These 3D printed corner brackets were developed for flat pack furniture that needed some additional fixings to strengthen and stiffen the joints.

Printed on their side the stiffening ribs are chamfered to be printed without any supports (and look much cooler IMO).

Modelled with 3.7mm holes to fit 3.5mm screws, spaced at ~5d (17mm) to prevent splitting of the wood.

Both countersunk and non-CS models are included.

Originally designed for countersunk screws, I had problems with countersunk head wedging into the part and splitting between print layers whe tightened. Therefore I'd recommend the non-countersunk versions using flat head screws. This should allow you to tighten them up much more without splitting the plastic.

For different sized screws I'd suggest just scaling up the whole part, e.g. for 4mm screws using 4.2mm holes 4.2/3.7 = 113.5% scale.