Machining MDF Raised Panels

Four out of four doctors agree: you can run MDF door panels in one pass on the shaper, if your cutters are sharp.January 2, 2014

This past summer I was contemplating the purchase of an Innovator head and thanks to some great advice from you guys and a small door job, I've finally picked one up. So now I want to see if I can learn anything new on how to go about machining the panels...

So here's my normal method. I'll set the shaper up with the head running over the work to ensure uniform tongue thickness. I drop the spindle speed down to something in the neighborhood of 4500 rpm's. I then run the whole batch of panels through, removing about 1/3 of the cut on all 4 edges. Then drop the cutter, re-run all the parts, and repeat a third time for the finish pass.

So it's a time consuming process to run them multiple times, but I feel it's too much material to run in a single pass. I'm wondering if there are any other techniques you use? Maybe bevel ripping most of the waste on the table saw first?

Also, last time I did raised panels I used Ultralight, as I had it on hand. Is this better than the normal stuff? Which version machines the best?

Forum Responses
(Architectural Woodworking Forum)
From contributor B:
For multiple passes on a raised panel, I get the cutter set so the tongue is correct, then simply move the fence to get your full cut. Start with a third or whatever.

They make a higher density MDF that machines better. I have used Plum Creek MDF for raised panels. The regular and especially the ultralight will have more porosity and not finish as smooth, maybe, as the denser.

From contributor P:
I second the double refined MDF for panels. What is the advantage with the Innovator Head?

From the original questioner:
I'm going to call my supplier and ask about the double refined version.

The Innovator head allows me to use off-the-shelf knives or custom knives in both HSS and carbide. For solid wood I've always felt HSS left a much better finish. It's also a significantly larger diameter than your off-the-shelf carbide tipped panel cutter, so should improve cut quality there.

From contributor J:
What am I missing here? With a proper shaper, proper tooling and a good feeder/hold down system, there is no reason why this should be more than 1 pass. 4 passes is insanity and if that's what you're doing and spending that much time, I personally would outsource. I guarantee you that door companies don't make more than one pass.

From contributor A:
We usually take either 2 passes on the shaper or 1 rough cut on the TS when using MDF for panels.

Contributor J's comment is valid for wood. Not many door companies use MDF. MDF dulls carbide pretty quick. I usually take a few minutes to rough them on the TS and it saves the shaper cutter carbide.

I nicked my finger on the table saw when roughing a few hundred panels (wainscoting). That dust is so slippery. Be careful. Put a wood guard over the exposed blade.

I second the double refined motion. It is most important when finishing. All of those crazy methods of sealing (bondo, joint compound, glue) really were to fill in the porous edge/face. Double refined is simply sanded to 220, pre-primed and sanded to 320, then prime the whole panel.

From the original questioner:
I can take pretty big cuts in solid wood, but taking a full pass, even in hardwoods, is a little more than I care to try. Especially the end grain which I often hand feed, as the panels are narrow.

I don't know if door companies are doing multiple passes, or if they even use 3/4" material? I do know that my doors are better quality than any door manufactured by a large plant.

I may try dropping one pass through the shaper and go to a 2 pass system. I'd like to keep it on the shaper, as I have a custom hood that captures a lot of that dust, which is probably the worst part of working with MDF!

From contributor M:
I'm with contributor J on this one. There is no way you can't run a MDF panel in one pass on your shaper, especially if you are using your Martin.

When I make doors I run mine with a 5/8" thick panel and still run those on my shaper in one pass. There is no doubt door companies do the same.

With a power feeder to hold the panel down and at least 7 1/2 hp, you will not have any issues. I've got 10 hp on my shaper and it doesn't even break a sweat.

From contributor M:
I meant to say when running 5/8" thick panels, they are solid wood as well as MDF. The MDF requires a lot less hp than solid wood.

10/25 #12: Machining MDF Raised Panels... ...
From contributor L:
The only time I run more than one pass is when the cutter is starting to dull and I need the panels now. Everything is run in a single pass. Not running a big shaper, 3HP Delta with a 3/4" spindle. Stop babying the machine. You bought it to do work. Make it work.

