Sander belt splice breaking

[capncarl]

I learned something today. I’ve been having a rash of sanding belts breaking on my 6 x 48 Delta sander and 4 x 36 sander. Some of the belts lasted only a few minutes before they broke. Previously a belt would last until there was no grit left on the belt. I buy belts from several vendors at a local car show and parts swap meet, usually Klingspor or other German mfg”s because of the good price. A tear down and parts inspection of the sanders didn’t reveal any unusual wear or any reason for the belts to break prematurely. After breaking 12 belts I decided to Google it and see if anyone else has this problem. I learned that these belts with a tape splice only have a one year shelf life. Now I know, don’t buy a trunk load of belts from a source that you don’t know how old they are.

capncarl

[leehljp]

I have some belts that are several years old and they seem to last. I have a 6 - 48 Sears belt sander, and it seems like (without me going and looking) that they are lap spliced with some kind of flexible glue. I have had your experience when I have tried HF of different sizes. It was HF that I noticed they had tape spacing. My last batch (5) of 6-48 was purchased from Grizzly at their store in Springfield MO sometime around 2012 or 2013.

I took that 6-48 sander with me to Japan in '89 and carried about 10 belts. I used a belt about every 3 to 5 years or so and had 4 left when I came home in 2010. I still have 2. I did not have any to separate after all those years on that sander. Only on my 3-24 sander have I had the separation - from HF with tape splice.

I guess you can tell that I don't do a LOT of sanding, but when I need it, it is there. My dad got it from someone as a payment for something he did for them. He didn't have any use for it so he gave it to me.

[Jim Frye]

Yep. I had some 3M purple 3x21belts of various grits for several years. When I went to use them this year every splice failed after a few minutes of use. I kept the severed belts to use for profile sanding.

[LCHIEN]

Yeah, Iearned that the hard way, too. Whole box of useless belts. Cut them up for hand sanding; stapled to a piece of scrap 2x4.

[Carlos]

I wonder if that's an environmental thing. I've never once had a belt come apart, and I've got some going on ten years here. We have plenty of heat, but no humidity.

[capncarl]

All of the sites I googled had much the same response as those already in this site, some folks had never had a belt failure ( they all seemed to live in cold Canada) and suggested it was just a misuse problem or machine issues, while a larger percentage had experienced belt failures themselves.

It seems that the belt splicing materials are sent to the belt manufacturers frozen in dry ice. There are statements that the spliced belts do have a one year shelf life.

All of my sanding belts are kept in my air conditioned shop so they never get below 60 f in the winter and never above 80 f in the summer. What temperature they were stored at before I purchased them is anybody’s guess. Considering the vendors I purchased them from there is no way of telling how old they are. When i purchased this batch of belts over a year ago there was no problem with splices breaking. They started breaking in mass about 3 months ago.
When I was down to my last 3 remaining 6 x 48 belts I attempted to repair a splice that was pulling apart in the center. I cleaned under the bias ply splice tape best I could and tried to heat the splice tape up a bit with a Liester heat gun made for splicing single ply roof membrane. I started off with the heat as low as it would go, which would make you move your hand out of the way really quickly, the splice tape just curled up and disappeared. No repairing this belt with this heat gun.

My 6 x 48 sander runs quite fast but doesn’t generate much heat on the idler roller or sanding plate, heat is barely detectable with your hand on these parts after a broken belt is removed. Whereas the 4 x 36 sander runs at a much slower speed and generates a lot of heat on the idler roller and sanding plate.
When I saw that I was not going to be able to finish my project using the 6 x 48 sander I pulled the 4 x 36 sander out of storage along with its 8 unused belts which were several years old. The first 2 belts broke within minutes of use and I was able to get to a good stopping point before the 3rd belt broke.
The only source of belts I have locally is Lowe’s, with only 120 grit Shopsmith brand belts in stock...... at $17.95 ea. OUCH!! As a precaution I clamped my 2 remaining belts splice between 2 boards in hopes the splice would miraculously heal under pressure. In the meantime I will limp along on the Shopsmith belt and if it breaks I can return it. I haven’t seen this brand on Lowe’s shelves before so I’m confident they are fresher that my belts.

Happy sanding

capncarl

[Carlos]

Interesting. My belts may see 40 in winter and 110 in summer. But the humidity...almost never over 35 and normally below 20.

[jon_ramp]

Some belts have directional arrows on the inside of the belt and others do not. I recently saw a Youtube video by Next Level Carpentry titled Pro Tips for Better Beltsanding. He said that running the belt the wrong direction of those with a directional arrow indicator will break very quickly whereas those without the arrow can go either way.