Thread: Does Sandpaper direction matter for drum sander

They would not go to the trouble of marking them if it did not matter.
Regards

Originally Posted by A Duke

They would not go to the trouble of marking them if it did not matter.
Regards

Not entirely sure about that. The belts are just cut from a roll. The roll has, presumably, many other uses some of which definitely require adherance to a direction - such as when joined to make continous belts. I dont think it necessarily follows that the presence of arrows matters in all cases.

In any case I'm curious about the logic behind it rather then just yes or no.

Arron

From quite a few years metal polishing, same concept but a linisher or polishing lathe instead of a drum sander.

The bulk stock has the arrows printed on it when it is being made. It is then cut into strips for final use, and joined if required for belts etc. When we use a belt for the first time, we mount it so that the arrows point in the direction of rotation, and work it that way till it is not cutting well due to having blunted the approach side of the abrasive particles. This point is roughly 60% of the total belt life. To get the balance of belt life, we then mount it in the opposite direction (arrow opposing direction of rotation) and have fresh abrasive to work with, extending the working life of the belt. In the course of use, the belt might have been mounted, used and dismounted up to 50 times, depending on workflows and finishes required. These belts use a taped butt splice oriented at approx 45 degrees to the length of the belt, and the splice itself is not directional.

For a drum sander, reversing is probably not practical if the abrasive is mounted on the drum in a spiral wind due to the tapers at the ends of the strip needed to form the spiral , but with small inflatable drum surface finishing units we used the reversing technique to good effect.

The abrasive is defintely not grain oriented in a particular way on the backing sheet, or spiral wind drum sanders and disk sanders would be far less effective because the approach angle for the grains would never be optimum for the rotation.

Further to my shaking head about, I have a Jet 22/44 and I cut the replacement sanding strips out of large rolls which have no arrow directions marked on them, however I still have an original pre-cut sanding strip that came with the machine and it does have direction arrows marked on it.

With the sanding strips for the Jet (I assume its the same with other machines) due to the long tapering ends that have to be cut on each new strip in order to fit onto the sanding drum the sanding strip can only go onto the drum in one direction. So if you buy a 50 metre roll without any direction arrows marked on it then it won't make any difference.

I too have the Jet 22/44.

I'm holding a pre-cut from a box of Jet [Klingspor] belts.

Rod, you said "due to the long tapering ends that have to be cut on each new strip in order to fit onto the sanding drum, the sanding strip can only go onto the drum in one direction."

I don't see that. Holding the taper end up [grit facing forward], the square side of the tapered cut is to the right; flip it end-on-end, and the square side of the tapered cut is still to the right. So the strip CAN be reversed ... and that agrees with JET's manual [pg 23].

But there is an arrow printed on the back. I'm certainly no expert here [but an engineer with experience with similar processes and materials] but I would think that, in manufacturing, the grit is flocked onto a moving substrate fabric belt ... and that would give a "leaning" bias of the grit and it's that bias' initial aggressiveness that should be feeding into the work initially. After a while, the bias is polished off, and further use actually creates a more aggressive bias on the backside of the grit ... at which time you can reverse the strip to take advantage of it.

My head scratching comes from the direction in which to install the belt initially. I'm trying to get a clear, unambiguous response from Jet to this question: "after a new strip is installed, should the arrow on the backside of the cloth on the underside of the drum be facing the front of the machine or facing to the rear?" Or, I guess you can ask, "should the arrow be going [initially] in same direction as drum rotation?"

Appreciate feedback at [email protected].

Thanks,
Blackbeered.