Overnight Sensation Build -- Two Sets

[Soundslike]

Re: Overnight Sensation Build -- Two Sets

Continuing with the veneering process -- Disaster strikes!!

I think I mentioned earlier in this string that I'm new to wood veneering. This was my first wood veneer project, and I did encounter some difficulties. The primary difficulty for me was in trimming the veneer, once it was applied to the enclosure. It may have been my choice of veneer, but I found the material extremely fragile -- given half a chance it would split. I was concerned about that issue when I purchased the materials from a local Rockler store, so I went the tool you see in the photo below. It isn't going to be a tool I use often. I found the tool to be unreliable, or maybe untrustworthy would be a better word. Despite great care, the veneer would unpredictably split in places, or even worse, tear a piece out if I was attempting a cross-cut (across the grain).



The tool features a special blade (looks a lot like a rectangular utility knife blade) and guides that are supposed to produce a flush cut. Maybe with a bit of practice it would be possible to get consistently good and accurate cuts, but I ended up abandoning the tool in favor of a sanding block. To make the tool work reliably, you'd have to inspect it closely before each cut to make sure there weren't any splinters of wood between the blade and the holder. If there were splinters, the blade wouldn't make a decent cut. Changing the blade frequently is also necessary. I found a simple sanding block with 150 grit paper to be the most accurate and least troublesome way to trim the veneer. That of course means that you'll want to cut the individual pieces pretty close to the final trimmed size so that you don't end up with a lot of overlap to remove. For those unfamiliar with the basics of veneering, you must trim each piece after it is applied, before moving on to the next piece.

Regarding the difficulties I encountered, here's an example:



That tear-out you see there has been cleaned up with an Exacto knife -- it looked much, much, worse before I trimmed it up. But, it did give me an opportunity to explore ways of correcting (maybe patching would be a better word) the damage. I damaged the veneer by using too much force with the trimmer described above -- I was pushing it pretty hard, but not nearly as hard as as the force used with something like a hand plane. Once the damage was done, I was left with a couple of choices -- attempt to remove the veneer, or repair the damage. I opted for the repair route because a new piece of veneer wouldn't match, and because removing the veneer was likely to result in new imperfections, perhaps even making matters worse.

I sorted through the scrap pieces of veneer and found a piece that matched the damaged area fairly well. I then made a paper template to arrive at the general shape of the torn-out area, simplified of course to eliminate the shards and fibers of wood that remained. I chose to use an irregular shape, as opposed to some easily recognizable shape such as a square, circle, or oval, because it would be much more difficult to spot, once in place. The template was used to produce a slightly enlarged piece of veneer that would become the "plug" or patch-piece. The plug was then placed over the damaged area and the outline carefully traced onto the torn-out area as precisely as I could. I then enlarged the damaged area with an Exacto knife cutting out the veneer within the area defined by the traced line. I removed as much of the adhesive from the surface as possible, then glued the plug in place.





Looking over the photos again, I can see that I smoothed the shape of the plug and cutout somewhat. You can see that I achieved a fairly close fit -- not perfect but things were looking up.

I used a wood filler that's made specifically to closely match the color of Cherry wood to conceal the part line. The repair was next sanded to make sure it didn't protrude above the surrounding area.

The patch is actually difficult to find and unlikely to be noticed without close inspection.



For those who are interested, I offer the following observations about veneering:

1. It produces a great looking result that's hard to equal or surpass with other methods.
2. It is easier to produce a good looking finished product with veneer, than it is with paint. Some will argue with this, so to clarify let me point out that when one attempts to evaluate an argument for one type of finishing method or another, one must know what sort of result the proponent has in mind. I'm talking about high-quality, high gloss finishes. Semi-gloss, or satin finishes are far less demanding as are hammer-tones (but, they do look nice).
3. I will use a paper-backed veneer in the future, whenever possible.
4. So far, I haven't found a method of trimming I like, other than sanding. I haven't tried a flush trim bit and a router yet, but I have tried utility knives, pocket knives, the infamous little trimmer I described above, saws, planes, and files. I will sand the edges to size, rather than risk damage from other methods.
5. Don't give up if you damage something -- it probably can be repaired if you're careful and patient.

[Mark65]

Re: Overnight Sensation Build -- Two Sets

That repair is brilliant. No other word for it. I saw it in Tucson, and if you hadn't pointed it out to me, I never would have noticed it. The jagged line matching technique is just a flat out GREAT idea, it's damn near invisible after finishing.

