Veneering without end grain showing

[Joel Wesseling]

Hello, Im a new member and was directed here by Joe at VeneerSupplies.com
Hoping you can help with a question with some picture to help.

I'm in the process of building loudspeakers with Baltic Birch plywood.
I use dodo joints and the end grain is exposed at cabinet sides and front.
The ply end is 100% flush trimmed a few days after assembly.

The veneer went on nicely and didn't notice any problems but after a few sprayed shellac coats I could see the end grain showing through.
Its clear this is permanent so I need to rethink what happened and how to fix.

Am I going to need a sheet material or dummy veneer to cover the entire surface first or is there another solution?

I do like raw veneers so not crazy about going to a veneer with a backer.

I would appreciate any help..

Joel

[Van Huskey]

I use dodo joints


There is your problem, using an extinct joint will never work correctly...:D

I can't really help since I haven't had this issue, too late now but count you feel the joint with your fingernail?

As an aside, being a closet audiophile I am curious what transducers you are using and in what type of array. Really nice job on the veneer except for the one issue.

[Clarence Miller]

try investing in a lock mitre bit. They are kind of a PITA to set up but I liked the joint so much I built a dedicated bench top router table with a 20" tall fence.

[Karl Brogger]

.............They are kind of a PITA to set up but ..............


Ladies and Gentleman, understatement of the year.

[johnny means]

No real need for a lock miter. Assuming no one will ever be viewing the inside of the enclosure, you could just use a miter joint and glue a block on the inside corner of each joint. If you really want to get fancy you could veneer you panels first and use a v-fold, for absolutely invisible seams.

[matt tennessen]

for your current set, I guess you can always veneer over what you've got and the end grain shouldn't telegraph through.
Unless you plan on making a ton of cases and have room for a dedicated set-up, I don't know that I'd go with the locking miter bit. Mitering the edges and adding glue blocks, cutting a spline, or using biscuits are all pretty quick and easy.
If you're having trouble mitering the edges, I'd try joining the top and sides with a deep rabbit, that way you're reducing the amount of ply edge as compared to a butt joint. If you're flush trimming the end, make sure you're sanding it smooth too as that router bit is probably not leaving a finished edge due to the make up of plywood.
Finally, have you tried two-ply veneer? I know Rockler sells it, its thicker so less telegraphing and you can sand it a little more. The veneer selection is probably a little more limited but check it out.

[Phil Thien]

Wow, I'm stunned that is happening. How thick is that veneer?

I'd normally miter the corners of a speaker enclosure because that is always how I did it anyhow. Never used a dado there.

Now I'll never try.

[Jeff Bratt]

Are you looking to fix these speaker boxes - or to prevent this problem in future construction? Sure looks like the 100% flush trim isn't completely flush. Is the end grain part proud or recessed? In either case, depending on how thick the veneer is relative to the "step", a couple swipes with a card scraper should smooth out the visible ridge. For future projects, changing to a non-extinct joint may be the best answer...

[Joel Wesseling]

Thanks for the input.

I'm going to try to repair by scraping or edge trimming again.
Worse case I veneer again.

I'm using 1/42" veneer

Flush trimming is done with undersize bearing to slightly cut into side face which requires a bit of sanding

really like raw veneer for selection and price and also less noticable edge overlap

Planning to build more of these for small business so need to get it right.
I believe now what happen was that the glue expanded(thickened) the end of the side panel in the dado joint. I then edge trimmed to soon and went right into the veneering process. Eventualy the ply retracted to its original thickness creating the overhang..

I need to wait longer before trimming but I think the best thing might be to move the end grain to the top and bottom of boxes and use a sacrificial birch veneer applied top to cover end grain . The front has same issue so birch veneer on there as well..
Then veneering all surfaces can be done..
Maybe no Telegraphing with this idea??

Thanks, Joel

[Pat Barry]

Joel, I'm confused why you are using an undersized bearing with the flush trim bit. That defeats the purpose of the bit doesn't it. I think a better solution would be to use the bearing that the bit was designed for and then sand as needed. I think the best solution wold be the miter joint, reinforced with corner blocks. I suspect you will have enough room inside the cabinet for the corner blocks. If you are making a bunch of them, then use biscuits to help make your assembly go quicker and reinforce the corners with the blocks to booot.

[Jim Rimmer]

There is your problem, using an extinct joint will never work correctly...:D

I can't really help since I haven't had this issue, too late now but count you feel the joint with your fingernail?
After giving him grief about the dodo joint? :D

[Joel Wesseling]

The plywood is 17ply 24mm BB and cutting a 45 could be difficult with the light duty motor I put in my vintage SCM saw but I realy like the dado for strength and have fixtures and templates to build them with dado. Spent along time building the Templates and dado guide platform etc..

Have several trim bits from whiteside, freud and infinity. They all except one freud leave the edge slightly proud. The one freud cuts into face ever so slightly. When I run it about 1/2inch below the joint I get this perfect smooth flush trim except for a small line on the side face that is easily sanded out. Seems easer then sanding the BB end grain??

The step can be felt with fingernail.

Joel

[Joel Wesseling]

I put some water on the end grain of a scrap piece today the thickness increased about 3mm.

