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Don't grind your teeth over dull or chipped cutters.

A dull or chipped cutting tooth can cut down on productivity, accuracy and quality of cuts. WOOD & WOOD PRODUCTS reviews some of the available profile grinders on the market today and finds answers to two commonly asked tool-grinding questions.

With the tremendous variety of profile cutterheads on the market, the ability to keep cutting tools sharp remains as challenging as ever. Some woodworking companies rely on outside grinding services to accomplish this task, while others, especially those who use a moulder extensively, do all or some of their profile grinding in-house.

Whether a company does its own grinding or ships its tools to an outside service, two critical factors are: knowing when a cutting tool is dull, and, finding ways to extend the life of the tooling.

To answer these questions, W&WP contacted several companies who market grinding machines and asked them two commonly asked questions.

Q. What are the signs operators should look for to determine when profile cutterheads need regrinding?

Dane Stafford, Colonial Saw -- Load monitors (ammeters) are the best control of gradual dulling. Visual inspection is less precise.

Karl Frey, SCMI Corp. -- Look for discoloration of blades. Dull blades run hotter causing knives edges to turn black.

Pat Hutchinson, Equipment Ltd. -- A small white line will appear along the cutting edge, best seen by looking at the face of the tool. Poor surface quality is also a sign that the tool is in need of regrinding.

John Hughes, Autogrind Co -- Some of the signs to look for include: deterioration in surface finish, rise in cutterhead noise level, increase in power consumption and feeding problems, and a tendency for the tool to burn the wood.

Jon Morris, Michael Weinig Inc. -- Good operators will look for wear in the tool before seeing it on the machined surface. Look for darker areas behind the cutting edge caused by heat buildup, then check for edge recession and edge rounding. It is also a good practice to utilize ammeters on moulder spindles. An increase in power draw indicates tool wear very effectively.

Q. What can woodworking companies do to attain more cutting time between sharpenings?

Stafford -- The sharper the cutter, the longer it will run. Sharpness can be defined as individual knife sharpness and, of equal importance, concentricity at all points of the profile. A finish grind pass with a borazon wheel is recommended when grinding four or more knives in the head.

Leo Nielsen, Nielsen Tool Co. -- Check what wood is to be machined. Is it hard, soft, knotty? Grind the correct relief or grinding bevel. Often, knives are ground with too thin a bevel which results in nicks and shorter life. Is the correct type of steel being used? Different steels are for different wood types. Sometimes it is wise to use a primary and secondary bevel. When grinding a profile, check with a magnetic dial indicator to see if all knives are in the same cutting circle.

Frey -- Most knives need to be sharpened not because they are dull but because of nicks from staples and grit in the wood. Closer examination of the wood will add to blade life.

Hutchinson -- O.D. (outside diameter) finish is one of the most important aspects of how long a mill-to-pattern cutter will run between sharpenings. To achieve this, an operation must rough grind with a coarse grit wheel and finish with a very fine grit wheel. Your template must be free of defects and the grinding wheel must be in good shape.

Hughes -- Dress the grinding wheel before the final grind. Grind all knives at the final setting. Spark-out carefully and evenly on all knives.

Morris -- A.B.C.! Allow sufficient time for grinding and regrinding. Problems with poor quality grinding often relate back to rushing the grinderman. Beware of overheating during the grind! This applies to both rough and finish grinding. Correct geometry, in particular a correctly ground side clearance must be initiated from the cutting edge.

Roundup of available equipment

Here is a look at some of the profile grinders currently available. For more information, circle the corresponding numbers on the Reader's Service Card or refer to the Red Book Buyer's Specification Guide.

Tekmatex Inc. offers the Stehle profile copy grinder that has been designed for router bits and moulder heads. The exact transfer from a template permits production of an exact duplicate and can perform coarse- and extra-fine grinding.

Autogrind Co. offers the Autool Model PR200X that is suitable for HSS, stellite or tungsten carbide tipped cutters. It automatically develops the true cutter profile needed using a template formed either to a drawing or shaped to fit square on a sample mould. A built-in diamond dresser dresses the grinding wheel to half-round, square or single- or double-angle section. The grinding wheel offsets automatically when tilted for side clearance and grinds the cutter only where needed avoiding spoiling the edge where opposite side clearance is required.

