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Can the DBS-22 Sharpen Spot Drills?

Started by Dr.Al, July 25, 2023, 10:13:43 AM

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RickKrung

Quote from: Dr.Al on July 28, 2023, 04:43:49 PM...snip...

Having said all that, centre drills are very short, so I'd be surprised if you can hold them in the jig. Also, I tend to break the fragile tip long before they go blunt, so I probably won't ever need to sharpen a centre drill  ;D

For that matter, spot drills are quite short too: perhaps that's a limiting factor regardless of geometry? My smallest spot drills (3 mm diameter) are about 50 millimetres long I think; when you set the drill protrusion with the stop on the DBS-22, how much sticks out of the clamp?

I have not followed through in the discussion from a while back about the use of pin vises for holding smaller diameter drill bits, but it seems to me that pin vises would be an excellent solution for holding center drills and spot drills for sharpening with the Tormek.  I still need to turn the hex handles round on the Starrett pin vise, but maybe I'll get to it one of these days. 

Rick
Quality is like buying oats.  If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

aquataur

#16
I have come to the understanding that spot drills and center drills are the machinist´s choice for a lathe or any other device (like a mill) that has a very tight grip on the tool, plus an equally well fastened work piece.

They are a bad choice for the layman´s cheap drill press, let alone hand operated units, because they are not ground to any particularly special shape that would foster a good hole start.

As I (hopefully) layed out on my recent contribution ("Musings...") the hobbyist is far better off with a small (store-bought) drill with some form of web thinning (split point), followed by the final drill with practically any grind you like.

Since you seem to belong to the prior clientel and thus seem determined, the answer is: no, you cannot sharpen them on the Tormek if they are small.

Gadgetbuilder talks a lot about this subject. He advises against center drills for certain reasons and recommends sharpening spot drills to a 4F shape. He also explains several reasons to not sharpen them to the 90° or whatever acute angle they commonly have.
That all said, bear in mind that he comes from the lathe corner. I found that a short stubby drill I had sharpenend to those specs bears no advantage on a drill press, however a 4 mm (store bought) drill with split point was far superior for starting holes.

Drilling on a lathe is not the same as drilling on a drill press or manually.