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Technical Education
by Curtis Hicks
Determining the Proper Grit Sequence for Wide Belt Sanding
Before determining the correct grit sequence the following needs to first be considered:
- Number of Heads the machine has.
- What type of heads (i.e. metal drums, rubber drums, platens)?
- What grit do you desire to finish with?
- Total Amount of stock to be removed.
- Feed Speed Capabilities.
Setting grit sequence is actually a practice of simple math. How much stock do you need to remove and how many heads do you have to get the work done? Lets use a common wide belt machine set up. Consider you have a (3) Head Wide Belt Machine with Head 1 metal drum, Head 2 Rubber drum, Head 3 Platen. The customers wants to remove at total of .025, would like to do it in one pass, and would like to finish with a # 220 grit scratch. Their feed speed is 25 feet per minute. Looking at the stock removal chart below at 25 fpm, the maximum removal for a # 220 grit belt is .002. That will be the total stock removal from the platen head. That leaves another .023 of required stock removal. Keep in mind it is normally not advisable to skip more than one grit in a grit sequence. Therefore, the 2nd head cannot be any coarser than #150 grit. A # 150 grit belts maximum stock removal is .007. That gives a total stock removal of .009 so far. Keeping with the same rule, the coarsest the first head can be is #100 grit. A # 100 grit belts maximum stock removal at 25 fpm is .016. The total maximum stock removal using a #100, #150, #220 grit sequence is .025. Therefore, in this situation, the desired stock removal can be achieved in one pass while finishing with #220 grit
GRIT |
10FPM |
15FPM |
20FPM |
25FPM |
30FPM |
35FPM |
40FPM |
45FPM |
50FPM |
24 |
.310” |
.210” |
.155” |
.125” |
.105” |
.088” |
.076” |
.068” |
.062” |
36 |
.230” |
.150” |
.115” |
.090” |
.076” |
.065” |
.057” |
.050” |
.045” |
40 |
.155” |
.096” |
.072” |
.062” |
.054” |
.044” |
.039” |
.034” |
.031” |
50 |
.104” |
.064” |
.048” |
.041” |
.032” |
.029” |
.026” |
.023” |
.019” |
60 |
.072” |
.048” |
.036” |
.029" |
.024” |
.021" |
.018” |
.016” |
.014” |
80 |
.062” |
.043” |
.032” |
.025” |
.021” |
.017” |
.015” |
.014” |
.013” |
100 |
.043” |
.027” |
.020” |
.016” |
.013” |
.011” |
.010” |
.009” |
.008” |
120 |
.032” |
.020” |
.015” |
.012” |
.010” |
.009” |
.008” |
.007” |
.006” |
150 |
.018” |
.012” |
.009” |
.007” |
.006” |
.005” |
.004” |
.004” |
.003” |
180 |
.010” |
.006” |
.005” |
.004” |
.003” |
.003” |
.002” |
.002” |
.002” |
220 |
.005” |
.003” |
.002” |
.002” |
.001” |
.001” |
.001” |
.001” |
.001” |
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