wood-and-plastic tool: metal is out of scope for a brad point except the thinnest soft sheet, where the aggressive geometry binds anyway [1] [4].
Anatomy: center spur, spurs, lips
Four parts do the work, and Popular Woodworking's cutaway labels them brad tip, spur, lip, and flute [2]. The center brad is a needle point: it enters first and locates the hole, which is what a twist drill's chisel edge cannot do on a flat surface [1] [5]. The two outer spurs sit at the rim, proud of everything else, and they score the circumference of the hole ahead of the cut [1] [5]. The lips sit behind the spurs and plane off the base of the hole inside the already-cut line, handing the waste to the flutes [1] [5].
That order of operations is the whole difference from a twist bit. Wood drilled across the grain produces long strands of fiber that a twist drill lifts and tears at the hole edge; the brad point's outside corners lead, cutting the periphery first, which maximizes the chance the fibers are cut cleanly rather than pulled out [1]. ICS Cutting Tools describes the same mechanism for overlapping holes: the center spur holds the drill on target while the two cutting spurs make contact, so even overlapping holes can be drilled [3].
Popular Woodworking's guide adds the two failure modes this geometry exists to prevent: a twist bit can be tricky to start in the exact spot required, while the brad point starts without wandering and its spurs reduce splintering at entry and tear-out at the back side [2]. A sharp bit plus a backing board still does the most for exit quality [2] [6].
When to choose a brad point over a twist bit
Choose the brad point when placement and edge quality matter: dowel joints, shelf pins, screw clearance holes in visible work, and any hole marked to a line [5] [6]. Popular Woodworking calls it the best choice for most small-diameter holes in woodworking, common sizes 1/16 to 5/8 in, and notes it locates precisely and keeps from wandering [2]. A twist drill remains the tool for metal, and it drills wood acceptably, just with a wander-prone start and a rougher exit [1] [7].
Two boundaries keep the choice honest. Above roughly 1/2 in, brad points give way to other wood borers: woodworking guidance caps practical handheld brad point work at 1/2 in, and above that a spade bit, hole saw, or Forstner takes over, a comparison our wood boring bits page owns [6]. And depth is bounded by the spurs: once the spurs are buried past the hole rim the clean-shear advantage is spent, so brad points are for through-holes and shallow holes, not deep boring [1] [5].
Brad point drill bit size chart
The chart below lists the common fractional diameters with overall and flute (working) lengths, in inches, from two manufacturer tables that agree size for size: Bosch's B146xx brad point series and W. L. Fuller's series 251 jobber-length brad points [8] [9]. Where McMaster-Carr's W. L. Fuller listings add a max drilling depth, it tracks the flute length within rounding [10].
| Diameter | Decimal | Overall length | Flute length | Sources |
|---|---|---|---|---|
| 1/16 | 0.0625 | 1-7/8 | 7/8 | [9] [11] |
| 1/8 | 0.1250 | 2-3/4 | 1-5/8 | [8] [9] |
| 3/16 | 0.1875 | 3-1/2 | 2-5/16 | [8] [9] |
| 1/4 | 0.2500 | 4 | 2-3/4 | [8] [9] |
| 5/16 | 0.3125 | 4-1/2 | 3-3/16 | [9] [10] |
| 3/8 | 0.3750 | 5 | 3-5/8 | [9] [10] |
| 7/16 | 0.4375 | 5-1/2 | 4-1/16 | [8] [9] |
| 1/2 | 0.5000 | 6 | 4-1/2 | [8] [9] |
| 5/8 | 0.6250 | 7-1/8 | 5-3/16 | [8] [9] |
Read the chart with two notes in mind. First, brad point lengths are manufacturer-specific, not standard: Bosch's series runs shorter than Fuller's at several diameters (its 3/8 in bit is 5-3/16 in overall where Fuller's is 5 in, and its 1/2 in is 5-15/16 in against Fuller's 6 in, each with proportionally less flute), because each maker sets its own length series [8] [9]. The chart's 3/8 through 5/8 rows follow Fuller's series; Bosch's equivalent diameters are listed in its own table [8]. Second, the 1/16 in row needs its own caveat: Fuller's jobber-length table lists 1/16 in at 1-7/8 in overall with 7/8 in of flute, but that size is shared across the regular-point and fast-spiral variants while the brad point column itself starts at 5/64 in [9] [11]; Popular Woodworking nonetheless gives 1/16 to 5/8 as the common brad point range, and McMaster's fractional filter starts at 1/16 in [2] [10]. Treat 1/16 in as the edge of the range where availability varies by maker, which is exactly what the two tables show.
