Knocking off the edge of MDF trim

[Robbie H]

Hey everyone, brand new to this forum, excited to hear responses. I am making MDF “farmhouse” or craftsman style trim for all baseboards, door casings, shiplap, etc. for my house...it’s a lot. All of that to ask, I am wondering about anyone’s experience in knocking off edges for this much material. I don’t want a significant round over since we are going with a more shaker style, but for painting, it might be best to take a small amount. Sandpaper seems like too much work for this much material, as does using a plane. I have a great router table, but I’m wondering if I even need to do this (knock off the edges) or will the paint hold better than I expect? Any experience or advise here is appreciated.

[Chestnut]

trim router with a bearing guide would be the easiest. When I did trim for my previous house that's what i did. Another option could be a few quick swipes with a block plane.

I'd take the tool to the wood not the other way around. For the length and amount of material for trim it'd be more work on a router table than having the bit in a handheld router. They make some really small round over radius bits. I think i have one that is 1/16th" radius.

[Robbie H]

Thanks for the advice. Thinking of planing what is 66 sheets of MDF cut into trim makes me tired! Ha!

[Chestnut]

5 minutes ago, Robbie H said:

Thanks for the advice. Thinking of planing what is 66 sheets of MDF cut into trim makes me tired! Ha!

Thinking of painting that much trim is giving me daytime nightmares..... i did around 450 LF of mdf trim ... never again. I'll nail up oak before I'll do MDF again. It did look nice though.

[Chet]

I think Drew has you on the right path with a small trim router.  Even if you don't presently own one it would be worth the purchase.  Small price to pay for the time savings and you will find it useful down the road, I am sure.

Welcome to the forums Robbie.

[..Kev]

I'd also be spraying that much trim before installing!  Easy to come back and touch up.

[Brendon_t]

I think @Chestnut is on the right path there. And to tag onto it, for that many feet, not only bringing the tool to the work but also batching out operations will be a huge Time saver. 

I hope you're planning to spray the paint. That much rolling would probably give me an aneurysm 

[drzaius]

I can speak as a bit of an authority cause when I was younger & dumber I made all the base, door & window trim for my 2800 sq ft house what has 33 doors & 13 large windows. I have no idea how many lineal feet that is, but it's a lot. I used 5 x 10 x 3/4" MDF sheets. I now have a special hatred for the stuff.

The guys are right about taking a small router to the wood, unless you have the room to set up long in feed & out feed extensions for your router table. The advantage to the router table is that you can get almost 100% dust collection & MDF dust is just about the worst there is. I remember being literally ankle deep in MDF dust in the living room/millwork shop & it was hell. I was taking off a 1/2" round over though & it sounds like you just want to break the edge. 1/16" round over should be plenty.

Pay attention to what kind/brand of MDF you buy cause the quality varies wildly & that's not hyperbole. Most of the stuff from the big box stores is very weak, splits on the edges if you look at it wrong, disintegrates into fuzz if the corners are bumped, & soaks up moisture like a sponge. I'm currently building a big subwoofer cabinet & I'm using water resistant MDF (Medex). I'm not going to say I like it, because it's still MDF, but it's worlds ahead of the cheap stuff. A lot stronger & the edges are not nearly as fragile. It isn't actually that much more expensive.

Spraying is a great idea, but it's a good idea to preprime the edges with a glue size cause they can soak up a ton of paint before they will look good.

And welcome to the forum.

[Tpt life]

I am struggling to understand if you are wanting to do more than ease edges. Easing edges for painting is super simple and quick for MDF by hand with a sanding sponge. You barely need to remove anything, just the “sharp.” MDF sucks paint in so coverage is not an issue. The fragile edge might be a concern with rough handling, but not installed. If you truly want a round profile, then the guys are right. If not, the power tool is noisy and sometimes more of a hassle. 

[Robbie H]

2 hours ago, ..Kev said:

I'd also be spraying that much trim before installing!  Easy to come back and touch up.

Yessir! You can bet on that!

[Robbie H]

1 hour ago, drzaius said:

I can speak as a bit of an authority cause when I was younger & dumber I made all the base, door & window trim for my 2800 sq ft house what has 33 doors & 13 large windows. I have no idea how many lineal feet that is, but it's a lot. I used 5 x 10 x 3/4" MDF sheets. I now have a special hatred for the stuff.

