Self-drilling fine thread screws for hardwood

[FS7]

Oh, and the head needs to be less than 3/8". The last step of my crib building is attaching the sides to the front and back. It won't physically fit into the nursery assembled, nor would it make sense to glue it in there. Besides, once the kids are grown, I'm turning it into a bed.

I have 3/8" cherry pyramid plugs, but that limits me to screws with a head size of 3/8" or less. I already know that Kreg screws will fit, but they don't make fine thread screws that long and coarse threads aren't going to work with bubinga. For the crib mattress supports, I intended to use threaded inserts, but I had to go up three drill sizes to get the inserts in without destroying the wood. I ended up just tapping the bubinga like it was metal, and the screws hold with incredible strength. This means that coarse screws are out.

I have GRK trim screws that will work, but I am concerned about splitting and thread stripping. The other GRK and Spax screws I have are *just* slightly too big to fit in the hole.

This isn't a common measurement I see provided on fastener sites. All I need is a good self-drilling screw (seems like most nowadays are) with fine threads, a length of about 2 1/2", and a head size (preferably washer head) of 3/8" or less. Is this a unicorn?

[AHill]

I'm not clear about whether these screws are going into the metal inserts, or just into a new hole.  If the latter, then why self-drilling?  Why not drill a pilot hole and then use a "normal" screw? Bubinga is pretty hard, and as you say, there's a danger of splitting.

[Steve N]

Spax screws are mostly self drilling tips. You would just need to figure what material, and head type you wanted. I have never had a Spax screw fail, can't say that about every brand I've tried. Slightly higher priced, for premium quality. I get mine at Menards, but have seen offerings of them at HD, and Lowes, though Menards seems to have a better choice of them. Like Allan I am not sure why self drilling on a woodworking project is important. Because a self drilling screw will go into wood, doesn't mean it couldn't split it as well, as it goes in. If I have taken more than a few minutes to make something, I'll always take the few seconds to drill pilot holes.

[Splinter Puller]

Have you tried the Kreg screws?   This is all I use for most hardwood.

[Routerman]

Why not just tap the thing?
The pull strength of a no. 10-24 machine screw, 1" into side grain
of dry maple, is >500 pounds.

[FS7]

I should have added more detail. The legs on this crib are about 1 5/8" square. The front and back are single units (now, after a quart of glue and 8,000 loose tenons). I was going to use threaded inserts and machine screws to hang the crib mattress support from the front and back, but the recommended 3/8" drill wouldn't even let the insert in, 13/32" caused bulging, and 27/64" finally worked. After testing drilling and tapping the wood directly, I opted not to use the inserts as I don't have a drill press and my confidence in my ability to not destroy the piece during the installation of twelve inserts was far too low. There are no inserts there.

The sides consist of two "I" shapes with slats in between - 1 5/8" x 3/4" walnut on the top and bottom, with 2 5/8" x 3/4" bubinga oriented vertically in between. I plan to screw into the side pieces (the bubinga) through counterbored holes on the front and back. I plan to drill pilot holes as well as I can, but in my experience so far (having tested with offcuts) is that regular screws may snap in bubinga. There did seem to be a sharp difference between self-drilling and non-self-drilling screws, so I don't trust regular screws not to snap or burn even with pilot holes.

I can counterbore significantly, I suppose, and use Kreg fine screws to attach them. The reason I ruled them out is because of the length limitations (max length for Kreg fine screws is 1 1/2"). I know they fit, but this requires me to drill out the legs much more than I have. Another option is Spax "regular" screws, but the problem here is that unless I countersink within the counterbore (not the easiest task without a drill press) thread stripping is a major concern.

[JGrout]

Why not just drill and tap the threads and use coarse thread machine screws with flat or oval heads? meets your criteria and is a shop solution

you can get a 75% thread cut in the hardwood with the proper bits and a tap 

It just seem easier to fab in the shop disassemble then reassemble 

JMO 

Joe

[FS7]

It is an option. I have the taps and I just tapped thicker bubinga to do this. I would just need to drill out the legs larger so the only thread engagement is in the sides.

I can pretty accurately drill through the legs, but drilling straight into the side pieces might be a pain. I'd have to assemble (clamp), drill, unclamp, tap, and then reassemble. It's possible.

[Cooler]

Kreg screws are self drilling.  They come in several sizes.

[JGrout]

If you are concerned about the alignment use a shop made doweling jig or buy a cheap one at HF and use it to drill the initial holes in the shop made block .  Drill a 1/4" (for 5/16" screw) or 3/16" (for 1/4") hole through the piece then re drill with the larger 17/64" drill for 5/16" or 13/64 for 1/4" x 20 threads  in hardwood.  Attach a couple of side pieces to the jig align it with your located existing hole in the legs punch a center take it apart clamp the guide on the part and drill then tap 

I know it seems like a lot but really is not all that bad