I have some 5 mm underlayment from Home Depot and I was wondering if anyone had any experience with how well it cuts in the glowforge and if it is laser safe?
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This underlayment is basically 3 ply plywood with interior glue.
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I think that is up to the MSDS sheet from the manufacturer. Usually you can find it online.
This is the product by the way: http://www.homedepot.com/p/Underlayment-Common-7-32-in-x-4-ft-x-8-ft-Actual-0-196-in-x-48-in-x-96-in-431178/203183010
I asked at a local Home Depot if they had an MSDS on hand for the product but they did not. I looked online one but did not find anything for this specific plywood. I did find a couple of similar ones and they indicated there should not be an issue.
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I don’t know about the Home Depot Lauan, but the Lauan Lowes sells is usually from: http://www.patriottimber.com/msds/ I think they call their Lauan revolution ply and it listed as low formaldehyde.
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If this is Home Depot’s 5mm Tri-Ply underlayment (usually about $13-14 a sheet, with 3 layers of pine core and what used to be labeled as–and still appears to be sometimes-spalted birch outer layers), I will say that, while it could potentially, like any plywood, be somewhat dangerous to laser glue-wise, I’ve been cutting with it regularly for about a year and a half as my go-to plywood and it lasers extremely well. It cuts consistently, has a low number of voids, and the surface quality is nice and takes stains and finishes really well. Here’s some pics of stuff I’ve designed and made with the HD underlayment:
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Thanks @jrnelson! The thickness on that plywood is consistent enough (right at .2 inches) that I can design everything, even the table, with flatpack joinery and not have to worry about the slots not fitting together properly. I set my slot width to .200, and with the laser kerf, that provides just enough wiggle room.
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This looks like it could be like “luan” it is sometimes called “doorskin”.
These have a softer interior core, but are technically plywood.
All wood and glue should be OK to laser.
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These ones aren’t quite luan – instead of having a lauan mahogany front, they’ve got birch on the front, and there are three core layers instead of one, so it doesn’t tend to warp nearly as much as the cheaper plywoods (though I’d avoid the Lowe’s $25 equivalent – I used to use it, but it’s only got a single-layer, void-prone warpy core). The top and bottom veneers are still a little on the thin side – it’s no baltic birch, but it will take sanding with 220 and has a fairly robust edge, especially if you finish it. And until my 
arrives, it’s definitely much easier to afford in my cost margins than baltic birch, with all the laser rental costs I’m paying.
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Thank you for the awesome responses! This helped a lot!
I think this material will hopefully work out well for some projects that do not need to use material which is as expensive as the proofgrade. At $13 for a 4’x8’ sheet, I cut it to get the following sheets which fit into the GF -
12"x20" panels: 9
11&5/8" x 20": 3
11&5/8" x 16": 3
11&5/8" x 15&7/8": 1
That is 16 panels from a $13 sheet. Which, including what is taken out from the blade kerf, is about $0.41 per square foot.
That beats the pants off of any of the proof grade material. Though there is no tape covering, and obviously much lower quality control, and no baked in settings.
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Is it possible to buy a full sheet of 3ply Baltic birch? I have bought 12x24 sheets on amazon for 60$ it would be nice to find a local big box store to pick up a 4’x8’ sheet 
Yes. A full sheet is almost always 5’x5’ though. Woodcraft and other wood stores carries it.
There are some manufacturers now making 4x8 sheets of Baltic Birch - I think there’s a Russian manufacturer and there was a U.S. based one that was doing it for awhile but it’s not easy to find and since it’s from untraditional sources might not be easy to order either.
You won’t find it at big box stores like Home Depot or Lowes. Too specialized a market. Their birch (not Baltic Birch) ply is standard plywood with odd glues, patches, knots, layers, etc. with a birch veneer.
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I did See 1/4" Baltic Birch ply at Menards yesterday in 4x8 sheets. I want to say is was around $34.
I can’t speak to quality. Both faces looked quite nice.
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Did you get a look at the manufacturer’s name? That’s Birch ply pricing but about 1/2 what the 4x8 BB manufacturers usually charge. They should have a mfg certificate if it’s really Baltic Birch and not just Birch. If there’s a patch on the backside it’s a unique bowtie-ish shape.
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It was labeled BB, I’ll check next time I’m there and let you know.
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You should ask them to price match their online price!
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It’s Halex “Baltic Birch”. Also sold as Arctic Birch.
Their stuff is usually Russian sourced. It’s not necessarily made to the Baltic Birch EU specification but it is better than standard Birch plywood. It is (supposed to be) all Birch but the glues are variable. For 1/8 & probably 1/4" it’s probably not far off from the ply count required but in thicker sizes it tends to use fewer (30-40%) inner plies. For our uses they really can’t cut down the ply count because we’re only dealing with 3 or 4 plies in the spec’ed stuff. For thicker ones where 12 plies turns into 8 thicker plies you lose a bit of the structural integrity as there are fewer grain alternations.
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So, I have been cutting with the 5mm underlayment and so far so good. After a few tests and trails, I settled on these settings for pretty consistent cutting:
Power: Full Power
Speed: 130
Focus Height: 0.198"
These settings can probably be improved on, but this is what works. After transporting the material to a drier climate, a lot of it has a little bit of a warp. If the material is flat, then you could probably go faster.
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I am at the point where I have gone through 3 4’x8’ sheets of this material, and it still seems to work well. There was some warping which leads to some poor cuts. However, for less than $1 per 12"x20" sheet, I can handle that.
I am still cutting at the same settings listed above. However, the sides are pretty black, but no more so than what I have come to experience on thicker material.
This coming weekend I will be picking up some more of this material. It will probably be a workhorse material for me going forward as well.
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I’ve been cutting this material as well. Full power at 150 (on my Basic) has cut reliably so far; I’m going to keep ramping up the speed slightly until it fails to cut all the way through.
I’m curious why you chose to focus at .198" instead of .2? Is that the actual thickness you are measuring, or are you intentionally focusing slightly under the surface? (I’m brand new to this, so I welcome your insights.)
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