I'm putting in new interior doors in my house and now I'm starting to trim the doors. I cut a few pieces to 45 degrees and they seem to fit together well, but I've never done this before, so I need validation :-) Is this joint good or can it be improved? The molding is pre-primed MDF and I plan to spray paint it after I have all the pieces ready. I think that the line should be almost unnoticeable after painting. I could even touch up the joint with some paint after installation to make it even less visible, if necessary. The slight gap on top can probably be closed by putting in a brad nail from the top. What do you think - good, OK or bad?

 

I'd check your saw and cutting technique. MDF can flex and squirm during cutting, more than solid wood. Clamping close to the cut might help.

Cut two pieces of hardwood and see if they exhibit the same gap. If so, saw needs adjustment.

Yes, the joint could be a bit better but it isn't bad!

 

Looks like that old crack in the upper right hand corner could be kicking your top piece out just a tad, so, if you haven't, you might try working it down a bit. Otherwise, as Gunguy said, it isn't bad. Keep your saw table dusted off, so you don't get a build up behind the stock, and, if you have closet interiors to do, that's not a bad place to start, until you work the bugs out. To Gunguy's point, saws need to be checked periodically for proper alighnment, etc., and, if you're using the blade that came with the saw, it might be worth considering a new one, because they don't always put the best blades on them at the factory.

 

It looks good, but would probably be better if you had a better blade. All the microchips along the edges of the miter tell me that the blade is vibrating as you cut, either as you cut down or as you bring the saw back up. A better trim blade won't do that. Course it could be the saw too.

Cut slowly. Then after a cut, leave the saw down until it stops spinning. You should also be gluing those miters together. Titebond makes a moulding glue thats nice and thick and after you wipe it down with a damp rag, it works good as a filler. You should note that nailing the corners together will sometimes split the MDF. It doesn't like being nailed that direction. You are right that it will look good after it's painted.

 

Only if you caulk it Paint alone will never fill a crack. Siliconized acrylic latex caulk forced into the crack with the excess wiped off will make the joint disappear. I couldn't begin to count the number of joints I've caulked that were bigger/worse than those and made them disappear.

If you spray the woodwork you'll need to do an extra neat job of puttying the nail holes. Sprayed enamel will accentuate any flaws in the woodwork while brushing can hide minor flaws.

 

Three cheers for Marksr as caulk is the only way to close the gap in a PFJ/MDF installation. Very curious as to why the OP would want to spray the trim? Makes no sense, as the amount of masking that would have to take place would more than chew up time involved to brush on two coats.

 

Ever used Titebond moulding/trim glue?

 

The trim need to be installed by installing the top piece first.
Then the sides.
You have no nails in the top or side of the trim where the two pieces meet that needed to be first to draw them together.
Then you install a nail about 6" down into the jamb.
That joint has to be nailed tight before working on nailing down the sides.
You only need 3/16 exposure on the jamb. To much and there's not enough left to nail to.
Looks like you used a blob of caulking to fill the nail holes. Using painters putty, or fast and final patching compound will not shrink or leave that mess on the surface.
Those flaws in old paint and drywall should have been addressed before installing the casing.

 

If you look at the picture there are clamps holding the short pieces of trim which are test pieces. The MDF probably came that way, preprimed. Always scuff sand it before painting with 150 grit or similar. (3M sandblaster sanding sponge works best on that profile)

 

Thanks for your feedback guys! It's very helpful.

To clarify, I have not installed or nailed any pieces yet. I just cut the top piece and clamped down two scrap pieces on the sides to see how things fit roughly. When I start installing, I will nail the top first and I will glue the pieces together as I go, but right now I simply want to get the best fit possible - baby steps. Glue and caulk suggestions in this thread will come in handy later. Also, I am not going to spray paint the trim in place. The plan is to measure and cut all the pieces, then spray them elsewhere. I am casing 6 new doors, so spraying instead of brushing should save me some time and will look better. And finally, I am using spackle to cover nail holes. It seems to work OK, but isn't the easiest thing to cover up.

