What boat model are you working on?

  Hammer to fit? You know that is a recipe for disaster. Find the correct drill bit. Parts should fit together like they belong.  If it is close, wrap some 80 grit sand paper on a dowl, or drill bit and sand the hole larger. You do want the hole large enough so you can finish the interior of the hole with epoxy and/or varnish/or paint to keep the wood from rotting.

Joel

   Since you already drilled the hole, make bigger w/ a rattail wood file or a dremel w/ sanding bit. I had 6 of these on my Cosine Wherry and the dremel worked just fine.

I'll agree with the others that something like that shouldn't be so tight that it want's a hammer to seat it.  I assume you are talking about "top mount" sockets here, right?  I'd widen out as suggested above, making sure that it was loose enough for the thing to slip in after sealing up the exposed wood with epoxy.  I wouldn't epoxy the fitting in, if that's what you're thinking.  Stuff like this should be bedded with sealant, maybe something like 4200, to keep water out without permanently gluing the fitting to the boat.

Yes, the risers can crack.  Had one crack on our PMD (angle type, not top mount) after we'd rowed the boat some, probably due to my not getting one of the pilot holes for the screws right.  Removed oarlock socket, epoxied all back together, and reinstalled with no further trouble.

No stupid questions here, Fred.  Yours was especially not stupid.  <;-)

.....Michael

   You know I don't have a clue what boat you are building. But all the rowlocks, oar locks, etc. I've ever installed were there when I measured to drill holes, prepare the mounting face, etc.  Measure and size the hole.  Don't be a hammer mechanic. It's not such a good thing in wooden boat building. 

You can enlarge the hole with a twist drill through a shim stock(s) to prevent splinters. Or sand/file out like others suggested. 

A lot of consumer grade drill bit sets don't include a lot of the available intermediate sizes, especially over 3/8".  You can get bits in 1/32" increments from 5/8" up to 1" at some places and 1/16" increments are more common, so a 11/16" should be easy to find, then 3/4".  Most of these can be found w/ reduced shanks so they'll fit in smaller drills.  Check online at woodworking catalogs, or use the ol' standby, McMaster-Carr like me.  I have sidemount oarlocks on my skerry, so this isn't a step I had to take.  Even if you have the exact right size, it'll still be good to file or sand it a bit to make room for (I assume) a seal coat of epoxy or varnish before installing the lock.

BTW, if you go get bits online, I'd recommend shopping for an inexpensive dial or digital caliper for measuring things like diameters, etc.  Much easier and more precise than trying to eyeball w/ a ruler.  I reach for one all the time.