The Folded Cloth Trick (get truly round holes in sheet metal)

[graham-xrf]

I am surprised that I got to the age I am without discovering this one until now, but such is life. I hanker to progress my electronics-related project, but I am presently distracted by maintenance repairs and construction. I guess I am just learning some stuff late.

I have always known that one can clamp sheet metal layers together, and get somewhat better results with the drill going through, even though that be a bit wasteful. I have also once clamped sheet metal between a couple of chunks of scrap wood.

I have no idea why this cloth trick works, but enough folk do recommend it.

 

[Eddyde]

My guess is, the rag fills the flutes of the drill so it can't bounce around inside the hole as easily.

 

[graham-xrf]

My guess is, the rag fills the flutes of the drill so it can't bounce around inside the hole as easily.

That is very plausible!

Allegedly, it also stops the sudden snatch deeper cut-in that happens when the drill is nearly all the way through. I will have my chance to try it out soon on something where the metal is a bit less than 1mm thick, and I only get one chance to get the holes right for nut inserts.

I am thinking the denim rags that came from my last pair of (retired) blue jeans might work OK.

 

[stupoty]

If depth isn't a problem the stepped cone drills are very good for sheet metal.

Stu

 

[RaisedByWolves]

The way that drill press is wobbling around would drive me nuts.

Neat trick though.

 

[porthos]

can't imagine a drill press with that much wobble

 

[pontiac428]

Single flute bits (like step bits) solve the hole problem with sheet metal. There is a simple, pointed straight flute grind similar to a D-bit with a lot of back relief for that is specialized for sheet metal also. It's not the metal that's the problem, it's the grabby helix and lobe wobble that make twist drills awful in sheet metal.

 

[Provincial]

Where possible, I use Whitney punches. I keep picking them up at garage and estate sales for $5.00 or so, and most are missing at least some of the punches and dies. I have one with a full set, but the other three have enough dies between them to cover all the sizes. I have a 4 out of 6 chance of having the right die set installed on one tool ready to go.

 

[porthos]

i too have had good luck at garage sales with whitney punches. good thing for us that most don't know what they are looking at.

 

[RaisedByWolves]

Single flute bits (like step bits) solve the hole problem with sheet metal. There is a simple, pointed straight flute grind similar to a D-bit with a lot of back relief for that is specialized for sheet metal also. It's not the metal that's the problem, it's the grabby helix and lobe wobble that make twist drills awful in sheet metal.

I prefer a fishtail drill for sheet metal.


We had machines that drilled holes in copper tubing during my apprenticeship and I sharpened thousands of those by hand.


Like this but with a point in the middle.