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do i neeeeeeeeeeed to screw?

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Silverwind:
I used a nailgun with wood glue.  Also internally I used some L brackets with screws for additional support.  So far so good.

Crazy Cooter:

--- Quote from: Ldsfunaz on September 23, 2005, 01:57:26 pm ---
but from what you guys are saying, is it totally useless to screw where the glue has already dried?



--- End quote ---

Mostly.  If you srew it after the glue is dry, it will crack the glue and then only be held by the screws.

nostrebor:

--- Quote from: Mark70 on September 23, 2005, 02:27:50 pm ---Glueing and Screwing goes together like concrete and rebar. 

You can build a crappy little 3" thick slab for your lawn building with just concrete, but if you're putting a foundation under your house you'll be using rebar.  If you want to build a parking garage you'll be using a lot of rebar.

I actually look at the glue as a supplement to the screws.  The screws address any shear forces across the joint and the glue will assist the screw threads in resisting pullout force.

--- End quote ---

Speaking from experience in professional design you have this backwards. The screws supplement the glue. Years of testing have proven that glue has superior holding and shear strengths, when applied correctly, over mechanical fasteners. This is especially true in MDF, which has a proven history of poor performance in pullout/pullthrough of mechanical fasteners. I STRONGLY urge builders to always use glue with MDF as it was designed to specifically be attached with adhesive. If you want to supplement these connecting points with mechanical fasteners in MDF, always drill pilot holes first, and use the correct type of fasteners. This would be fasteners that do not have tapered shanks, and have coarse threads. DO NOT over tighten mechanical fasteners in MDF or you will fracture the MDF and cause real losses in holding strength.

My professional advice to the OP is use both. If you choose to use only one use adhesives.

On the parking garage comment... design will not only require a considerable amount of rebar, it will require either prestressing strands (Prestressed concrete construction) or post-tension reinforcing (Cast-in-place concrete construction) as well. Effective span is greatly increased in this way, and designers love to push these spans. This subject is close to me right now. My firm is on It's fourth garage this year.

Mark70:

--- Quote from: nostrebor on September 23, 2005, 03:53:24 pm ---

Speaking from experience in professional design you have this backwards. The screws supplement the glue. Years of testing have proven that glue has superior holding and shear strengths, when applied correctly, over mechanical fasteners. This is especially true in MDF, which has a proven history of poor performance in pullout/pullthrough of mechanical fasteners.

On the parking garage comment... design will not only require a considerable amount of rebar, it will require either prestressing strands (Prestressed concrete construction) or post-tension reinforcing (Cast-in-place concrete construction) as well. Effective span is greatly increased in this way, and designers love to push these spans. This subject is close to me right now. My firm is on It's fourth garage this year.

--- End quote ---

You're building SOME parking garages if you're prestessing.  Antyhow, lets not derail this fine gentleman's thread with our architectural jibber jabber.

Regardless of the semantics, we agree that you should be using both screws and glue.  I was using my "common sense" muscle in stating that the screws are addressing the shear forces, specifically because of their poor pullout strength in mdf.  I wouldn't be counting on a screw for pullout in MDF.  Glue may also be superior in shear to the screws as well simply due to the sheer (not shear) area of the connection.  Again, regardless, we agree that you should be using both screws and glue.

prOk:
Use a good glue (wood or poly) and 1x1 blocking with air nails or staples..    Don't forget, glue only forms a surface bond.  MDF is like cardboard.. even though the first layer sticks well to the blocking, the first layer will easily peel away from the second.  You need some kind of physical bond to pull the two together tightly and hold.  Screws work too, but it's cheaper and easier to shoot nails/staples in if you have a compressor.

Even pac/mspac cabs did have blocking and small staples, but one more thing to remember is that they had the added reinforcement of the steel wings mounted to the monitor that helped hold the cab together all these years.   It wasn't all glue that did thejob :)

I've built at this point probably 50 arcade cabinets by  hand all following original models.  I always see people overdoing some things and under others..  2x4 frames are way too much, while some of the 1/4 inch thick cabs i've seen are way under..  Simple well cut pieces with a decent glue, small blocking and some staples will hold extremely well and not become heavy as a tank to deal with!

/brian

http://www.rgvac.com

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