Jared and Dave - Thanks so much for your response. Just noticed the mdf on Home Depot for delivery. Was hoping to get 4x8 sheet but may have to settle for 2x4 piece.

Again - much appreciated.

If your doors are paint grade and there is no spec' for woodgrain showing through the finish (MDF panel will be smooth rails and stiles will likely show some grain (because they are wood) then MDF is fine. Adjust your m&t accordingly for the material you have available.

If you are spec'd for wood grain then ply would be best. If its your own home, you will meet some sarcasm in that the hope is this forum is met with people who are tasked with doing these things for profit.

It pretty much boils down to are you burrying all the wood grain under the finish? Or are you looking for some semblance of the door construction to appear as wood? If your trying to make it look like the hood of a corvette the heck with wood and go with machined MDF doors? Skip the maple/poplar all together?

Mark B. Thanks for the advice. Helps a lot. Intent is to paint everything so I may go with mdf for rails stiles and insert.

I use 3/8" MDF and run it through my panel cutter so it has a 1/4" tongue which fits the slot nicely. Gives the door a bit more heft and if you knock on it, it doesn't sound cheap.

Lots of folks here are heading you in the right direction.
If you are able to match your panel thickness to the dato in your stiles you can use what ever material you want.
Like Mark said some finish schedules turn out better on certain types of material.
Generally mdf is a lot smoother than wood grain, so certain spray finishes will appear nicer on the smoother material.
Choosing your material carefully and good sanding will most often produce good results.
A rule of thumb for sheet goods is that plywood core with a veneer outside will be the most wavey, particle core with veneer will be a lot flatter and mdf will be the flattest, you will also get a little more variance in thickness on ply’d core. Some off shore ply may even make you want to pull your hair out.
Poplar and maple both have a tight grain so will turn out nice.
You will need a cnc and the proper tooling to build a one piece MDF shaker looking door.

Yes, the inauguration had a positive effect on me. I am still nearly giddy.

And feeling magnanimous, I will agree to the controversy over the circular saw’s invention. I never knew.....

But, as a sidebar on Wikipedia, the discussion about Sister Tabitha watching wasted motion as “2 men operated a whipsaw” comes into question. This shows how far removed most of us are from basic work.

A two man saw requires each man pull while the other man merely follow, then pull when his cohort reaches the end of his stroke. The saw cuts in either direction, but only as one man pulls. Pushing by anyone stops all progress. Anyone that has tried using such a saw figures this out very fast.

The story as I heard it is that while said Tabitha was watching the operation of a new sash saw, she mentioned half the time and effort were wasted. A sash saw, typically water powered, used a straight saw blade that cut on the down stroke. The saw then stopped and reversed the movement until it could be sent back down again. Upon reflection, Sister T came up with the idea of “chisels on a wheel” or the circular saw.

If nothing else, this is a better legacy than lending their name to the pursuit and manufacture of what most hope to be the cheapest cabinet door.

Don’t use poplar. It moves around with the temp/humidity. It’s not an inherently stable wood. It grows like a weed. Looks like a purple & green weed. Has the stability of a weed.

It’s good for trim and things like wainscoting that are fastened to a wall.

Soft maple has been or standard for 40 years. Maple is even better but costs more.

As Leo noted 3/8” reduced to a 1/4 tongue by back cutting with a router or shaper. It can also be done easily with a dado set in the table saw.

Mdf is better because it’s cheaper, heavier & paints better than decent 1/2” cabinet ply.

You can glue the panels into the frames with regular wood glue.

Adam,
How come you glue the panels to the stiles and rails? I figured the stiles and rails would move a lot more than the mdf panel?

I am with Leo on using 3/8 MDF and dado the back to fit the groove. I build kitchens but the MDF at the big box stores in my area are of a much lessor density in the sheets sold by big box stores. This comes very obvious when you paint machined surfaces of the cheap MDF. It absorbs paint like a sponge. I use maple for my rails and styles. Good luck with you journey

We glue the panels (cabinet ply or mdf) into the stiles and rails to prevent movement of the panel. Movement causes the paint to crack. It also keeps the panel from rattling & centered. We are not talking about a messy glue job. Little cleanup.

This should not be done with solid wood.

"I figured the stiles and rails would move a lot more than the mdf panel?"

This statement is worth dissecting.

Solid wood stiles and rails can move, and will move if the conditions are right. But how much can a 2" wide stile move? It won't change in length since wood does not change in length.

The MDF panel will not change in dimension with the MC range we normally see in normal conditions.

Let's use Red Maple as an example. The Shrinkulator wants initial RH and ending RH. We will assume your shop is fairly dry, say 15%RH, and the lumber will arrive at 6-8%. You build the cabinets and ship them to the jobsite.

The end of the project and the completed house will be 30% RH. This will cause wood 'movement' of .020". Twenty hundredths. One-third of one-sixteenth of an inch. Not much.

So the movement in the stiles and rails will be very little - a door could grow by as much as 0.040" This will matter to the inset doors people, but is not much of a factor because the guys that do inset know how much to figure for clearance when a door is inset.

Will the 0.040" potential gain in door width make problems for your project? Remember: wood moves only as a result of a change in Moisture Content.

David,
Thanks for the great description and explanation of the shrinkage. It was very helpful, I wish I had your knowledge when working with solid wood.

just FYI .020" is actually 20 thousandths not 20 hundredths . I have never thought it a good idea to glue any panel inside the door frames. We typically use the space balls or similar spacing to allow for movement or expansion/contraction. The balls also keep the panel centered inside the frame. Some people do not like the space balls there are other alternatives for the same function. We typically do this regardless of the door material because it works either way.

Shaker door panels are usually made thicker and rabbeted out from the back to be just below flush with the back of the door. The thicker panel makes for a more solid feeling substantial door as stated before. 1/4" panels is not the best idea. Good luck with your build.

I did not watch the inauguration. Did not have the stomach for it I guess.... ;)

Thank you, Peter, for correcting my error on hundredths/thousandths. You have it right.

Those nuns beat it into me "tenths, hundredths, thousandths, then Angel Hair." Some things you can never change, no matter how hard you try.

One of the things about painted doors that annoys me is the cracking at the panel and the stile/rail joints.

If we make them ourselves, using plenty of glue(TB1) on the wood joints and glueing the mdf panel in there is effectively zero cracking.

I’ve read many many threads in the finishing forum about caulking doors. It is simply not necessary if you make really good doors.