I've got a few pieces of furniture that I obtained with some missing screws (a futon frame and a headboard). How do I determine from the object what size screws are necessary from the measurement of the hole itself? Also washer size. Are these standardized in such a way that the guy at HD can get it right from a trace of the hole? I know this is a silly question but I tried to buy one just by looking at it and they didn't fit. Thanks.
You can measure the hole with a tape measure, as long as you are VERY accurate. Measure at the widest part of the circle and get it to the closest millimeter if you can.
For length, the easiest I can think of is to get a bamboo skewer or something else slim enough to go into the hole where the screw would go - measure it to exactly the width of the wood you're trying to hold together, then let the HD guys help you figure out how much you need to add to allow for the screw head & enough threading to get a good hold.
Washers are less picky - but I'd get the widest you can that won't overlap the edges of your wood (i.e., don't get one wider than the width of the piece of wood it will be up against, because then you'd be scraping yourself on the washer all the time ) A wider washer means more surface area to hold the weight pushing against the screw, so its easier on the wood. A huge washer might be overkill, but can't hurt anything except aesthetics ;-)
If you're trying to fit into an existing nut that is already attached somehow to the furniture, then you have the additional problem of thread size. I believe there's only 2 common thread widths used for furniture (correct me if I'm wrong, carpenters), so just look at the nut & see if the threads seem very close together or are wide enough that you could easily run your fingernail along them. If you have to buy the nuts too, then that's easy to match the bolts when you find them.
Hmm...just realized you said 'screws', not 'bolts'...if you really meant 'screws', as in something that screws directly into the wood & doesn't need a nut on the end, then the measuring ideas should still work - but you need a screw just a touch wider than the hole so that it grabs onto wood that hasn't yet been disturbed by the previous screw. Another option is to stuff the hole full of wood putty and screw into that once it has dried, but I don't trust this method as much, personally.
Ruh-roh. Well, you can measure the depth of the hole and get a good idea on the diameter as BackYardZoo said, but threads per inch is another matter. Maybe buy an assortment of sizes and try those out. Then take back what doesn't fit and buy the rest of them at that time.
Actually, On both of these pieces, I'm thinking it's more important to hold them together with a bolt than that the screw actually hold onto the wood itself if that makes sense. If I get the bolt close to the hole size, it should work. Are headboard and bedframe screws not standardized?
I don't know if there is a standard size screw/bolt for headboards and bed frames. As long as the screw (carriage bolt in your case) is long enough to pass through the headboard and bracket on the frame and an extra bit of length for the nut and washer you should be fine. Seems like I had to drill holes in our old headboard because the first frame didn't match up. Then we got a new frame and it didn't line up so we said forget about attaching the frame to the headboard - just push it up against the wall and it looks just fine (especially for overnight guests).