The guys are right about taking a small router to the wood, unless you have the room to set up long in feed & out feed extensions for your router table. The advantage to the router table is that you can get almost 100% dust collection & MDF dust is just about the worst there is. I remember being literally ankle deep in MDF dust in the living room/millwork shop & it was hell. I was taking off a 1/2" round over though & it sounds like you just want to break the edge. 1/16" round over should be plenty.

Pay attention to what kind/brand of MDF you buy cause the quality varies wildly & that's not hyperbole. Most of the stuff from the big box stores is very weak, splits on the edges if you look at it wrong, disintegrates into fuzz if the corners are bumped, & soaks up moisture like a sponge. I'm currently building a big subwoofer cabinet & I'm using water resistant MDF (Medex). I'm not going to say I like it, because it's still MDF, but it's worlds ahead of the cheap stuff. A lot stronger & the edges are not nearly as fragile. It isn't actually that much more expensive.

Spraying is a great idea, but it's a good idea to preprime the edges with a glue size cause they can soak up a ton of paint before they will look good.

And welcome to the forum.

Great advice. I actually am using Medex because some applications will be in wet areas. I read a good bit and it does look like a better MDF.

[Robbie H]

30 minutes ago, Tpt life said:

I am struggling to understand if you are wanting to do more than ease edges. Easing edges for painting is super simple and quick for MDF by hand with a sanding sponge. You barely need to remove anything, just the “sharp.” MDF sucks paint in so coverage is not an issue. The fragile edge might be a concern with rough handling, but not installed. If you truly want a round profile, then the guys are right. If not, the power tool is noisy and sometimes more of a hassle. 

Only easing the edges. But with all trim, door casing and shiplap going into for a 3,400 sf house, that’s a lot of sanding...maybe it’s the easier route!

[wdwerker]

You definitly want to use the absolute best blade you have to rip the trim. Spend the money for quality dense MDF, not the home center crap. Pre prime or glue size the edges before you sand. Then look at sanding mops.  120 grit will be good for what you are doing. A corded drill will run it just fine.

https://www.ptreeusa.com/abrasive_sanding_mops.html

[Robbie H]

Grateful for all of the responses. Thanks everyone!

[VizslaDad]

I thought this was an interesting approach to edge treatment, especially if you have to run a ton.

[Tom King]

I know this thread has some age on it, but we just did this last week.  I spray it with oil based primer first, and edges are hit with sanding sponges after being hardened by the thinned down primer.   I keep a cheap HVLP sprayer just for this primer.   It never gets taken apart for cleaning, but just run some thinner though it.

The primer has to be thinned a lot, but I don't bother to measure it.  The thinner it is, the more the edges soak up, and make sanding easy.  In the picture, I'm mainly watching how much the edge takes, and the flat surface gets covered in the process of spraying both edges.  It'll sand perfectly flat on top easily.  Thanks for your concern about no respirator, but that's one reason this job waits for the right day.

We spray it outside, on a light wind (needs to be enough to blow overspray away), Sunny day, the next day after a rain (to keep dust down).  The Sun and wind dry it in a hurry, so we do the sanding outside on the same windy day.  It's wiped down with damp rags to get loose dust off, after blowing with compressed air.

The flat surfaces get sanded at the same time.   The primer sands so easily, that it only needs a pass in one direction, and then back once, and done with 150 and sanding block.

This was for one of my beaded board ceilings, with MDF boards to cover joints.   Paint is left off plywood ends because boards to cover joints will mostly be held on with Powergrab, and very few nails-maybe three per board to ease sanding effort after it's up.

Once installed, it'll get sprayed with an airless sprayer.

edited to add:   I forgot how it applies to the original question here.   We use fine sanding sponges to quickly knock off the sharp edges.  They sand easier after being hardened a little with the thinned primer, that has soaked in some, and that's plenty to allow paint to turn the corner without separating.

 

[Chestnut]

Looks nice. I suppose you don't need the most fancy sprayer in the world when you are sanding down and covering things up again.

[Tom King]

A good sprayer does the finish work.   It doesn't matter much for the primer, and I don't want to put anything but water based, or bourne stuff through the airless rig. It's too much trouble to clean it with solvents.  That sort of primer is all that ever goes through that cheap HVLP sprayer, and it's not good for much else anyway.  I expected it to die long ago, but it keeps on working.  It's the cheapest one that Wagner sold maybe a couple of decades ago.

[drzaius]

If you don't mind, I think we'd all enjoy seen photos of the finished project.