Kudos!


Mark

[Paul Carmody]

Re: Overnight Sensation Build -- Two Sets

Hmm. I'd considered using one of those Band It edge trimmers, but always figured it was too much money to spend on a tool I wouldn't use much. So I've always done the edges with a utility knife. It actually works surprisingly well, you just gotta go slowly. But still, I've always had to clean up the edges with a sanding block. Maybe Randall can chime in how the pros do it.

[Leroy R]

Re: Overnight Sensation Build -- Two Sets

Wow and I was concerned about little splinter type tear outs when I was trimming mine. That is a serious bit of damage you suffered there and like Mark said, your repair is brilliant. Even knowing it was there, I had to really look at the pictures to pick it out after your repair.

I used that band-it tool when I did my IB sub project to trim my edge banding and didn't like it either. It would get stuck at points and if you were going along with any momentum, I could see it easily tearing the veneer. Using a razor knife with a guide with the grain and a guide with a sawing motion when cutting across the grain worked well for me. When cutting across the grain I did about a 1/4" relief cut at the end that I was cutting toward to help prevent tearout when I reached the end of my cut. I have now purchased a 1/4" flush trim bit for my trim router and will probably use that for my next project to see how it works compared to the razor knife.

[Leroy R]

Re: Overnight Sensation Build -- Two Sets

My mom lives in Mesa. I'm going to have to meet up with some of you guys there next time I am in town visiting her to see some of your projects in person.

[Randall Kepley]

Re: Overnight Sensation Build -- Two Sets

Hey guys, Paul mentioned I might chime in and I would love to, you guys seem so eager to help one another and this is just the kinda place I like to be in. First off throw all hand-held edge trimmers in the TRASH !!! As you just found out they a disaster waiting to happen, they sometimes work ok on long grain but on end grain they will ruin your day in a split second.

One tool that is fool proof and it works on long or end grain is a Veneer saw which I suggest that if anyone here is doing or planing to do veneer it is a must have tool. Very cheap but worth their weight in Gold! Heres a link http://www.veneersupplies.com/produc...eneer-Saw.html buy the presharpened version. The saw is designed to cut in 1 direction, Micro fine teeth and it only cuts from the top side. You could have taken your cabinet, laid the veneer saw flat on the MDF and w/ very light strokes slit through the veneer like a lazer leaving a glass smooth edge. This technique can be used on long or end grain.

The other technique is if you own a laminent trimmer using a flush cutting bit w/ a bottom bearing not a top bearing heres a link http://www.rockler.com/product.cfm?p...h%20trim%20bit
since your close to a rockler I linked to them. This will also leave a glass smooth finish and will not only follow straight line but curved also. It works pretty well on end grain but I would advise making sure the bit was very sharp and going very slow. Nothing takes the place of a veneer saw on end grain.

BTW, Looking at the size of the tear out on the box it looks like the Glue didnt adhear very well in that area. Take your finger and start tapping on the rest of your veneer in about 1" increments and see if you hear or feel a hollow sound or feel anywhere if you do shoot me a PM and Ill tell you how to fix it. Hope this helps guys, sorry it was so long. R.K.

[mtmpenn]

Re: Overnight Sensation Build -- Two Sets

Hey Randall,

I have that exact veneer saw and have had difficulty going cross grain (paper backed flat cut walnut veneer). Going along the grain I was able to get just about perfect smooth cuts. If I took my time and made a lot of slow passes with cross grain it was better, but not perfect. Any other special tips/tricks?

Also, how do you feel about using files (and any specific files you would recommend)? I used a file to trim some edge banding (at a woodworking class) and I was impressed with the result. I don't know what kind of file they used. Soundslike, what was your impression of using a file?

I recently bought a laminate trimmer and will be experimenting with that on my next build.

[Randall Kepley]

Re: Overnight Sensation Build -- Two Sets

Hey Randall,

I have that exact veneer saw and have had difficulty going cross grain (paper backed flat cut walnut veneer). Going along the grain I was able to get just about perfect smooth cuts. If I took my time and made a lot of slow passes with cross grain it was better, but not perfect. Any other special tips/tricks?

Also, how do you feel about using files (and any specific files you would recommend)? I used a file to trim some edge banding (at a woodworking class) and I was impressed with the result. I don't know what kind of file they used. Soundslike, what was your impression of using a file?

