Well the R&D continues to take place with hopes that the 10 gauge metal bending brake will actually perform its function. The fingers and the clamping mechanism have been fabricated but not completed. I’m holding off on putting the finishing touches on those items until I can perform a test run of the system. This way if things don’t work out I will be able to modify without having to undo too much.
The only other main component of the setup left to build is the slider guide for the circular saw. The idea is to build a plate that will bolt to the circular saws factory shoe assembly. The fabricated plate will act as a guide between the 3″ channel and the saw. The guide will allow me to make an accurate “scribe” line in the 10 gauge sheet metal. Not only will it ensure the cut line will be straight but it will also control the depth of the cut.
I started with a scrap piece of 4 inch x 3/8″ flat bar and plasma cut it down to turn it into a 3″ x 12.5 inch rectangle. Here I was able to get some more milling machine practice under my belt. As much as it is not crucial that the guide is perfectly square I figured I would take the time to end mill the steel to get my 90 degree corners. With the steel cleaned up and milled to size I opted to mill a partial slot down each edge the length of the metal. The slots will eventually allow the 3″ channel to straddle the flat bar thereby creating guides that will allow the circular saw to travel down the length of the channel.
Ok…I screwed up, just a bit. It was the math. Trying to keep track of edge finder offsets, end mill diameters, and depth of cuts had me doubling instead of halving. The first milling cut went twice as deep as it was supposed to on the guide. My first reaction? I have to start over (yeah right…that wasn’t actually the first thing that went through my head). My second reaction? This is a good thing. So this is how I see it. Screwing up on the first cut is way better then screwing up on the last cut. I have a hard time mentally coping with the mistake, I don’t have an issue making the mistake, I just want to fix it. The wrong cut will not affect the function of the guide…much. So I decided to trek on and continue to machine the same piece of metal. If I had more confidence that a second mistake wouldn’t happen I may have actual started over. This way if the arithmetic goes wrong again I feel better about the fact that I am learning something. In the end that is more valuable than a perfect guide.
Once the edges were milled just enough to allow the guide to smoothly travel down the 3″ channel it was time to mill out a center slot wide, and long, enough for the 7 1/4″ carbide blade to fit through. No problem here. I chucked up my OSG 3/8″ four flute end mill and with a few passes I had a beautifully clean center slot chiselled out.
Next item on the list was to mount the milled plate onto the saws factory aluminum shoe plate. It was a simple procedure that involved clamping the 2 plates together and drilling a couple holes through them. The milled guide plate got tapped with a 6 mm x 1.00 pitch thread and then had a couple of stainless steel studs threaded in and welded. The aluminum shoe plate was mounted on the bed of the mill and the drilled holes were slotted to allow for fine adjustment of the saw to the guide plate. The two plates can now be bolted together and adjusted to fit the milled slot of the 3″ channel accurately.
With all the main components somewhat fabricated I was able to perform a few test bends to make sure the engineering would turn a plan into reality. A scrap test section of 10 gauge sheet metal was clamped down under the 3″ channel. The circular saws depth of cut, as well as parallel, adjustment were made. The initial scribe cut through the sheet metal was straight and the depth was fairly uniform. The scribed metal then got slid over and re-clamped under the bending fingers. All I had was a couple pairs of Vise-grips to use as leverage for the bend. The force needed to make the bend was more than I had anticipated. It was somewhat good news in that it meant that there was still a substantial amount of metal supporting the bend. The down side is that it puts an excessive amount of flex on the bending fingers. The amount of force required also causes the angle iron that performs the actual bending to flex excessively in the center. On the ends the angle iron has the hinges to support it and therefore the flexing is greatly diminished.
So it was time to add some “seat of the pants” additions to the brake. First thing is to address the flex that occurs in the angle iron when the bend is being performed. I figured a truss style design was in order. I needed to take the forces that are applied to the angle iron, reverse them, and use them to stabilize the steel. I utilized a 40″ section of 1/2″ cold rolled round rod I had and created a truss that tensioned the angle iron in the opposite direction that it wanted to flex. The idea is that in order for the steel to flex it would have to actually stretch the 1/2′ rod. There is obviously not nearly enough force placed on the angle iron during the bend that would cause the rod to stretch therefore the angle irons flex was greatly reduced. If none of this makes sense to read just look at the pictures, you’ll figure it out pretty quick.
Life was busy this week so the saw guide and the truss is all I have to show for my efforts. It’s looking like the brake will in fact perform its intended function so I will continue on working on the final components. These will include the actual clamping system; the C-clamps are intended to be temporary. Other required items are the leverage handles and an addition to aid the clamping fingers from flexing due to the force of the bend.