How to measure a machine blade for a custom order
Nine out of ten custom blade problems start before production: the measurements sent were taken from a worn knife, or the hole pattern was mirrored. This is the list of numbers we need, how to take them properly, and the five mistakes that cost the most time.
The eight numbers we need
- Length — overall, tip to tip.
- Height / width — from the cutting edge to the back.
- Thickness — measured on the body, never on the bevel.
- Hole diameter — each size if they differ.
- Number of holes and whether they are slotted.
- Hole pitch — centre to centre, not edge to edge.
- Hole position — distance from the back edge, and from each end.
- Bevel — angle, and the width of the ground face.
Plus, if they apply: corner radii, notches, slots, relief cuts, the direction the bevel faces, and the machine make and model.
Measure like this
Thickness
Use a caliper on the flat body, at three points along the length, and write down all three. Measuring on the bevel gives a number that is too small, and a knife made to it will not fit the clamp.
Height
If you are measuring a used knife, remember it has been ground. A knife that started at 160 mm may now measure 152 mm; if we copy 152 mm you receive a knife that is 8 mm short from day one. Send both the current measurement and, if you have it, the machine's specification or the original drawing.
Hole pattern
Measure centre to centre between adjacent holes, then overall from the first hole centre to the last. Use the machine's clamp or a new spare as the reference if the old knife is broken. Note which face the countersinks or threads are on.
Bevel
Record the included angle if you know it, and measure the ground face width with a rule. The width of the bevel plus the height of the knife tells us the geometry even when the angle is unknown.
Photographing the blade so we can read it
- Lay it flat on a plain surface, in daylight or under a diffuse lamp. No flash on bare steel.
- Put a steel rule along the full length, in the same plane as the blade.
- Take one photo of each face, straight down, filling the frame.
- Take a close-up of any stamped number, logo or part code — that alone can identify the machine.
- Take a close-up of the edge, at an angle, so we can see the bevel and any nicks.
The five mistakes that cost the most time
| Mistake | Result | Avoid it by |
|---|---|---|
| Measuring thickness on the bevel | Blade too thin, will not clamp | Caliper on the flat body, three points |
| Copying a worn knife exactly | New blade is undersized | Send current size plus the machine spec or old drawing |
| Hole pitch measured edge to edge | Holes do not line up | Centre to centre, plus overall span |
| Mirroring the hole pattern | Blade fits only one way — usually the wrong way | Send photos of both faces, state which face is which |
| No machine model | We have to guess at the clamp geometry | Photo of the machine nameplate, or the stamped code on the blade |
What a usable drawing contains
All dimensions with tolerances, material and hardness, hole and slot geometry, bevel angle and which face it is ground on, corner treatment, quantity and any marking requirement. PDF or DWG is ideal; a clear hand sketch with every dimension written on it is also workable. What we will not do is produce from a verbal description of "the same as the old one" without a reference — that is how costly mistakes are made.
Send the measurements, photos or drawing, and we come back with a quotation and a drawing for your approval. No steel is cut until you sign off on that drawing.
Frequently asked questions
Can you make a blade from a photo without a drawing?
Yes, if the photo has a ruler in frame and shows both faces. We will produce a drawing from it and send it back for your approval before production. A stamped machine code or nameplate photo makes the fit much more reliable.
Do you need the original drawing?
It is the fastest and safest route, but not a requirement. Many of our orders start from a measured old blade plus photos. We always issue a drawing for approval, so the final reference is a document we both agree on.
What is the minimum order for a custom blade?
One piece for a trial, then batch production once the fit and the edge are proven on your machine.
How do you handle tolerance on length and hole position?
Tolerances are agreed on the approved drawing, per blade type and machine. Tell us the critical dimensions for your clamp and we will hold to them and state them on the drawing.