I recently bought a laminate trimmer and will be experimenting with that on my next build.

It sounds to me like your veneer saw has never been sharpened or isnt sharpened correctly or is just very dull. A sharp veneer saw doesnt know the difference between long or cross grain, here is a link to sharpening your saw if it has never been sharpened or is dull , follow the instructions and you will be amazed.http://www.joewoodworker.com/veneering/saw-sharpen.htm

Ive never been crazy about using files on veneer, as you stated you have used files on "edge-banding" which does pretty good but you have to remember edge banding is about 5 times as thick as veneer. Once the veneer is properly cut getting a perfect edge is easily achived w/ sandpaper. Hope this helps. R.K.

[Soundslike]

Re: Overnight Sensation Build -- Two Sets

From Paul Carmody:

... I've always done the edges with a utility knife. It actually works surprisingly well, you just gotta go slowly. But still, I've always had to clean up the edges with a sanding block. Maybe Randall can chime in how the pros do it.

As others confirm, the Bandit trimmer is not the answer to the veneer trimming challenge. I suspect that Randall has cleared up what the tool is actually intended for -- trimming edge-banding which is a thicker material less prone to splintering and tearing.

From Leroy R:

I used that band-it tool when I did my IB sub project to trim my edge banding and didn't like it either. It would get stuck at points and if you were going along with any momentum, I could see it easily tearing the veneer. Using a razor knife with a guide with the grain and a guide with a sawing motion when cutting across the grain worked well for me. When cutting across the grain I did about a 1/4" relief cut at the end that I was cutting toward to help prevent tearout when I reached the end of my cut. I have now purchased a 1/4" flush trim bit for my trim router and will probably use that for my next project to see how it works compared to the razor knife.

Leroy offers some good suggestions about using a "razor-knife" which I assume is the same thing as a utility-knife Paul commented about. He also reports having difficulty even when using the Bandit tool on edge-banding. The problem I observed with mine is that splinters can easily get lodged under the blade, between the plastic blade holder and the blade itself. The bade is then free to move outward from the edge guide and even change the cutting angle. Once that happens, the tool is likely to mess something up -- it's not going to produce a good result, and it's very likely to damage the veneer. Maybe I should have paid more attention to the salesman's shoulder shrug when I asked him for a cutting tool recommendation -- in hindsight, I guess that was an indication that he wasn't particularly enthusiastic about this tool.

Regarding the use of a router, I noticed in Randall's reply that the bit he recommends is a spiral-cut type, as opposed to a general purpose flush trim bit. I was hesitant to use the trim bits I have, because I was concerned about tear-out, but the spiral-cut type is an option I'd like to try. Good Ideas Leroy... Let me know when you're in the area and we'll get together, not that I have a whole lot to offer.

From Randall:

Hey guys, Paul mentioned I might chime in and I would love to, you guys seem so eager to help one another and this is just the kinda place I like to be in. First off throw all hand-held edge trimmers in the TRASH !!! As you just found out they a disaster waiting to happen, they sometimes work ok on long grain but on end grain they will ruin your day in a split second.

Randall, it's good of you to share your knowledge gained through experience doing it for a living. I'm a firm believer in getting the best advice I can whenever I'm going to be venturing into a new area ..., you obviously have the kind of knowledge we need here. A whole lot of good advice based on a professional's experience. I'm ordering my veneer saw right away.

I do have a couple of follow-up questions for you Randall, if you have the time to reply.

What are your opinions regarding paper-backed, vs plain veneer types? I've assumed that paper-backed types are easier to work with, and more resistant to the problems we've discussed here -- is that true in your experience?

What type of adhesive do you recommend? Do you like the water based types? For those looking for something locally available, what would you recommend?

As I'll describe later in this thread, I did use a flush-trim router bit to trim the baffle flush to the surface of the veneer. One potential problem I discovered is that it would be very easy to mar the veneer with the guide bearing. It probably needed lubrication -- I've found they get dry pretty quickly, but lubricating the bearing always brings at least a risk of slinging oil onto the workpiece. The slower and more hesitant you are, the more time the bit has to mar the veneer. How do you deal with this issue? I was able to sand out the affected area -- it appeared a bit burnished where the bearing contacted the veneer and didn't take too much to remove it.

