The 2 side cuts for the inlet openings needed a fixture to get a straight cut and to hold the torch at an 18 degree angle while making the cuts.. For the top and bottom cuts the angle is formed by tipping the plane of the cut 18 degrees from perpendicular while holding the torch perpendicular to the flange in the plane of the cut. For the sides the 18 degree angle is in the plane of the cut while the plane of the cut is perpendicular to the flange.
I cut 2 slots in the piece of angle to provide clearance while making the cuts. I left the center piece so I can clamp the flange in place while cutting.
The pocket will get held to the angle by the screws which hold the roller guides in position.
In this case I will use the left hand guide for the cut on the left side of the flange and and the right guide for the right side cut.
To do this I made an "L" shaped table which is attached to the back of the angle. The vertical slots allow the height to be adjusted to get the 18 degree angle. The side slots allow the side guides to be adjusted to position the rear roller. They also hold the 2 pieces together to form the table.
I need to adjust all these movable parts, wait for the current snow storm to end and then try this out.
Thursday, February 26, 2015
Monday, February 23, 2015
Cobra Torches)and build a fixture to guide the torch. The first issue was the 18 degree angle. The 2 roller guides are independently adjustable so you can set the torch to cut at an angle.
To set the angle I needed a gauge. I drilled a hole the diameter of the copper cutting tip in a piece of plywood and drew a line at 72 degrees to the center line of the tip and 1/16" beyond the end of the tip. With this gauge slipped snugly over the tip it was easy to set the rollers to the 18 degrees needed and maintain the required tip clearance from the steel.
To position the roller up or down to square up the tip angle you just adjust the nuts in the 4 corned of the roller. To measure the angle of the cutting tip to the roller I made another wood block to slip over the tip and used the square to adjust the height of the roller. It rolls nice and smooth.
The widest 3/16 steel I can get locally is 3" so I used a piece of 1" and a piece of 3" to make the base. The 3" piece is screwed to the angle so the roller can smoothly pass over them. The 1" piece is bolted down along with a piece of 1/4" steel which guides the roller. I decided I needed a track for the roller so I used a piece of 1/2" angle for the other side of the track.
You place the flange in the pocket and slide it against the stop. The flange just sets there while you make the cut.
On both the left and right guides the screw holes are slotted to allow adjustment. I played around rolling the torch quite a bit before cutting parts to get all the adjustments where I thought they would need to be for this to work, which it does.
The fixture is in the vise which is on the fire bricks. I placed a piece of steel to catch the slag. The mess from my first experiments with the cutting torch is still stuck to the bricks. Let's face it, it was molten steel as it was blown clear of the steel. I probably could have guessed it would stick to the bricks.
The flange is setting in the fixture ready to cut.
It's adjusted left to right to cut tangent to the outside of the corner holes.
I found that it cut better if I started in the back, stop position, then without the extra cutting oxygen, slowly move forward to heat the flange. Then pause in the start position until the hole edge starts turning red. Once the hole starts turning red squeeze the oxygen button and start slowly pulling back to the stop position, better a little slow than too fast and loose the cut. When the rollers hit the stop release the button and lift the torch.
The slag from the first cut is on top so it doesn't get in the way.
A quick whack with a hammer shears off the slag.
A very clean part with crisp straight cuts. On to the side cuts.
Wednesday, February 18, 2015
The mounting holes are oblong to fit on 5/16" studs. One hole in the fixture is centered on the outer end of this hole. The other is just touching the edge of the inside of the hole. The idea is to drill the 2 holes in the flange with a 3/16" drill, then drill the outer one with a 5/16" drill. To finish the hole I plan to use a 5/16" rat tail file and just file down to the bottom of the inside hole.
The inside hole also serves as a pivot for belt sanding the radius and flats on each end of the flange. This shape should simplify making the ends and give them a little more steel to stiffen them when bolted to the cylinder.
Using a 3/16" transfer punch the centers of the 6 holes are marked on the steel.
The end of the flange is scribed on the steel. Before I clamped the fixture on I used a blue felt marker to highlight this area. It's easier to see the scribe line when cutting the ends.
With the first part ready to drill the fixture is positioned to mark the next piece. The flanges are 3-1/2" long and I'm using a 48" piece of steel so I spaced them every 3-5/8" from each end. You get 13 pieces from the strip of steel.
To keep the piece flat on the table I de-burr each hole after drilling.
I need to locate the pivot hole over a 3/16" bolt so after drilling the holes I opened them up slightly with a #11 drill. The hole fits snugly over AN-3 bolts.
I made a wooden fixture to hold the steel while drilling at the 18 degree angle. At first I only made it wide enough to hold a part. It was easier to hold a strip with a few parts on it so I widened the area with the angle on it and drilled a clearance hole for drill chips to fall through.
I still had trouble with chips sticking to the wood. It was however a lot easier to make this from wood than steel.
Then it's just a matter of drill a hole, clean up the chips, de-burr the hole, and drill the next hole.
I used my block of plywood with a bolt sticking up as a fixture for cleaning up the ends and getting a nice radius.
A light touch to the belt in the opposite direction and you have a nice finished end ready for a quick de-burring with a mill file.
The next step was to increase the size of the bolt holes. I made a fixture to hold the flange while drilling. I've grown tired of parts whirling around the drill bit.
To locate the fixture I put the 3/16" bit in the drill and lowered it to the outer hole, then clamped the fixture to the table.
The difference is I want the edge of the 5/16" drill to line up with the edge of the 3/16" hole.
I started by using the 3/16" bit to locate the hole like with the outboard hole.
With the fence holding the fixture from moving fore and aft I measured the position of the fixture along the fence. I added 1/16" to this measurement and locked the vernier as a gauge to position the fixture 1/16" to the left so the 5/16" bit would now drill in the correct location.
After cutting out the inlet hole I'll finish this oval in the vise with a 5/16" rat tail file.