Plug cutter sizes: diameter chart and the screw to plug match

A plug cutter is a short hollow tube with cutting teeth on its end: spin it into a piece of scrap and it cores a solid wooden cylinder, a plug, that you glue into a counterbore to hide a screw head below the wood surface ^{[1] [7]}. The tool has no pilot and no point; it stays in its own board, and Fuller's classic four-flute cutters do not eject the plug at all, you break it out with a screwdriver or saw the board free ^[1]. This page carries the size chart for the standard diameters from 1/4 to 5/8 inch (with the larger catalog sizes noted), the shanks and set contents you actually meet at the store, and its main asset: a plug to screw matching table that names the plug diameter for each wood screw gauge and each common lag bolt, cross-referenced against our countersink size chart.

The one-minute answer

Three facts cover most of what people ask. First, the retail standard is six diameters: 1/4, 5/16, 3/8, 7/16, 1/2, and 5/8 inch, with 9/16 and sizes from 3/4 up to 1-1/2 inch available from specialist catalogs ^{[1] [7]}. Second, the plug must be a hair bigger than the hole it fills: standard straight cutters are ground slightly oversize for a press fit, and tapered cutters flare from the nominal size to about 0.010 or 0.025 inch oversize so they tap in tight ^{[1] [4]}. Third, the match to the screw runs one step behind the head: a #8 wood screw hides under a 3/8 plug, a #10 to #14 under 1/2, and a 1/4 inch lag, whose hex head spans 0.505 inch across corners, needs 9/16 ^{[2] [8]}.

What a plug cutter is, and straight versus tapered

The body is a hollow cylinder, like a very short pipe with teeth ground at one end and a shank at the other; many designs add an ejection slot down the side so the plug can be pried out after the cut ^[7]. Because it only cuts a thin annular groove, it works in a hand drill, but the plug comes out cleanest in a drill press at a moderate speed, and slower speeds are the general recommendation to avoid overheating and tearout ^[7]. Cut plugs from scrap of the same species so grain and color blend with the workpiece; the plug grain runs the same direction as the surface grain so the joint line disappears under finish ^[4].

The two geometries differ in what the plug looks like. A straight (standard) cutter produces a parallel-sided plug, ground slightly larger than the counterbore diameter so it press-fits a straight-walled hole every time ^[1]. Parallel sides also make straight plugs usable as dowel stock for joinery, which is why plug and dowel cutters are usually sold as one family ^{[7] [1]}. A tapered cutter flares the plug toward its base, from the nominal size at the tip to roughly 0.010 inch oversize on Fuller's tapered series (0.025 on the hex-shank quick-change version), and leaves the end chamfered so the plug starts easily in a counterbored hole ^{[1] [5]}. Veritas takes the idea furthest with its Snug-Plug cutters: the first 1/8 inch of the plug is the stated size, then it flares at a 3 degree included angle, and the cutter shaves rather than tears the plug sides, so you tap the plug in until it seats, trim the waste, and the fit line nearly disappears ^[4]. The taper has a second job: because the plug base is slightly oversize, small drill press runout that would leave a straight plug loose is absorbed by the taper instead ^[4].

Which to buy: tapered for capping screw holes where fit matters (cabinet work, visible plugs), straight when you want dowel stock or plugs for straight counterbores drilled with a Forstner bit, whose sizes are on our Forstner bit sizes page. The distinction between the two holes the plug goes into, the cone of a countersink and the flat-bottomed counterbore, is unpacked in counterbore vs countersink.

Plug cutter size chart: 1/4 to 1-1/2 inch

The table below is built from W.L. Fuller's plug cutter catalog, the reference list of sizes, shanks, and maximum plug lengths, cross-checked against Veritas (Lee Valley) and Toolstoday's Timberline listings, which agree on every diameter they share ^{[1] [4] [6]}. The typical screws column comes from Fuller's wood screw chart, which gives each gauge a minimum counterbore diameter, and is explained row by row in the matching table further down.

Diameters and maximum plug lengths are the Fuller catalog values; Toolstoday's straight Timberline cutters (1/4, 3/8, 1/2, and 5/8 in, 3/8 in shank) and Veritas's tapered Snug-Plug sizes (1/4 through 1/2 in, 3/8 in shank) match at every shared diameter, and Baucor lists the same fractional run from 1/4 to 1 in and larger as manufacturable sizes. The typical screws column follows Fuller's minimum-counterbore mapping; WhatDrillBit's independent plug column agrees at the common gauges ^[3].

