HDPE -- kickback with planer

paulrussell · Post by **paulrussell** » Fri Jan 31, 2014 4:47 pm

I have a large half inch thick HDPE cutting board that I thought I'd repurpose. It had some deep cuts on both sides and I thought I'd resurface by running through my Pro Planer motor mounted (aluminum bed) SS planer.

It was about 20" wide, so I cut it in half and ran the first half through the planer without a problem.

Took the other half, started it through, and it kicked back and flew across the room. There was a nasty deep cut across the end, like the cutters had dug in and lifted the HDPE up off the bed. I regained composure, changed the cut depth to 1/2 of before and tried again (starting at the opposite end). Same results.

I have the old style rubber rollers. Is it likely a tension setting problem, time to replace the roller with the new style, or is planing HDPE a bad idea?

beeg · Post by **beeg** » Fri Jan 31, 2014 4:54 pm

How DEEP of a cut were ya taking?

paulrussell · Post by **paulrussell** » Fri Jan 31, 2014 5:29 pm

First (successful) pass was a little under 1/16th.
First kickback was at same depth, other half of material.
Second kickback was at just over 1/64th.

I've yet to re-attempt, but have cleaned rollers with denatured alcohol and adjusted tension per the manual (7-8 full turns of the screw). While doing so I noted that the feed roller is in generally good shape but has some areas which are somewhat compressed. I have never had any issues with wood, but HDPE is slippery in comparison.

I also have a suspicion that the HDPE is bowing longitudinally and the cut is starting deeper than the feed setting.

wa2crk · Post by **wa2crk** » Fri Jan 31, 2014 8:44 pm

Check the blades for build up from the first cut. The HDPE will probably soften and can stick to the blades which might cause extra resistance and a kickback. Your other observation is also valid in that the material may be too slick for the infeed roller to grip properly.
Bill V

Ed in Tampa · Post by **Ed in Tampa** » Fri Jan 31, 2014 9:23 pm

My guess is saw dust build up has lifted a roller and that is allowing the front of the plastic to rise up into the blade.

Give the machine a good cleaning and make sure each roller has full travel of movement and it's guides are filled with dust.

JPG · Post by **JPG** » Fri Jan 31, 2014 9:35 pm

Ed in Tampa wrote:My guess is saw dust build up has lifted a roller and that is allowing the front of the plastic to rise up into the blade.

Give the machine a good cleaning and make sure each roller has full travel of movement and it's guides are filled with dust.

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JPG · Post by **JPG** » Fri Jan 31, 2014 10:48 pm

I would be leery of feeding hdpe(or any plastic) through the planer.

In addition to the slickness/feeding issue, is the flexibility of it. That means it is deformed easily.(aka bending)

Consider the knives motion as it is fed into them. The blades descend from the outfeed side, become tangent to the workpiece at '6 o'clock and ascend towards the infeed side. The infeed side is where the cutting takes place. The ascending blade will tend to lift the workpiece up off the platen(table). This is a recipe for 'digging in'.

Tis similar to planing a too thin piece of wood.

I would take very shallow cuts and feed very slowly.

I think slow cutter speed would be advisable as well.

charlese · Post by **charlese** » Sat Feb 01, 2014 12:11 am

I fully agree with the scenario and recommendations of JPG.

nuhobby · Post by **nuhobby** » Sat Feb 01, 2014 7:42 am

+1 on the expert advice offered by all the guys.

Incidentally, I gave a very sharp repaired Millers Falls 14" jack-plane to my brother a couple years ago. He just loved it; like many of the present generation he had never encountered a really sharp plane before. He has used it a ton on his house repairs. He did comment that with synthetic decking "wood," the plastic would adhere to the blade.

rlkeeney · Post by **rlkeeney** » Sun Feb 02, 2014 6:25 am

Plastics tend to heat up when you cut them. Perhaps it is beginning to melt and stick to things.

I would not put put HDPE in a planer because its slippery and I would be difficult for the planer to get a grip on it. Not to mention that it might melt and gum up the works.