0

I have a 31” x 31” x 3/16” mild steel plate. I want to cut a 30” circle from the the plate.

Purpose: The plate/disc will be the base of a custom charcoal barbecue/raised fire pit.

I’ve seen various videos of people using angle grinders to cut circles from steel plates. But those methods seem cumbersome and laborious to me. I’m wondering if there might be an easier way to do it using basic garage tools.

I don’t have ideal tools like a plasma cutter or an oxyacetylene torch. But I do have a portable bandsaw (not yet used): DEWALT Portable Band Saw, Deep Cut, 10 Amp, 5-Inch (DWM120K).

Is there a way to cut out the disc using a portable bandsaw? I’m willing to drill a hole in the middle of the plate if needed for spinning or jigging. I don’t have a table apparatus for the portable bandsaw, but I can make one or put the saw in a vise.

5
  • You want your finished product to be a 31" square with a 30" hole in it?
    – Huesmann
    Aug 23, 2023 at 12:23
  • This might be a good point to outsource this particular part of the job to someone who has the appropriate tools. There's no shame in knowing where your DIY limits are.
    – FreeMan
    Aug 23, 2023 at 12:47
  • @Huesmann Oops, I tried to clarify the wording. I want the resulting product to be a circle/disc, not a square with a hole in it. Good catch.
    – User1974
    Aug 23, 2023 at 13:06
  • 3
    Wow! That edit totally changes the question! You're cutting away the square parts to leave a circle, not cutting a circle out of a square, leaving square outer corners.
    – FreeMan
    Aug 23, 2023 at 13:18
  • 1
    @User1974 yes, if you want to end up with a disc, the easy button is to simply draw a circle on the square and just nibble away the corners until you can fit the entire corner "overage" in the jaws of your saw.
    – Huesmann
    Aug 24, 2023 at 12:45

2 Answers 2

3

A quick maths check says to cut a circle into that square, your bandsaw would need to be able to cut a depth of:

(31"  x  sqrt(2)  -  30") / 2 = 6.9"

The instructions for the bandsaw you have say a max depth of 5".

So the only way you could use that saw to acheive your desired cut would be to round off a couple of inches from the outside corners of the square so that it is at most 40" across. But that may not be acceptable to you.


Ok, so based on the changes to the question, you are trying to cut out a circle from the square, rather than cutting out a circular hole.

In this case you should be fine using the bandsaw to cut out the circle. Again as the cut depth of the bandsaw is too small (see equation above), you will have to make two cuts, the first to remove excess material from the corners, and then a second pass to form the shape you want.

I would cut the circle slightly oversize - e.g. 31 1/16" - and then use a file and sandpaper to get the final shape. Remember to file in the opposite curve to the circle to avoid forming flat spots:

Motion of file on edge

2
  • Or, use the bandsaw for some of the cuts and an angle grinder to get into the "corners". This is probably the reason most videos the OP has watched show using an angle grinder. ;)
    – FreeMan
    Aug 23, 2023 at 12:46
  • You get to keep my up vote, even though the question has totally changed with the edit just made.
    – FreeMan
    Aug 23, 2023 at 13:18
2

Since you're cutting away the square parts of the plate to make it circular (not cutting a round hole in a square plate, as originally asked), you can use any tool you'd like, including sandpaper (if you're a masochist).

Draw your circle on the plate, fire up the band saw, bring the blade to the edge of the plate and start cutting!

When you get to the point where the saw doesn't have enough depth to reach from the edge to your line, just cut straight to the nearest edge to cut the excess away so now your edge is much closer to the line. Once that extra material is out of the way, go back to cutting the line.

You may find that your band saw cut is a bit on the ragged side, especially if this is the first time you've used the tool, so cut a bit outside the line so that when you're done, you can use an angle grinder, file, sandpaper, whatever to neatly get right to the line. How careful and thorough you are in this step, of course, depends on exactly how smooth you want your disk of steel to be.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.