Shank logic is simple: the small cutters (1/4 and 5/16) carry 1/4 in shanks, the mid range (3/8 through 5/8) comes in 1/4 or 3/8 in, and the large catalog sizes from 3/4 up take 1/2 in shanks ^[1]. Quick-change tapered versions put a 1/4 in hex shank on every size, Fuller's QP series (QP4 through QP10) covering 1/4 through 5/8 ^{[1] [5]}. Check your chuck range with the drill chuck size chart if you are heading past 3/8 in shanks.

Sets follow the size chart. Fuller's numbered sets (a set of 2 up to a set of 5) draw from 3/8, 7/16, 1/2, and 5/8 cutters with a choice of 1/4 or 3/8 shanks and ship in wood holders ^[1]. Toolstoday's Timberline 8-piece set pairs straight and tapered cutters in 1/4, 3/8, 1/2, and 5/8 in, and its 4-piece quick-release set carries the same four sizes on hex shanks in a self-ejecting style, the one mainstream exception to the plugs-stay-in-the-board rule ^[6]. Veritas sells a set of 5 (1/4 through 1/2) and a set of 3 (1/4, 3/8, 1/2) of its tapered Snug-Plug cutters ^[4]. A budget simplification worth knowing: Timberline describes its 3/8 cutter as covering #4 through #10 screws and its 1/2 as the #12 size, which works if you tap tapered plugs home, but it is coarser than the gauge-by-gauge chart below ^[6].

Which plug diameter hides which screw

This is the table the search results never give you: the plug size for a given screw, read off the screw's own head. The wood screw rows are built from W.L. Fuller's wood screw chart, which publishes each gauge's actual head diameter, its minimum counterbore, and a recommended plug size one step up at the top gauges, cross-checked against WhatDrillBit's independent plug and bung column ^{[2] [3]}. The head diameters are the same actual-head numbers behind the counterbore column in our countersink size chart, so the two pages read together give you the whole recess-plus-plug stack.

The two plug columns differ at #4, #6, and by one size at the top: Fuller's minimum counterbore is the tightest hole that clears the head, while the recommended column goes one size up where head seating matters; WhatDrillBit follows the tight end at #4 to #6 and the larger value from #10 up. Sources also vary at #12 exactly as our countersink page discloses (7/16 to 1/2 in). When in doubt, err one plug size large and rely on the taper or the oversize grind for the fit.

Lag screws follow a different rule because the head is a hex: the counterbore must clear the head across corners, which is the flats width divided by cos 30 degrees, not the flats themselves. The table uses the ASME B18.2.1 hex lag dimensions as published by EngineersEdge, with the head size chart at Wholesale Bolts agreeing on every across-flats value ^{[8] [9]}.

Each plug is the first catalog diameter above the maximum across-corners dimension: 9/16 clears 0.505, 5/8 clears 0.577, 3/4 clears 0.650, and 7/8 clears 0.866. The across-corners values are the B18.2.1 maxima; the arithmetic check (flats divided by cos 30 degrees) reproduces them to the third decimal.

For the holes themselves: the pilot and shank clearances for every wood screw gauge are in the pilot hole chart, and lag pilot sizes by wood hardness sit alongside the lag dimensions on the EngineersEdge page cited below ^[8].

Plug cutters and composite decking

Composite and PVC decking changed the plug question, because a lumber plug cannot match a composite board's color or grain. The decking industry's answer is brand-matched plug systems, and they come in two families, with a third fastening philosophy that skips plugs entirely.

The choice in practice: plug systems (Trex Hideaway, Cortex, Starborn's Pro Plug) are the face-fastened look with the screw hidden, strongest and the only option on stairs, borders, and square-edge perimeter boards; clip and edge systems (Trex Hideaway clips, CAMO) are faster across the grooved field but do not reach the edges, which is why builders routinely combine the two, clips in the field and plugs at the perimeter ^{[16] [13]}, with hand-installed clips and stand-up ClipDRIVE tools covering the grooved field ^[15]. A wood plug cutter still has one job on a deck: plugging structural screws and through-bolts in the wood frame and rail posts, where the lag table above applies.

Using one well

Four habits separate plugs that disappear from plugs that shout. Cut plugs in a drill press where you can: runout in a hand drill makes holes oversize and plugs undersize, which is precisely the failure the tapered designs exist to absorb ^[4]. Let the plug stay in the scrap until you need it; Fuller's cutters are designed for the plug to be broken out with a screwdriver or freed by sawing the board apart, and cutting a row of plugs then slicing them off at the band saw is the production method ^[1]. Glue and orient: match the species, run the plug grain with the surface grain, tap until seated, trim the excess flush, and the line nearly disappears ^[4]. And size the recess before the plug: cut the counterbore to the matching table above, or with a Forstner bit sized from our Forstner chart, then pick the plug cutter one step up.

