Process
Cut-to-length
Every CNC form ends in a cut. In 4–14 mm that cut is a process decision: shear is fast and leaves a fingerprint; saw is slower and cleaner. The print has to say what the end is allowed to look like.
What cut-to-length is
Cut-to-length is the station that separates the finished centerline from the coil. On a 3D CNC or 2D CNC cell it is usually in-line: feed, bend, cut. Some jobs are cut first and formed as blanks — short runs, huge diameters, or ends that need a saw face before any bend.
Length tolerance is not the same as centerline tolerance. A ±1 mm cut on a 400 mm frame leg is often invisible. A ±1 mm cut on a pin that has to bottom in a hole is a reject.
Shear vs saw
Bushing shear / knife — the default on CNC wire formers. Fast, no chip, slight end deformation (a “smile” or a pulled face). Fine when the end is a weld prep, gets a chamfer, or disappears into a plastic boss. Wrong when the end is a bearing surface or a visible cosmetic face.
Saw — square face, slower, chips to manage. Used when the end is inspected as a face, when deformation from shear would crack a coating, or when 12–14 mm high-tensile shears ugly.
Square cut is the default. Chamfer, coin, flatten, and thread are end forming, usually after the cut — sometimes in the same cell, sometimes as a secondary.
What changes from 4 to 14 mm
| Diameter | Inch | Cutoff |
|---|---|---|
| 4 mm | 0.157 in | In-line shear is typical. End smile is small; chamfer covers it. |
| 8 mm | 0.315 in | Shear still wins on cycle time. Call out if the end is a weld or a hole entry. |
| 12 mm | 0.472 in | Shear deformation is obvious. Saw or a dedicated end station if the face is critical. |
| 14 mm | 0.551 in | Heavy shear or saw. Light bushing nicks do not belong on this diameter. |
What the print should say
- Overall length and which datum it is taken from
- End condition: square, shear-ok, sawn, chamfer, or “form after cut”
- Whether burr is allowed, and on which side
- If the cut face is a weld joint, say so — flash and fit-up change
“Cut to length, deburr” is not enough on 12 mm stainless that has to slip into a tube. Put the end on the same drawing as the centerline.
Related
- Wire straightening
- End forming
- Wire form shapes — the rest of the alphabet after a straight
- Design for wire forming