Spelling rule for words ending in -el or -le

This one always seems to trip me up. On the one hand we have table, axle, angle, knuckle, noodle, etc and on the other we have *angel, bagel, gravel, *etc. Is there a rule behind all this?

Not really.

English sucks.

Well-published British linguist Larry Trask chimes in:

Thanks, bordle.