I think 1/4-28 is the standard Machine Screw thread, which is a good thing.
As a side-note...to add Red Speckling, without shine or sparkle, I'm going to add Red Pepper, probably chopped Red Pepper Flakes, to add Red to a Craw color. Maybe Do-It all in one, by using Zatarain's Big 'N Zesty Blackened seasoning...it's got Garlic, Black Pepper, Red Pepper, and a little Salt...and it's coarse. Maybe a Pinch or a Dash in 12 ounces.