What sizes does an adjustable wood bit cut?

It depends on the model. The IRWIN 44801 (No. 1R) adjusts from 5/8 to 1-3/4 in through 19 hole sizes in 1/8 in steps. The 45002 drill-press version covers 7/8 to 3 in with 19 sizes in 1/8 in steps. The hand-brace 44002 cuts the same 19 sizes in 1/8 in steps over 7/8 to 3 in, and the 44202 cuts 35 sizes in 1/16 in steps over the same range. The large 445002J covers 1-3/4 to 3 in. Vintage brace-era expansive bits follow the same 7/8 to 3 in pattern.

How fast can I run an expansion bit in a power drill?

Slow. The one mechanism writeup that prints an expansive-bit-specific ceiling says about 250 RPM, because the single cutter wing leaves the bit unbalanced and centrifugal load can overpower the wing clamp above 300 RPM. Independent shop speed charts put comparable large multi-spur boring tools at 250 RPM as well. Lock a cordless drill into low gear, feather the trigger, and use the side handle. A hand brace at roughly 60 RPM is the tool these bits were designed for.

Why is my adjustable bit drilling oversized holes?

Three causes, in order of likelihood: the wing clamp screw backed off under cutting load so the radius walked outward, the dovetail slot has worn so the wing rocks outward even with a tight clamp, or the spur is bent outboard and scribing a larger circle than the lip cuts. One workshop test documented a hole growing from 1-7/8 in at entry to over 1-15/16 in at exit from cutter slip alone. The fix for all three is the same: bore a test hole in scrap, measure it, and offset the scale marking rather than trusting the engraving.

Expansion bit or hole saw for a big hole in wood?

Use the expansion bit when you need one tool to cover many diameters or an odd size no fixed bit comes in, and when the hole is a through-bore. Use a hole saw when the diameter is a standard size, the stock is thin like a door, and you want the cut finished fast at a higher RPM. The expansion bit leaves a cone-bottomed hole driven by its lead screw; the hole saw cuts a ring and needs pilot-bit anchoring.

Adjustable wood bit (expansion bit) sizes, models, and RPM limits

An adjustable wood bit, also called an expansion bit or expansive bit, bores a range of hole diameters from one tool. A cutter wing slides along a graduated dovetail slot in the bit body and locks at the radius you set, while a lead screw at the centre threads into the wood and pulls the bit forward, so you are not pushing the bit, the screw is feeding it ^[19]. Fixed bits cut exactly one diameter each; the expansion bit trades some speed and wall quality for covering ten to thirty-five sizes out of one pouch ^[1] ^[19]. This page prints the boring ranges by model with sources, the RPM ceiling, why these bits drill oversized holes when they wear, and where they beat a Forstner bit or hole saw.

The range table by product

IRWIN is the brand that owns this category in North America, essentially unchanged for a century ^[19] ^[22]. Ranges below are taken from the manufacturer page and at least one independent retailer per row. Where retailers disagree, both figures are printed rather than averaged.

Model	Boring range	Hole sizes	Steps	Shank	Overall length	Sources
44801 (No. 1R, hex shank)	5/8 to 1-3/4 in	19	1/8 in	9/32 in, precision ground with 3 flats	5-1/2 in	^{[6] [7] [8] [10]}
45002 (drill press)	7/8 to 3 in	19	1/8 in	11/32 in, 3 flats	6-1/2 in per IRWIN data; some retailers print 5-1/2 in	^{[14] [15] [16] [17]}
44002 (hand brace)	7/8 to 3 in	19	1/8 in	Taper square, for brace	8-1/8 in	^{[1] [3]}
44202 (No. 2R, hand brace)	7/8 to 3 in	35	1/16 in	Taper square, for brace	8-1/8 in per most listings; AFT prints 8-1/2 in	^{[1] [2] [3] [4]}
445002J (large)	1-3/4 to 3 in	not stated	micro-dial	3/8 in reduced, 3 flats	6-3/4 in, ships with 1 blade	^{[11] [12] [13]}
Vintage No. 2 / No. 22 brace pattern	about 7/8 to 3 in	graduated scale	scale marks	Taper square tang	varies by maker	^{[19] [22]}

Model number notes and UPC confusion

Three things to know before you order, because listings in this category are messy.

The No. 1R and the 44801 are the same bit. Retailer pages for the 44801 carry the No. 1R name and the same UPC 024721100184 ^[7] ^[9]. It is sold as a drill-press bit, but the "drill press" in the name refers to the precision-ground shank with three equally spaced flats that seats in a 3-jaw chuck; IRWIN's own page describes the shank as fitting both drill presses and hand braces ^[7] ^[8].

