Directional Sandpaper?

You've seen the arrows, they're on every sanding roll or belt I own. Meant so that you can orient the sandpaper in the direction of movement on either a belt or drum sander. I've never paid any attention to them because I could never believe the grit was oriented in any particular direction. On pre made belts, I assumed it had to do with how the joint was made but that wouldn't explain the 100' rolls I use on my drum sander. Another builder friend of mine swears that the arrows are put there for a reason and that it matters. Anyone know the story on these arrows?

I have always assumed it is the overlap that makes the belt into a loop. It is more likely to hold together at high speed in that one direction.

mikeg0232 said:

I have always assumed it is the overlap that makes the belt into a loop.

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Me too. But that doesn't explain the arrows on the long rolls of sand paper they sell for drums sanders........

They don't know what you're going to use it for when they make it. http://www.klingspor.com/ref_asktech_coatedabrasivemakingprocess.htm

Well let's call Klingspor the authority then, since they also supply most of the belt material I use. Apparently, they don't even know what they are going to make out of the abrasives they carry. The belts I buy from them are butt jointed and taped on the back, making them multi-directional from their explanation. Then why do they also put arrows on them? The Jet/Performax abrasives that are made for their drum sanders, either in pre-cut or bulk form, also have arrows on them. It says right on the box: For Drum Sanders!
I'm not gonna worry about it. I just think the guy who's job it is to put arrows on everything needs to retire.

OK, I found the following in http://www.klingspor.com/ref_asktech_coatedabrasivemakingprocess.htm

Directional arrows are printed on jumbos for all materials that may be made into belts. No lightweight papers A, B or C will have arrows on them, but D, E & F as well as all the cloth backed material will. The arrow is used in the manufacture of lap jointed belts. It informs the belt line which side of the cut to size material will end up being the bottom of the lap and which end will be the top side of the lap so that skiving is done to the appropriate end. After the belt is joined, the arrow informs the customer of the direction in which that belt must be run. THIS IS ONLY APPLICABLE FOR LAP JOINTED BELTS! The arrow prints on all jumbos because again, we have no way of knowing what sizes or types of belt will ultimately be made from the jumbo. It’s very common for belts with same material and grit but different sizes to use different joint types. For example, the standard pump sleeve material CS309JF will always have a #1 lap. But a 3 x 132 in the CS309JF will usually have a #4 butt joint. Same material, same grit, different size and application. So even though the arrow is on all belts, you only have to pay attention to it if the joint is an overlap. Any belt with tape on the back, regardless of what the front looks like or the fact there are arrows on the backing, is a bi-directional belt! This can buy you some extra life as the butt or tape jointed belts can be run in one direction, then removed and put on to run in the other direction

I have no clue what it's saying. Someone, please make sense out of this and translate into plain language (either Japanese, English, Spanish or Hawaiian)

Cheers
Chief

I have it from a very reliable source that those arrows are printed on the back so that the little guy who rolls up the 100' rolls does not get confused and continues to push in the right direction. Early on, without the arrows they found him rolling and unrolling the same 100' section all day long as he would get confused and reverse directions frequently.

Makes sense when you think about it.

Yes, the arrows are designed for material overlap such that the direction of the belt will put the least amount of stress on the joint. For the most part, sanding belts will perform well in either direction, and you'll get twice the life out of your belt if you use it in one direction until it starts to "dull", then flip it around. The reason being that the leading edge of the grit is what is being used to sand, leaving the back edge of the grit untouched.

I have an older Crouch sander, so I have to order custom made sanding belts for it. I think they are 176" long. Depending on the grit, and the type of backing, some of the belts have arrows and some don't. I've had a few joints break while using the sander because I couldn't read the arrows. It's equivalent to a bandsaw breaking without the guards to contain it.

I also routinely use a belt cleaning stick to reduce clogging. It really extends the life of the belt as dust doesn't get "burned" in to the grit.

I always assumed it was because of the joint... maybe with the new technology and ability to 'butt up' as it were, there is no need for the arrows 'cept they have no need to change the print dies that put information on the back of their abrasives. Me, I've never paid attention to this anyway. Thanks for the brain-teaser Chuck

olgoat52 said:

I have it from a very reliable source that those arrows are printed on the back so that the little guy who rolls up the 100' rolls does not get confused and continues to push in the right direction. Early on, without the arrows they found him rolling and unrolling the same 100' section all day long as he would get confused and reverse directions frequently.

Makes sense when you think about it.

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Is this the little Guy ???