Don't confuse education with skill. Education may, or may not, teach you what to do. Skill comes from aptitude and experience.
Some of this will probably cover what Ian was going to say. Don't let that stop you Ian, there's usually more than one way to do something.
Marking Out.
You are halfway there Steve.......
One way to make a scribe line more visible is to use a wide marking pen to cover the area with black ink, then scribe. The 'correct' way to do it is to use Marking Out Blue, which is just a blue ink, but you can't buy that in the local newsagent like you can marking pens. You could always use a blue marker to make it look more professional I suppose......
The pic below shows my usual marking out tools on the metal working bench. A 4" pair of calipers, a scribe and a 6" ruler.
- Marking Out.jpg (90.79 KiB) Viewed 16047 times
The workpiece is a bit of 1.5mm hot rolled steel plate that has been draw filed to give a straight reference edge and scribed to mark out a 3.5mm strip. It's already got a dark surface, so the line scribed with the callipers is quite visible if you have plenty of light. If it was nice clean shiny cold rolled sheet, I'd have run a wide line of ink along that side of the workpiece. The calipers were set to 3.5mm using the ruler, then run along using the reference edge as a step to give a scribe line parallel to the reference edge. A few minutes with the piercing saw and a #2 blade, a bit of draw filing and you have a straight, flat strip with parallel sides.
The drawing shows the frames for my current project. I'd go crazy marking all that out on a steel sheet, so I just glue the paper image on a piece of steel sheet, drill a few starting holes and start cutting.....
Piercing Saws.
The next photo shows the jewellers saws I use for cutting out parts.
- Piercing Saws.jpg (117.27 KiB) Viewed 16047 times
The small saw is an Eclipse No. 50ps, bought from the long gone Model Dockyard in Melbourne 45+ years ago. This type is known in the jewellery trade as an English pattern saw and is my preference for cutting small parts in brass and steel. Not sure Eclipse still make them, but there are plenty of copies available. The throat depth limits it though for cutting large parts like frames.
For cutting frames and other long parts I use the larger German pattern jewellers saw with a 200mm throat, bought from the jewellers supplier in Melbourne that I use for a lot of small hand tools. That's also where I buy my saw blades. The german saw came with a small tapered handle I couldn't get used to, so I changed it to a larger one, which gives me a good grip.
Not shown in the photo is an Eclipse FS70 fret saw that only I use when the cut is too long for the german frame. As Ian said, it is unwieldy and difficult to use on metal and I only get it out when there is no alternative. The last job it did was cutting the frames and footplate for the big Bagnall 2-6-2.
Bench Peg.
The last photo shows my bench peg set up in the vice with a piece of steel clamped in place ready to cut.
- Bench Peg.jpg (143.14 KiB) Viewed 16047 times
It was made from a pine offcut in the bits box, with a cleat screwed and glued in place so it can be gripped in the small vice. As Ian has described it has a hole bored near the front and a wedge cut out, which is hidden by the front clamp. My toolmakers clamps are too small for this job and I use various size G clamps.
I'm left handed, so it is set up for me to cut a long thin strip on the side facing the camera. Which is also why the vice is bolted at the r/h end of the bench. There is an angle poise lamp clamped to the back of the bench to provide enough light for me to see the scribe line and follow it with the saw. The setup is at a comfortable height to use while sitting down and everything is in focus when I wear my workshop glasses. Swarf builds up and can obscure the line as you cut, so I keep a cheap paintbrush on the bench to brush it away as I go.
Saw Blades.
The jewellers supplier I use sells Indian made blades, German made blades and Swiss made blades. The Indian ones are cheaper and don't always cut straight, the German ones are better and if you have the money, the Swiss ones are best. Even the Swiss ones only cost me 40 cents each and while I've used the German ones for a long while, now that I don't break as many blades I recently bought some Swiss ones to try.
If you look on the net, you will find plenty of jewellery making sites with tables to tell you what size blade to use for what thickness metal and how to use a jewellers saw. Basically though it come down to Ian's rule of having at least 3 teeth in contact all the time. The same applies to any metal cutting blade, such as hacksaw and bandsaw blades, you need 3 teeth in contact to cut without jamming.
The only sheet thicknesses I use are 0.6mm and 0.8mm in brass and cold rolled steel, as well as 1.5mm and 3mm in hot rolled steel. Plus the occasional bit of K&S 1/32" and 1/16" brass strip.
I use #2 saw blades for the thicker steel sheets and #3/0 for the brass and steel sheets under 1mm. Blades last longer on straight cuts and longer again in brass. If you cut a lot of small radius curves, or sharp internal corners, the set on the side of the teeth wears rapidly and the blade soon jams as the clearance in the cut reduces. When it jams, it breaks.
Piercing saws are designed to cut vertically with the weight of the saw doing the work and the teeth point down so the blade is in tension while cutting. They aren't miniature hacksaws and don't work well when used horizontally. As Ian said, you get better with practice and eventually develop a rhythm that gives a smooth cut.
Regards,
Graeme