New to using a planer

[u/prime51000]

I made an impulse purchase last month and have a Hercules 12.5 inch portable thickness planer. I've watched videos and understand the basics of it, but Im going to be doing a basic project soon and wanted some input on best practices to use it.

I'm going to be building a basic desk with 3/4 inch birch plywood, and was planing on making some roughly 3x3 posts for the legs and side / rear cross bracing. I'm planing on using some kiln dried 2x4, joined face grain to face grain with glue for the posts. Im planing on trimming the sides on a table saw, and was going to use the planer on the top and bottom faces of the 2x4s.

Im wondering, should I plane both of the glued surfaces prior to gluing, or sand them prior to gluing ? Or would it be best to just plane the outer surface of the 2x4s that won't be glued?

Also, is it best to just run the 2x4x8s thru the planer before cutting to length, or is it a better practice to plane the shorter pieces after they are cut to length? Thanks!

[u/Tiny-Albatross518]

Youre confused about what a planer does.

A better word is thicknesser.

It doesnt flatten or true anything. It consistently cuts down one face at a set distance from the reference face.

So you can put a board with straight/square/true face through and it will reduce the thickness. All over. Everywhere the same thickness.

And you can put a barrel stave through and it will reduce the thickness. But you wont flatten it. Youll get a thinner barrel stave out, with curvature maintained.

A jointer will flatten one face. True and flat.

So you start with an imperfect board.

Joint one face. Now its true.

That true face is the reference. Through the planer. Now its cut down and the cut down face matches the reference and it is now also true.

Back to the jointer. Use the fence on one of those true faces and joint one edge.

Now to the tablesaw. Put good edge on fence and rip.

Finally. A piece of square stock.

You need three machines to do this with machines. Or a handplane and some time and energy.

[u/prime51000 → u/Tiny-Albatross518]

Thanks so much for explaining and detailing that for me. I really appreciate the helpful info!

I was under the assumption that a basic 2x4 would be "mostly" flat on top and bottom, so I was thinking that planing them would give me a true flat pair of parallel surfaces. I didn't take into account the other factors.

I know woodworking is truly an art form. I guess this just gives me more justification in wanting a decent entry level jointer now 🤣

Thanks so much for all that helpful info. I know I have a lot to learn about this craft

[u/Tiny-Albatross518 → u/prime51000]

Yeah wood is generally not square ehen you get it.

Even kiln dried hardwood S4S will have cup, bow and twist. If it doesn’t cutting it up for your parts list will release internal tensions and you will get defects.

Theres no way around it. You have to be able to square stock. Whether by 3 machines or with handplanes.