UPC 024721100191 belongs to the 45002. That barcode shows up on the 45002 across KSC Direct, Toolbox Supply, Shell Lumber, and True Value stores ^[15] ^[16] ^[17] ^[18]. We have seen the claim that the 44002, 44202, and 445002J share it too; we could not confirm that on any listing we checked, so treat model number, not barcode, as the identifier when matching bits to the table above. The 44202's own package carries a different UPC entirely ^[3].

Specifications genuinely diverge between retailers. The 45002 is 6-1/2 in overall in IRWIN's own catalog data ^[14] ^[15] but 5-1/2 in at Toolbox Supply ^[16]. The 44202 is 8-1/8 in at most sellers ^[2] ^[4] but 8-1/2 in in AFT's listing ^[3]. Home Hardware's Canadian listing says the 7/8 to 3 in brace bit "will cut 35 hole sizes in increments of 1/8 in", which cannot both be true with IRWIN's own statement that 35 sizes come in 1/16 in steps ^[1] ^[5]; trust the manufacturer page here. Where a spec matters to your work, measure the bit on arrival.

How the mechanism works

Three parts cooperate ^[19]. The lead screw at the centre threads into the wood and advances the bit one thread pitch per revolution, which is why these bits self-feed and why the operator's job is turning, not pushing. The adjustable cutter wing slides along a dovetailed slot and carries the spur, which scribes the hole perimeter just ahead of the cutting lip that lifts the chip. A clamp screw, IRWIN calls it the Lockhead screw, locks the wing at your chosen diameter ^[6] ^[19]. On hand-brace models a micro-dial screw sets the boring diameter directly ^[1] ^[2].

Two setup details decide whether the hole comes out clean. The wing must sit tight against the body with no gap, or shavings pack the gap and the bit stops cutting ^[22]. And the cutter arm is captured by an angled lower edge under a dovetail lip; sharpening should never touch the top surface of the arm, because removing metal there opens the very gap that kills the cut ^[22]. Sharpen the spur and lip like any auger bit, with a safe-edge file ^[22].

The RPM ceiling: keep it under about 250

These bits were designed for a hand brace at 50 to 80 RPM, and that is still the right tool ^[19] ^[21]. The one detailed mechanism writeup that prints an expansive-bit-specific number says do not exceed about 250 RPM, and explains why: the cutter wing sits on one side of the body with no counterweight, so the bit is unbalanced, and above roughly 300 RPM the centrifugal load on the wing clamp can exceed what the small screw holds. The wing slides outward, the diameter grows mid-cut, and in the worst case the wing leaves the slot entirely ^[19].

Independent speed data agrees at the class level rather than calling out expansive bits by name: a shop-tested drill speed chart puts multi-spur boring bits of 2-1/8 to 4 in, the same diameter league, at 250 RPM in both softwood and hardwood ^[20], and general guidance for expansive bits in drill drivers is simply to run the lowest speed the tool offers ^[21]. If you must use a power drill, lock it in low gear, keep it under 250 RPM, and hold the side handle ^[19]. For the full RPM-by-diameter logic and press pulley mapping, see the drill press speed chart.

Why the hole comes out oversize

A hole that mics larger than the scale setting has three usual causes, in this order ^[19]:

Loose wing clamp. The clamp screw backs off under cutting load, the radius walks outward, and you get a tapered or oversized hole. This is the most common failure and it is also the cheapest fix: tighten and retest.
Dovetail slot wear. On a well-used bit the slot widens over a few hundred holes until the wing rocks outward under load even with the clamp fully tight. At that point the bit is effectively scrap; the scale can no longer be trusted.
Spur runout. A spur bent outboard scribes a circle larger than the lip cuts, and the lip tears out to the scribed line. Spin the bit slowly against a steel rule to check.

This is not theoretical. One documented workshop test of a vintage expansive bit recorded a hole that measured 1-7/8 in at entry and a bit over 1-15/16 in at exit, from nothing more than the cutter slipping during the cut ^[22]. The working habit that absorbs all three causes: set the scale, bore a test hole in scrap of the same species, measure it, and offset the scale marking by the error ^[19].

A related failure has nothing to do with the wing: a bent lead screw. The screw does all the centring work because there is no outer pilot, so a screw bent by even a degree makes the bore wander off-axis. Roll the bit on a flat steel surface with the wing removed; if the tip lifts and falls, replace the screw ^[19].

