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40 mm Forstner bit buying guide

Updated: 2026-10-23

Amazon.co.uk listings that all say 40 mm do not tell the same story. A title can say 40 mm while the table says 41 mm, and a carbide bullet can sit against carbon steel. This is the checklist before you add a bit to the basket. Conditional picks are on the [best 40 mm Forstner bit page](/hub/drilling-and-accessories/forstner-bit-40mm/sub/forstner-bit-40mm-best). The full table is the [40 mm Forstner bit comparison](/hub/drilling-and-accessories/forstner-bit-40mm). Listings were read on 20 October 2026. A qualifying purchase can earn us a commission at no extra cost to you.

Amazon.co.uk listings that all say 40 mm do not tell the same story. A title can say 40 mm while the table says 41 mm, and a carbide bullet can sit against carbon steel.

Our top picks

TA-VIGOR TA-VIGOR 40 mm, carbide tip

Best overall

TA-VIGOR TA-VIGOR 40 mm, carbide tip
7.0/10about £9.46
View offer
Flintronic Flintronic 40 mm, round shank

Alternative

Flintronic Flintronic 40 mm, round shank
6.3/10about £8.99
View offer
ASNOMY ASNOMY 40 mm, carbide tipped

Rank 3

ASNOMY ASNOMY 40 mm, carbide tipped
8.5/10about £11.89
View offer
On this page
  1. 1.Check the diameter three times
  2. 2.Read the tip claim against the table
  3. 3.Shank, machine and review count
  4. 4.What the price bands buy

Check the diameter three times

At 40 mm a Forstner bit suits a grommet, a lock recess or a pocket. It is the wrong hole for a 35 mm concealed-hinge cup, and the word hinge on a title does not change that. The layout is on the 40 mm or 35 mm hinge-hole page. Read the title against the cutting-diameter row. Flintronic's title says 40 mm and the table says 41 mm, at £8.99. One review says the bit measured 40 mm. HSAWBIT prints a 39 mm minimum bore beside 40 mm. ASNOMY prints a minimum bore of 1.56 inches, about 39.6 mm. If the lines disagree, the Consumer Rights Act 2015 gives a remedy when goods do not match the description. This page is not legal advice.

Read the tip claim against the table

Treat carbide as a claim until the table uses the same word. HPHOPE, at £14.99, says high-speed steel in the bullets and carbon steel in the table. OUZHOU says carbide against carbon steel, and one review needed heavy feed in oak. ASNOMY and TA-VIGOR name carbide in the bullets and the table. The green DTGN bit, at £13.99, does the same and states a 64 mm depth. FBBEVWBK names a carbide tip and leaves the material cell empty. Flintronic says tungsten steel. HSAWBIT says high-speed steel, and the table names no material. Speed is on the how to use a Forstner bit page.
TA-VIGOR TA-VIGOR 40 mm, carbide tip

Testsieger

TA-VIGOR TA-VIGOR 40 mm, carbide tip
7.0/10about £9.46
View offer

Shank, machine and review count

Stated shanks run from an 8.5 mm hex on the DTGN bits to a 10 mm round on ASNOMY. An 8.5 mm hex belongs in a drill chuck, not a quarter-inch holder. A hex shank does not clamp the timber, and HSAWBIT forbids an impact driver. ASNOMY prefers a fixed drill above 40 mm. Both DTGN pages say use a press above 35 mm. TA-VIGOR does not list a hand drill. The silver DTGN bit is 4.6 from four ratings. ASNOMY's 2,476 reviews are large enough to include complaints. HSAWBIT's 287 reviews mix other diameters. The only row that also contains 35 mm is the YOKOCUT set at £18.72.

What the price bands buy

Singles here run from £8.68 to £14.99, and the set is £18.72. Bosch Professional lists a toothed 40 mm bit at £36.30 including VAT, and Famag's classic 40 mm at £49.26 including VAT. Stay in this set for a short run if you can measure the rim and clamp the work.

Common questions

Is 40 mm the right size for a cabinet hinge?
No, not for the usual concealed cabinet hinge. A Blum-style cup is 35 mm across and about 13 mm deep. Several titles here say hinge on a 40 mm bit. That word does not shrink the hole. Drill 40 mm only when the fitting drawing says 40 mm. Cup layout and the set that includes 35 mm are on the hinge-hole page.
Why does one listing say 40 mm and 41 mm?
Flintronic's title says 40 mm and the cutting-diameter line says 41 mm, at £8.99. A review says the bit measured 40 mm even though a drawing said 41 mm. The page does not resolve it. If 1 mm ruins the job, measure the rim or choose a listing where the title, the bullet and the table all say 40 mm.
Does carbide in the bullet mean the table is wrong?
It means the lines disagree, so quote neither as settled. HPHOPE says high-speed steel in the bullets and carbon steel in the table. OUZHOU says carbide against carbon steel. ASNOMY and TA-VIGOR name carbide in both places, which is the pattern to prefer when the tip matters. Agreement is still a listing claim, not a hardness test.
Is a hex shank safer in a hand drill?
It is less likely to spin in the chuck. It does not stop a 40 mm rim grabbing. HSAWBIT's hex listing still has a review of softwood jumping in a hand drill, and it forbids an impact driver. ASNOMY and both DTGN pages point you to a press at this diameter. Clamp the work whichever shank you buy.
Can I trust 5.0 from one review?
Not as evidence of a durable edge. FBBEVWBK is 5.0 from one rating at £8.68, and the title is "Not happy" while the body is a candle holder. YUEDAHOMEE is 4.8 from six ratings, and one text describes a 35 mm bit. Use a large sample, such as ASNOMY's 2,476 reviews, when you want the complaints as well as the praise.
Should I buy the six-piece set instead of one bit?
Buy the YOKOCUT set at £18.72 when you need 35 mm and 40 mm and you will use the other sizes. It is 4.2 from 148 reviews, with blunt MDF, a slow oak cut and walking in a hand drill in the file. If you only need one 40 mm hole, a single bit with an agreed diameter is the smaller purchase.

Related pages

Forstner bit

Forstner bit 40mm

Best 40 mm Forstner bit for the job in front of you

40 mm or 35 mm Forstner hinge hole on a cabinet door

How to use a Forstner bit at 40 mm without burning

Forstner bit vs hole saw when you need a flat bottom

Sources

Public UK sources from the research digest, last checked on 20 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the product display for this comparison.

  1. HSE: PPE overview (retrieved 20 October 2026)
  2. Consumer Rights Act 2015, section 19 (retrieved 20 October 2026)
  3. Bosch Professional UK, 40 mm Forstner bit 2 608 577 019 (retrieved 20 October 2026)
  4. Hart Wholesale, Blum 71B3550 (retrieved 20 October 2026)
  5. Furnica, 35 mm hinge cup guide (retrieved 20 October 2026)
  6. Katz-Moses Tools, Forstner speeds (US shop, rule of thumb) (retrieved 20 October 2026)
  7. Famag Tool UK, classic 40 mm Forstner bit (retrieved 20 October 2026)
  8. amazon.co.uk listings for the ASINs in this comparison (retrieved 20 October 2026)