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Riving knife thickness: body, plate, then the kerf

Updated: 24 October 2026

The rip starts cleanly and then stalls, and the new thin-kerf blade is the change you made last week. Riving knife thickness is the usual cause when the steel behind the blade is fatter than the slot the teeth just cut. Some listings never print a thickness, so you cannot compare the plate with the blade packet. The [riving knife comparison](/hub/hand-tools/riving-knife) shows which of the six amazon.co.uk plates state a figure. Peter F. took the inequality from HSE WIS16 and the rip-saw page. He did not measure a blade in a lab. A purchase through our links may earn a commission at no extra cost to you.

The rip starts cleanly and then stalls, and the new thin-kerf blade is the change you made last week. Riving knife thickness is the usual cause when the steel behind the blade is fatter than the slot the teeth just cut.

Our top picks

PACKOVE PACKOVE 2.5 mm

Best overall

PACKOVE PACKOVE 2.5 mm
1.2/10about £26.50
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Ohoho Ohoho N506855

Rank 2

Ohoho Ohoho N506855
8.6/10about £22.03
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RUB0B0SHOP RUB0B0SHOP N695948

Best value

RUB0B0SHOP RUB0B0SHOP N695948
7.1/10about £23.47
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On this page
  1. 1.The three thicknesses
  2. 2.What goes wrong at each end
  3. 3.What the listings actually print
  4. 4.Habits that are not the rule

The three thicknesses

Three widths sit in a rip. The blade body is the steel disc inside the teeth. The kerf is the slot the teeth leave, wider than the body because the teeth are set or ground wider than the disc. The riving knife is the plate that follows the blade in that slot. HSE WIS16 Figure 5 puts the knife thicker than the body and thinner than the kerf, with a chamfered leading edge. DeWalt’s UK DWE7492 manual states the same inequality. Read the body between the teeth, not across the carbide, and read the knife with a calliper. The code for your saw comes first, on the replacement riving knife page.

What goes wrong at each end

If the knife is thicker than the kerf, the wood stalls on the plate. The usual trigger is a thin-kerf blade in front of the knife that came with a standard blade. HSE’s rip-saw page says a range of knives may be required when the blades change. If the knife is thinner than the blade body, the kerf can close on the rising teeth. Thinner is not a safer guess. Height is the 8 mm gap. Thickness is this band. Do not sand or grind the plate to chase the stall. If it is too thick for the blade you want to keep, change the knife or change the blade. Once the plate passes, how to fit a riving knife is the sequence.
PACKOVE PACKOVE 2.5 mm

Testsieger

PACKOVE PACKOVE 2.5 mm
1.2/10about £26.50
View offer

What the listings actually print

Five of the six listings do not state a thickness. Ohoho’s N506855 page, both N695948 pages, the Ridgid-named BERPSE page and the ServiceNet A23013 page leave the figure off. The Generic page prints 21 x 2.5 cm, a length and a width. ServiceNet prints 2.54 x 2.54 x 2.54 cm, a cube. PACKOVE, at £26.50, is the only page that states a thickness, and it states two. The title says 2.5 mm. The dimension line says 0.2 cm, which is 2 mm. The page names no saw.

Habits that are not the rule

UK Workshop threads discuss aiming halfway between the body and the kerf, and a gap of about 0.2 mm under the tooth width. Treat it as workshop habit, not as HSE WIS16. A plate you have not measured does not pass because someone aimed at halfway on a different saw. Scott+Sargeant prints the same inequality and also a formula written as e = B + b / 2. Read as ordinary arithmetic, that expression can come out thicker than the kerf. Do not use it. If the plate fails, do not sand it, and do not buy the universal title only because it prints a number. The number disagrees with itself.

Common questions

How thick should a riving knife be?
Thicker than the blade body and thinner than the kerf. HSE WIS16 Figure 5 is that pair of inequalities, with the knife between the disc and the width of cut. Read the kerf and the body on the blade or the packet, and read the knife with a calliper. A title that prints one millimetre, or none, does not finish the check.
What is the difference between the kerf and the blade body?
The body is the steel disc inside the teeth. The kerf is the slot those teeth cut, and it is wider than the body. The riving knife has to be thicker than that disc and thinner than that slot. Measuring across the carbide and calling it the body will make a correct knife look too thin.
Why does the wood stall after a thin-kerf blade?
The knife is now thicker than the slot the new blade cuts. The original plate can be right for the blade the saw was sold with and too thick for a thin-kerf replacement. HSE notes that a range of knives may be required when the blades change. Do not grind the plate down to chase the stall.
Is halfway between body and kerf a rule?
It is a workshop habit described on UK forums, including a suggestion of about 0.2 mm under the tooth width. HSE’s rule is the band, not the midpoint. A plate in the middle of the band satisfies the rule. A plate you have not measured does not.
The listing says 2.5 mm. Is that enough?
Only if your blade body is under 2.5 mm and your kerf is over 2.5 mm, and only if the plate is actually 2.5 mm. The one listing here that says 2.5 mm also prints 0.2 cm, which is 2 mm, and it names no saw. Measure the plate you receive.
Can I sand the knife thinner?
No. Sanding or grinding changes a safety plate. If the knife is too thick for the blade, use a knife that fits the kerf or a blade that fits the knife. A ground plate on a saw used at work is a reason to stop and get a competent person.
Where do I read the kerf?
On the blade or the packet, where the maker marks the width of cut, and with a calliper if the mark is missing. The body is the disc inside the teeth, measured without the carbide. If the packet and the calliper disagree, believe the calliper on the blade you are about to fit.

Related pages

Best riving knife

Riving knife

Replacement riving knife: match the code before the stars

How to fit a riving knife without drilling the plate

Riving knife vs splitter: which plate moves with the blade

Sources

Public UK sources from the research digest, last checked on 22 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the display file.

  1. HSE WIS16, Circular saw benches (retrieved 22 October 2026)
  2. HSE, Circular saw benches — rip saws (retrieved 22 October 2026)
  3. HSE L114, Safe use of woodworking machinery (retrieved 22 October 2026)
  4. HSE, PUWER overview (retrieved 22 October 2026)
  5. DeWalt UK, DWE7492 instruction manual (retrieved 22 October 2026)
  6. Spare Parts World, N791854 for DWE7485 (retrieved 22 October 2026)
  7. Spare Parts World, riving knife 1004695-77 (retrieved 22 October 2026)
  8. Consumer Rights Act 2015, section 11 (retrieved 22 October 2026)