by Glenn W.

Material: Steel

Units: (in)

This Craftsman-style circle cutter is designed to be used in a standard Drill Press or Vertical Milling Machine only.

It is designed for cutting 1″ to 6″ diameter holes in sheet metal, brass, copper, plastic, wood, or other composite materials. You can also cut 1″ to 6″ diameter circular disks or wheels. This tool is only recommended for material thicknesses of 1/8″ or less.

Some examples of practical uses for this tool are:

• Cutting holes in automotive dash panels to fit around gauges.
• Cutting holes in sheet metal where hoses will pass through
• Cutting wheels for toys.
• Cutting round discs in aluminum for making fly-fishing reels.
• Practical uses are endless …

This tool is fully adjustable for cutting diameters from as small as approximately 1″ to as large as approximately 6″.

By simply grinding the proper angles and reliefs on standard 1/4″ HSS tool bits you can cut perfect holes or round discs, depending on the orientation of the tool bit cutting edge.

The attached set of drawings and assembly plans are based on a Sears Craftsman tool, model #25293 (pictured above). However, the design, dimensions, and components have been modified for improved performance and safety.

Proper cutting speeds, cutter relief angles, etc. will need to be established and adjusted according to the job at hand and the material being cut.

Important Notes:

• Speed of drill press or milling machine should NOT exceed 500 RPM when using this cutter.
• Always wear safety glasses when using this tool.
• Use of cutting oil or coolant will greatly improve cutter performance when cutting metals.
• Not recommended for materials thicker than 1/8″.

  Circle_Cutter_Plans.pdf (321.1 KiB, 651 hits)
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I’ve been working on Jan Ridders’ “Flame Eater” engine for over a year now. When I first started I didn’t have a mill (nor a plan as to how I would complete the project without a mill) but I started on the engine anyway. Eventually I turned just about every piece that could be turned and then hit a wall. Without a mill I could go no further. So the project got shelved for months while I searched for, purchased, and restored and Atlas MFC mill. A few weeks ago I finished my mill restoration and it was time to get back to my little Flame Eater.

Many of the pieces for this engine are easy to machine and require no explanation, but some are a bit more difficult. My intention here is to describe the more complicated pieces and the machining steps I used to complete them. My methods aren’t the only way to machine the engine, but if they worked for me, they should work for you as well. I’ll be documenting this project in several parts:

Part 1: The Cylinder
Part 2: The Piston, Valve, and Connecting Rod
Part 3: The Flywheel
Part 4: The Ball Bearing Support and Spirit Burner

So let’s get on with it.

Part 1: The Cylinder

Jan recommends using “pearlitic cast iron” or stainless steel for the cylinder, piston, and valve. I’d recommend trying to get cast iron if you’ve never worked with it before. It’s different than steel and very messy to turn, but I think that it’s properties lend itself well to the cylinder design. For one thing making the cylinder, piston, and valve from cast iron helps with lubrication because cast iron rubbing against cast iron is somewhat self-lubricating. With a flame eater engine you don’t want to use oil to lubricate the cylinder because it will eventually burn away and gum up the cylinder. Another benefit of cast iron is the fact that it was easy to cut the fins with a parting tool. The cast iron chips were short and broke away easily unlike steel, which often produces long springy chips that bind in between the two halves of the piece being parted off (or in this case between the fins).  In my opinion it would have been a little more difficult and taken more time to cut the fins in a steel cylinder. Whichever you choose, be sure to make all three parts out of the same material. If you make the valve and piston out of steel and the cylinder out of cast iron (or vice versa) they won’t expand and contract at the same rate leading to either a sloppy fit, or too tight a fit once the engine heats up during use.

(more…)

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My lathe’s tailstock has a lot of backlash (.006), a short throw (1.500), and sixty graduations (a number that has never made any sense to me). I’ve always found it difficult to drill to accurate depths.

For example, 0.875 divided by .060 equals how many rotations of the tailstock handle? It’s ridiculous to me that I need to do math (even simple math) just to drill a hole to a depth of 0.875. If my tailstock had 100 graduations things would be a lot easier … but it doesn’t. It has 60.

60? Really?

Now, about the backlash. I know what you’re thinking. Who cares about backlash in a tailstock? Apparently I do. My psychiatrist and I are working on that …

And yes I realize that 99.9% of the time the depth of a hole isn’t a critical dimension – but I’d still wanted more control and accuracy out of my tailstock.

At least, that was the case. But no longer! With the exception of the short throw all the other issues with my tailstock were resolved with one simple stop that you can easily make in an evening.

This project is very simple. The only thing that I can see tripping someone up is remembering to create thread relief for the cap screw. When you drill and tap for the 1/4-20 cap screw, you’ll want to also drill a .250 thread relief  to the halfway point (where the slitting saw will eventually cut) so that the dial stop is only threaded on one of the two sides. If you thread both sides the two sides won’t draw together when you tighten the cap screw.

I didn’t draw up plans because of the simplicity of the project and because each person will need to scale the project up or down to fit the size of their lathe. I did, however, make a build video. Let me know what you think!

If you make your own please post pictures on the forum.

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