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Bulletin No. 30
BS09
Delta Product
Machinery Information
Bulletin
November 25, 1986
Subject: Three Wheel Band Saw Blade Life Considerations
We occasionally receive inquiries concerning short blade life on the 10" and 16", 3-
Wheel Band Saws. Below are some thoughts and observations we have put
together on the subject that may help you in resolving this type of problem:
· We have tested Delta's blades in the lab and find them to be acceptable in
quality and durability. We have done cutting and idle testing, and the
blades last from one hour (cutting with 1/4" blades) to 72 hours plus (idling
with 1/8" blades)!
Proper blade guide adjustment and cutting technique can have a
tremendous impact on blade life.
· We have investigated several dozen chronic blade breakage reports and, in
the vast majority of cases, the users were not using Delta blades. They
were having their blades "welded up" locally from bulk band stock. We
have acquired some interesting knowledge on the subject of blade welding
in the field:
Butt Welding Machines are inexpensive (about $500-$800) but they
cannot be used efficiently on blade stock thinner than .022".
Electronic Welding Machines will properly weld ultra thin blade stock (.012"
to .022"), but they are very expensive! About $8000 to $10,000.
Few, if any, mill supply houses, dealers, hardware stores etc., have
Electronic welding equipment. Therefore, they do not stock "ultra thin"
blade band stock.
· Most three wheel band saws utilize smaller diameter wheels than
comparable capacity two wheel machines. Therefore, the blade must bend
around very small radii three times for each band revolution, as opposed to
larger radii, two times on a comparable capacity two wheel machine. This
condition results in increased blade fatigue which shortens blade life.
· To minimize the impact of the fatigue factor on three wheel machines, we
use much thinner (more flexible) blade stock. Delta's 16" model uses blades
that are either .018" or .020" thick. The 10" machine uses blades that are
only .014" thick.
-2-
· To use blades welded of commonly available band stock (.025" to .035") invites
premature blade failure. The thicker the stock, the quicker the blade will
fatigue and break.
· Delta catalogs a limited offering of 3 wheel band saw blades for general
purpose applications. Customers requiring special purpose bands (such as
1/4" x 18 TPI for cutting plastics) can obtain these blades in ultra thin band
direct from manufacturers such as Starrett or Simmons on a special order
basis. But, lead times may be long and prices high. To save time and money,
many users tend to go to their local mill supply house and have their blades
welded out of whatever blade band stock is available. Usually .025" to .035"
thick. The result - premature blade failure!
If you've read this far you have learned that:
1. Three Wheel Band Saw Blade life will, in most cases, be less than comparable
capacity two wheel band saw blade life. This is due to the fact that the smaller
wheels used on 3-wheel band saws increase blade fatigue which shortens
blade life.
2. In order to minimize the effect of this fatigue on blade life, three wheel band
saw blades are made of very thin band stock which is not normally available
from sources other than the band saw manufacturer, and,
3. To use band saw blades that are thicker than the manufacturer's
recommendations invites excessive blade fatigue and breakage.
Assuming you are using the proper blades and still experiencing excessive breakage,
you should look to one or more of the following areas for the source of the problem:
1 Improper blade tension.
2 Improper guide adjustment.
3 Improper blade support bearing adjustment.
4 Forcing a wide blade around a short radius.
5 Dull or pitch covered blade or insufficient set of the teeth.
Most of the above problem areas are addressed in your owner's manual but certain
points deserve additional comment.
Excessive blade tension on three wheel band saws is unnecessary and will contribute
to excessive blade breakage. Make all tracking and tensioning adjustments with the
blade guides and back up bearing away from the blade. Apply only enough tension to
keep the blade on the wheels. Rotate the wheels by hand while making initial tracking
adjustments. Proper tracking is achieved when the blade runs in the center third of the
wheel tires. Once initial tracking is achieved, readjust the tension. Because three
wheel blades are thin and flexible (see discussion above) they require only light blade
tension. Adjust the tension to the point where the blade does not slip on the wheel and
then add 1/4 to 2 turn of additional tension. That should be sufficient for most cutting
operations with most blades.
-3-
Once the blade is properly tracked and tensioned, adjust the table 90 degrees to the
blade and set the table tilt scale indicator, if one exists, to 0 degrees. As with the
tracking and tensioning adjustment above, this table square adjustment should be
made with the blade guides and back up bearings away from the blade.
Next, adjust the blade guides and back up bearing. Important: the guides and back up
bearings should not alter the blades path from the top to the bottom wheel. They serve
only to keep the blade in that path when cutting forces are applied. To move the blade
out of its natural path will bend the blade as it passes each set of guides causing
fatigue and premature blade breakage!
The side guides should be brought into the blade and locked into position. Get into the
habit of placing a piece of paper (a corner of this bulletin would do nicely) along side the
blade when the side guides are adjusted. After locking the guides, remove the paper
and you will have sufficient clearance for the blade weld to pass through the guide
without hanging up and damaging the blade.
Finally adjust the back up bearing, again using a paper "shim" to insure the presence of
a slight gap (bearing to blade) after adjusting. Remember the blade should contact this
bearing only when cutting pressure is applied otherwise both the blade and bearing will
fail prematurely.
If you need assistance beyond the scope of this publication, we suggest you visit your
local library or contact your high school's vocational education instructor. Both are
excellent sources of information on the use and care of general purpose woodworking
machinery.
Delta Technical Service /pag
Doc. No. 2478C