What to Specify on a Base Plate Drawing

A base plate is one of the simplest parts to cut and one of the easiest to get wrong, because the plate usually sets the position of everything built on top of it. The drawing has to carry that intent, not just an outline with holes in it.

Outline, material and thickness

Give the plate size, the thickness and the material. Base plates regularly run into the range the five axis plasma table handles, from 1/8 in through 4 in plate, in carbon steel, stainless or aluminum, with a cut area of 6 ft by 12 ft. Anything larger is reviewed as a multi piece assembly before it is quoted.

Say whether the plate is a stock size or cut from a larger sheet, because that changes what the corners and edges look like.

The hole pattern

• Hole size, position and quantity for every hole.
• Which holes are clearance and which are tapped, with the thread callout on the drawing.
• Which holes are counterbored, and the depth and diameter of the counterbore.
• Any hole that is milled rather than drilled, such as a slotted or oversized opening.
• Which hole group is the datum for the pattern.

On this machine the plasma torch cuts the outline while a separate drilling head drills, taps, counterbores and mills in the same program, on the plate still sitting on the table. A tapped hole pattern quoted as part of the plate does not need a second handling, which is where hole positions usually drift.

Bevels and weld preparation

Bevels are where a base plate drawing tends to be quiet. The table cuts contour bevels on five axes, so the drawing should state the bevel angle, the land or root face, and which edges are beveled. Where a bevel is only needed on part of an edge, mark the extent. Bevel angle, land and finish are confirmed per part at quote.

Critical dimensions

Two or three dimensions usually matter more than the rest on a base plate: the hole group relative to an edge, a diagonal that keeps the pattern square, or the distance between two anchor groups. Mark them. A drawing where every dimension carries the same weight tells the shop nothing about which one to hold when a plate has to be adjusted.

What the drawing does not need to decide

KorFab does not size the plate, choose the anchor layout or design the connection. Those decisions come from the responsible design team. The review covers whether the part as drawn can be cut, drilled and beveled as specified, and what it takes to do it.