I'm using my father's miter saw (photo 1). It has a 40 tooth 10" blade - probably original equipment. It's a safe bet that the saw has never been checked for alignment. I'll try to figure out how to align it. I found a 60 tooth blade laying around in my garage, left by a previous home owner (photo 2). I may try using this blade to lessen the chipping.

I tried the cutting techniques you guys suggested - clean the work area, cut slowly, then stop while the blade is still down. I still got about the same amount of chipping (photo 3).

I also cut two pieces of scrap laminate at opposite 45 degree angles. They exhibit the same chipping and the same "veer" on top right (photo 4). Does that mean that the saw blade is not aligned correctly?

 

Oh...wow...for trim you need a 60-80 tooth carbide blade. New blade is a must.

 

So this other 60-tooth blade I found might work? And what about alignment? Is it possible to tell if the blade is misaligned from the experiments that I did?

 

The blade that's on the saw now is a 40 tooth carbide, suitable for rough cuts. The other blade you have pictured is a Dewalt 10" 60 tooth "fine crosscut" blade, which- if it's sharp- will do a better job of cutting than the other one. It's no 80 tooth, but it's better. As mentioned, an 80 tooth will give you the best cut.

The saw... well, that could be the other part of the problem. Once you change blades you will have a better idea of how it performs. A $99 saw isn't going to give you the same results as a $599 saw, so don't expect perfection from your dad's saw. You could buy an 80 tooth blade and have the same/similar results if the saw has a vibration. You're doing paint-grade work which is the most forgiving, so I wouldn't sweat it too much. If you were nailing together those sample pieces that are pictured on the bottom- all stained and finished wood... those joints might not be acceptable. Just depends how picky you are.

The "veer" can be from a dull blade... or it could be the saw. When cutting, if the saw has to labor to get through a cut, it will usually push the blade to one side or cause it to vibrate. The hinge of the saw could be a bit loose as well. If you can see or feel any wiggle in the saw and can wiggle it either left or right as you operate the saw up and down, then it's not really tight enough to do fine work. Like I mentioned, your more expensive saws will just be of better quality and have tighter tolerances. But don't sweat it, I think those miters will paint up just fine once you glue and/or caulk and paint them.

 

It would be better to use painter's putty. Spackling needs primer and is more apt to be knocked out of the hole if the woodwork gets any abuse. Prepainting the trim before installation can save some time but you still need to apply the finish coat after the woodwork is nailed up. That allows you to cover the putty and caulk with paint plus take care of any minor damage done to the paint during installation.

What paint will you be using? what kind of spray equipment do you have?

 

Laminate flooring can not be installed on a 45 like that.

 

Pre-painting may or may not save you some time. After the trim is installed, you have to caulk all areas where two pieces of wood meet. If you look at the closeup of the trim samples in place you will see a ton of lines that need caulking. You will have to run a full coat of paint after caulking to blend the caulk with paint and mask the painters putty in the nail holes.

If you have stain grade trim that you decide to paint and you have to prime it first, then pre-painting before it is installed of the prime and one top coat can be a time saver. But the finish coat is always done after the installation.

 

Getting back to the original question, your crack is no more or less than that of the factory window trim, which you will need to caulk anyway (or painter's putty), so I say you should be just about through by now. Never cut laminate from the top. Always cut from the bottom, then kiss the blade goodbye for any other fine work. Laminate and trim aren't uttered in the same blade breath.

 

I replaced the 40-tooth blade with the 60-tooth one. It seems to cause the same amount or maybe slightly less chipping. I also sawed through a 2x4 to check bevel alignment. I was cutting slowly, but about half way through there was a lot of smoke and I had to stop. Does that mean that the blade is dull? Anyway, it works OK on my MDF trim. It looks like a new 80T blade is about $50, so I decided to make do with what I have and use caulk to cover up any imperfections, as some of you suggested.

Now I have a few questions about the other topics that were brought up.

