Re(: VERY Basic Question - how to get to 90 degrees

[Glenna Rose]

>> probably missing the obvious. > >> For example if I buy a 2'x 4' sheet of wood and there is not a perfect >90 >> angle on at least one angle, will not all my cuts that are up against my >> fence on the table saw be off? > >For "practical" purposes the 'factory' edges of sheet goods are considered >"square" ... and are generally "square enough" for woodworking purposes.

Unless one is buying seconds which have not been cut square; remember he said 2'x4' not 4'x8'.

Often, for utility projects, I buy from Shurway which sells seconds and trims. They have cuts in 2'x4' pieces which can easily fit in my Prius with the advantage I don't have solicit a pickup to haul it or to struggle with a large sheet of 3/4" plywood! If I use these for anything that matters, my wonderful (old-time and good quality) carpenter's square helps to ensure the wood is square.

Glenna

[Swingman]

You know, Glenna, sometimes you just have to give people the credit for having the ability to take one key bit of information of which they were not aware, then solving the remainder of their problem themselves.

Kindly "remember" I was SIMPLY imparting information, of which he may not have been aware, to an obvious newbie about "factory" edges on sheet goods.

Now, for all of you who think it is absolutely imperative to take it upon yourselves to qualify every little bit of posted information with exceptions and "what ifs", you tell me the last time you saw 2' x 4' sheet goods for retail SALE without at least TWO factory edges, whether it be "seconds" or not?

While not impossible in some flavors like BB, it is likely as rare as hen's teeth at most places a newbie is likely to shop.

.... _think_ about it.

[igor]

WHAT IF you want the ply heartwood? Don't they cut that from the center of the sheet? And, WHAT IF pigs had wings? Ha, got ya there! -- Igor

[Morris Dovey]

Er, while I know better than to jump into the middle of this one, I'll mention that my local discount lumber dealer whacks 4x8 sheet goods into 2x4 "Handy Panels". It's possible that they make one longitudinal cut and one transverse cut; but I'd be willing to offer odds that they make three transverse cuts - and that the center two panels have factory edges only on the 2' ends. Even when one of their 2x4 panels will fill my need, I still buy an entire 4x8 panel and cut it down myself to ensure squareness.

There've been a few times when I've found entire pallets of their

4x8 plywood off-square. I use plywood panels in fabrication of solar panels; and I learned early on (the hard way) to CNC cut /all four/ sides of each panel to ensure straight edges and square corners.

If it hasn't been a problem for you, that's great - but my experience leads me to believe that Glenna is wise to put a square to (at least) her seconds and trims whenever squareness matters.

[Swingman]

Now go back and read what I said about "at least TWO factory edges".

Now go back and read what I said about it being possible, but rarely being a problem.

One the issue of being "wise", here's another one to "qualify", "except", and "what if" on for awhile:

An experienced woodworker picks and chooses that material which saves him time and effort. IOW, if you need a factory corner because you don't know how to handle squaring your work, then for goodness sakes ONLY buy a 2 x 4 piece that has one!!

[Frank Ketchum]

I know exactly what you mean. I sit and shake my head sometimes when I read helpful "clarifications" that people add to other posts. It is usually something so patently obvious that it is a waste of everyone's time to read. I always think that if the op does not understand already these helpful points then they have far greater problems than the question they asked.

Frank

[Swingman]

AMEN, brother!!

[Morris Dovey]

Well, I never claimed to be wise. (-:

Well yes, your count was correct; but the more important point is that the center 2x4 pieces may not be anywhere near square at

*any* corner, even /with/ two factory edges.

You lost me there. Rarely a problem because [1] you have a supplier who reliably provides square goods, [2] rarely a problem because your usage isn't heavily dependent on squareness, or [3] rarely a problem because you nearly always check and correct any lack of squareness?

Only superficially true - and then only when cost is not a factor. Beginners *need* to learn how to square their work. In the real world, experienced woodworkers make cost trade-offs and nearly always find themselves jointing, ripping, resawing, thickness planing, etc. rather than spending the significant amount that it'd take to have suppliers perform those operations. I have a waist-high stack of rough sawn cherry in my shop in which I expect to invest more time and effort preparing for use than I will spend actually incorporating into projects - not because I'm inexperienced, but because I'd never be able to justify the cost of any other approach (not to mention that I'll enjoy every relaxing second of it!)

On the commercial production side, I buy solid (but unreliably sized and shaped) plywood because doing so provides a net production cost savings. I save about $7/sheet at the cost of approximately 133 seconds/sheet of additional CNC machine time. That savings works out to roughly $190/hour of machine time for those parts and so (in my shop) is a good trade-off; and it allows me to sell the finished product for less than I could otherwise - always a 'Good Thing'.

[Swingman]

LOL ... you're just trying to be funny now, right? :)

[Morris Dovey]

Partly yanking your chain - and partly pointing out that what you labeled exceptions, qualifications, and what-ifs are normal, fundamental, and quite real in other contexts that you seemed to have not considered.

[Lawrence Wasserman]

The 3 cut method might be used on MDF, OSB, particle board, etc. but for plywood, the only panels I've seen with the face grain running perpendicular to the long dimension were in the cull bins.

[Swingman]

Actually, the above bit of condescension is both unbecoming and misguided considering the following:

" ... sometimes you just have to give people the credit for having the ability to take one key bit of information of which they were not aware, then solving the remainder of their problem themselves."

Not a bad idea to keep in mind, _before_ you go pointing out what you erroneously think others "seemed to have not considered".

[Morris Dovey]

That's the way I think they /should/ be cut. Last time I was there (to dig through the so-called "select" SYP 1x6s) I passed by the stack of "handy panels" and the panel on the top of the pile was cut the other way. I wasn't curious enough and didn't have time to see if the whole pile was cut that way - and I wouldn't have noticed at all but for what struck me as the unreasonable cost charged to the consumer for the convenience of having the piece pre-cut to 2x4.

Normally when I buy plywood, I get fifty sheets at a time and have it delivered to the shop; but next time I'm back in that yard, I'll make a point of checking...