Best Router Bits for Draught Proofing & Sash Restoration: 2025 Expert Review
DR Joinery
Expert Joiner & Sash Restoration Specialist
Draught proofing a traditional sash window isn't just about sticking some foam strip to the frame. In York's older properties, where nothing is square and the timber has shifted over a century, effective draught proofing requires precise machining. You need to route channels for pile carriers and reshape staff beads that have distorted over time.
Many homeowners attempt this with standard DIY tools, but without the correct router bits, you risk tearing out the delicate grain of aged softwood or shattering the edge of a new hardwood bead. A clean route is essential for the draught seal to sit flush and function correctly without jamming the sash.
In this review, I've selected three router bit options that assist in the various stages of draught proofing and sash restoration: a budget set for flush trimming repairs, a comprehensive kit for shaping new beads, and a professional Trend cutter for precision profiling.
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Specs vs. The Real World
The Spec: "Universal 1/4" Shank Compatibility"
"Fits any router for easy use."
Whilst they fit 1/4" collets, many heavy-duty site routers in the UK use 1/2" collets for stability. Ensure you have the correct collet sleeve or a dedicated 1/4" trim router for these finer bits.
The Spec: "Tungsten Carbide Dipped vs Tipped"
"All carbide bits stay sharp forever."
Cheaper 'dipped' bits lose their edge quickly on hardwood like Oak or abrasive materials like old painted timber. For high-volume work, solid carbide or thick tipped bits (like Trend) are essential.
My Top 3 Recommendations
Three options to cover different needs and budgets
Bohaner 4 Pcs 1/4 Inch Shank Flush Trim Pattern Router Bit Set
Bohaner
Before you can draught proof, you often need to repair rot in the sill or sash stiles. Ideally suited for trimming 'dutchman' repairs flush, this set is excellent value. The top bearing allows you to use the sash itself as a template for a perfect flush finish.
The Good
- Great value at roughly £3.25 per bit
- Heat-resistant coating helps prevent resin build-up
- Includes four different lengths for various sash thicknesses
The Bad
- Not suited for continuous industrial use
- Bearings may require regular lubrication in dusty environments
Installer Tip:
When repairing a rotten section of a sash window, glue in your new timber block slightly proud of the surface. Use these trim bits to rout the new timber perfectly flush with the existing stile before cutting your draught-strip groove. It saves hours of sanding.
Priced at £12.99 at the time of writing
Check Price on Amazon15pc Router Bit Set 1/4" Shank for Woodworking & Edging
FHGSPQWM
If you are replacing staff beads or parting beads as part of your draught proofing project, you need versatility. This 15-piece set provides the straight bits needed for cutting the rebate for the brush pile, plus roundover and moulding bits to match the period profile of the original Victorian joinery.
The Good
- Comprehensive selection for shaping custom beads
- Includes straight bits essential for cutting draught channels
- High speed steel construction offers decent longevity
The Bad
- Generic brand name (though performance is solid)
- Shanks require tight collet securing to prevent slip
Installer Tip:
Use the straight bits in this set to cut the initial groove for your pile carrier. If working with Accoya, take shallow passes (3mm at a time) to ensure a clean channel without burning the timber.
Priced at £27.39 at the time of writing
Check Price on AmazonTrend CraftPro Guided Profiler Router Cutter Bit
Trend
Trend is a staple in any UK joiner's toolbox. This guided profiler is the problem-solver for tricky heritage work. Its high-quality tungsten carbide tips handle hardwoods like Oak or dense old pine with ease, and the guide bearing ensures you can follow existing frame contours without gouging the work.
The Good
- Professional grade Tungsten Carbide stays sharp longer
- PTFE coating prevents resin build-up (crucial for pine)
- Safety K-Mark ensures correct shank insertion depth
The Bad
- Higher cost for a single bit
- Requires specific care to avoid chipping the carbide tips
Installer Tip:
When draught proofing, you often encounter layers of old paint. This Trend bit is robust enough to cut through, but for the sake of your health and the bit's life, strip the paint back first. The bearing guide is brilliantly smooth, making it perfect for final trimming of staff beads once they are tacked in place.
Priced at £16.09 at the time of writing
Check Price on AmazonFrequently Asked Questions
What size router bit is best for sash window draught proofing?
Can I rout into old windows with lead paint?
Should I replace the beads or route the existing ones?
Why do I need a bearing on my router bit?
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