HDPE surface attachment

A little background before my question. A few years back I built a 4X8 outfeed table around my Uni. Top was a sheet of 3/4" MDF with a few coats of varnish. Worked well as an assembly bench and outfeed table, with the saw in the lefthand corner. Bearings went out on the Uni and I had to tear apart the outfeed table to get at the Uni guts. Lets just say the glued and screwed MDF top doesn't look as good now as it did a week ago. Starting the re-assembly of the saw and I'm planning the outfeed table (aka assembly bench). Planning on a sheet good top. Last evening I found a 1/4" sheet of HDPE in black with a slick smooth side and a slightly textured reverse side (not rough, more like a textured formicia). Think it would make a great surface. I want to be able to remove it for the next time I need to replace bearings, and here comes the question. Does anyone have any experience with attaching HDPE to a large flat surface? I'm thinking of screws with a countersink...but would appreciate your suggestions and thoughts.
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On 3/29/2015 8:31 PM, Bruce Kaatz wrote:

Probably the best method. Adhesives don't hold it.
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"Bruce Kaatz" wrote:

------------------------------------------------------------------------ Trap the HDPE sheet with fiddles to the 3/4" top material, then attach HDPE with #10-24 flat head stove bolts.
The fiddles trap the HDPE sheet preventing horizontal movement while the stove bolts keep the HDPE sheet in place without overloading flat head bolt connection.
When it is time to replace, simply unbolt it to remove.
Lew
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What's a fiddle?
Puckdropper
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Make it to fit, don't make it fit.

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"Puckdropper" wrote:

----------------------------------------------------------- Nautical. a small ledge or barrier raised in heavy weather to keep dishes, pots, utensils, etc., from sliding off tables and stoves. --------------------------------------------------------- A nautical term as defined above.
In this application, a fiddle would be a wood strips 1/4"-1/2" thick x 1" min wide x 18" long.
Strips are attached to 3/4" top face with screws with 1/4" of the fiddle raised above the 3/4" top surface trapping the HDPE.
Lew
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Not sure how well that would work for the OP's intention of using it as an outfeed table and assembly table. Seems like you wouldn't want any projections, not even 1/4".
John
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John McCoy wrote:

1/4" above the PLY, inside edge beveled, the other material edge beveled to fit under.
What I don't understand is the necessity for it if the material is going to be screwed/bolted to the ply.
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dadiOH
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"dadiOH" wrote:

---------------------------------------------------------------- Strictly belt & suspenders.
Bolt the leading edge of the HDPE to insure that there can be no hang up of the material being fed thru saw.
Depending on how you design it, the bolts can also serve to hold the fiddles in place.
Lew
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Ah, got it. I had missed that the HDPE was also 1/4" thick. Now I see what Lew was envisioning.
John
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On 3/29/2015 7:31 PM, Bruce Kaatz wrote:

I'm thinking, go back with the same if you liked it. I really don't think you will be replacing bearings again. These saws were built to last more than a life time for anything much less than commercial use.
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On 3/29/2015 8:31 PM, Bruce Kaatz wrote:

I've never done large sheets of HDPE but for runners and such I've always found that carefully countersunk machine screws work well. I wonder if there could be problems with expansion and contraction rates between the substrate and the plastic. Like I say, I've never used HDPE in big enough chunks for that to matter.
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On 3/30/2015 8:55 AM, BenignBodger wrote:

[snip]

Sounds like a plan. To preserve the "removability" you don't have too many options.
Not sure that I'd worry too much about the expansion/contraction. Assuming his substrate is plywood or some other dimensionally stable material he should be good. As insurance, I'd make the holes slightly oversized or... maybe stick with the count sinking but elongate them and use a pan head screw that would allow for some movement all around.
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Thanks for the suggestions. I'm thinking the stove bolts will work fine to hold the HDPE in place. Maybe a maple edge around to go with the fiddle concept. And I hope you are right Leon about not needing another set of bearings. It isn't a bad job replacing them, but not something I want to do very often. Thanks for the help with my project. It is appreciated.
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The plywood responds to humidity, while the HDPE does not, so buckling is likely in some seasons. I'd use flat head machine screws the go through an oversize hole in the plywood, with a fender washer and pair of nuts on the underside of the plywood. This will allow sliding to take up relative growth while keeping the HDPE flat. Do not overtighten. Having two nuts on the same screw allows the nuts to be tightened against one another without compressing the wood. You may need some screws in the middle of the HDPE sheet, as these often come with some curl.
Joe Gwinn
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