Expansion bit vs Forstner vs hole saw

This table covers only the expansion-bit angle of that question. For the general spade vs Forstner vs hole saw comparison, which owns the rest of that ground, see wood boring bits compared; for Forstner size runs, Forstner bit sizes, and for hole saw diameters and arbors, hole saw sizes.

Property	Expansion bit	Forstner bit	Hole saw	Sources
Diameter range from one tool	7/8 to 3 in, or 5/8 to 1-3/4 in, continuously adjustable	One fixed size per bit, 1/4 to 3 in available	One fixed size per saw, 3/4 to 6 in available	^{[1] [19]}
Speed ceiling	about 250 RPM	down to 250 to 500 RPM at 2 in and larger	roughly 250 to 450 RPM at 2 in and larger	^{[19] [20] [23]}
Hole bottom	Cone from the lead screw, fine for through-bores only	Flat and clean, the only choice for hinge cups	No bottom, through-holes only	^{[19] [23]}
Feed	Self-feeding, the lead screw pulls	Operator pushes	Operator pushes, pilot bit anchors	^{[19] [22]}
Cost to cover many sizes	One bit, retail listings from a 10 dollar closeout to about 49 dollars	15 to 40 dollars per fixed size, 200 and up per set	8 to 20 dollars per size plus about 30 for an arbor	^{[9] [12] [19]}

Translation: the expansion bit wins when you need odd diameters no fixed tool comes in, or many sizes from one pouch, and the hole is a through-bore. For any blind hole that mounts hardware, use a Forstner, because the lead screw's cone makes the expansion bit useless for a hinge cup that needs a flat seat ^[19].

Buying and using checklist

Match the shank to the tool: taper square for a brace, 3-flat ground shank for a drill press or hand drill chuck ^[1] ^[8].
The 44202's 35 sizes in 1/16 in steps is the one to pick when you need in-between diameters, for example boring for odd vintage hardware; the 44002 covers the same range in coarser 1/8 in steps ^[1] ^[4].
The 445002J ships with one blade and no markings; 1-3/4 to 3 in only ^[11] ^[12].
Verify the cut on scrap before the workpiece, every time you move the wing ^[19] ^[22].
In a power drill: low gear, under 250 RPM, side handle installed ^[19] ^[21].

For the general spade vs Forstner vs hole saw decision table: wood boring bits compared. For RPM logic and press pulley mapping: drill press speed chart. For hole saw diameters by task and arbor compatibility: hole saw sizes. For choosing a bit by material: drill bits by material. Back to the drill comparison table.