Glue
XSleeper, are you saying that Titebond trim glue is thick enough to fill gaps and eliminate the need for caulking? Is it better than other variations of Titebond wood glue or other brands of wood glue?

Caulk
I have a tube of caulk shown in the photo below. Will this type of caulk work well for filling the gaps?



Covering nail holes
When I search for painter's putty on Home Depot web site only one result comes up and it has 2/5 stars rating. I think that people who gave the product low ratings didn't apply it correctly, though. Will this work? Also, I haven't used my brad nailer yet, but from what I understand the nail holes are really small. Can this putty be used to fill such small nail holes?

DAP 16-oz. White Painter's Putty 53-12242 at The Home Depot

Painting
I'm not planning on repainting everything in place. I'm just going to spot paint puttied and caulked areas. I figure that if I use the same paint, maybe with some Floetrol to minimize brush stroke marks, small patches should blend in. Although it says on Floetrol bottle that it may reduce the sheen of paint, so I'm not sure about using it. I'm using Olympic One "Paint + Primer in One" satin enamel from Lowe's. My sprayer is Graco Spray Station 2900 turbine driven HVLP. This sprayer has worked great for me so far.

 

If the blade smokes, yes its dull.

The Titebond moulding & trim glue is thick, not runny and is a good filler for cracks like what you will normally have at a miter. If you fill every miter and wipe the excess with a wet rag, yes it will take the place of caulking those miters. It's the best glue to use for paint grade MDF, IMO. But you will still have to caulk any LARGE gaps, along with all the edges where your trim meets the jambs and wall.

As mentioned by the others, you will have to recoat everything with one final coat after your nail holes are filled with the painters putty. Touchups will be obvious as brush strokes in the paint sheen. You may even find that the painters putty takes 2 coats to completely cover.

The brad nails will occasionally blow some of the surrounding primered MDF surface away from around the nail head, making it a little larger than you think sometimes. You generally want to lightly scuff sand after the nail holes are filled to smooth and remove any loose debris, but since the trim will be prepainted, you may want to use a tack cloth instead. The nail putty in those nail holes needs to be rubbed perfectly smooth prior to paint. I'm not a big fan of DAP Alex, I usually use the White Lightning.

 

I also prefer the 'white lightning' brand of caulk. The main thing is for the caulk to be a siliconized acrylic latex caulk [not to be confused with silicone caulk] A damp rag/sponge can be helpful for smoothing the caulk ..... and helps keep your fingers cleaner

I prefer to use SWP's 66 Glazing instead of regular painter's putty because it's not as oily but the product you linked will work. You'll probably need to take some out of the can and roll it around in a dry rag to remove some of the excess oil [years ago we added 'whiting' to dry it out]. The correct way to putty the holes is to push and twist the putty into the hole and then level it out with your putty knife, I normally just use the side of my thumb as it's usually just as effective and quicker. The oilier the putty is, the more apt it is to need a primer to keep the oils in the putty from bleeding thru latex paint [not an issue with the old oil base enamels]

As noted above - enamels don't touch up well! Plan on applying the final coat after installation. It's not just brush marks versus sprayed. Paint touch ups always show under the right conditions. Flat paint touch ups have to have the right angle of sight and lighting to be seen but the more sheen a paint has, the easier it is to spot the touch up.

 

You can probably find a blade much cheaper than $50. Everyone (esp the Pro's) has a favorite brand, but there's no need to spend more than about $20-25 unless you are doing it for a living. HD normally has DeWalt 2 packs, one fine and one coarse, for around $40. Or you can buy a single Oldham or Avanti for 1/2 that. Not as nice as a Diablo or Makita...but they get the job done.

 

marksr, what is "SWP's 66 Glazing"? Does SW stand for Sherwin-Williams? Is this the product?

Glazing Compound - Homeowners - Sherwin-Williams

Gunguy45, I can't find an 10 inch 80 tooth miter saw blade on Home Depot or Lowe's or OSH or Ace web sites for $20-25. Can you post a link? I found a Harbor Freight 80T blade for $27.99, though. With my 25% discount it'll come out to under $25.

