Broken glass coffee & end table question

[mark page]

A question for the mechanical engineering grads out there. I once made a "broken glass" table in my early years and would like to do it again as a set of end tables and matching coffee table. I have no problem making the tables per se, but need help with the glass part. I need a little help in getting the right thicknesses of the glass for strength integrity. This is the concept I previously used IIRC. I had a 3/8 inch pane of tempered glass as the base under-layer, a 3/8 inch pane of colored tempered glass as the "broken" layer, and a 1/8 inch pane of glass as the cover "top" layer. The question is with the appx dimensions of glass being 40x22 inches or so, what are the minimum thickness of the glass panels required to be structurally sound and kid proof. The load weight would be the usual coffee table stuff, plates, couple books, drinks, etc. but don't want an accidental trip to be catastophic? I am also looking to keep the actual weight of the unit as low as possible but still needs to be "kid proof". IIRC the one I made previously weighed a ton. Thanks for any help provided. Also as a side note, this is one of the only projects that I actually get to break something that is pre-planned.

[Jamie Buxton]

I don't have the answer to your question, but would you describe this "broken glass" technique a bit? What does the panel look like when you're finished? How do you make it? Do you have pics?

[mark page]

I'll try to explain as I do not have pictures of the previous table as it was done in my high school years. Outside of the structure of the table which is basic and no need to go into details on that: There are three layers of glass. The supporting glass which is the bottom layer, this one is the strength of the total design and most critical. The second layer is the color of choice tempered glass which will be broken (I'll describe later how). The third layer is the top layer which holds the broken glass in place and is usually a thinner thickness layer. The secret to the whole procedure of the broken glass is very simple. Winter times are the best to create one of these as the temperatures are in your favor. The table top is created with dado's the width of the total glass. The dado's are lined with industrial rubber padding and oversized for compensation of wood expansion and contraction. The padding keeps the "broken" glass from separating and gapping itself. Very critical for final continued appearance.
Now at one of the width ends (narrow side) of the top, a hole is pre-drilled through the dado at the same level the colored tempered glass will be. Allow the top with glass to become as close to freezing temps as you can get it. The colder the better. Take an eight penny nail, punch awl, etc. and insert into the pre-drilled hole. One good hard quick whack with a hammer and the colored tempered glass will shatter like a broken windshield in a car, and be self contained. Once completed the good part comes as when guests arrive and attempt to sit a beverage or other item on your glass table top, they stop in amazement as they think the glass is broken and will fall loose if they touch it. The table I did was a small end table design and the final project was very heavy using IIRC 8/4 wood plus the weight of the glass. On this possible new project I am thinking I would like a 3 inch reveal of wood around the glass, instead of the glass continuing to the aprons and using the aprons for support. Questions arise on the needed thickness of the glass for strength plus the glass "framing" thickness. One idea is to use a 4/4 top rabbited with a 4/4 bottom frame rabbited around the glass to save on cost and weight, plus the glass could be replaced more easily if a mishap did take place. I hope by my description that you can visualize what I am thinking about and wished that I had pictures of the previous table. Thanks for any ideas and help. I still have some youngsters at home that can tear up an anvil in a sandpile with no other tools involved, so am looking also for some safety margins in the glass thickness that can survive the kids.

[curtis rosche]

i would say use plexi, but i dont know what i am talking about, i am just wandering through today

[Lee Schierer]

That's a really neat concept. You should contact one of the woodworking magazines with your finished mesigns. I'm sure they would publish it.

I would consult the local glass company. They have tables that show what thickness of glass is needed to span a distance for shelving. They also know how much weight can be applied.

As far as making it kid proof, I would go with tempered glass for all layers as accidents do happen and it would be better if the glass breaks to have it do so safely. Tempered glass may also be more resistant to impacts.