Screws for mounting MDF panel

[michael2211]

I am adding some panels to the inside back of a large cabinet. The panels are 1/4” mdf that have been laser cut (they have intricate design cutouts and will be backlit). They will be mounted to a 1” wide frame that will keep them 2” off the back of the cabinet to make room for LED lighting strips (the frame will be permanently attached to the cabinet and made of solid wood). What would be the best way to screw them to the frame so that the mdf does not split and so that I can remove them in the future should I ever need to get to the lighting strips? Short drywall screws (and is there even enough mdf thickness to be able to countersink)? Or play it safe and use a hex or button head screw and forget about countersinking? Or something else?

[cwsmith]

I do not particularly like MDF as my experience with it has been poor.

I don't see where MDF used as you describe (as a backing panel) would be under stress, but still I'm not sure if counter sinking a screw all by itself would be wise, especially if you need to pull the piece out from a wall in order to remove the panel. (That might well stress the MDF and cause a tear).

If you use drywall screws, I think that "bugle-head" will cause the MDF to mushroom around the edge of the screw head, like a moon crater. My personal opinion would be to use screw with either a countersunk or finishing/cup washer. The washer will keep the MDF from distorting and provide secure holding of the screw, minimizing the chance of the MDF pulling out around the screw head.

Not sure if you local hardware store would have these, but I'd take a look. If not, places like Rockler or Lee-Valley would. ( http://www.leevalley.com/us/home/Search.aspx?action=n )

I hope this helps,

CWS

[mpc]

My initial gut reaction would be to avoid screws completely. Not knowing how the rest of the cabinet is built (solid wood, plywood, etc.) I wonder if wood movement in the cabinet might occur. MDF doesn't do well with tension stresses. So, if the cabinet "grows" in size at all due to wood movement or flexes at all when it's moved around, the MDF is likely to split/tear if rigidly attached to the cabinet.

Thus my inclination to change the 1" wide wood frame into two pieces. The back half would be permanently attached to the cabinet and would incorporate a rabbet for the panels to sit in. Then the front half could be attached to the cabinet with small screws, sandwiching the MDF panels in place. Conceptually like a floating panel in a cabinet door. A bit of a bevel on the front frame piece would make it less obtrusive.

If screws must be used, I'd get screws that are flat on the back of the head and run them through oversize holes in the MDF. "Waferhead" screws, short pocket hole screws, or washer-head screws.

Can small magnets be embedded into the MDF or 1" strips and a small screw on the other piece used as a target?

mpc

[michael2211]

Thank you @cwsmith and @mpc for your comments. The panels are already cut to size so I am stuck with going with screws, though had I asked this question several weeks ago I would have seriously considered the split frame idea. At this point it seems that going with screws whose heads protrude with a flat back is the safest way to go. Luckily with the cutouts, the panels are pretty light. These are probably too tapered but they would go with the look of the cabinet:

http://www.blacksmithbolt.com/store/p/749-6-X-1/2-Door-Screws-Black-Oxide.aspx

Or some nice finishing cup washer like these would look good:

https://www.belmetric.com/finish-washer-solid-body-c-4_1341/

Is there any benefit to having or not having the threads go all the way to the head? Thanks.

[michael2211]

Using magnets is an interesting idea. I will play around with that idea to see if it can work.

[JoeyGee]

If you're concerned about wood movement (which honestly, I wouldn't in this situation) I would just make slightly oversized holes in the MDF and use a trim washer to hold the panel in place.

[Condoman44]

Is there any room to use hidden Velcro strips? It would eliminate any screw issues and make then removable.

[d_meister]

I would use Truss head screws and, like CapnCarl suggested, make the hole in the MDF oversized. The screw should not be tightened at all, allowing the MDF to "slip" That stuff definitely moves with humidity.

[michael2211]

I think the one issue with magnets or velcro is that there is nothing to keep the panels flat; they're vertical so some screws would (hopefully) keep them from warping. Here are two photos. There are three shelves total (two of the ones with slots). The cabinet will be for a stereo system and records.

(Can't seem to post images…)

[trungdok]

Maybe you could use removable caulk like seal n peel as a "glue". Another option is just some double-sided tape.

[michael2211]

Here are a couple of photos of the panels, pre-paint. The cabinet will be a stereo/record cabinet:




I think the screw with oversized holes ideas may work best. With magnets, velcro, tape, caulk, etc. I worry that the boards will warp over time.

[capncarl]

I'd suggest hanging the panels with a couple of closet screws (square bent screws similar to cup hooks) from the back frame. Next suggestion would be to wire the panel to the back frame like a twist tie.
capncarl

[michael2211]

Thanks all for the comments and ideas. Another question about the MDF; I will be attaching large panels of amber mica to these (so they glow a nice orange when lit from behind). I believe mica is just the mineral bound in shellac. What would be the best way to attach the mica to the mdf? Would PVA glue work with a shellac surface? Or some extra strong double-sided tape? Thumbtacks? Unfortunately, mica does not come in sheets as large as the panels so I will have to make a few intricate cuts to hide the seams behind the cutouts.