Two practical notes on fit and buying. Shank and cutting diameter are the same on brad points up to 1/2 in, so a 1/2 in bit needs a 1/2 in chuck; above that, Fuller ships oversized shanks that may not fit and offers grinding to size, a boundary our drill chuck size chart covers [9]. And for a first set, the woodworker's guidance is to buy a 7-piece HSS set in the sizes you actually use (1/8 through 1/2 covers furniture and cabinet work) rather than a 29-piece index, then upgrade individual sizes as they dull [6]. For standard twist drills and their length classes, see jobber drill bit sizes.
Brad point drill speed chart (RPM by diameter)
Brad point speeds sit below twist drill speeds in wood because the spurs need time to shear the rim. The Engineering ToolBox table gives per-diameter RPM for brad point bits in softwood and hardwood; A Butterfly House publishes the same numbers in drill-press form [12] [13].
| Diameter | Softwood RPM | Hardwood RPM | Sources |
|---|---|---|---|
| 1/8 in | 1800 | 1200 | [12] [13] |
| 1/4 in | 1800 | 1000 | [12] [13] |
| 3/8 in | 1800 | 750 | [12] [13] |
| 1/2 in | 1800 | 750 | [12] [13] |
| 5/8 in | 1800 | 500 | [12] [13] |
The pattern is simple: softwood keeps 1,800 RPM across the whole range, while hardwood steps down as diameter grows, 1,200 at 1/8 in to 500 at 5/8 in [12] [13]. Popular Woodworking's Spring 2005 chart carries the same logic (hardwood column 1,000 RPM and falling through the fractional diameters, softwood above it) [2]. For twist drill wood speeds, metal speeds, and the surface-feet formula behind all of it, see the drill speed chart; for press pulley mapping, the drill press speed chart.
Brad point bits in metal and plastic
Metal: no, with one narrow exception. The brad point has an extremely fast cutting geometry, no point angle combined with a large lip angle, so the edges take an aggressive cut with little point pressure; in metal this makes the bit bind, and in thin soft sheet it punches through and can leave the bit's cross-section behind [1]. Fuller scopes its brad points to wood, plastic, and sheet metal, which confirms how narrow the metal allowance is [9]. For metal drilling, use a twist drill or step drill; our drill bits by material guide owns that choice, and how to drill through metal covers technique.
Plastic: yes, with speed discipline. Wikipedia notes brad points are also effective in soft plastic, because a handheld twist drill smears the hole edges through side friction and heat where a brad point's spurs score the rim first [1]. PlasticRanger calls the spur-point bit the gold standard for the same reason and gives speed bands by plastic: under 500 RPM in acrylic, 500 to 1,000 in polycarbonate, 1,000 to 1,500 in PVC and HDPE [14]. ToolCompatibility gives brad points 1,200 to 2,000 RPM in general plastics, slower for acrylic and PVC [15]. The overlap says: run the bottom of the band in anything brittle or melty, back the work with scrap, and withdraw often to clear chips and heat [14] [15].
Related
For the larger wood borers (spade bits, Forstner bits, hole saws): wood boring bits compared. For bit materials and coatings: drill bits by material and drill bit coatings. For speeds in every other material: drill speed chart and drill press speed chart. For the pilot holes these bits drill for screws: pilot hole chart. For standard twist drill lengths: jobber drill bit sizes. For plug cutters that make the dowels hiding these holes: plug cutter sizes.