The Model 746 profile grinder from Foley United Co. produces precise cutting heads due to its Micro Precision Dressing System (MPDS), the company says. The MPDS features a retractable hydro-tooth rest blade, dial indicator, positive locking mechanism and a new stylus bar.

The Rondamat 936 tool grinder from Michael Weinig Inc. can produce the profile template which previously had to be made by hand. The machine grinds each planing knife with the highest precision, the company says. The low priced version of the 936 is the Rondamat 934, with planing knives that can be produced manually in the cutterhead with the same accuracy, the company says.

The Image 150 profile grinder from Wadkin North America Inc. fits on a workbench or is available with an optional base cabinet stand. It features an arbor assembly that ensures minimal downtime when changing tools, the company says. Using a single sleeve arrangement, it can accommodate different bore sizes.

Nielsen Tool Co.'s Model 130 profile knife grinder features a special cross roller bearing system in the profile table assembly. This helps achieve accuracy when grinding finely detailed patterns into moulder knives, the company says. The profile grinder comes standard with a built-in diamond dresser which establishes an exact point of reference. As the wheel wears, the Diamond Dresser is swung into place and the wheel is fed into the dresser, returning to the original "zero point."

Colonial Saw offers a variety of profile grinders including the new Schneeberger Sirius six-axis CNC profile grinder. It is capable of grinding all compound relief angles in profile tools in a single set-up. It integrates a single probe with a Fanuc 15MA controller and Fanuc AC digital servomotors to produce profile, relief and clearance machining in carbide and HSS.

The Model 75-12 profile grinder from SCMI Corp. features the Micro Precision Dressing System (MPDS) that grinds accurately from knife-to-knife. MPDS features: a retractable hydro-tooth rest blade allowing the dresser to be positioned exactly at the correct dressing point. The MPDS, with the use of a dial indicator, sets the diamond nib so a true wheel dimension is maintained. Finally, a stylus bar permits the operator to set the stylus so it will remain square and perpendicular to the template even when changing stylus sizes.

New from Vollmer of America is the CA300 fully automatic profile sharpening machine for band saws. The CA300 is fully CNC controlled and thus uses no cams. It can use corundum wheels for wet or dry grinding as well as CBN wheels for wet grinding. It features the use of linear technology which creates the conditions necessary for the use of unlimited grinding programs. Settings are made at a central control panel.

Equipment Ltd. offers the AKEMAT P2 precision tool and saw profile grinder for grinding of solid carbide inserts, cutters and knives. It permits control of side and bottom clearances without changing the set-up or tilting the grinding wheel. Placing one P2 grinder beside another creates a dual station profile grinder. Modular design permits the tool holder to move between the machines making it possible to rough and finish grind in one set-up.

Lach Diamond Inc. says its new series of Universal grinding machines can grind any desired profile fast and precise with repetitive accuracy. The Series M-1050 grinding machine with up to 8 axes grind PCD tooling tooth by tooth gently and precisely. From its "start" model with two NC-controlled axes (XY) to the 8 axes-model M-1050-C (5 axes NC-controlled) the grinder can sharpen all multi-toothed PCD tooling with up to 600mm diameter and a maximum cutting width/profile length of 120mm in one setup.

Diehl Machines' DMG-12 multi-function grinder can profile grind, clearance angle grind, straight knife grind, and with available options, milled-to-pattern face grind, surface grind, router bit and fingerjoint knife face grind.

Sharpline Tool Co. U.S.A. offers the Mark IV Universal Grinder featuring a 180[degrees] rotating head that operates with an interchangeable selection of mounting jigs and grinding wheels. The compact grinder, which requires an area of two cubic feet plus space for the interchangeable system components, sharpens most edges and with its assortment of grinding wheels and mounting jigs blade changeover can be done in one or two minutes.
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Publication:Wood & Wood Products
Date:Sep 1, 1993
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