DIY Metal (bending) Brake

[DLPublic]

As a newcomer to this site, having just embarked on a AC15 build (see http://el34world.com/Forum/index.php?topic=20416.0), I thought I would share some pictures of my DIY sheet metal bending brake here.  The total outlay to build the brake was £4.00 as I already had all the other bits on hand.

I might add though this was my third attempt to make one suitable for the job in hand, i.e. to make the AC15 chassis from 1.2mm mild steel and 2mm aluminium.  The previous two attempts failed due to a) the wood used was too thin and bent under pressure and b) the first hinges used were too weak which also bent under pressure.  The final design used 100mm x 50mm (approx) - 4" x 2" - timber for the two (hinged) base parts and would probably have used similar for the top part if I had bolts long enough to go through that thickness.  Instead I used two pieces of 25mm (1") timber securely screwed together as can be seen in the photos.  The hinges were the only purchase and these are 4" x 3" x 3mm thick grade 13 ball bearing fire door hinges.

The front face of the top section (i.e. the two timbers screwed together) is sawn with a 5 degree (approx) angle to permit bending metal slightly beyond 90 degrees thus allowing for spring back.  It is also faced with a strip of 2mm aluminium countersunk screwed.  The important part was to align the hinges correctly so that when the front part (with the lever handle) was lifted to 90 degrees, the edge was exactly level with the front edge of the other hinged part.  This turned out NOT to be aligned with the centre of the hinge pins!

The two bolts are recessed into the lower part (I used a forstner bit) which being coach bolts prevents them falling out.  I used large square steel washers (left over from when I built my house) to prevent the nuts from compressing the top section of wood.  The top part bolt holes are slotted to allow it to be positioned back a bit to cater for thicker sheet material such as the 2mm aluminium.

As you can see, the whole contraption is simply clamped to a suitable surface (in my case a workmate) during use.

I have included a couple of images of the completed chassis.  The only bit I was unable to do with the brake was the mounting flange which is bent in the opposite direction to the rest.  This had to be done by hand using a vice, pieces of wood and a rubber mallet, hence not so neat as the other bends.  Also I used a dremel router to cut a v-channel in the 2mm aluminium (approx 0.75mm deep) prior to bending.

[PRR]

Excellent build!

I like the metal reinforcement. Angle-iron seems obvious, but really the lower leg has little to do, and the soft alloy is easier to counter-sink the screws into.

The "ball bearing" feature of the hinges is not needed here. The balls support the weight of the fire-door down along the pin axis. Here you only have stress perpendicular to the pin. Probably the most important point is the pin fitting snugly, no-slop, in the eyes. This is hard to tell in the store, easier with spare/salvage hinges you can play with.

Slop may be why hinging-center is not quite on pin-center? 

> in my case a workmate

Damn fine thing to have. I've had one since the late 1970s. I just snagged a second one, at the curb, dusty and with one stray cut but otherwise in fine shape. Both have the alloy H-frames; some snobs say that is best. Guy who invented and promoted the ShopMate passed-away recently.

Question: in the US a "2x4" is 1.5" by 3.5", generally within 1/16" (not counting wane). In my youth the bought size was 1-5/8 by 3-5/8, but ~~1960s the lumbermills "did tests" and determined they could supply just-as-strong in the smaller size. OTOH my house was built of trees felled on this land and sawed on site, so my 2x4s are Full Size (within 1/8"). How big are your '2x4's today?

[shooter]

my house was built of trees felled on this land

Same, some of mine run about 28ft ft from basement to center ridge board, with bark!
sorry for the hi-jack
Nice brake btw

[DLPublic]

PPR...

I like the metal reinforcement. Angle-iron seems obvious, but really the lower leg has little to do, and the soft alloy is easier to counter-sink the screws into.

Angle iron (or angle aluminium) would not work as the front face is not 90 degrees.  I did think iron would be better but it would need to be thick enough to be countersunk and as I already had the aluminium bar, I used that.  Seems OK.

The "ball bearing" feature of the hinges is not needed here.

It was not a feature I needed but it was what was available at the best price.

Slop may be why hinging-center is not quite on pin-center? 

I can assure you the hinges have absolutely no slop in them at all.  That was definitely a requirement.
Being grade 13 (i.e. can support 120kg), they are very sturdy.

How big are your '2x4's today?

Not too sure how big proper stud wall timber (i.e. what was traditionally known as 2 x 4) is as everything is metric these days.
I seem to remember when we built our house (over twenty years ago) the stud wall timber had slightly rounded edges.

The timber I used measures 95mm x 45mm so about 3.75" x 1.75" in old money with no rounded edges.

I also have had my workmate for some considerable time.  I built a folding workbench in the garage but I need to move my car outside to use it.  The workmate is great for small projects especially on dry and sunny days (yes we occasionally get them!) when I can take it outside.

Anyway thanks both for the comments.