Gluing primed MDF.

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11-22-2019, 10:08 AM
Jeff C Johnson

Gluing primed MDF.

Hello. I am considering making a torsion workbench and was eyeing the 1x4 mdf boards at the box stores for their consistency in width. I could rip them on my t-saw, but I figured the 1x4's would be more precise in case I get any drift on my rip cuts.

All the boards I see at the local big box stores they are pre-primed. I assume I would need to do a light sanding to remove the primer to get glue to stick to the edges of these boards? Or does Tightbond work on primed material well?

Thanks.
Jeff
11-22-2019, 10:57 AM
Jamie Buxton

Titebond does not glue well to painted surfaces.
11-22-2019, 1:20 PM
Jeff C Johnson

Quote:

Originally Posted by Jamie Buxton

Titebond does not glue well to painted surfaces.

Yeah, that was about what I thought too. I'll just make my own with the tablesaw
11-22-2019, 3:18 PM
Doug Garson

If you are concerned about ripping 1" MDF sheets on your table saw (I wouldn't want to do it on my saw), you could buy the 1 x 4's and just skim off half a saw curf on your table saw to get rid of the paint. More expensive than starting with a 4 x 8 sheet but easier on the back.
11-22-2019, 3:27 PM
Jeff C Johnson

Quote:

Originally Posted by Doug Garson

If you are concerned about ripping 1" MDF sheets on your table saw (I wouldn't want to do it on my saw), you could buy the 1 x 4's and just skim off half a saw curf on your table saw to get rid of the paint. More expensive than starting with a 4 x 8 sheet but easier on the back.

when I say 1x4 mdf, they're actually 3/4" thick. Yeah, I hear you on the labor side. I would probably have it ripped into thirds (32") at the shop, then in half (16") on the saw, then do 3.5" rips.
11-22-2019, 3:52 PM
Doug Garson

Yes, that should work ( I assume by shop you mean the store you buy the MDF at) although I have heard some stores won't cut MDF on their panel saws due to the fine dust.
11-22-2019, 4:07 PM
Jeff C Johnson

Quote:

Originally Posted by Doug Garson

Yes, that should work ( I assume by shop you mean the store you buy the MDF at) although I have heard some stores won't cut MDF on their panel saws due to the fine dust.

Interesting -- didn't know that. I'll need to ask next time I'm there. I know HD and L both have dust collection on their saws, but I'll ask.
11-22-2019, 9:57 PM
Jim Becker

Don't assume those pre-primed MDF boards at the home center are all exactly the same width...and for a torsion box that is dead flat, they really do need to be absolutely spot on.
11-22-2019, 10:07 PM
Doug Garson

Quote:

Originally Posted by Jim Becker

Don't assume those pre-primed MDF boards at the home center are all exactly the same width...and for a torsion box that is dead flat, they really do need to be absolutely spot on.

That's easily resolved by recutting them to remove the paint and set the width.
11-22-2019, 10:39 PM
Edward Dyas

Quote:

Originally Posted by Jeff C Johnson

Hello. I am considering making a torsion workbench and was eyeing the 1x4 mdf boards at the box stores for their consistency in width. I could rip them on my t-saw, but I figured the 1x4's would be more precise in case I get any drift on my rip cuts.

All the boards I see at the local big box stores they are pre-primed. I assume I would need to do a light sanding to remove the primer to get glue to stick to the edges of these boards? Or does Tightbond work on primed material well?

Thanks.
Jeff

Keep in mind the primer isn't just on the surface, it's penetrated into the MDF and you would have sand deep enough to remove that before you could use any PVA glue. About the only adhesive you could use would be epoxy but you would still need to remove most of the primer.
11-23-2019, 8:28 AM
Rob Charles

Quote:

Originally Posted by Edward Dyas

Keep in mind the primer isn't just on the surface, it's penetrated into the MDF and you would have sand deep enough to remove that before you could use any PVA glue. About the only adhesive you could use would be epoxy but you would still need to remove most of the primer.

And that primer can vary in thickness & can be quite brittle.
11-23-2019, 8:42 AM
Peter Kuhlman

I would just use my track saw for this on full sized sheets. I would use a stop block or measure and mark with a knife to get accurate cuts. Could contain the majority of the dust that way. If no track saw I would rough cut out in the driveway and then rip on the table saw for finished edges.