By the way, I may have the problem you talked about. Right after completing the speakers, I left normally dry Arizona for an extended RV trip, eventually ending up in Corpus Christi, Texas, on the gulf coast. We were staying about 1/4 mile from the ocean and the humidity was incredibly high. In fact, the breeze blowing through the window at night would condense into moisture on the window screen. You can imagine what happened -- the veneer curled up in a few places. Now that I'm back in Arizona, the veneer is settling back down, but it obviously needs the repair I think you alluded to above. I'll PM you if you prefer, but I think other's could benefit from what you have to say.

Thanks again for your help.
Ron

[Mikers]

Re: Overnight Sensation Build -- Two Sets

Quote "As I'll describe later in this thread, I did use a flush-trim router bit to trim the baffle flush to the surface of the veneer. One potential problem I discovered is that it would be very easy to mar the veneer with the guide bearing. It probably needed lubrication -- I've found they get dry pretty quickly, but lubricating the bearing always brings at least a risk of slinging oil onto the workpiece. The slower and more hesitant you are, the more time the bit has to mar the veneer. How do you deal with this issue? I was able to sand out the affected area -- it appeared a bit burnished where the bearing contacted the veneer and didn't take too much to remove it."

What if you fit the front before veneer by using masking tape on the cabinet to mimic the thickness of the veneer. This way your front panel will fit flush once veneer is applied but you don't risk screwing up your veneer by trying to fit the panel directly to it. that's my suggestion.

[Leroy R]

Re: Overnight Sensation Build -- Two Sets

I wonder if putting a strip of masking tape or the self adhesive shelf paper I talked about in my tritrix thread would help protect the veneer from the bearing. It would slightly space the bit away from the surface, so the flush cut would be off by the thickness of the tape, but that would be easily sanded out during the prep for finish. Heat generated from the bearing might cause the adhesive from the tape to melt into the veneer surface though, so that might not work either.

[swander]

Re: Overnight Sensation Build -- Two Sets

Great job on the repair. Only you will ever notice it.

FWIW - I recently veneered my set of OSMTM's (first time veneering) and had excellent results with the flush-trim bit. I set the bearing just barely below the thickness of the veneer and had no issues with the roller marring any already covered surface. The edge required a very light sanding after trimming. I also used paper backed Cherry.

I used the iron-on method with Titebond III as the adhesive and have had no bubbles or issues of any kind. I diluted the glue a little with water and applied about 2 coats with a brush to both surfaces. Let it fully dry and iron on. Veneer roller came in handy.

[Randall Kepley]

Re: Overnight Sensation Build -- Two Sets

From Paul Carmody:



As others confirm, the Bandit trimmer is not the answer to the veneer trimming challenge. I suspect that Randall has cleared up what the tool is actually intended for -- trimming edge-banding which is a thicker material less prone to splintering and tearing.

From Leroy R:



Leroy offers some good suggestions about using a "razor-knife" which I assume is the same thing as a utility-knife Paul commented about. He also reports having difficulty even when using the Bandit tool on edge-banding. The problem I observed with mine is that splinters can easily get lodged under the blade, between the plastic blade holder and the blade itself. The bade is then free to move outward from the edge guide and even change the cutting angle. Once that happens, the tool is likely to mess something up -- it's not going to produce a good result, and it's very likely to damage the veneer. Maybe I should have paid more attention to the salesman's shoulder shrug when I asked him for a cutting tool recommendation -- in hindsight, I guess that was an indication that he wasn't particularly enthusiastic about this tool.

Regarding the use of a router, I noticed in Randall's reply that the bit he recommends is a spiral-cut type, as opposed to a general purpose flush trim bit. I was hesitant to use the trim bits I have, because I was concerned about tear-out, but the spiral-cut type is an option I'd like to try. Good Ideas Leroy... Let me know when you're in the area and we'll get together, not that I have a whole lot to offer.

From Randall:



Randall, it's good of you to share your knowledge gained through experience doing it for a living. I'm a firm believer in getting the best advice I can whenever I'm going to be venturing into a new area ..., you obviously have the kind of knowledge we need here. A whole lot of good advice based on a professional's experience. I'm ordering my veneer saw right away.

I do have a couple of follow-up questions for you Randall, if you have the time to reply.

What are your opinions regarding paper-backed, vs plain veneer types? I've assumed that paper-backed types are easier to work with, and more resistant to the problems we've discussed here -- is that true in your experience?