From contributor G:
How can you make money running 3 passes, then you still need to sand to the profile? I run MDF and hardwoods all the time with my rp heads and get about 400 panels before a cutter needs sharpened. Sanding profiles quickly with 200g. I believe a pass through the table saw is nothing more than a waste of time.

From the original questioner:
Okay, okay, lot of peer pressure building up here;>) I am running the Martin so power is not a problem. I worry more about the quality of the finished cut when trying to hog too much in a single pass. I'm not overly worried about making multiple passes when I do raised panels, as they are so rare for me to make! This will be my second set, and I'm pretty certain last set, for this year! I guess this time I'll try running them through in a single pass and see what happens... and adjust if necessary.

From contributor D:
Real men shape both sides of a raised panel (passage door) in one pass.

But seriously, larger door shops will do all panel raising with a single or double end tenoner - top and bottom all at once. This keeps the tongue accurate, among other things. I have often wanted 10hp so I could run two Innovators at once and fly through a stack of panels. But nowadays, I only do 2 to 12 at a time, so maximum efficiency is not so crucial. I also cannot imagine what a failure would be with two Innovators spinning.

With my 7.5 hp SCMI and a single Innovator (correct - I am not a real man), I will typically remove a hip or ogee raise one side that is 2" wide and tapers to 5/8" or so - running the cutter from above. If everything is sharp, I'll do so in one pass. If things are narrow or dull, I'll cut 95% on one pass, then a second pass just cleaning up.

Personally, I draw the line at MDF. Ran a job of those panels once, 22 years ago, and I still find some of that nasty dust in a back corner every now and then. Nasty - and slippery!

From the original questioner:
Now I feel pretty foolish! So I set up the Innovator with it's nice new sharp carbide blades, and set up the shaper for a full pass. So for the setup I'm just going to run the panel by hand a little, check the fit, adjust, run a little more, check the fit, repeat as needed. I'm figuring it's going to be a pretty heavy cut based on my last few experiences running panels. The stuff slid right through and cut like butter! Not only did it cut easily, the finish was much better than what I'm used to getting!

So, looks like maybe my old raised panel cutters maybe needed to be sharpened a bit. I guess I just assumed I was taking too big a bite in the panels in the past, instead of realizing the carbide must be really dull! And unlike HSS, it's hard to judge the sharpness of the carbide, at least for me! So you guys were right, and I am once again humbled by how little I really do know about this silly craft I'm involved in.

From the original questioner:
I never claimed to be a real man! I sometimes watch YouTube vids of guys running old equipment like squarehead molders, or old flat belt driven equipment and realize how squeamish I really am!

I was even nervous running the Innovator at first, with the way you have to set the carbide knives within the backers and get everything flushed. I stood behind the machine when I first fired it up.

This job doesn't require the bottom cutter as the panels stand proud. I believe the proper terminology is fielded and raised panels? I don't mind the MDF much, as I built a surround to direct most of the dust right into the collection hose. The benefits of being able to use a little glue on assembly and not having to worry about movement makes MDF a first choice for paint grade for me.

From contributor L:
Whenever I change my jointer or planer knives, right after I power up the machine, I back away 3 or 4 full steps. Just don't need to take the chance. I'd rather not be a man than be a man with a knife embedded in him.

When you take a light pass off MDF, it will usually fuzz up more than the single pass. Plus every pass you make dulls the carbide that much more, so the less passes you make, the more machining you will get out of a particular cutter.

And another thing, I have a cutter for MDF and solid wood. As far as I am concerned, as soon as you run the MDF, the cutter is no good for solid, as it really takes the edge off fast.

From contributor D:
Well, it is good that you found out the MDF was so easy to run in one pass. Your masculinity may not be called into question just yet.

The big Tegle and Sonner shaper I learned on always had a nice hefty chunk of 8/4 that was used to put between the spindle and the operator on start up. We used mostly hand ground lock edge loose knives (shaper steel), so it was good insurance from flying knives. This machine was also built a bit low, so the 8/4 helped ensure we all stayed real men, considering the exposure.