Sources

IRWIN, product page 44202 Hand Brace Adjustable Wood Bits: 44002 cuts 19 standard hole sizes in 1/8 in increments, 44202 cuts 35 in 1/16 in increments, micro-dial screw, taper square shank for hand brace (irwintools.com/product/44202/hand-brace-adjustable-wood-bits)
Toolbox Supply, Irwin Tools 44202 listing: cuts 35 standard hole sizes in 1/16 in increments, diameter 7/8 to 3 in, overall length 8-1/8 in, taper square shank (toolboxsupply.com)
AFT Fasteners, Irwin Hand Brace Adjustable Wood Bits 44202 (6 pkg): 44002 19 sizes 1/8 in, 44202 35 sizes 1/16 in, 7/8 to 3 in, 8-1/2 in OAL, package UPC 20024721100041 (aftfasteners.com)
J.C. Cayer, Irwin 44202 No. 2R Lockhead Adjustable listing: 7/8 to 3 in, 35 sizes in 1/16 in, overall length 8-1/8 in, micro-dial screw (jccayer.com)
Home Hardware Canada, Irwin 7/8 to 3 in Adjustable Lockhead Wood Drill Bit: 8-1/8 in OAL, square shank, states 35 hole sizes in 1/8 in increments, diverging from IRWIN's 1/16 in claim (homehardware.ca/en/78-3-adjustable-lockhead-wood-drill-bit/p/1015056)
Amazon, IRWIN Tools 44801 Drill Press Adjustable Wood Bits listing: 19 hole sizes in 1/8 in increments, 5/8 to 1-3/4 in, 5-1/2 in overall length, 9/32 in shank, Lockhead screw, UPC 024721100184 (amazon.com/dp/B004GZHICS)
Acme Tools, Irwin No. 1R 5/8 to 1-3/4 in Hex Shank Adjustable Wood Bit, SKU 44801: 19 sizes 1/8 in increments, 5-1/2 in length, 9/32 in shank fits drill presses and hand braces, 0.24 lb, HSS, UPC 024721100184 (acmetools.com)
Toolbox Supply, Irwin Tools 44801 Lockhead Drill Press Adjustable Wood Bit listing: 5/8 to 1-3/4 in, precision ground shank with 3 equally spaced flats for 3-jaw chucks, wedge type blade lock, slow feed screw point, 5-1/2 in OAL, 9/32 in shank (toolboxsupply.com)
ABSupply, Irwin 44801 Drill Press Adjustable Wood Bit No. 1R 5/8 to 1-3/4 in Hex Shank: 19 sizes in 1/8 in, listed at 48.67 USD, UPC 0 24721 10018 4 (absupply.net)
Preston Hardware, IRWIN 44801 Drill Bit listing: 5/8 to 1-3/4 in diameter, 5-1/2 in OAL, 9/32 in shank, cuts 19 size holes in 1/8 in increments (prestonhardware.com)
Amazon, IRWIN 445002J Large Adjustable Wood Drill Bits listing: 6-3/4 in long, 1-3/4 to 3 in diameter, only 1 blade included, micro-dial, 3/8 in reduced 3 flats shank (amazon.com/dp/B00CHFV0PK)
Cripe Distributing, Irwin 445002J Large Adjustable Wood Drill Bits 1-3/4 to 3 in: 6-3/4 in long, one blade, 3/8 in reduced 3 flats shank, listed at 10.00 USD closeout (cripedistributing.com)
Precision Tools, Irwin 445002J Large Adjustable Wood Drill Bits: 6-3/4 in length, 1-3/4 to 3 in, single blade, micro-dial adjustment (precisiontoolsf.com)
Amazon, IRWIN Tools 45002 Lockhead Adjustable listing: boring range 7/8 to 3 in, 6-1/2 in overall length, one-piece drop forged, precision ground shank with 3 flats (amazon.com/dp/B00004YO6Y)
KSC Direct, Irwin Speedbor 45002 Drill Press Wood Bit: 7/8 to 3 in diameter, 6-1/2 in overall length, 11/32 in shank, carbon steel, 19 different hole sizes in 1/8 in increments, UPC 024721100191 (kscdirect.com)
Toolbox Supply, Irwin Tools 45002 Lockhead Drill Press Adjustable Wood Bit: 7/8 to 3 in, 11/32 in shank, overall length printed as 5-1/2 in, diverging from the 6-1/2 in in IRWIN catalog data, UPC 024721100191 (toolboxsupply.com)
Shell Lumber, Irwin 45002 Drill Bit listing: 7/8 to 3 in, cuts 19 size holes in 1/8 in increments, Lockhead screw, UPC 024721100191 (shelllumber.com)
Lowery's True Value Brooksville, Lockhead Drill Press Wood Bit Adjustable 7/8 to 3 in: SKU 750932, model 45002, UPC 024721100191, Irwin (lowerybrooksville.shoptruevalue.com)
Firgelli Auto, Expansion Bit Mechanism Explained: dovetail slot and cutter wing construction, lead screw self-feed, about 250 RPM ceiling with unbalanced-wing and clamp-centrifugal reasoning, oversized-hole causes (wing clamp, dovetail wear, spur runout, bent screw), expansion vs Forstner vs hole saw comparison table (firgelliauto.com/blogs/mechanisms/expansion-bit)
Carbide Processors, Shop Tested Drill Speeds chart: multi-spur bits 2-1/8 to 4 in at 250 RPM softwood and hardwood, Forstner 1-3/8 to 2 in at 250 to 500 RPM (blog.carbideprocessors.com)
Wonkee Donkee Tools, How to use an expansive bit: use a drill driver at slow speed to prevent digging-in and motor strain, set a drill press to its lowest RPM (wonkeedonkeetools.co.uk/expansive-bits/how-to-use-an-expansive-bit)
Tiny Shop Woodworks, Expansive Auger Bits Part 1: Irwin No. 2 construction, dovetail capture of the cutter arm, gap causing seized cuts, sharpening precautions, documented hole growing from 1-7/8 in entry to over 1-15/16 in exit from cutter slip (tinyshopww.blogspot.com)
WorkshopCalc, Complete Forstner Bit Size Chart: imperial sizes 1/4 to 3 in, speed bands 2,400 RPM at 1/4 to 1/2 in down to 500 RPM at 2-1/4 to 3 in in softwood (workshopcalc.com/reference/forstner-bit-chart)