What type of adhesive do you recommend? Do you like the water based types? For those looking for something locally available, what would you recommend?

As I'll describe later in this thread, I did use a flush-trim router bit to trim the baffle flush to the surface of the veneer. One potential problem I discovered is that it would be very easy to mar the veneer with the guide bearing. It probably needed lubrication -- I've found they get dry pretty quickly, but lubricating the bearing always brings at least a risk of slinging oil onto the workpiece. The slower and more hesitant you are, the more time the bit has to mar the veneer. How do you deal with this issue? I was able to sand out the affected area -- it appeared a bit burnished where the bearing contacted the veneer and didn't take too much to remove it.

By the way, I may have the problem you talked about. Right after completing the speakers, I left normally dry Arizona for an extended RV trip, eventually ending up in Corpus Christi, Texas, on the gulf coast. We were staying about 1/4 mile from the ocean and the humidity was incredibly high. In fact, the breeze blowing through the window at night would condense into moisture on the window screen. You can imagine what happened -- the veneer curled up in a few places. Now that I'm back in Arizona, the veneer is settling back down, but it obviously needs the repair I think you alluded to above. I'll PM you if you prefer, but I think other's could benefit from what you have to say.

Thanks again for your help.
Ron

Ron, I want to thank you for your kind words to me and Im sorry im just getting back w/ you tonight, Ive been up to my eyeballs in Taxes (always fun when you work for yourself) But I will be more than happy to address your questions and I also want to say that , Please dont think Ive tried to Hijack your thread. Its quite obvious you have put alot of time and effort into this thread and I dont want to detract from what this is realy about and thats "Your great pair of OSB builds" and they do look great by the way. I also want to say the advice I give may not be the only route to take in any given certain situation but I can promise you what ever advice I give, is advice that is tried and true and I use w/ great success every day. To me this is how I make my living and not just a hobby. Theres alot of crappy advice on diff forums and Im not in the habit of steering anyone in the wrong direction and as you can tell I tend to rattle on.......;) So lets look at the questions.

1. My advice on paper backed veneer is I dont have any, sorry I started veneering yrs ago w/ plain veneer and havent strayed yet. One Ive never been a big fan of contact cement and wood. Contact cement never dries hard it always stay flexable which IMO is a big problem w/ a product that can "Breathe" and believe me wood does breathe! Here in N.C. we go from about 20% humidity in the winter to about 95-98% in summer! Everything thats wood moves in the south!

2. As far as my adhesive of choice theres only 2 I use for my large flat pieces I stand by Titebond Cold press glue. http://www.titebond.com/ProductLineT...=4&prodline=19
IMO there is none better. Now when Im edge banding this doesnt work so well and for a good while I would use Tite bond 1 or 2 I would apply a nice amount to each surface, let it dry and then use the Iron-On method. Which works ok but yellow glue like contact cement never quite dries hard which allows the veneer to move. Then I found this product which Im currently in Love w/ http://www.veneersupplies.com/produc...neer-Glue.html Great stuff and not expensive either , be sure to read the reviews!

3. Router bearing marks, the quick and easy method to avoid this is to lightly spray the bearing w/ 100% silicone lubricant which can be bought for about $5 at lowes or homedepot. notice I didnt say WD-40, the reason for this is silicone seems to be 1000 times slicker than WD and much easier to clean up. Spray the inside of the bearing , not the outside , spin it w/ your finger for a few seconds then take your air hose and blow the excess lubricant out of the inside. It will run smooth as glass. And when your using it apply as little pressure as needed to the Veneer. As stated in another post , plain old green painters tape works great and is so thin you wont hardly be able to feel the diff and it will take very little sanding to get it smooth. Also when you set the depth on the cutter only set it deep enough to get the job done. The deeper you set it the more likely you are to wanting to "Tip" the router and bit which can be a hazzard in and of itself! The safest way with no chance of marring is to buy you one of these little tricks http://www.mcfeelys.com/product/LT6-...t-Euro-Bearing Its cheap, rubber and Will not mar as the bearing spins inside of the square! I personaly dont use this mainly because Ive routed more liner feet than probably 50 people would in a life time and I just know how much pressure Im applying.

4. The last subject you mentioned is one weve already covered and that is the Humidity you experienced while traveling, which IMO goes back to the contact cement. You would be much better off using "Heat Lock" and go w/ the iron method, much more stable.

