Thanks for sharing the drawing, maybe we can also have a try, great work, and nice profile photos
Absolutely! Would love to see pictures if you do!
With that said, it is important to keep in mind that these dimensions only apply to .040 Alclad being bent on a 1/8" radius brake.
If you have a different radius brake or are using different thickness metal, your numbers will be a little bit different, but its still pretty easy to figure out.
If you are not familiar, with how to calculate setbacks and bend allowances for sheetmetal, here is a quick tutorial of sorts I guess.
To calculate the layout, you start with the mold dimensions, which are the exterior dimension of the toolbox, or really any project you wish to layout.
I then calculate my setback and bend allowances, which are as follows.
For 90 degree bends
Setback is calculated using the formula
SB=T+R
SB = K(T+R) where K is your K-factor, T is the thickness of your material and R is the radius of your bend, which is also the radius of your brake. Because the K-Factor for a 90 degree bend is 1, we can simply the formula to be SB=T+R,
Bend allowance is calculated using the formula
BA =(2π (R + 1/2 T)) /4
BA =(2π (R + 1/2 T)) /4 where T is the thickness of your material and R is the radius of your bend, which is also the radius of your brake.
Once you know the setbacks and bend allowances, you can calculate your leg distances for layout.
On a piece of sheetmetal that you are making a single 90 degree bend, you would calculate the distance of the legs by taking the first leg of the bend and subtracting a setback, then measure your bend allowance distance and then add the second leg distance minus another setback.
For bends other than 90 degrees
To calculate bends which are other than 90 degrees, you need to know the K-Factor. You can either
calculate the K-Factor or you can use a
K-Factor Chart
Once you know the K-Factor, you can calculate your setbacks and bend allowances. It is important to remember that you need to calculate setback and bend allowance for EVERY angle you bend and to make sure to use the correct values for the correct angles when doing your layout.
To calculate setback for bends other than 90 degrees
SB=K(T+R)
SB = K(T+R) where K is your K-factor, T is the thickness of your material and R is the radius of your bend, which is also the radius of your brake.
To calculate bend allowance for bends other than 90 degrees
BA = (0.01743R + 0.0078T)N
Bend allowance = (0.01743R + 0.0078T)N where R is the radius of the bend, T is the thickness of the metal and N is the number of degrees in the bend which you wish to make.
On a piece of sheetmetal that you are making a single bend, you would calculate the distance of the legs by taking the first leg of the bend and subtracting a setback, then measure your bend allowance distance and then add the second leg distance minus another setback.
Once you have all of these dimension, you can make your layout, much like this
View media item 69130
For reference, the toolbox's mold lines are 18" x 7" with a 4" front and a 5" back. Using a 1/8" radius brake, my bend allowance for .040" alclad is 0.2280" and setback is 0.165"
Now the easiest thing to do is take a micrometer and a sharpie and begin laying out everything on a piece of sheetmetal. Make all of your cuts and relief holes first and then you are ready to start bending everything up.
To layout your bends as they will be positioned in the brake, measure the distance of the radius of the bend, in my case, 1/8" or 0.125" from the intersection of the leg line / bend allowance line which is sitting under the brake. This measurement is your sight line, which you will align to the front of the brake edge. You should just see your sight line and it should be tight to the front of the radius. Lock in your brake and make your bend.
Its important to remember that if you want precision for your final product, you need to keep every aspect of your precision within the tolerances you set for the project. I kept all of my measurements on layout to +/- 0.0005", however, I know that there was error from using a ultra fine tip sharpie for layout, in that even though they do have a pretty precise tip, its line thickness can vary dependent upon pressure, ink flow, etc.
To prevent cumulative error, remember that its best to set a reference edge to make all of your measurements off of and make all of your measurements from that edge when possible. This will prevent gain in length because you are not having to estimate exactly where the center of your sharpie line is from which to base your next measurement.
For rivet layout, its important to keep a good edge distance and good equal spacing, as you don't want your rivets to be too close to the edge, but you also want them to appear symmetrical and visually appealing.
I used
2D spacing for my rivets, which means 2 times the diameter of the shank of the rivet, which in my case was a #4 or 1/8" rivet. I found my edge spacing, marked out all of my end rivets, then measured the distance between end rivets in a given rivet line and divided it by the total number of desired rivets in the line, minus 1 rivet. I would then use this number to determine the spacing to be used between rivets.
To determine proper rivet diameter, take the thickness of the thickest sheet to be riveted (not the total thickness, but single thickest sheet), multiply it by 3 and then multiply that by 32.
In my case, having two sheets of .040" material, I took 0.040 x 2 = 0.12 x 32 = 3.84/32" or 4/32 = 1/8" or a #4 rivet.
To determine proper rivet length, take 1.5 x the diameter of the rivet being used and add that to the total thickness of all materials being riveted together, then multiply that by 16.
In my case, on joints where I had two 0.040" thick pieces of material and was using a 1/8" rivet, I took (1.5 x 0.125) = 0.1875+(0.040+0.040) = 0.2675 x 16 = 4.28 = #4 length rivet.
Thus, the majority of rivets I used were 4-4 rivets, but again, this is all dependent upon the material you use and only applies when using solid aluminum rivets.
Just my two cents.
