How to pick the right slicer blade
August 8, 2016
by Jim Kline
Scalloped cutting edges for slicing bands vary in pitch (distance between scallop tips) from 0.5, 0.33 and 0.25 in.
Different bread formulations will affect the way blades wear as well as the quality of the slice obtained.
White. These soft products require a blade with a feathered profile for smooth crust penetration and minimal internal tearing. Consider using a blade with a double bevel, and for the best slicing, both bevels should have a polishing grind in the same direction as blade travels. Make sure the honing equipment is operational, installed correctly and is well maintained. Set honing frequency to approximately every 3,000 loaves. Run the machine at the top of the manufacturers’ recommended blade speed, normally 1,200 ft per minute.
Wheat. These products are similar to the white products in many cases and normally use the same type of blade. Coarse-grained products and those with multi-grain toppings, however, may require more frequent hone operation than white breads. If these products have a hard crust, look to a single-bevel blade.
Breakfast. Raisin, nut and other breakfast-type breads quickly damage the blades’ edges. A single-bevel blade is preferable for longevity. These blades must be honed often to maintain sharpness. The slicing unit needs a spray system installed to apply water to the blades. The sugars in these products can build up on the drum and in the blade guides, causing the blades to stick and resulting in the unit seizing up. Use 4-prong blade guides to limit buildup. Some bakeries reduce blade speed so the water becomes more effective on the blade.
Potato. These loaves are typically the cottage-style wide loaves. The larger loaf size means more internal moisture and higher internal temperature. Blades must be kept lubricated and sharp. Select a double-bevel blade with polished parallel grinds to limit buildup on the blade. Use ceramic honing stones, and hone more frequently to keep the blade edge sharp.
Low-fat, no-fat. Products made without significant oil are difficult for blades to slice. The lack of lubrication causes excessive friction, which heats the blade and can cause buildup on the side of the blade. Blade and drum scrapers must be installed in these slicing units. A gravity-fed oiling system is necessary and preferably a spray system as well. Honing frequency must be increased. Use of a single-bevel blade for crust penetration and a parallel grind for interior slice texture is recommended.
Low-carb. New-age formulations that suit the low carb market require a blade with a very sharp edge. A single-bevel blade with a parallel grind is preferable. Honing must be done more frequently using a ceramic honing stone. Machinery should have a pressurized spray system supplying intermittent oil spray to the blade and a gravity-fed oil sys-tem with blade scrapers on both drums to keep the blades cool and clean.
Hard crust, dense product. Any product with a very hard crust or a very dense texture such as a European rye will require a durable blade edge. Use of a single-bevel blade will maximize blade life. Use of ceramic honing stones can improve the blade edge with frequent honing to provide a superior slice texture.
Troubleshooting slice problems
When slicing problems occur or when replacing blades, always save the used blade for inspection. By examining the blade carefully, the bakery engineer may find evidence that some other component on the slicer is the source of the problem. For example, damage on the non-slicing edge is a sign of backing roller wear, and sheared scallop points indicates worn blade guides or that the blade is cutting into something very hard.
Saving the blade lets its manufacturer identify whether the blade was sub-standard before it was installed. If the package in which the blades were shipped is available, the blade manufacturer can glean more information concerning the exact production of the blades. The packaging information should always be kept on hand until a new set of blades has been installed. The packaging and the blade samples allow the manufacturer to identify problems within their own manufacturing process and to analyze the metallurgical properties of the blade. The long-term result of such actions is that bakers get improved blades compared with the first blade that was ever bought.
The next step is to inspect the machine where the blade was installed. Look for any abnormalities that could have damaged the blade such as worn or loose parts. If blades are installed, check their tension and calibration of the tension gauge.
Other indicators can also help find problems before they affect production. Should any of the following occur, take time to do a thorough analysis of the slicer as soon as production can accommodate the inspection.
Bread crumb texture. How the slice looks can be a good indicator that something is not right. Crumb consists of two types: (a) the darker, dry particles that come from the crust of the product and (b) the fairer, moist particles from the interior of the bread loaf. Dark crumb is seen before and after the slicing unit, and light crumb appears only after the slicing unit. A high volume of light crumb means that something needs to be corrected. The first places to check are blade tensioning and hone stone positioning.
Slice thickness. If sliced products show both thick and thin slices in the same loaf, something is wrong. In this case, look at blade tensioning, lattice rigidity and blade guides to find which is not properly supporting the blade.
Blade wear. If blades experience accelerated wear, the tension may be too high. Also, blade guides may have worn out, or a honing stone is out of position. Look for anything that may be damaging the blade edge. Any other component that shows accelerated wear is also an indicator that something is not right inside the unit.
Blade tension. Incorrect blade tension is the main reason that blades do not operate correctly, and improper tensioning affects, directly or indirectly, many other components of the slicing unit. Make sure that operators and maintenance personnel set up and operate the slicer’s blades at the manufacturer’s recommended tension.
Information in this section was adapted from Cox (2007).
Cox, P. 2007. Slicer Maintenance and Instruction. Hansaloy: Davenport, IA.
More on this topic can be found in “Baking Science & Technology, 4th ed., Vol. II,” Page 572, by E.J. Pyler and L.A. Gorton. Details are in our store.