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Faithfull Holesaw Sets for UK Tradespeople — Electricians 9pc, Plumbers Cobalt 9pc and Flat Bits
Getting clean, accurate holes through timber, plasterboard, metal, and plastic is a daily requirement for UK electricians and plumbers. Whether you're chasing cable routes through joists, cutting back-box holes in plasterboard, or boring pipe penetrations through floors, the right holesaw or flat bit makes the job faster and cleaner. Faithfull's holesaw sets and flat bits are purpose-built for trade use — robust enough for site conditions, with HSS bi-metal construction that handles the varied materials a sparky or plumber encounters on every job.
APM Electricals stocks two dedicated Faithfull holesaw kits — one optimised for electricians, one for plumbers — plus individual flat bits for timber-boring work. Here's what each product is designed for and why tradespeople reach for them.
Faithfull Electricians Holesaw Set 9pc
Designed around the drilling requirements of first-fix and second-fix electricians, this 9-piece set includes the holesaw sizes most frequently reached for when running circuits, fitting consumer units, and installing accessories. The set covers penetrations for back boxes, cable entries, conduit, and trunking — the workhorse operations on any domestic or light commercial electrical install.
All saws in the set use HSS bi-metal construction: a hardened high-speed steel tooth ring welded to a flexible steel backing. Bi-metal outperforms carbon steel by a significant margin on abrasive materials like dense plasterboard, hardwood noggins, and engineered timber. The teeth hold an edge longer, reducing the frequency of set changes on site.
The 9-piece configuration ships in a carry case with arbor, making it practical to move between jobs without individual sizes getting lost. For electricians who haven't yet standardised on a holesaw system, this kit covers the sizes needed from day one.
Faithfull Bi-Metal Cobalt Holesaw Kit — Plumbers 9 Piece
The plumbers' holesaw set differs from the electricians' version in two key ways: the included sizes are selected for pipe penetrations and sanitary installations, and the tooth specification is cobalt-enhanced bi-metal. Cobalt (M35 grade) delivers higher heat resistance than standard HSS, which matters when cutting through harder materials — cast iron flanges, old steel pipework, and dense masonry board (Aquapanel, cement board) that appear on bathroom and heating refurb jobs.
Pipe penetrations require precise sizing to suit push-fit sleeves, compression fittings, and back-plate elbows. The plumbers' kit is specced to align with common UK pipe diameters: 15mm, 22mm, and 28mm copper and plastic MDPE, as well as larger sanitary waste pipe sizes. Getting the right hole first time eliminates the bodged-collar packing that creates leak risk further down the line.
Like the electricians' set, this kit ships in a carry case with arbor. The cobalt specification adds marginal cost over a standard bi-metal set but pays back in tooth life, particularly on site where saws cut all day without the opportunity to cool properly.
Faithfull Flat Bit 16mm
For boring cable holes through timber joists, noggins, and stud partitions, a flat bit is the standard trade choice. Faster than a spade bit at depth, more portable than an auger, the flat bit drives through 3x2 timber in seconds with a standard SDS-plus or cordless drill at full speed.
The 16mm flat bit is the go-to size for single-core twin-and-earth T&E and armoured cables: wide enough to thread conduit, tight enough not to compromise structural members unnecessarily. At 16mm this also suits 15mm copper pipe runs through timber frames — useful when a plumber needs to thread pipe through joists in a tight ceiling void without switching bit types.
Faithfull's flat bit construction uses a full-face hardened tip with a centring point. The centering point registers cleanly before the cutting edges engage, reducing bit walk on the entry face — a common problem with cheaper flat bits that wander before the tip grips.
Faithfull Flat Bit 20mm
The 20mm flat bit handles the next size up from the 16mm — larger cable bundles (particularly multi-core armoured SWA or grouped T&E in busy zones like ring mains with multiple spurs), and 22mm copper or plastic MDPE pipe penetrations through timber. On boarding-out jobs, 20mm also works for waste pipe where 32mm or 40mm plastic waste runs need to be pulled through a joist bay at the feed end.
At £6.99 individual flat bits are consumable rather than investment items — a set covering 16mm, 20mm, and a couple of 25mm sizes is standard van stock for both electricians and plumbers. Keeping spares means a blunted bit gets replaced during a job rather than struggling on with a slow, burning cut that scorches the timber and risks the structural integrity of a joist.
Choosing the Right Holesaw
The most common mistakes with holesaws come from using the wrong size (which forces improvised packing or collar adapters) and using the wrong material spec (standard carbon steel on stainless steel or cast iron, which blunts immediately). The quick decision guide:
- Standard plasterboard, soft timber, MDF: Standard bi-metal HSS holesaw, any speed
- Hardwood, chipboard, OSB: Bi-metal HSS, moderate speed with regular clearing
- Steel conduit, sheet steel, old cast iron: Cobalt (M35) bi-metal, slow speed with cutting fluid
- Stainless steel, hardened steel: Cobalt bi-metal, very slow with fluid — multiple passes
- Ceramic tile (emergency only): Diamond holesaw, not bi-metal
Overheating is the primary failure mode for holesaws on site. A bi-metal saw that's been run at high speed through dense material without pause will blue at the teeth and lose hardness permanently. Running at lower speed and withdrawing frequently to clear swarf extends tooth life significantly — especially on the larger sizes (50mm+) where heat builds faster.
Holesaw Sizes for Common Trade Applications
For UK electricians the most-used sizes are:
- 25mm: Single-gang plasterboard back box, junction box entry
- 32mm: Heavy conduit entry, 25mm conduit with bending radius
- 44mm: Double-gang back box, round patress
- 54mm: Fan back box, larger patress
- 64mm: Ceiling rose base, surface mounting box
For plumbers:
- 19mm: 15mm copper pipe through timber (with gap for expansion)
- 25mm: 22mm copper, plastic pipe through joist
- 32mm: 28mm copper, 25mm plastic MDPE
- 44mm: 35mm copper, 40mm waste pipe feed-through
- 54mm: 42mm copper, 50mm waste pipe
Why Faithfull for Trade Drilling?
Faithfull has supplied the UK trade for decades and is stocked at many merchants specifically because of its consistent quality at competitive price points. The holesaw sets in particular represent good value for tradespeople who want a complete kit without paying premium SDS accessory pricing — bi-metal cobalt construction at under £55 for a 9-piece set puts Faithfull well within reach as everyday van-stock tooling.
APM Electricals carries the full Faithfull range including screwdrivers, drill bits, holesaw sets, flat bits, and tape measures — all held in stock for next-day trade supply. Both the electricians' and plumbers' holesaw sets, plus the 16mm and 20mm flat bits, are available to order now.
Shop Faithfull Holesaw Sets and Flat Bits at APM Electricals
APM Electricals is a UK trade electrical and plumbing supplier based in London. We stock a broad range of Faithfull hand tools and drilling accessories alongside our electrical, plumbing, and heating ranges. Order before 2pm for same-day dispatch on in-stock items. Visit us at 24 Western Avenue, London W3 7TZ, call 020 8702 8080, or email info@apmi.uk.
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