Looking for tool recommendation...clean up cut holes

[whizbang]

I am looking for recommendations on tooling I can use to square up the edges of holes or slots on thicker material. I know nature of plasma cutting will result in some taper to the edges, especially thicker material like 1/4" and up but I want to be able to clean up the edges and improve it in some cases.

What I am looking for is preferably a die grinder bit with 1/4" shank that is not a double cut carbide burr because they grab and are hard to control. I have tried sanding drums for port and polishing of various quality and grit and design, they all burn up in about 30sec. I'd be interested if there are any diamond or sintered style abrasive bits with 1/4" shanks.

Appreciate any insights or recommendations.

[weldguy]

I have never had much luck doing that. The cut edge is so hardened it dulls out everything, smaller holes I can get away with a cobalt drill bit but larger holes that doesn't work so well. Carbide burr in a die grinder with some WD40 is about the only thing I have found that will work decently. Curious if anyone else has found anything else to work well.

[djreiswig]

You can buy single cut burrs.

[moosehorn]

I have had success by using oxy/acetylene torch to heat the surrounding metal to cherry red and allow it to cool naturally which anneals (softens) it.

[Scratch]

I used to make a lot of “weld yourself” bead lock kits for off road vehicles. There would be an inner ring that they weld onto their own steel wheel, and an outer ring that bolted onto the inner ring with the tire bead sandwiched between the two. They were made from 1/4” hot rolled steel and they needed 24 holes in each ring, and those holes needed to be 7/16” each.

I would plasma cut them smaller than needed (don’t remember the size) then drill each hole out with a cobalt drill bit on my drill press at the lowest speed my press will go. Since there were two rings per wheel, that makes 8 rings per vehicle set, and I probably sold at least a hundred or so sets over the years. If I say 100 sets that makes 19,200 holes I’ve drilled out with that one bit. I spray painted the bit yellow since I used it so much. Ive never sharpened it and it’s still probably one of the sharpest bits I have.

[SegoMan DeSigns]

I found that if you over-burn slots at least the the thickness of the material it leaves a cleaner hole, for cleanup I use an oblong carbide in the die grinder. Holes I normally tap so I print a drill template to punch the holes with then drill / tap as needed:

Drill Guide (1).jpg

Drill Guide (2).jpg