Scary Sharp Practitioners - Gluing Glass to MDF?

[Randy Klein]

I've been currently using a granite plate for scary sharp. But I now have some 1/4" float glass I'm going to give a go at. I know most use 3/4" MDF as a backer for the glass to add rigidity.

Are you gluing the glass to the MDF? If so, what glue will bond those two?

[John Keeton]

Randy, I used 3M spray adhesive to bond glass to hardboard. Seems to hold well as there is little stress on the bond.

[Zahid Naqvi]

No glue here, I use a couple of pieces of wood that have a rabbit a hair thinner than the plate glass. I screw these down on the MDF and tighten them to hold the glass in place. I can unscrew these holders/clamps when I need to remove the glass for any reason. Something like the crude image below
100296

[Greg Cole]

I use adhesive on the paper when needed as you can find some sandpaper with an adhesive backer (I get mine from LV), some needs a shot of 3M Super 77 IIRC.
The super 77 holds the sand paper well, but as John said it's not an unbreakable bond by any means, neither is the paper with an adhesive backing. I use a combo of stones and sandpaper in my sharpening....

[Randy Klein]

I use adhesive on the paper when needed as you can find some sandpaper with an adhesive backer (I get mine from LV), some needs a shot of 3M Super 77 IIRC.
The super 77 holds the sand paper well, but as John said it's not an unbreakable bond by any means, neither is the paper with an adhesive backing. I use a combo of stones and sandpaper in my sharpening....

I was asking about the adhesive bonding the glass to the MDF backer. Not the sandpaper to the glass.

[Ray Gardiner]

Hi Randy,

I glue wet & dry to both sides of the glass, and just flip over for different
grades. The glass should be supported, but if you glued the mdf to the glass
you could only use one side.

Regards
Ray

[mike holden]

Randy,
I DO NOT glue my paper down. Just spritz it with water and it will sit snug on either glass or granite till you pick up a corner, to place the next grit down.
Water also acts to wash the swarf away. Yes the paper curls as it dries - so? It uncurls when rewetted and put down again.
Simple, effective, inexpensive.
Mike

[Greg Cole]

I was asking about the adhesive bonding the glass to the MDF backer. Not the sandpaper to the glass.

Ok, so I can't read so well sometimes. :eek:
Gorilla glue sticks to every-damned-thing... turns fingers a nice shade of brown too. Or a couple dabs of epoxy....

[Aaron Wingert]

Randy,
I DO NOT glue my paper down. Just spritz it with water and it will sit snug on either glass or granite till you pick up a corner, to place the next grit down.
Water also acts to wash the swarf away. Yes the paper curls as it dries - so? It uncurls when rewetted and put down again.
Simple, effective, inexpensive.
Mike

I'm liking this idea....
Might try that before I try adhesive!

[David Keller NC]

Randy - Because of the surface chemistry characteristics of glass, silicone adhesives are one of the best "stickies" to use with it. That said, the glass to MDF interface has so much surface area that I'd think most any glue that will bond to non-porous substances will work well.

BTW - for those that use 3M's "77" spray adhesive (I use it to stick multiple pieces of wet/dry to my jointer table for flattening long plane soles), you can remove the residue from it after peeling off the used sandpaper very easily with mineral spirits, kerosene, or laquer thinner. The mineral spirits has the added advantage of being compatible with the solvents in paste wax, if you want to follow up by waxing a machine table after using it for this purpose.

[Chris Schumann]

Take care with mineral spirits on your power tool tables. My Jet manuals warn that it can take the paint off.

[John Schreiber]

Rather than glue the glass down, I'd capture it on the sides with a frame which still allows the glass to be lifted out. An alternative would be a couple of holes drilled into the MDF then some dowels stuck in to keep the glass from sliding.

Another thought is that if you plan to use Scary Sharp with water, MDF sucks up water and its shape distorts. I don't use water, so that would be OK for me, but don't use MDF it it might get wet.

[John Downey]

OK, dumb question here...

Why switch to 1/4" glass if you have a granite plate?

[Randy Klein]

OK, dumb question here...

Why switch to 1/4" glass if you have a granite plate?

Two reasons:



You can only fit about 3 at most, but usually just 2 different grits on the granite. That's too limiting to me, especially when working the backs. I now have 10 1/4" glass plates (since they were only $2 a piece), so I can have many more grits loaded up to go. Plus, smaller chance of contamination.
I would like to actually use my granite as a reference plate and not have to decide if I should junk the paper that's on it at the time.

[Vivian Ecker]

I affixed my 3/8 inch thick glass to mdf with several closely spaced long strips of carpet tape. It worked well for the flattening of my #5 plane sole. And it gives the glass a classy reverse pin-stripe look. ;)

Vivian

[glenn bradley]

I clamp the glass in place (http://www.sawmillcreek.org/attachment.php?attachmentid=40005&d=1149358963). As far as the paper goes, I am another 3M spray adhesive user here. It goes on quick, any residue cleans off quickly with naphtha when replacing worn out paper. If the paper is not glued down across the surface it can 'wave' as you pass similar to smoothing a sheet out on the bed with your hands. This leading 'hump' may foul your edge and cause a need for more strokes to get to your desired result. This same problem occured for me when holding paper down by just wetting it to the glass.

This was just my experience and probably varies based on your abrasive and technique so may not be a problem for everyone (or anyone but me :p). All I know is I get better results in less strokes when I glue it down.

[David Gilbert]

I used Weldbond to glue my glass onto 3/4" MDF boards. I'm not sure that it is all that different from Elmer's white glue but the Weldbond bottle says it is for gluing glass to other things like wood, cement, stone, etc.

I made five at one time and just spread out the glue on the glass, stacked them all up and put some weights on the top. It took a day or two to dry. It went from white to clear. The glass is never going to come off the MDF. One suggestion I would make is to glue the glass so it's close to the edge of the MDF. That way when you flip over the blade you can more easily hone off the back side.

Cheers,

[Tony Baideme]

I don't glue the paper to the glass, I use water or if dry I might use tape at the front corners. My glass is 16"x16"x3/4". No need for a backer board.

Aloha, Tony

[Derek Cohen]

SS is a useful method when the blades are narrow and would damage a waterstone.

I do not recommend MDF as a backing for sandpaper or glass-plus-sandpaper - use a hardwood instead. If you are using water as a lubricant, is will cause the MDF to swell.

I have a few waterstone-sized sections of 5mm glass that are glued to hardwood (with 3M spray contact glue).

I attach wet&dry sandpaper with poster spray contact glue. This has a lower grip and is more easily removed and cleaned off (with spirits/alcohol). I cannot recommend water alone (relying on surface tension) as the sandpaper will dry and curl, and you will end up dubbing an edge.

Regards from Perth

Derek

[David Keller NC]

"
Take care with mineral spirits on your power tool tables. My Jet manuals warn that it can take the paint off. "

Wow - that's really weird. I've never heard of mineral spirits being an effective solvent for any cured finish - paint or otherwise. Laquer thinner is another story entirely - I wonder if there was a translation error in the manual?

[Randy Klein]

If you are using water as a lubricant, is will cause the MDF to swell.

I use oil as a lubricant. Will that swell MDF?