[johnny means]

Joel, if you're going to be doing this type of work with any regularity, you might want to rethink your construction method. Veneering over a joint like that is pretty much always going to be a crap shoot. You could even finish one and have it look amazing, only to have the joint mysteriously appear in a few weeks. Remember, all three components there, the plywood face, the end grain, and the veneer are going to spend there lifetime trying to move around in different ways. Even within the end grain itself you'll have long grain plies trying to grow proud of the end grain plies. Often, if you run your finger across the edge of a piece of uncut BB you'll notice a slightly ridged surface, it wasn't made that way, it was at one point cut perfectly smooth.

[Joel Wesseling]

Johnny, what if I move end grain to top of cabinet then cover with 1/8 mdf. this way no end grain is exposed before veneering? Maybe the grains move independenly from the veneer?

The front shows end grain around perimiter as well but planning to use thick hardwood about 1/8" covering front. I guess the edge could be a problem here as well?

Joel

[matt tennessen]

Joel, I don't think I understand how you're using a dado on these. Are you cutting a dado and then trimming the edge so that your dado is essentially a rabbit? If so, you could cut a deeper dado, leaving 1/8" of material left, then you wouldn't have to apply the extra 1/8" material you mentioned.
Ultimately though, I think you may have to come to a compromise. Eventually the extra steps are going to add considerable time/cost to your boxes. You may find that its more cost effective to rethink your construction method. This is why we make prototypes. Or at least "prototype" is what we call all of those strange things lying around our shops that we poured effort into before we put it in reverse and tried a new idea. If you don't want to try miters, I still think its worth checking out two-ply veneer--its all wood, not paper backed so when you sand it, you don't see that edge the way you do with paper backed veneer.

[Chris Fournier]

I make Dodo joints all the time, but I spell it DohDoh as would Homer Simpson - and for the same reasons!

I believe that your problem lies with the substrate preparation more than anything else. I would bet that the joint was not actually totally flat before the veneer was applied. Take a pencil and cover the area of the joint - say three inches in from the edge in pencil. Now take a handplane set for a very light cut or a very flat block with sand paper and work a few passes over the penciled area and I bet that you'd find that the area around the joint was not flat. If your glue up was not perfectly 90 degrees you can imagine the results given by flush trimming.

You could:

Continue with the cabinet building technique that you're currently using and use a little "bondo" over the joints and treat the box a bit like a car body panel and fair it out with filler and carefull sanding - this is easy and will give you great results.

Use a different construction technique to build your boxes. Mitres are nice but not terribly easy to get perfectly 90 degrees and uniformly tight unless you are really jigged up for the joint.

Use a different sheet good - I am no speaker expert but MDF seems to be a go too product for speakers - even at the mid to hifi level. It is denser than Baltic birch and it would be far more consistent in that density than plywood.

Standard commercial veneer is very unforgiving when it comes to telegraphing the substrate. Perhaps you can source thicker veneer in the species that you choose - this is quite available.

You're really not that far away from the results that you're after, keep at it!

[Dave Tesch]

bondo is what the pro's use.

i dont really understand the use of baltic birch for these cabs; i mean the whole point of baltic birch in audio cabs is that it is light, strong, void free, and has many thin plies. all of which are great to make a strong lightweight speaker suitable for banging around in a truck and being setup/torn down on a daily basis.

many top model cabs are built with baltic birch; JBL SRX is i believe.

but i am not seeing a great value in using such expensive wonderful plywood in a home setting, especially if you are covering it up with veneer. you could just veener a butt jointed (gasp) MDF box assuming it will never see a truck or rigging.

i rebuilt the two smaller black wedge speakers in this pic this last summer.

http://inlinethumb39.webshots.com/45094/2368416770026985969S500x500Q85.jpg (http://outdoors.webshots.com/photo/2368416770026985969XSOvnw)

if you look close, you will see i didnt even bother to fill in the knot on the one.

they are all braced butt joints and built to ride in a truck (and take a beating)

http://inlinethumb46.webshots.com/18669/2480104100026985969S500x500Q85.jpg (http://outdoors.webshots.com/photo/2480104100026985969bnLehz)

http://inlinethumb08.webshots.com/46983/2367753800026985969S500x500Q85.jpg (http://outdoors.webshots.com/photo/2367753800026985969urxGkr)

i did edge band them though, i suppose if i was going to build home speakers out of baltic birch i would want to see the baltic birch. its quite a nice looking board i think. i wonder if you could incorporate a type of edge banding over the end grain and skip the veneer, i bet that would look very nice.

[Pat Barry]

Joe, I think you need to reconsider doing a reinforced mitre joint on the baltic birch box to get a clean, tight fitting corner, then do the veneer. You can cut this on your tablesaw. You don't need to do the lock miter router bit. I doubt the other techniques will be as efficient or clean.

[Jason Raksnis]

I dont know why your not using MDF. Trying to veneer BB end grain is ALWAYS going to give you problems. Plywood moves to much, even BB. MDF is ver stable and dead flat. I use lightweight MDF all the time and its a pleasure to work with.(besides the dust) If you wanted to try some you can try leaving the end grain short maybe by a 1/16" and then fill it with bondo. Then sand that down flush with your sides. You can even fill it proud and then route it off witha flush trim bit. Then come back and sand with a stiff block. just maybe?

jason