OK, real quick; I’ve got over 23 years as a first class job-shop, journeyman and production machinist and in that time I had owned several versions, (light & heavy duty), of General’s circle cutters. Often, (when the time and the job permitted), we’d make many of the tools that fell in the “circle cutter category” such as screw extractor’s, fly cutters, etc. The ‘actual’ Tool Specs: Further down, I note that several of the dimensions regarding this tool are conflicting with specification references listed at the bottom of Amazon ad page. I explain this in more detail after the basic review, (“Amazon ad spec conflict”). So these are the ACTUAL measurements I took directly from the tool I received: Chucking shank dia: .373 (3/8) Cross bar Dia.: .437 (7/16) Cross Bar OAL: 3.032 (3 1/32) Main body dia. (max): .747 (3/4) Main body OAL (including pilot drill): 3.460 (59/128) (w/o pilot drill): 2.345 (11/32) Pilot drill dia.: .25 (1/4) Pilot drill OAL: 1.504 (1 ½) HS Tool Steel cutter: .187 x .177 (3/16 square) HS Tool Steel OAL: 2.325 (2 21/64) *These measurements are subject to variations from tool to tool dependent on the post-process working tolerances. However, the working tolerance differences would be negligible. Construction: The Crossbar has a flat-bottom, 5/32 wide, groove milled along its length to permit a good , tightening surface for the set screw when making cutting diameter adjustments. Unfortunately, this groove can, and will affect the tool steel’s cutting approach angle and if milled incorrectly and without holding tight tolerances, it can influence the cutting tools approach to be ‘ahead of the centerline of the tools drill point centerline. In wood, this may not be such a big deal, but if cutting metal, the tool will be subjected to massive chatter problems, heat and wear. If you don’t know what you’re actually dealing with, it could even cause the tool to kick back and/or break. ALWAYS WEAR safety glasses when using this tool. (really, you should wear safety glasses when running any kind of power tool, period.). Performance: Most circle cutters of this kind really should be used on a drill press or milling machine. Someone who is experienced with the circle cutter and a hand drill can certainly get what they want from a circle cutter of this kind. However, if you’re planning to cut the material you’re not familiar with, such as mild steels, using a circle cutter and a hand drill can be very difficult if not dangerous. If it’s at all possible, use a drill press even if it means having to remove the part from its location in order to put it on a drill press table. Also, refer to the machinist handbook for your speeds and feeds, (cutting surface footage), if you plan to cut steel or iron and haven’t an advanced knowledge or experience with that material. Frankly, for most uses such as cutting holes in plywood so that a cable can be passed through it, or cutting out round disk shapes from common woods and plastics, this tool will do very well. But Circle cutters come in many different quality levels and of course, if you plan to do a lot of repetitive work such as sheet-metal cutting, (and no punch press is available), you really need to get a much higher quality cutter than this. Rich Amazon ad spec conflict: The General’s light duty version really isn’t much different than their ‘heavy duty’ model. However, their Amazon Ad regarding the tool’s specs are conflicting with themselves, (Product Description section titles listed near the bottom of the Ad page). Example: “From the Manufacturer”: “…This tool has replaceable 3/16" high speed steel bit and replaceable 11/64" pilot drill…”. Then “Product Description”: “…Replaceable 3/16" High Speed Steel Bit & Replaceable 11/16" Pilot Drill…”. An 11/64 drill diameter is .172”, (rounded to the nearest of 3 places after the decimal). A 11/16 drill diameter is a whopping .687”! We’re talking about a difference of 33/64, (.515”), between the two! Typically, a circle cutter tool is used to cut a hole, thereby eliminating any concern for the tool’s pilot drill diameter. But there can be many instances when the specifications of the pilot drill diameter can be, and is, important. Circle cutters like this one can be used to cut out blanks where the OD of the blank is the target dimension. In my case, I needed the circle cutter to make a 2 ½ inch OD by 2 1/8 inch ID x .060 thick ring from a flat piece of PTFE material. But what if I needed the ID to be no larger than 3/16 of an inch? Despite the conflicting specs, I bought the tool anyway because as I said, I’m familiar with General and their tool’s basic design and dimensions and I knew that the tool would work for the project I planned. Still, it bothered me that they dropped the ball on such a potentially important dimension specification, and that it wasn’t the only example.
