Another
I have finally figured out how I was going to make the bending jig for the lower archbar of the truck. This is the only bar that needs to be bent, but also needs some accuracy to the finished product. So a jig was in order. I made it out of aluminum because I have lots of it, plus it will need some welding.
Here's how I went about it. I took the dimensions from the print and drew up the basic shape on AutoSketch. I added the dimensions I needed so I could get and idea of how it was going to fit on the rotary table. Each side of jig is 10.5° from the center line. Then up from the center line to the bottom of the jig is 4.128" minus half of the cutter which has a dia. of .250". The 1.530" dimension will come out automatically when the sides get cut on a 10.5° angle.
Next problem to be solved was how to mount it on the rotary table. I used a piece of 3/4" MDF secured to the rotary table.
Here's the template placed on the MDF to see how the jig will fit. Looking good so far.
Next the rotab was placed on the Bridgeport mill and zeroed in.
Here's my first error I made. Drilled the hold down holes to close to the bottom.
So another piece of stock was cut and the holes relocated. I mounted the messed up plate on top so I could use it as a scrap piece to see if I indexed the table right. Glad I did because I made two more minor errors as I went along.
Anyway, I set the 4.003" dimension to the y-axis so I could use the x-axis powerfeed. As you can see that the scrap piece did get milled a little bit.
Next I indexed the table around 90° to 270° minus 10.5° or 259.5° to cut the first leg of the angle. But I forgot something.
After I had finished the first cut at about .125" depth I turned the table to 280.5° to cut the other leg. That's when I came to me, I needed to add .125" to the "Y" axis readout on the one leg and subtract .125" from the "Y" axis on the other leg from the center line to get the 1.530" deminsion on the bottom of the jig.
Glade I had used the srcapped piece for a trial run. Once I had that done it was just a matter of a couple of passes to finish the jig.
Another shot of my error.
Action shot, looks like it isn't cutting.
Milling out the other side. Take notice of that bolt sticking out.
Notice it isn't sticking out any more? The clamp nut on the arbor ran into it making a pretty loud racket turning at about 700rpm. Needed to clean my pants after that.
So here they are the bad piece on the left and the good one on the right. Next it needs to be trimmed to the correct heighth.
I used a set of jo-blocks to set the veriner heigth gage and scribed a line. This set the heigth to 3.300".
This will give you and idea of how the flat bar will be bent. The bar actually needs to be laid on it's side for the bending.
There's a few more things I need to do to finish the jig. That will be the next installment.
I've also had some time to contemplate the gears that need to get used. I had sticker shock when I found out the price. Now I need 8 sets of gearing, both gear and pinion, for the four trucks. Boston gears would cost me $716.40, Martin Gears would cost $660.40 that doesn't include shipping and handleing. I am very seriously considering making my own. I'll elaborate on that though a bit more later.
That's it for now.
Bernd
