How I deal with Kerf
A customer recently asked how I achieve such straight holes with no kerf when they purchased a set of Radius Plates for a Harbor Freight Radius Roller. The answer is simple: I use a plasma cutter to cut the plates, and then I punch the holes using an Ironworker.
Kerf is a common issue with plasma cutting, especially in non-high-definition plasma tables. Kerf happens when the plasma cut leaves a hole that’s smaller at the bottom than at the top. To compensate for this, you can adjust the hole size in your design by adding about .050 inches to make the hole slightly larger.
In thinner materials, kerf isn’t usually a big issue, but the thicker the material, the more noticeable it becomes. I solved this problem by investing in a 65-ton Ironworker for punching precise holes. Drilling is also an acceptable method if you only need to make a few holes. However, since I often run batches of the same product, I prefer to set up the Ironworker and punch the holes for accuracy and efficiency.
If you're using a plasma table, you can sometimes reduce kerf by adjusting your cutting rules. Your table should slow down when making turns or cutting curves. Adjusting the feed rate—either speeding it up or slowing it down—can also help minimize kerf. Below is a set of rules I use on my machine, which might serve as a helpful guide:
0.25" before the end of a cut, set the feed rate to 98%.
For circles smaller than 1.25", set the feed rate to 50%.
For shapes smaller than 1", set the feed rate to 50%.
For arcs smaller than 0.625", set the feed rate to 60%, from 0.015" before the arc to 0.015" after.
These rules help me get more precise cuts and minimize kerf, especially on thicker materials.
