Making large polypropylene washers - Woodworking Talk - Woodworkers Forum
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post #1 of 13 Old 07-12-2020, 11:25 AM Thread Starter
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Making large polypropylene washers

I like to add a polypropylene washer between the top and base of my pepper mills to prevent wood-to-wood contact.

I’ve been making the washers out of polypropylene from milk jugs, but I have a heck of a time cutting nice, clean concentric circles. The washers are typically 1-1/2” ID by 2-1/8” OD

Any ideas on how to make these?

I’m picturing a punch of sorts, but I’m open to ideas. I tried a compass with a sharp edge, but it tended to skate around on the polypropylene.
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post #2 of 13 Old 07-12-2020, 11:46 AM
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hole saw with milk jug sandwiched between plywood?
use rubber cement to glue in place and for multiple layers
BigJim and thegrgyle like this.
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post #3 of 13 Old 07-12-2020, 11:51 AM
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I've never done this so this is just an idea.
Make a trammel with a utility knife blade screwed to the end.
You could make the trammel with a fixed or adjustable length.
You should be able to press harder than with a compass cutting through the polypropylene.
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post #4 of 13 Old 07-12-2020, 11:52 AM
where's my table saw?
 
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I have made my own punches ....

By using a short length of thin wall tube, I sharpened the edge, either inside or outside with a die grinder or on a sanding belt. Then you can press a short length into the material with a drill press arbor, a bench vise, and arbor press, or on a cutting board use dead blow mallet. I would make crosshairs on the material to keep the centers centered. Do the outside/large diameter first.



A Forstner bit would work for the small hole. A hole saw may work for the larger hole, but it will leave a rough edge.


This method works for aluminum:

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #5 of 13 Old 07-12-2020, 12:02 PM
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Quote:
Originally Posted by Quickstep View Post
I like to add a polypropylene washer between the top and base of my pepper mills to prevent wood-to-wood contact.

Iíve been making the washers out of polypropylene from milk jugs, but I have a heck of a time cutting nice, clean concentric circles. The washers are typically 1-1/2Ē ID by 2-1/8Ē OD

Any ideas on how to make these?

Iím picturing a punch of sorts, but Iím open to ideas. I tried a compass with a sharp edge, but it tended to skate around on the polypropylene.
Youd get really close to that dimension with an 1 1/2" and a 2 1/4 hole saw bit

Im picturing doing this on a drill press with a chunk of wood below the part.

Start the hole with the 2 1/4 but just enough to make the pilot hole, and make 1/2 the cut of material. Then swap bits to the 1.5" drill through, then back to the 2 1/4 and line up the kerf and finish the cut.

Im sure there are other ways.

Maybe a good pair of offset sheet metal snips. Im assuming thin plastic. I use sheet metal snips to cut circles and such to make gaskets all the time.

Sent from my SM-G930V using Tapatalk

Dave H

Last edited by furnacefighter15; 07-12-2020 at 12:54 PM.
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post #6 of 13 Old 07-12-2020, 12:30 PM Thread Starter
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I've drilled the center hole using a Forstner bit with mixed results. Sometime it cut cleanly, other time it grabbed and ripped it to smithereens. I haven't tried a hole saw; I just assumed that would be worse.
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post #7 of 13 Old 07-12-2020, 03:40 PM
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Look up gasket punches, sounds like exactly what you need

I need cheaper hobby
etsy.com/shop/projectepicfail
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post #8 of 13 Old 07-12-2020, 04:11 PM
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large diameter chassis punch
https://www.mcmaster.com/knockout-pu...ole-punches-9/


punch the big diameter, use same center hole to punch small diameter.
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post #9 of 13 Old 07-13-2020, 12:08 PM
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Quickstep, Since you obviously have a wood lathe, you might try sandwiching the milk jug plastic (several) between blocks of wood and lathe turn the OD to the right size. Seems like some manufacturers do it that way.

Gary

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post #10 of 13 Old 07-16-2020, 07:15 PM
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Quote:
Originally Posted by gmercer_48083 View Post
Quickstep, Since you obviously have a wood lathe, you might try sandwiching the milk jug plastic (several) between blocks of wood and lathe turn the OD to the right size. Seems like some manufacturers do it that way.
Or use a toaster oven or panini press to melt the HDPE from your milk jugs. Then press it into a mold to make a block and turn it on your lathe. There are many videos on YouTube about melting HDPE plastic and turning it on a wood lathe. Iíve made a few mallet heads out of old milk jugs and laundry soap bottles. HDPE melts at about 350 deg F.

Hereís one video to get you started:
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post #11 of 13 Old 07-17-2020, 11:17 AM
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On the lathe, make a groove in the cap to accept an o-ring, skip the washer.
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post #12 of 13 Old 07-18-2020, 10:35 AM Thread Starter
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Well, here’s what I did. Thanks everyone for the suggestions that lead to this solution.

I drilled a 1-1/2" hole in a piece of PVC board and used that as a clamp of sorts to hold the polypropylene as I drilled the ID using a Forster bit. Going slow was the key. Then, I took 2 more pieces of PVC and drilled a 1-1/2" hole half way through one of them and turned a 1-1/2" stub on the other one. I stacked the drilled polypropylene on the stub and sandwiched it with the piece with the hole in it and turned the O.D.

The PVC turned very easily, but the polypropylene grabbed a little bit when I went across it, making me end up with a very slightly smaller O.D. Then I wanted, but not a biggie.

Because the stacking "jig" also gets turned in the process, I'd need to make one each time I need to make washers.
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post #13 of 13 Old 07-18-2020, 04:33 PM
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my experience has been cutting the OD / larger diameter first, then clamping from the ID to the OD, and cutting the ID / smaller diameter - works best on thin materials.
I was using 1 gal milk jugs....
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