Cutting Down 4′ x 8′ Sheets of Ply

Cutting a 4-foot by 8-foot sheet of plywood to fit in your laser can be daunting, especially if you don’t have the best tools for the job. Luckily, most big-box stores (Home Depot/Lowes/etc…) can do this for you. Here I’ll discuss the best way to accomplish this at the store and we’ll use Home Depot as an example.

A panel saw is a vertical saw that allows you to cut large stock such as a 4 foot by 8 foot piece of lumber.  The photo above is a typical one and, as stated, most lumber stores will have one on hand.  These can also be purchased or “made” (usually as kits) for the home shop.

Attitude is Everything

When approaching an employee to cut your wood, be sure to maintain a friendly and patient attitude.  Although they are “supposed to” help you, they may be picky about what they will or will not do for you based on their interpretation of what’s allowed.  It helps to try to maintain a relationship with the same person(s) who use this saw as they see you coming and know what you will want.

“We don’t do project cuts”

I hear this occasionally.  Because they do not wish to try to be precise and held accountable if the wood is not cut within tolerance, the stores typically do not guarantee any kind of accuracy.  This is fine.  Our laser stock has quite a bit of margin so being off up to 1/2 inch is no big deal.  Tell them this and tell them it does not have to be very accurate at all.  This will generally get you past this hurdle.

On to the actual cuts

The rest of this post will deal with how to cut the wood with a couple diagrams and tips you can show the person doing the cutting.  All-in-all, this process should take about 7 minutes at the panel saw. The Glowforge has a bed that is 12″ x 20″ but, in reality, it can only cut 10.96″ x 19.5″ which leaves a fairly good margin on a 12″x20″ stock.  The goal here is to maximize the use of that 4’x8′ piece of lumber.  Done correctly, you can get 20 pieces of good laser stock from a single sheet.  So, let’s continue…  

To optimize the use of this stock, you can follow the diagram above.  Typically, you would want to cut vertically, then lay the pieces on their side and cut the remainder vertically as well.  Note that we are shooting to end up with 12″ by 19.2″ pieces but with kerf, they will be slightly smaller. What is kerf? Kerf is the term used to identify the amount of material lost when cutting.  In this case it refers to the width of the sawblade.  In this case, it is negligible and not a concern in this process.

19.2″??

Once in a while, as soon as you mention a cut of 19.2″, they will balk and start the “project cut” argument.  Again, this is only an approximate cut and does not need to be accurate.  However, it is quite satisfying when they do cut good 19.2″ strips and you end up with 5 equally wide pieces of wood to start with!  One way to make this measurement easier is to use the Tape Measure Trick, read below:

The tape measure trick

Nearly all tape measures have a black diamond mark at regular intervals to help construction workers lay down joists.  These marks are at, you guessed it, 19.2″.

You can use this to easily mark all the 19.2″ cut locations on your stock.

Rotate and continue

Once you have made the initial vertical cuts, you can stack the 5 pieces and rotate them 90 degrees (on their side) and make the three 12″ cuts in one go.  If you purchase the Home Depot “1/4″ birch ply it is actually 0.20″ thick.  A stack of 5 of this is 1” thick which is usually the maximum thickness they will cut.  They will, sometimes, argue about making stacked cuts like this but it will only increase the amount of work necessary to make your stock.

7 total cuts

If done correctly, the total number of cuts needed for a single 4’x8′ sheet is seven.   If you cut more than one sheet at a time this count goes up but not in increments of 7 as you can stack your cuts to reduce the amount of work.

Cheat Sheet

The image below is a single-page cheat sheet that you can provide to the employees (or whoever is cutting your wood) to help simplify the explanation of your cuts.

You may also download a PDF version of this sheet below:

cutTemplate.pdf

More tips

Make your mark

If you go to the same stores regularly, you may ask if you can make a mark on the saw with a marker to make finding that 19.2″ size easier.  I have never had anyone turn me down for this as it makes those initial cuts go much easier.

Use a bumper

If you can find a scrap piece of wood and a clamp, clamping the wood to the saw at the 19.2″ mark will also speed things along as they can simply slide the wood to this “bumper” and make cut after cut.  Really speeds things up!

Don’t make the 12″ cut

While it is great to have wood that is max-width for your machine (19.2″) it is not always necessary to have a solid 12″ high piece.  You can leave off making the 12″ cut and just bring home the 19.2″ strips.  This way you can cut to as you need if you have the necessary equipment at hand to do it (namely a table saw).

I do this myself and store the wood in a small cubby to cut down as I need it.

Store it flat!

This plywood is typically made of a junk core sandwiched between your desired wood and a piece of scrap material.  Because the “front” and “back” of the wood are different types of wood and densities, the stock tends to warp if not stored properly.  Keep your wood stored horizontally (seen above).  Even put something heavy and flat on the stack to help avoid the warping.

Conclusion

Acquiring materials for your projects inexpensively can be difficult.  There are a lot of choices out there for acrylic, wood, mdf, and other materials and many, many vendors.  However, the wood you can find in large sheets at your local stores can make some really beautiful products and cut the cost of materials to a third of that from any of those other sources.  Of course if you need special material or something you simply cannot find locally, you do not have much choice. By using the tips above you may realize you can find local materials of various types and not only save on these costs but also acquire the materials much faster!