Drilling holes in thin sheet
Drilling holes in thin sheet
(OP)
We are having trouble drilling in 11GA 304 stainless steel.
We drill lots of closely packed holes 3/8" od. No matter how we fixture and clamp the sheet to the table the sheet is still warping and creating a gap between the sheet and the table causing vibration in the sheet while drilling. This causes chipped drill bits and eventually broke ones.
We're using a guhring drill specifically for the application and confirmed speeds/feeds w/ guhring.
Any ideas or help?
We drill lots of closely packed holes 3/8" od. No matter how we fixture and clamp the sheet to the table the sheet is still warping and creating a gap between the sheet and the table causing vibration in the sheet while drilling. This causes chipped drill bits and eventually broke ones.
We're using a guhring drill specifically for the application and confirmed speeds/feeds w/ guhring.
Any ideas or help?





RE: Drilling holes in thin sheet
What condition is the 304 sheet, like is it half hard, full or somewhere in between?
What you using for coolant?
You didn't post the precision needed so I have to ask, Could you use a perforated plate?
RE: Drilling holes in thin sheet
They're expensive, but some outfits do nothing else but contract cutting.
There will be a thin HAZ, so the sheet will 'weld funny'. If that's important, you can cut the holes a little undersize and take off a few thou with a die grinder.
You can pack the holes just about as close with a waterjet, and with no HAZ, though the sheet will arrive covered with fine abrasive dust that you'll want to clean off.
Again, contract cutting is available.
Either way is probably much cheaper than drilling.
Mike Halloran
Pembroke Pines, FL, USA
RE: Drilling holes in thin sheet
Try a "Lip & Spur" drill bit (AKA Brad Point). These work beautiful on sheet metal and on plastic.
The point is scalloped between the center and margin so that you have a center "point" to accurately start the hole and the lip at the margin cuts only the perifery at first making a clean round hole.
RE: Drilling holes in thin sheet
I've used a hand-held electric punch to go through Hastalloy-X plate 5/16 thick. That worked much faster than drilling.
If you only have a few parts to make - or don't want the expense of an elaborate setup, clamp plywood sheets on both sides of the plate, then drill through the backing plate and steel.
RE: Drilling holes in thin sheet
Our work surface is as rigid as possible, we have a solid sacrificial plate underneath and we are using flood and thru coolant drills. We're clamping down but i guesse when the drill leaves the sheet its pulling and flexing it. We could clamp down very close to each hole and not have as much as a flexing problem but the vast number of holes we are doing, and them being closely packed, makes this impractical.
I am thinking this problem is happening because of the drill maybe pulling the sheet metal when it exits it and also a small bur on the back sides of the holes is happening which helps create gap between sheet and sacrifical plate. I am hoping another tool may be better, maybe a end mill specifically for drilling?
RE: Drilling holes in thin sheet
Here is one example but it can easily be sourced.
RE: Drilling holes in thin sheet
RE: Drilling holes in thin sheet
Have you tried a spring-loaded clamping device that presses down on the sheet around the drill?
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
RE: Drilling holes in thin sheet
We are doing 1000s of holes per sheet of 3/8"OD on a 29/64" triangular pitch.
RE: Drilling holes in thin sheet
RE: Drilling holes in thin sheet
Given your dimensions I can get 30, but the web thickness for all practical purposes is too thin for drilling.
I would not even attempt this without making an indexable jig from thicker materials using drill bushings.
RE: Drilling holes in thin sheet
RE: Drilling holes in thin sheet
Why not have a 'pattern' piece above with slightly oversize holes, this could act to clamp the part being drilled over almost the entire surface. Obviously this pattern part will be even more tricky to machine, especially as it will probably need to be a good bit thicker gauge to have adequate stiffness - but you only need to make it once.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Drilling holes in thin sheet
Why not have a 'pattern' piece above with slightly oversize holes, this could act to clamp the part being drilled over almost the entire surface. Obviously this pattern part will be even more tricky to machine, especially as it will probably need to be a good bit thicker gauge to have adequate stiffness - but you only need to make it once.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Drilling holes in thin sheet
99 Dodge CTD dually.
RE: Drilling holes in thin sheet
It sounds like you are stuck with what you've got unless something can compromise. What is this for?
I would vote for the perforated sheet: if you can go with a slightly larger spacing or a slightly smaller hole diameter or a thinner sheet then a perforator might be able to help.
Next choice is laser, last is waterjet.
RE: Drilling holes in thin sheet
I've done custom engine gaskets from very thin copper plate (much thinner and much angrier to drill through than this) and successfully used the sandwich method listed above. Put 2 pins between the sandwich pieces so that you can use it as a pattern.
RE: Drilling holes in thin sheet
RE: Drilling holes in thin sheet
You will kick yourself when you finally try getting a sheet laser-cut. You could probably push the web between holes down to .01", if open area is important to you.
Mike Halloran
Pembroke Pines, FL, USA
RE: Drilling holes in thin sheet
RE: Drilling holes in thin sheet
If you insist on drilling these yourself, you're going to have to reduce the number of plates you put in each stack.
The top portion of the stack shouldn't be too bad, but chip removal might not be the best towards the middle/bottom. And as you correctly guessed, the sheet would deform slightly (more as you get further away from the clamps) as the drill exits each hole, and the burr behind the sheet when the flex occurs can create additional problems (even if imperceptible at visual inspection, you will hear about it during assembly).
Reduce the number of plates in each stack, and change clamps as much as is practical to keep it close to the work. Or from the sounds of it, change to a different method of manufacture.
Whose bright idea was it to design a heat exchanger that big in diameter with 3/8" tubes?
-TJ Orlowski
RE: Drilling holes in thin sheet
Designer and <a href="h ttp://www. coilingtec h.com/comp ression-sp rings.html">compressing springs</a> enthusiast
RE: Drilling holes in thin sheet
I don't know if they go as low as you require but it's worth a call.
They have several tools for thin materials.
http:/