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Last Edited: December 2, 2018, 11:47 am
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Introduction to the Mark /// Slitting Saw
Article © MAIL User: Pfeiffer
There are many ways to saw cut rings. This one is called a "slitting saw". Basically, it is a mini-table saw with very fine tolerances. I tried many cutting methods over the years, and settled on this style because it is both versatile and powerful. It will cut any metal cleanly and easily (including titanium), with a wide range of wire and ring sizes from tiny jewelry to husky armor.
Guide track for coils. I have since upgraded this with a solid aluminum track that I had made at a machine shop. The upgrade was necessary because the wood wore out quickly. The solid aluminum also helps as a heat sink to pull heat away from the blade.
The track is easily removed to service the saw blade.
Here is another view with the track removed. You can see the fine tolerances needed to use a blade this thin without breaking it.
A wooden slide is used to hold the coil down for cutting. I use this method because it can accommodate any size coil easily, and I have fine control over the feed pressure which varies considerably with different metals and sizes. The cut rings drop off the track neatly into a bucket.
The track is raised on stands to make room for other components
The feet can be moved around to adjust the alignment perfectly (then bolt it down)
Another view of the Headstock. This is by far the most important component and there is no substitute. Do not skimp on this or you will be wasting both your time and your money.
It's not glamorous, but you need a way to fit the headstock arbor under the track
A slit in the track to receive the saw blade
Another view of the blade in the track
Power Supply. This is a 3/4 HP swamp cooler motor from Home Depot
Gear Train. You need to slow the speed way down
It's not a great picture, but two sets of pulleys are needed to step the speed down slow enough for proper cutting.
Lubrication - I do not have a picture to show you, but both lubrication and cooling are required to cut stainless or titanium. I use a pump system from MicroMark, with a very fine spray nozzle, and water-soluble cutting fluid. Lubrication reduces friction (and thus reduces heat). Water in the mixture serves as a coolant to suck the remaining heat off the blade while it is cutting. Without it, the blade will loose its temper (hardness) and get dull in a matter of seconds.
Headstock - This is a product from a company called "Taig". The second set of pulleys comes with the headstock. It is surprisingly inexpensive, about $65. I cannot say enough good things about it. It is rock solid and very tight tolerance.
Blade - The blade is called a "Jeweler's Slitting Saw" blade. The size is 1-1/2" diameter. For blade thickness (kerf), I like 0.010", but anything up to 0.020 will yield very acceptable results. A little thicker blade is less likely to break, but the thicker kerf is more noticeable on tiny rings.
Number of Teeth - This is tricky and needs to be figured along with the speed of the blade. You will need to research this and understand it before investing in a system like this. This topic could be another whole article.
Speed - The gear train reduces the speed from the motor considerably. I run this saw at 100 rpm's at the cutting edge for stainless. The speed of the blade (rpm's) depends on: the diameter of the blade, the number of teeth, and what kind of metal you are cutting. I go a little slower for titanium. You can go much faster for copper and aluminum. The saw actually cuts better when you run it slowly. It is like nibbling away a little bit at a time. You can actually feel the teeth cutting while feeding the coil in by hand.
Gears - you need to calculate the speed from proportional size of the pulleys. Start from the speed of the motor and add enough pulleys to slow it down to your desired cutting speed. The second set of pulleys near the headstock are very easy to adjust to change speeds.
The Sound of Good Cutting - if you hear squeeking and rubbing, your track is probably not aligned perfectly. Adjust the feet and try again. For stainless, the blade is going slowly, and it sounds like a slow steady filing sound. The machine overall while running sounds about like a sewing machine.
Burrs - stainless and titanium in particular are very difficult to cut cleanly. The jagged edges of the cut are called burrs and they are scratchy and unsightly. Tumble polishing afterward helps, but it is very difficult to clean up burrs. I make jewelry so burrs are absolutely unacceptable. Best advice is not to make them in the first place. Having a solid saw and operating it correctly is how I do that.
Initially, I didn't realize how much was involved to cut rings well. I started with much simpler set ups, and found that they really didn't get the job done. Then I tried a premade ready-to-use ring cutting "product" that purports to solve all these problems. It didn't. I don't care what anybody says...that was a waste of $200.
It took many revisions, rebuilds, failed experiments, and a lot of learning, to get to this design. This is the solution to all the problems that I encountered. This is what works. This is what it takes to cut hard metal well and efficiently, without burrs, and without your equipment breaking down and needing frequent repairs and rebuilds.
If I had a machine shop, this saw could be more sophisticated and more robust. But for a garage project on a reasonable budget, I am very satisfied with it.
Mark /// means it is the third fundamental re-design and re-build in the development to this point. Actually, I call this machine "Hansel", and my coiling machine "Gretel". I find they are more cooperative when I talk nice to them ;-)
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