Sources
- Wikipedia, Drill bit, brad point bit section: aka lip and spur and dowel drill bit, spur center point with four sharp corners, periphery-cutting lips severing fibers before the base of the hole is planed, soft-plastic effectiveness and hole-edge smearing with twist bits, binding in sheet metal (en.wikipedia.org/wiki/Drill_bit)
- Popular Woodworking, What's the Difference Between Drill Bits and Your Guide to Drill Bits (Spring 2005): brad tip / spur / lip / flute anatomy labels, best choice for most small-diameter woodworking holes, common sizes 1/16 to 5/8 in, suggested brad-point speed chart hardwood and softwood, wandering and tear-out problems solved (popularwoodworking.com/techniques/drill-bit-difference; media.popularwoodworking.com/app/uploads/Your-Guide-to-Drill-Bits.pdf)
- ICS Cutting Tools, Brad Point Drills: smooth accurate holes in wood with minimum tear-out, center spur prevents walking so overlapping holes can be drilled, also known as Dowelling Bits or Lip and Spur Drill Bits, carbide-tipped variants also cut plastics and hard fiber plates (icscuttingtools.com/brad-point-drills.htm)
- ShunTool, Brad Point Bits: centre point will not skate, outer spurs sever fibres at the rim before flutes lift waste, for wood board and most plastics only, one hole in steel destroys the spurs (shuntool.com/tools/brad-point-bits)
- Woodwiki, What Are Brad Point Drill Bits: anatomy and spur-scoring explanation, when to use and when not to, six jobs that call for a brad point, technique (woodwiki.org/guides/brad-point-drill-bits)
- Woodwiki, What Are Brad Point Drill Bits: seven sizes cover furniture and cabinet work 1/8 through 1/2 in, buy a 7-piece HSS set first and upgrade individual sizes, maximum practical handheld size 1/2 in, backing board as the essential tear-out prevention (woodwiki.org/guides/brad-point-drill-bits)
- Woodwiki, What Are Brad Point Drill Bits: twist bits as the common default and their wander and tear-out trade-offs (woodwiki.org/guides/brad-point-drill-bits)
- Bosch Professional, Brad Point Drill Bits product table: B146xx series 1/8 to 5/8 in with working length L1 and total length L2 per diameter, e.g. 1/8 x 2-3/4, 3/16 x 3-1/2, 1/4 x 3-5/16 working 2-1/4, 7/16 x 5-9/16 working 3-1/2, 1/2 x 5-15/16 working 3-1/2, 5/8 x 7 working 4-1/4 (boschtools.com/us/en/brad-point-drill-bits-43540-ocs-ac/)
- W. L. Fuller, Drills catalog, Regular or Jobbers Length series 251 Brad Point HSS: flute and overall lengths per diameter, 5/64 x 2 in, 1/8 x 2-3/4, 3/16 x 3-1/2, 1/4 x 4, 5/16 x 4-1/2, 3/8 x 5, 7/16 x 5-1/2, 1/2 x 6, 5/8 x 7-1/8, brad points scoped to wood, plastic, and sheet metal, oversized shanks above 1/2 in may not fit a chuck (wlfuller.com/drills)
- McMaster-Carr, Brad-Point Drill Bits: W. L. Fuller round-shank rows 1/8 x 2-3/4 in overall 1.63 in max drilling depth, 1/4 x 4 in overall 2.75 in depth, 5/16 x 4-1/2 in overall 3.19 in depth; fractional size filter from 1/16 in by 1/64 steps (mcmaster.com/products/brad-point-drill-bits/)
- W. L. Fuller, Drills catalog: jobber-length series shares flute 7/8 in and overall 1-7/8 in for 1/16 in drills across regular-point and fast-spiral variants, brad point series beginning at 5/64 (wlfuller.com/drills)
- Engineering ToolBox, Hardwood and Softwoods Recommended Drill Bit Speeds: brad point bits 1/8 through 1 in by softwood and hardwood RPM, 1800/1200 at 1/8, 1800/1000 at 1/4, 1800/750 at 3/8 and 1/2, 1800/500 at 5/8 (engineeringtoolbox.com/drill-bit-speed-hardwood-softwood-d_1451.html)
- A Butterfly House, Drilling Wood: What's the best speed: brad point bit drill-press speed chart, identical RPM values to the Engineering ToolBox brad point table, with the theory that larger bits and hardwoods run slower (abutterflyhouse.com/drill-speed-wood/)
- PlasticRanger, How To Drill A Hole Into Plastic: heat as the enemy, spur-point (brad-point) bits the gold standard for plastic, speed bands under 500 RPM acrylic, 500 to 1,000 polycarbonate, 1,000 to 1,500 PVC and HDPE, stop if plastic melts around the bit (plasticranger.com/how-to-drill-a-hole-into-plastic)
- ToolCompatibility, What Drill Bit for Plastic and PVC: brad point bits excellent on plastic, prevent wandering and melt less because edges cut cleanly, 1200 to 2000 RPM general, slower for acrylic and PVC (toolcompatibility.com/what-drill-bit-for-plastic)