10", 80 Tooth Alternate Top Bevel Design Circular Saw Blade

 

Yep, that's the stuff it isn't oily like Dap's painter's putty. It's what I always buy. It keeps my fingers cleaner and since I can also use it to glaze windows, I only need to carry one can

Since I don't use my saw commercially, I've always bought the cheaper blades at Lowes or HF and have been well satisfied with them ..... besides if I do mess the joint up any - I can fix it with caulking or putty.

 

IMO you don't need an 80 tooth for what you're doing. A sharp 60 tooth would be fine and will be in your price range. Just go to Amazon and type in Dewalt 10" 60 tooth and you will get a variety of brands and results that are in the $25 range.

A sharp 60 tooth will be fine. In fact the Dewalt blade above is for "fine crosscuts" and is the same as the one you used that was dull. The two pack Vic referred to is $36 and has that blade included.

 

I wasn't talking about an 80 tooth necessarily. But if that 60 that you have is smoking in use, a new 60 would be worth the investment. That's what I have on mine and for even stain grade trim, it works just fine. I'd guess a cabinet maker would need an 80, but I never have.

 

Just picked up this DeWALT blade for $30 at Lowe's. Hopefully it'll give me nice cuts. Also got some White Lightning caulk. I'm curious to see the difference between Alex and White Lightning, so I'll try both. Thanks for all your help and Happy Holidays!

 

Happy cutting! If you want it to stay sharp, don't cut any laminate with your new blade!

 

Oh man, I just tried cutting through a few wood shims stacked together and it started smoking. Some of the teeth started turning black. It couldn't be the blade or the material. Is something wrong with the saw? It seems that the original 40 tooth blade is the only one that will cut through anything of any thickness. I think I stopped early enough to not mess up the blade.



Some of the teeth started getting black.

 

Are you pushing the saw too fast? does the blade run true?

 

Yeah, I'd say the blade isn't running right. I've only got a 10" as well and it will cut a 2 x 4 or a couple of stacked oak 1x2 w/o smoking or slowing, even with a 60T blade.

You do have to let the saw and blade do the work. If it bogs or slows, you are trying to force it or it has a problem.

Do you have an inner and outer washer on the arbor? Pretty sure most saws have them.

Any chance you have a dial indicator? If not, you should be able to clamp a block beside the blade and visualize any wobble.

 

No, I was deliberately cutting very slowly. What do you mean by "run true"?

 

Does the blade wobble any?

run true means no wobble

 

I was just researching this on Google and a response to a similar problem was "are you cutting too slowly?". Is it possible that cutting too slowly would cause this?

Yeah, I have both washers. I'm going to try to cut faster. I'll also check for wobble by clamping a block next to the blade.

 

The only way I can see a slow cut doing that is if the wood is moving a little while it's being cut. The 2 main reasons for a burnt cut are dull blade or too fast a cut. BUT I'm a painter, the carpenters should be along shortly with more/better info for you.

 

I think it was a false alarm. I finished cutting that stack of shims at normal speed and there was no smoke. I also made a test cut of the MDF trim and I see less chipping, as expected.

Original stack on the left and a new one on the right.

 

maybe there was a coating of wax or oil on the blade ?? glad it's working good now

 

My guess is that the blade is wobbling, causing vibration. Cutting slow might actually be allowing more time for this vibration to set up, getting incrementally worse as the saw runs. If you cut a piece of wood, and examine the cut, you should not see a bunch of saw blade lines on the end of the cut... it should be smooth. If there are lines, that's usually blade wobble.

As others mentioned, you can check this by clamping a piece of wood next to the blade, then by carefully turning the blade by hand as you examine whether or not the gap between the blade and the wood stays even. If the gap opens and closes as the blade turns, that's wobble. Sometimes it will check out when checking by hand but will vibrate only at high speeds.

At any rate, if you have it figured out and the cut has improved, then you done good.