Thanks for the lesson, now let me give you one. Center drills are for making centers in a part that needs to be held on a live or dead center. Spot drills are for centering your hole before you drill it. Here is some miniture spot drills that I have used in the past, http://www.harveytool.com/products/product_detail.php ?product_id=11400&category_id=1&product_family=Min iature+Spot+Drills<font face="Verdana, Arial" size="2">Originally posted by Rustybolt:
Tiny drills are made for drilling very thin materials.The next questiion would be; how do you center them? Almost any center drill is going to have a chisel point that is going to leave a flat an the bottom. No matter what the material you don't dare dwell at the bottom of the hole or the drill will instantly dull.You have to be careful of the coolant used so as not to accumulate chips and pack the hole and thus break the drill.
I looked at the spot these make under a microscope and they hardly make a flat at all. I would make sure my part is indicated in nice and flat, and then set the spot drill to go in .002", that way the top of the hole would have a nice small chamfer.
As for not dwelling at the bottom of the hole, all I can say is duh. I also use the same coolant whether or not I drill .015" holes on the cnc or drilling 1" holes, I just set it to take such small pecks that chip packing isn't an issue.
As for the other stuff you said, yeah small drills aren't usually made for going that deep, and to be honest I would turn down that job if anyone ever brought it in to my shop.
[This message has been edited by mochinist (edited 08-17-2001).]