I have a problematic bi-fold with 4 panels. Two opening left and two right that bind on the meeting edge of the two pairs.
This problem is usually solved by beveling the meeting edges by a few mm but this set of doors is 56mm thick and each panel is only 500mm wide so the bevel angle seems to have to increase massively based on the pivot point of the hinge being so close to the meeting edge.
My question is this. Is there a way to calculate the required bevel angle that would allow the panels not to bind?
I’ve already cut an 11 degree bevel that does not have enough clearance and I would like to find a formula where I can work this out beforehand. I’m just guessing at the moment.
Replies
Use this online calculator to calculate the angle and hypotenuse using the opposite side(the thickness of the door 56mm) and the adjacent side determined by measuring the gap at the back when the front of the doors meet divided by 2 then subtract 1-2 mm for the allowable gap(actually half of the gap since both sides will be tapered) at the back, keeping in mind the gap at the front will be much larger.
https://eguruchela.com/math/calculator/triangle-angle
Based on your drawings it looks like you have fixed pivot hinges rather than the traditional spring-loaded pivot points of bi-fold doors which let the doors slide back a bit as they close this could make it impossible to maintain your desired 4mm gap at the front edge. The laws of geometry and physics are pretty unbending in things like this.
I have a couple of sets of bifold doors. I didn't need any bevel where the doors meet, as the hardware swings them out of the way.
I would like to know what type of hardware can swing a bi-fold door out of the way, unless you are referring to the spring-loaded pivots that let the doors push past each other. All household doors have some type of taper on the latch side typically 4-5° and not noticeable unless you look for it. The problem of clearance is made worse as the door gets thicker and the OP's door is over 2" thick
The two ends are on pivots, not hinges. The closest the two middle sections ever get is when the doors are fully closed. When opening, they immediately begin moving apart. They don't encroach on each other's space at all. Absolutely no need to bevel the edges. They could be 5 inches thick and still be square.
I'm not really sure how you could make bifolddoors weathertit for outside use. I've never seen them used that way, and seems like a poor application.
Check the drawing...hinges. I think the term bifold is not what you have in your head.
Yes. Mine are exactly the same, except with pivots at the far left and right, rather than the hinges. To make it watertight, it makes everything close tighter than the hinges do. But outside, I'd find a completely different solution.
The drawing calls out weather sealing so I'm assuming these are exterior doors. It feels like the amount of overlap you have in the opening will determine the angle for you. Since you've already beveled the edges I'd stay away from any calculators... I suggest you make 1:1 templates of the doors in edge-view, including templates for the space between them and lay it out full-scale.
Cutting them on an angle will make the doors look uneven a bit from each side with the center stiles changing in width. It will also make for very challenging installation of locking hardware. A center batten on one of the doors might be the way to go.
In use you'll probably always be closing doors this size one side at a time. Ideally you'll have the ability to open one of the center panels like a traditional single door to get in and out without having to open the bi-fold. I'm not sure your hinge positions will allow that to happen.
Tough to tell with the limited detail in the drawing.
I did the maths with the assumption that the mating edges make contact when the hinges are aligned such as in your second image. At this point, the length of the four doors adds up to 2024mm since the position of the hinges pushes the corners out. The opening is 2000mm so we have a 24mm interference. To cut away 24mm from a 60 mm thick door requires a 21 degree bevel.
To get better accuracy, one needs to know the exact pivot point position which is beyond the door thickness. I used 60mm meaning that the hinge axis is 4 mm beyond the door faces.
That sounds about right but mm are not my strength. The problem is going to be that it will be impossible to achieve a gap on the front edge anywhere near 4mm and weather tight. The doors needed to be made oversized and mated an an angle like he showed in his first drawing of course that means one door always would need to be opened first and closed last but just slightly.
That how I calculated it, the doors meet on a diagonal just as showed, now to get exactly 4mm , about 3/8'' will need adjusting as the accumulation of tolerances will make just about impossible to get that gap perfect just by measuring. The inside end of the bevel could be made square allowing to place a seal that closes square between the two doors.
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