Can SDS bits be sharpened?

Can SDS bits be sharpened?  I'm getting good use out of the $7 bits is get at the hardware store. At least a dozen holes before noticeably dulling and slowing. Can they be sharpened? 

It’s not the lack of sharpness that makes them reach the time to replace.  It is the very small loss of metal that causes them to drill a hole just a teeny bit too small.  This ever so slightly smaller hole can foul the expansion clip and ruin a placement.  

SDS is irrelevant to this question -- it is a description of the fastening/attachment mechanism between the drill bit and the drill.  What will determine whether or not a bit can be sharpened, or usefully sharpened, is the type and material of the tip.  

Yes they can. I sharpen them before the first use as they always are a bit dull new. 

Mike's comment is correct. I've never had to sharpen a bit before it has worn out. Mic your bits if you get to that point.

Hand drilling and bit sharpness is a different game though if you're talking about that.

I've been drilling smaller holes in river cobbles so that I can screw them onto my home wall (so in this case no need to maintain a consistent hole diameter). It doesn't seem like sharpness of the carbide blob makes a difference. A small carbide tipped SDS bit will go through all the cobbles I've tried like a hot knife through butter, but then when the carbide is consumed drilling progress stops like a switch has been flipped.

SDS shanked drills don't work like a twist drill you would use on steel or wood i.e. they don't produce a chip so it's not as much about a sharp edge. Rather they are percussive drilling so rely on the hardness of the carbide tip of the hardened steel drill body and axial movement capability of the drill bit/shank to pulverize a small bit of the substrate, more like a chisel. That is a simplified explanation that ignores the geometry of the tip.

The carbide typically wins the hardness fight and has resistance to the heat generated but it's not indefinite. Eventually the heat and abrasive wear reduce the diameter of the edges of the drill. I think I recall the tolerances for a mechanical anchor being something like .010" which is about 3 pieces of paper total, so 1.5 pieces of paper per side. This is why you need to use a new bit after approximately 10 (+/-) holes if you're installing mechanical bolts. In Vermont granite in the NE of the state I get 9 1/2" x 4" holes before I'm under-sized and installing the bolt becomes noticeably more difficult.

I was hand drilling some holes in hard granite today, and the agonizingly slow progress led my mind to wander back to this thread.  I feel like the geometry of the contact surface of the bit has to make a difference on how well the bit pulverizes the rock.

I imagine it's much less of a consideration with a power drill.  I'm not sure when I'll next be drilling again, but I think I'll experiment with filing sharper leading edges on the bit before I do. 

See this Taco post:

http://www.supertopo.com/climbing/thread.php?topic_id=2621354&msg=2621519#msg2621519

and this-

http://www.supertopo.com/climbing/thread.php?topic_id=2190293&msg=2218575#msg2218575

Just FYI, tungsten carbide dust is incredibly toxic if inhaled. Look up the health risks and make informed decisions.