Drilling holes in thin sheet

[mielke]

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?

 

[maayhemm]

as a laser operator who cuts 304 and 316 stainless all day we use nitrogen as assist gas. no HAZ to speak of. only problem i see would be slight warpage of your plate which could be flattened using a roller after operation is complete. each 3/8 hole would take 2.0 seconds including pierce and travel to next hole. laser is the way to go.;

 

[TJOrlowski]

As someone who's learned this lesson the hard way (we had some soft baffle material in a HX with 3/8" tubes where we ended up drilling the baffles individually - thankfully only 328 tubes):

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

 

[engineer4fun]

I totally agree the laser-cut they will get it down to where you want it.

Designer and <a href="

http://www.coilingtech.com/compression-springs.html">compressing

springs</a> enthusiast

 

[unclesyd]

You might want to give Blair Equipment a call about your problem.
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://www.blairequipment.com/holcutters/holcutters.html