5. The last thing Id like to cover is Vacuum pressing. I know most people dont and wont justifie the expense of vacuum pressing for a hobby, but it can be done much cheaper than most would think. This one is very economical for any budget and even though its manual " It will get the Job done"! http://www.roarockit.com/tap.php?id=13 not the fastest for big panels but most speaker parts it would work fine. Now for a little more money and I think you mentioned you have a Rockler close by this isnt a bad deal. http://www.rockler.com/product.cfm?p...vacuum%20press This will do just about anything that comes down the pipe as far as speakers go. I personaly use the large unit I built from Joe Woodworker It will pull 5.5 cubic ft per minute and I use several diff size bags depending on what project Im working on. But I promise you there is no substatute for a vacuum press in veneer work.

Sorry this was a little long winded, but Ill be happy to help any way I can. Thanks R.K.

[Soundslike]

Re: Overnight Sensation Build -- Two Sets

More good ideas -- thanks Leroy and Swander.

Continuing with the build process -- after completing the veneering of one set, I flush trimmed the baffles with a router and a flush-trim bit. A flush trim bit does a great job of matching up the baffle with the box and I ended up with the baffle perfectly matching the surface height of the veneer. As I mentioned in a reply to Randall above, I did experience a little superficial marring of the veneer surface -- I say superficial because it was easily removed with light sanding, but it did cause me think I'd be wise to guard against that in the future. Leroy and Swander suggested using tape and that does seem likely to either prevent a problem, or at least raise my comfort level. I also rounded over the edges (top, bottom and sides) with a 1/2" round over bit and router, and flared the ports on both sets with the same bit. The vents were originally epoxied in place flush with the outer face of the baffle on one set, and the back on the other set. That meant that routing around the port opening would involve cutting the PVC which left about 1/4" of contact area between the PVC and the MDF where they are mounted. The PVC cuts easily, providing you don't rush and move the router in the correct direction.




I then sealed the baffles with diluted mixture of fiberglass resin (30% acetone). As I stated earlier, I like the resin process and will use it again. In the interests of complete disclosure , I should point out again that the resin doesn't flow out as well as paint which leaves brush marks that must be sanded out. See the next photo where I've knocked down the high areas to reveal the brush strokes. It does sand out easily though, providing it has been allowed to cure adequately.


A thinner mixture would most likely reduce the brush stroke effect. Once again, be sure to work in a well ventilated area, and wear a respirator. They're readily available at home improvement centers, paint stores, you can even get a Binford from HF -- it's actually a reputable brand.

In the next photo the resin coating has been sanded smooth. I've also applied a coat or two of urethane varnish to strengthen the veneer (the baffle was masked). Until it was coated, it had a tendency to snag on everything, and was easily damaged even with careful handling.



I sprayed on two coats of lacquer-based high-build black automotive primer. The front ported enclosures were painted on all sides -- of course the veneered pair was masked so that only the front baffle was painted (you never know--someone might wonder about that).

Since I'm on the topic of spraying -- I've discovered that the high-build primers require a pretty decent gun to apply. The stuff is full of solids, and it's thick (naturally). It takes a bit more work to clean your gun, and since this was a small project, I opted for a small detail gun rather than break out a gravity feed. Next time I'll leave the detail gun on the shelf -- it simply isn't up to the task. I could have thinned the primer, but then you end up with something less than high-build.



I'll continue tomorrow -- I'm getting tired...

One more thing; I just noticed Randall replied while I was composing this message. Great information Randall -- it's great of you to take the time to respond. Particularly after working on (ugh) income tax. I'll have more to say tomorrow. Thanks for being so helpful...

[jim85iroc]

Re: Overnight Sensation Build -- Two Sets

Great build info. One comment on the high build primer... rather than deal with dedicating a gun specifically for it (since a thicker nozzle really should be used), I just buy my high build primer in spray cans. Duplicolor stuff is available everywhere, and works great. SEM also sells their version, though I have yet to use it... I've been happy with the Duplicolor stuff. When you seal the MDF, it doesn't take a lot of high build primer to get a smooth paintable surface. I've even built enclosures without using a sealer... just using extra coats of the high build primer to seal the wood. That's how the tall cabinet in the attached pic was done, prior to the automotive Urethane finish. After a wetsand & buff, the black paint was mirror smooth, just like you'd expect from a high quality automotive urethane finish. That said, a coat or two of sanding sealer or equivalent will result in a much faster & easier primer application.