Related references on this site: the full recess geometry in countersink size chart, the two hole types compared in counterbore vs countersink, large-diameter wood holes in wood boring bits, and standard twist drill lengths in jobber drill bit sizes.

Related

For the recess the plug sits in: countersink size chart and counterbore vs countersink. For drilling the counterbore itself: Forstner bit sizes and wood boring bits. For the pilot under the screw: pilot hole chart. For the bits in the chuck around the plug cutter: jobber drill bit sizes and drill chuck sizes.

Sources

1. W.L. Fuller, Plug Cutters catalog page: standard, SS, carbide, and tapered quick-change series; plug sizes 1/4 to 1-1/2 in with maximum plug lengths and shank options; set contents; oversize grind figures; non-ejecting plug handling (wlfuller.com/plug-cutters)
2. W.L. Fuller, Wood Screw Chart: actual head diameters, minimum counterbore diameters, and recommended counterbore (plug) sizes by gauge #2 to #18, with the matching plug cutter instruction (wlfuller.com Wood Screw Chart PDF)
3. WhatDrillBit, Wood Screw Countersink Size Chart: plug and bung (counterbore) column by gauge #4 to #14, independent of Fuller (whatdrillbit.com/wood-screw-countersink-chart)
4. Lee Valley, Veritas Imperial Tapered Snug-Plug Cutters: sizes 1/4 to 1/2 in, 3 degree taper with first 1/8 in at stated size, shaved plug sides, 3/8 in shanks, runout compensation, sets of 3 and 5 (leevalley.com)
5. Hardwick and Sons, W.L. Fuller Four-Flute Tapered Plug Cutter Hex Shank: QP4 to QP10 cutting diameters, maximum lengths, overall lengths, 1/4 in hex ball shank, 0.025 in oversize taper (hardwickandsons.com)
6. Toolstoday, Timberline Straight and Tapered Wood Plug Cutters plus 8-piece and 4-piece sets: 1/4, 3/8, 1/2, 5/8 in diameters, 3/8 in straight shanks, 1/4 in hex quick-release, self-ejecting style, gauge coverage notes (toolstoday.com)
7. Baucor, Plug Cutter Drill Bits guide: hollow cylindrical body with outer cutting teeth and ejection slot, plug formation and removal, slower speed recommendation, common diameters 1/4 to 1 in and larger (baucor.com/collections/plug-cutter-drill-bits)
8. Engineers Edge, Standard Hex Lag Screws per ANSI/ASME B18.2.1: width across flats and across corners maxima and minima for 1/4 to 1-1/4 in lags, plus lag pilot hole sizes by wood group (engineersedge.com)
9. Wholesale Bolts, Lag Screw Head Size Chart: across-flats head sizes 1/4 to 3/4 in, independent corroboration of the B18.2.1 flats values (wholesalebolts.com)
10. Trex, Decking Plugs product page: plugs made from the same Trex shell material with genuine embossing rolls, ribbed edges, tap or hammer installation, 80 count packs, depth setter and plug system screws sold separately (trex.com/products/accessory-hardware/trex-hideaway-decking-plugs)
11. LBM Journal, Trex Hideaway fastener collection overview: collated fascia plugs, first approved plug system for Enhance scalloped decking, color-coded counterbore bits, plugs made from decking shellstock and embossing rolls (lbmjournal.com)
12. FastenMaster, Collated Cortex for Decking: plugs made from the same material as market-leading deck boards, collated strips with pre-aligned grain, TORX ttap drive, ProjectLife warranty, brand list (fastenmaster.com/products/collated-cortex-for-decking)
13. FastenMaster Cortex installation literature: setting tool drives fastener to preset level below deck surface, two screws per joist, plug tapped flush, 3/16 in predrill at butt joints, plug removal with a trim screw (decksdirect.com/media/documentation/cortex_literature.pdf)
14. CAMO Fasteners, DRIVE stand-up tool: edge, clip, and face fastening with collated screws and universal clips for a fastener-free surface, board compatibility matrix (camofasteners.com/products/drive/camo-drive)
15. CAMO Fasteners, Products overview: hidden deck clips installed by hand or with ClipDRIVE and DRIVE tools, exterior fastener lines (camofasteners.com/products)
16. TUDS, Hidden Deck Fasteners in Canada, Comparing CAMO, Cortex, and Clip Systems: plug-and-screw versus edge-screw versus clip approaches, Cortex for stairs and perimeters, brand-matched plug kits (tuds.ca)