Hyd-Mech S-20H, Operations & Maintenance Manua

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Pg 10
S22Hna 2002a
BLADE BASICS
Technology is rapidly changing all aspects of production machining. Metal cutoff is no exception. The
advances made in the bandsaw blade industry have definitely brought down the cost per cut, despite the three fold
higher price of the newer technology blades. Variable pitch (following page), bi-metal blades (like the 3/4 or 4/6 bi-
metal blade supplied with the machine) last much longer, cut faster, and more accurately than the conventional
carbon steel blades. In order to take advantage of the superiority of bi-metal blades, it is critical to property “break-
in” a new blade. This is accomplished by taking two or three cuts through solid four or five inch diameter mild steel
at an extremely slow feed rate. These two or three slow cuts sufficiently lap (polish) the new blade so that it does
not snag the material being cut. Proper break-in will alleviate blade vibration, improve surface finish and accuracy,
and improve expected blade life.
1. A new blade must be properly "broken-in". Proper break-in will alleviate blade vibration, improve surface
finish and accuracy, and extend blade life. The most convenient way to do this is to cut the intended work-piece,
at the standard recommended blade speed for that material, but with the feed rate reduced to about 25% of
normal. Near the end of the first cut, increase the feed rate again, and once again when the blade approaches
the end of the second cut. Keep increasing feed rate in this fashion, so that normal feed rate is reached after
300 to 500 sq. cm of cutting.
2. Generous coolant application is essential with almost all materials. A high quality and well mixed
coolant will dramatically extend blade life, and will increase cutting rate and surface finish. On those few
materials where coolant is undesirable, a slight coolant flow or periodic oiling of the blade is necessary to
prevent the blade from being scored by the carbide guides.
3. The stock being cut must be securely clamped in the vises. Stock movement during cutting will strip
blade teeth. Noticeable stock vibration reduces cutting performance and blade life - consideration should be
given to reorientation of the stock, or additional clamping measures (e.g. wood between vise jaws and work-
piece).
4. The proper blade speed for the work-piece material must be selected.
Use the following chart as a starting point.
- Blade speeds higher than recommended will quickly dull the blade. Blue chips are evidence of excessive
blade speed.
- Lower than recommended speeds will not prolong blade life, and will require reduced feed rate - but
reduced speeds may be helpful in reducing vibration, and will increase blade life in that case.
5. The proper feed rate must be applied. Feed Rate is the speed which the head "free-falls", and is set with
the feed rate control knob. The head will descend more slowly when the blade encounters the work-piece but
the force of the blade on the work will not be changed unless the setting is changed. Verification of proper feed
rate is provided by the appearance of the cut chips which ideally form nicely curled "clock springs". (Note that
cast irons, and interrupted cuts result in short, broken chips even at ideal feed rates).
- Excessive feed rate will result in short blade life and/or crooked cuts.