Interesting experiment with holding power of screws in MDF

[Derek Larson]

Ok let me begin by saying that I am building a small linen cabinet with raised panel doors and I have to do it on a tight budget. So natural I was going to build the doors with poplar wood face frames and rails and stiles and mdf door panels. Then i began wondering just how weak mdf really is when it comes to holding screws. So with the wife away I began my experiment and you might be surprised at the results. I took a scrap piece of mdf it was roughly 12" x 24" and I attached two hinges to it and to another scrap about the size of a face frame and hung it to my floor joists and I made marks to check for any movement. I then began attaching weights to starting out at 5lbs.

[Derek Larson]

It currently has 70lbs. attached to it and it has not budged (I got scared and stopped at 70). Each time I added a weight I would let it hang on there for a few minutes and then when I took the weight off I would shut the door and each time it aligned up perfectly. I have more pictures but you get the idea. The screws came with the hinge and they were a half inch each, and each hinge has 5 screws, three for the door two for the face frame.

[Josiah Bartlett]

It is likely in your case that the screws are mostly under shear load, and you will find that they hold very well in that case. It is in the case of tension load (trying to pull the screws straight out) that really causes failures in MDF. If you cut a nice mortise for the hinges in the MDF it will be even stronger.

[Derek Larson]

Yes I agree with you it is under shear load, however it most of the applications (at least that I will be using mdf for) will be with the screws under shear load. I honestly just assumed that the screws would just pull out but it is holding really well. I also stopped at 70lbs but it seems like it would have held more I would say at least another 10-15 lbs. Again I just thought this was interesting because I just made an assumption that such small screws in mdf would pull out much easier. I hope others find it interesting and informative, I also plan on keeping the weight on it over night to see the results over a prolonged period of time.

[Frank Townend]

Thanks for posting Derek. Is there any value in drilling, inserting the screws, backing out the screws, squirting a few drops of CA, and reinserting the screws?

[Derek Larson]

Good question Frank, I will say that I did drill pilots and then screwed in the screws, I can try that but I am not sure exactly how to test that vs. just drilling a pilot hole because I never got the first experiment to fail:D

[Peter Quinn]

Have you tried lifting the weights over your head and then moving out of the way and letting them drop to the ground? I'd be curious to know how they handle a shock force like might be exerted when a clumsy husband like me walks into an open door he didn't see with a full laundry basket in hand. I can tell you maple doors exert an equal and opposite force on one's shins!:D I still can't figure out why they call soft maple soft, doesn't feel soft to me.

I'd guess MDF would do pretty well with cup hinges though I could see a wood face frame being more suitable than MDF with those. Pretty interesting experiment.

[Derek Larson]

Peter, I will try that tomorrow, I think that will be interesting however I will have to devise a way that will allow me to do it safely, like maybe cutting a rope and having it fall above a mattress or something. Any suggestions on how much weight to start with?

[Bill Keehn]

Isn't that more of a racking force? Because the load is not directly under the hinge the door wants to rotate. The top hinge is being pulled down and out, while the bottom hinge is being forced down and in.

[Derek Larson]

Bill, I would buy that. But if you think about it that would mean that one most likely the top would have most of the force if anything proving that these screws will hold up to a significant force. That is if I am thinking about the physics correctly.

[Larry Edgerton]

Little trick I use with MDF. I drill all of the screwholes and then with a syringe put a drop or two of West System in each screwhole. MDF will suck it up like a sponge immediately, so you can then go ahead and put in your screws. The epoxy strengthens the area all around the screw and it will hold many times more than plain MDF. If you need to get the screws back out put them in a rag sprayed with WD40 and shake them a bit before driving them.

[Peter Quinn]

Peter, I will try that tomorrow, I think that will be interesting however I will have to devise a way that will allow me to do it safely, like maybe cutting a rope and having it fall above a mattress or something. Any suggestions on how much weight to start with?

I weigh 150#, I'd start with something less than that I guess? 70# seems like a good starting point. I guess it will be tough to set it up safely. You might avoid the whole scenario by watching where you walk, though this has not worked for me.

[Bill Keehn]

Bill, I would buy that. But if you think about it that would mean that one most likely the top would have most of the force if anything proving that these screws will hold up to a significant force. That is if I am thinking about the physics correctly.

Derek, If you mean the racking force, or the tension on the screws, then yes I agree. But keep in mind that the tension probably less than 30 pounds. It depends on the triangle created by the two hinges and the attachment point. Think trig. It's probably good enough for this application, but who around here is satisfied with good enough? :D


As far as screws in MDF go, I like stainless steeel sheetmetal screws, the largest diameter that will work in your application. Unlike wood screws they are not tapered (except at the point) and they have thread along the entire length. It is best to predrill for MDF. Sheet metal screws are measured by the outer-thread diameter, so you need to pre-drill an undersized hole.

[James Gillespie, Jr.]

Also note that you didn't secure the bottom of the face frame, so some of the weight is transferred into the frame piece as is evident by it bowing in your photos. Brace the bottom of that frame so it can't bow and repeat your test. You may have different results.

[Derek Larson]

I agree with you James, and actually I went down to check on the door this morning and the frame snapped above the hinge. However there were no sign of the screws pulling away out from the MDF at all. When I get home I will retry the experiment and secure both top and bottom. The main reason for this test was sheer curiousity, I am by no means encouraging anyone to use mdf for the face frame members or the rails and stiles. With that said for the very simple and small linen cabinet that I am making I may try all mdf.