Anyone plane UHMW polyethylene? Gotchas to watch for before I start?

[Justin Meyer]

I'm making runners/ spacers for window sashes. I'm using 3/4" x 3/8" miter slot stock which is the closest I can get from McMaster-Carr, but it's just a touch too think...I'd like to plane it down about 3/32" to ~.300". Would this stock be too thin and flexible, maybe get picked up by the segmented head? I'd appreciate any thoughts....

[Peter Rawlings]

I've machined UHMW lot of ways but don't think I ever planed a piece. It tends to be "stringy-er" than HDPE which I have succesfully planed with a Byrd head and milled flat on conventional blade jointer. At that thickness it may want to move around before and after pressure rollers in planer, but I doubt it'd break. More likely it would snipe so I'd have some excess I could cut off ends to correct length and take light passes.

Have you got a piece to experiment with? I've taken 1/2" HDPE to 1/4" successfully with planer.

[Dan Friedrichs]

I've had similar problems and reservations about running it through a power planer. FWIW, a sharp block plane works great.

[Frederick Skelly]

I too use a hand plane.

[Mark Hockenberg]

I've routed and edge sanded it. Like Peter, I found it to be really stringy.

For planing how about this - Leave it long to deal with snipe / Glue it to a stable piece of lumber - Maybe in a wide dado / Then run through the planer

[Justin Meyer]

I've routed and edge sanded it. Like Peter, I found it to be really stringy.

I'm really surprised one can effectively sand UHMW PE, I rather assumed it would clog up the abrasive in very short order.

For planing how about this - Leave it long to deal with snipe / Glue it to a stable piece of lumber - Maybe in a wide dado / Then run through the planer

Going to give this a try on my planer sled if the prototype works as intended!

[Mark Hockenberg]

[QUOTE=Justin Meyer;2952757]I'm really surprised one can effectively sand UHMW PE, I rather assumed it would clog up the abrasive in very short order.

How right you are! I made a mess of the paper on my disk sander.

[Curt Harms]

I've routed and edge sanded it. Like Peter, I found it to be really stringy.

For planing how about this - Leave it long to deal with snipe / Glue it to a stable piece of lumber - Maybe in a wide dado / Then run through the planer

I've never done it but if I were to try, the snug fit dado seems like what I'd try. Maybe piece of ply with 1/4" thick strips forming the dado glued to the base piece.

[Justin Meyer]

So, hand planing UHMW PE worked, but was a bit tricky. I had to take almost 0.020" shavings to reliably get a "bite" on the material. Clamped the material from the back so it was in tension, and it still tried to wander a little. Blade was sharp, so my technique is off (one edge about 0.020" thicker than the other after 5 passes), but the result more than acceptable.

IMG_20191007_183617_1024px.jpg

I notched the pieces on the table saw, sprayed the blade and cabinet interior with Static Guard, which worked great!

IMG_20191007_193452_1024px.jpg

Only needed to plane one strip of PE, if I have to do more I'll definitely try the planer...probably with a sled or at least a piece of melamine over the tables.

[Frederick Skelly]

Thanks for following-up with us Justin. I always appreciate hearing how the advice here works out.
Fred

[Bill Dufour]

I do not know why people insist on gluing sacrificial wood strips longer at each end to reduce snipe. Just shove the loose boards in along with the good wood but start them a few inches before the good wood. Of course gluing does reduce the handling time at the planer but the extra time for glueup and edge jointing the sacrificial wood seems like more work to me..If you are really planning 20 foot pieces, remember you only need the sacrificial piece at each end nothing needed in the middle of the cut.
Bill D

[Mark Bolton]

I do not know why people insist on gluing sacrificial wood strips longer at each end to reduce snipe. Just shove the loose boards in along with the good wood but start them a few inches before the good wood. Of course gluing does reduce the handling time at the planer but the extra time for glueup and edge jointing the sacrificial wood seems like more work to me..If you are really planning 20 foot pieces, remember you only need the sacrificial piece at each end nothing needed in the middle of the cut.
Bill D

That works until the loose boards skew, slip, feed at a slightly different rate than the others. This is especially true if you dont have segmented feed rolls. Its why most planers without segmented feed rolls state never to feed multiple boards at the same time/ganged even though most all of us do it. But the few slightly thinner boards in the stack, or an errant chip(s) get between a board and a non-segmented feed roll and other parts will stop feeding/slip/skew or fly back if your planer doesnt have anti-kickback pawls. Beyond that it can become a juggling act if things dont feed perfectly.

I never bother with either and just leave parts long. A planer is a roughing tool not a finishing tool. You just have to plan for a few inches of possible waste.

[Brian Holcombe]

Same experience as Mark.

Accurate jointing greatly reduces and can eliminate snipe. If a board is flat against the bed it doesn’t flop up into the cutter and snipe.

[Mark Bolton]

Same experience as Mark.

Accurate jointing greatly reduces and can eliminate snipe. If a board is flat against the bed it doesn’t flop up into the cutter and snipe.

Ive beat this drum for years to no avail but in my experience most all chased snipe, other than someone just learning/starting out letting the board drop on in and out feed, is actually caused by mechanical slop/flexure in the planer head itself. I have tried this even with planers up to like a 15" 4 post import with thick stock. You can lift up on the end of the material enough to literally have the outfeed end of the machine off the table/floor, and if there is slop in the head (the planer head walks/racks up on to, and off of, the part) you will get snipe. No amount of in-feed or outfeed support will make it go a way. Of course if its a support issue thats easy, but often times even with way more support than necessary it will still be there. Its mechanical slop in the assembly even when engagning post locks.

I had a friend with a 15" 4 post planer that would snipe and one time he was planing 6/4 material and he lifted the outfeed end enough to see the edge of the planer up-weight off the floor as it was coming out and there was still snipe. Locking the post locks helps, but it was still measurable.

If every inch of the material is absolutely needed/valuable, adding sacrificial material to the part or a hand plane would be a better option in my opinion.

[Rod Sheridan]

I'm making runners/ spacers for window sashes. I'm using 3/4" x 3/8" miter slot stock which is the closest I can get from McMaster-Carr, but it's just a touch too think...I'd like to plane it down about 3/32" to ~.300". Would this stock be too thin and flexible, maybe get picked up by the segmented head? I'd appreciate any thoughts....

I tried it once, it was pretty funny.

After that I used a hand plane.............Regards, Rod.