Machining UHMW polyethylene question

[davidpbest]

I use that material for a lot of things in the shop. It is terrific for tool holders/racks It cuts great with woodworking tools like table saw, spindle shaper, router bits, as well as with end mills, fly cutters, etc. Running a small piece through a jointer is asking for an accident to happen IMO. A few project examples:

PM1340 Chuck Saddles

Making saddles to hold the heavy chucks for the PM1340 metal lathe. Material is King Starboard which is a brand of HDPE marine building material available from Tap Plastics. It's similar to delrin.

flic.kr

PM1340 - Felt oil wipers for bed-ways

These are replacements for the wipers on the carriage and tailstock. Instead of wiping the bed-ways dry, the felt leaves a thin film of oil. Click on each photo for details.

flic.kr

 

[Larry$]

Ditch the 1/4" shank router bits! Spiral bits, either router or milling cutters work well. I've kept the drops from our commercial CNC work with it for my hobby fiddling. Great stuff. Yes, the shavings create a mess! A sharp hand plane produces a perfect finish.

 

[hman]

Here's a link to a 10" Forrest blade. Kinda spendy ($145) compared to big box store saw blade prices, but according to the recommendations above, probably well worth it:

Woodworker II - Thin Kerf :: 10" Woodworker II Saw Blade - 20 Teeth - Thin Kerf - Forrest Saw Blades: Quality Saw Blades & Dados

With this one all purpose blade you can rip cut 2 - 3 thick hardwoods resulting in a smooth-as-sanded surface

www.forrestblades.com

... and here's an 8" no-melt blade for plastics($229):

No Melt Saw Blades for Plastic Sheets and Extrusions :: 8" No-Melt Saw Blade - 60 Teeth - Forrest Saw Blades: Quality Saw Blades & Dados

The No Melt saw blade is especially designed for cutting single or multiple stacked sheets of plastic without chipping or melting these materials. For use with acrylics, delrins, ABS, styrenes, PVC, and both high and low melt nylons.

www.forrestblades.com

 

[RaisedByWolves]

I have worked with it.
If you have a mill, it fly cuts well. Or face mills.

If you have a jointer, I would try that. if not, a router table with the outfeed fence shimmed with two playing cards from a deck of cards. Set the outfeed level with the router bit and it will act as a jointer. The chips are stringy... If you have a spiral bit, use that in the router.

To get a real straight cut, you may want to back the opposite side with a piece of aluminum or wood that's straight. Use doublestick tape to attach .. the idea is to provide backing so it loses its floppiness/flexibility.

Fly cut with a sharp bit was always my go to.

The thing to keep in mind is that you need to hold it tight enough in the vise so it does not slip, but not so tight that you deform it and wind up with flat surfaces that turn concave when you release it from the vise.

 

[RandyM]

Just run a sander over it. It will smooth out just fine.

I have also found that acetal machines much better than UHMWP and it has very good lubricity also.

 

[stupoty]

As they are short bits you could try sticking abrasive papers to sheets of glass and "lapping" it smooth and flat.

Stu

 

[dml66]

Since you have the aluminum jig and can screw it to the blocks i'd try a solid carbide helical pattern bit. 1/2" shank in a router table would give the best results, and be safer with a small part. up or down cut bit will not matter, but the compression ones can leave a 'center' line. up cut in a router table would probably be easier making part from slick stock, since the bit will want to pull the part to the table. I have never had much luck with the router-table-as-jointer trick. The AL jig looks good, just needs fussing with the details.

I have a compression 1/4" shank bit inbound. After reading up on the up, down and compression bits, including customer reviews, I haven't found very many folks who weren't satisfied with the finish results using the compression. If the bit shows a marked improvement over my straight bit, I'll see about getting a 1/2" one.

 

[dml66]

As they are short bits you could try sticking abrasive papers to sheets of glass and "lapping" it smooth and flat.

Stu

Just run a sander over it. It will smooth out just fine.

I have also found that acetal machines much better than UHMWP and it has very good lubricity also.

Everything I read prior to working with UHMW plastic is that abrasives will not produce a good finish. That said, I do have some scrap pieces, and I do have sandpaper from 180 grit to 3000 grit, it can't hurt to give it a try

 

[dml66]

Forrest also makes beautiful no melt plastic blades!

Unfortunately, I don't have a table saw. I do have a DeWalt sliding compound saw, I'll check to see if Forrest makes a blade that'll fit it.

 

[woodchucker]

Unfortunately, I don't have a table saw. I do have a DeWalt sliding compound saw, I'll check to see if Forrest makes a blade that'll fit it.

You can use a 40 tooth Freud diablo. Almost as good