Problems cutting HDPE sheet

[Captain Spaulding]

I dumpster scavenged some HDPE from a cabinet shop that does outdoor kitchens. It’s King Starboard, so I believe it’s good quality.

My wife has a potting bench that has some adjustable wooden shelves that have warped. I thought the HDPE would be a good replacement. Shelves are 10”x14” and just a bit less than a 1/4” thick.

I set up my table saw to cut to width off of a 15” x 36”x1/4” piece. Fed moderately slowly. I was surprised to see both sides of the cut had warped 1/4” or more back 6”-8” from the cut edge. I put my hand on the cut edge before the saw spun down and it was barely warm.

I’ve worked with HPDE before and never experienced anything similar. I’ve routed it, thickness planed it and cut numerous 5-1/2” width sections on the table saw with the same blade.

I can‘t see it being anything but heat, but why am I experiencing it now? The blade is not dull.

 

[rlitman]

Something's not right. Warped inches away from the cut? Heat from the blade isn't going to travel that far. It hardly travels deeper than the width of the kerf. Sure, if your blade's not sharp (or is gummed up), it's normal to form a burr (it happens in plastics even with sharp tools sometimes), but what you describe doesn't make sense to me.

 

[PCustoms]

I dumpster scavenged some HDPE from a cabinet shop that does outdoor kitchens. It’s King Starboard, so I believe it’s good quality.

My wife has a potting bench that has some adjustable wooden shelves that have warped. I thought the HDPE would be a good replacement. Shelves are 10”x14” and just a bit less than a 1/4” thick.

I set up my table saw to cut to width off of a 15” x 36”x1/4” piece. Fed moderately slowly. I was surprised to see both sides of the cut had warped 1/4” or more back 6”-8” from the cut edge. I put my hand on the cut edge before the saw spun down and it was barely warm.

I’ve worked with HPDE before and never experienced anything similar. I’ve routed it, thickness planed it and cut numerous 5-1/2” width sections on the table saw with the same blade.

I can‘t see it being anything but heat, but why am I experiencing it now? The blade is not dull.

Pictures?

I've got plenty of starboard, cuts and machines like butter.

Any chance they somehow "planned" the sheet?

 

[Captain Spaulding]

Something's not right. Warped inches away from the cut? Heat from the blade isn't going to travel that far. It hardly travels deeper than the width of the kerf. Sure, if your blade's not sharp (or is gummed up), it's normal to form a burr (it happens in plastics even with sharp tools sometimes), but what you describe doesn't make sense to me.

It warped from the cut up to several inches from the cut.

 

[PCustoms]

I set up my table saw to cut to width off of a 15” x 36”x1/4” piece.

I think that might be your problem. This material is flexible, and creeps over time.

 

[Captain Spaulding]

Pictures?

I've got plenty of starboard, cuts and machines like butter.

Any chance they somehow "planned" the sheet?

I’ll get some pictures tomorrow. Did another cut with a faster feed and it still warped. Maybe not as bad. Made a cut on a scrap of 1/2” and it was perfect. I’m thinking it’s the material or thickness. Might not be Starboard. Total lack of quality control in this dumpster! You get what you pay for.

Shut down the shop and came inside and cracked a beer.

Frustrated is not a proper mood to be working with power tools!

 

[PCustoms]

I’ll get some pictures tomorrow. Did another cut with a faster feed and it still warped. Maybe not as bad. Made a cut on a scrap of 1/2” and it was perfect. I’m thinking it’s the material or thickness. Might not be Starboard. Total lack of quality control in this dumpster! You get what you pay for.

Lol, could be why they pitched such large pieces. I've had plenty of extruded materials get some weird stress and go wonky when cutting

Shut down the shop and came inside and cracked a beer.

Frustrated is not a proper mood to be working with power tools!

 

[Captain Spaulding]

Lol, could be why they pitched such large pieces. I've had plenty of extruded materials get some weird stress and go wonky when cutting

They build huge outdoor kitchens and they don’t save scraps. They ended up with a building full of countertop and sheet good scraps a few years back and they decided to stop keeping it. Their supplier will take full sheets back. Sounded like a good idea to keep it, but it turned into a big, inaccessible pile and they needed more space. If you can’t readily find and get what you want, it’s just wasted space.

 

[PhantomEB]

Offtopic….What TPI blade do you use? I need to cut some cutting board soon for spacers for my skidplate.

 

[johnre]

What did the chips look like that came off of the cut? Whenever I've cut HDPE, it made little curly chips that clearly indicated that the cutting edges were doing their job correctly, the feed rate was correct, and it was being cut, not abraded.

 

[mreisner]

I cut hdpe and uhmw from time to time. I use an aluminum siding blade and it works well.

 

[blazemaster83]

I use starboard all the time at work, cuts like butter on the table saw with a sharp blade. I've cut 1/4" up to like 2" thick never had an issue. A dull blade will melt it, and can be grabby. Something is goin on...

 

[4x4Pete]

Maybe this is the reason it was thrown out?

 

[Captain Spaulding]

Here’s a side view. Hard to get it to show well.

 

[PCustoms]

Here’s a side view. Hard to get it to show well.

Is that edge closest to the camera what you cut?

 

[whateg01]

So when you say warped, do you mean it bowed? I would be tempted to cut a piece oversized and stick it in the oven to relieve stresses and then recut. Obviously this only makes sense because it's scrap to begin with.

 

[Captain Spaulding]

Is that edge closest to the camera what you cut?

Yes

 

[PCustoms]

Yes

Looks rough, and almost not like their HDPE that I'm used to but certainly hard to say.

To me it looks like a sheet that was stored upright or bent.

 

[rlitman]

Looks rough, and almost not like their HDPE that I'm used to but certainly hard to say...

Looks more like LDPE to me, but looks can be deceiving with this stuff. I'm wondering if it wasn't already warped, but in a more 3D sense than simply cupped, and by cutting it, it released tension and now shows it's true colors. Like reactive wood.

 

[paranoid56]

yea, not sure thats HDPE, i cut it daily, get it sharp blade and run it fast. cuts like butter