Darryl Keil Last Activity 2025-02-12 2:48 PM
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Dave Peterschmidt

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Joined: 2007-07-15
Location: Eau Claire, WI

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Subject : Outside corners without visible glue line?
Posted : 2007-07-15 1:07 PM
Post #33944
Hello,
I'm going to be veneering speaker cabinets. On a test attempt, I used flat cut maple to veneer a cabinet using Heatlock (PVA) adhesive. I did the veneering by applying a veneer to each face of the speaker, trimming the edges flush with a router. The problem I'm having is that the glue lines on the trimmed edges are dark and very visible against the light colored maple. Being new to veneering, I'm thinking there has to be a technique which will make an invisible seam on the corners as I've seen many veneer projects which have outside corners with seamless veneer. There will be both 90 degree corners and 45 degree corners on the cabinets. The glue lines show up the most on the 45s, which are the ones on the front of the cabinet, unfortunately. One thing I'm going to try is to soften the veneer and "form" it under heat to about a 45 degree angle, then see if it will glue down without breaking. I might be able to make that work, but it's not a solution for the 90 degree corners. Can anyone give me some idea how to make a corner seam that gets rid of these visible glue lines?



 
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Brian Gray

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-15 2:29 PM
Post #33946 - In reply to #33944
Here's how I did a pair of speakers a while back.

http://www.briangray.net/projectdetail.cfm?ProjectID=26

Instead of bothering with the veneer chipping and breaking on the edges, I added hardwood strips. This also would eliminate your glue lines.




 
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Brian Gray

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-15 3:00 PM
Post #33947 - In reply to #33946
Also...you'll probably find that most people here will recommend that you use a urea resin adhesive rather than a PVA...be it standard PVA, or the Heatlock brand.

I'm assuming that you don't own a vacuum press, and this is why you are going with the Heatlock. That being said, I understand....a vacuum press is not a small investment.

However, if veneering is something that you feel you might want to get more advanced with, consider a vacuum press and urea resin adhesives. Or at least have enough manual clamps with deep throats so you can press small panels with them and not have to invest in a vacuum press yet.

I have found that heating PVA's work fine with very small surface areas, but anything that could be considered a panel is probably going to be very tough to get right with heated PVA.

My experience is that when heating PVA over larger surfaces, glue will bond in one area, and then the heat and moisture exchange will tear the veneer away from the bonded area, causing cracks...

I tried the Heatlock stuff once out of curiosity, and couldn't get it to work in a panel situation. I would say that anything that is larger than your iron is not a candidate for Heatlock. It's impossible to heat the entire panel uniformly. And even then I wouldn't use the Heatlock, because the application is so small that manual clamps would do the trick.

Merely my 2 cents...

However, since you are at the stage where you are concerned with glue lines, perhaps you have quite successfully used the Heatlock on a large panel. Perhaps you could share your procedure...I couldn't get it to work, and was pretty frustrated with it.




 
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Dave Peterschmidt

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-15 4:37 PM
Post #33948 - In reply to #33947
Brian,
Thanks for the quick reply. Putting edge strips on is one possibility, but I prefer the look of having the entire panel veneered. I really like the look of the display stands Don Stephan has on his website. Something like that is what I want to do. I have definitely considered using a vacuum press as I'm going to be manufacturing these speakers for sale. I wanted to try the iron-on method first as it seemed simpler with a much smaller up-front investment.

To veneer using heatlock, I've been using paper backed veneer and have successfully finished a cabinet roughly 24x10x10 with no tearing issues or other problems. The job looks very nice other than the dark glue lines on the corners. To apply the veneer I simply rolled a thin layer of Heatlock onto both the substrate (MDF) and the veneer. Once dry to the touch, I positioned the veneer in place, covered it with a cloth, and began to iron from the center outward with a medium-hot iron, moving the iron continually but slowly, pressing down a bit to seat the veneer. Once the main surface was well attached I made another slow pass around the outer edge, angling the iron over the corner to get a good edge bond. I found a heat level of slightly below "cotton" to work well. Any hotter and it was browning the cover cloth. Note that I wasn't using raw veneer here, but rather a 10mil paper back. Perhaps raw veneer is more difficult to deal with when using iron-on PVA or something?

I have checked out Unibond 800 and might well go with that and a vacuum press. I like the fact that the website says it has a neutral tan color which may blend better with lighter woods. It sounds like that would make less visible glue lines if I can't find some other way to eliminate them. Looking at Don Stephan's stands, it's hard to tell from the photos if there are glue lines or not, but I suspect not. If not, how did he achieve that?



 
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Brian Gray

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-15 9:53 PM
Post #33949 - In reply to #33948
Thanks for the explanation on the Heatlock PVA.

I did not use paperbacked when I tried it, so maybe that was the issue for me.

As far as Dan's stands goes...he's a regular here...I'm sure he'll chime in soon on this one.

If not, email him...he's a super nice guy.


 
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Dave Peterschmidt

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-16 1:41 AM
Post #33950 - In reply to #33949
Thanks Brian.

I'm not sure what the differences are between paperbacked veneer and flitch veneer, aside from the obvious paper backing and processed form factor. Perhaps the paperbacked is processed somehow to make it more dimensionally stable. The stuff I was using was made by Cedan and it was relatively easy to iron on.



 
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Bruce Berman

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-16 11:44 AM
Post #33951 - In reply to #33950
Dave,
From your description of the dark veneer edge it sounds like you may be seeing the end-grain of your veneer. You may also be seeing the glue line of the PVA glue plus the backer. You should go back to the standard format for speaker assembly. You should veneer your panels before assembly and then cut your 45 degree bevel assembly joint (lock miter ect.). This will hide your glue line on the sides.
And as mentioned by others here you probably should be using a plastic resin type glue especially where exposed corners are involved.

Bruce Berman
The Miracle Veneer Trimmer




 
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Dave Peterschmidt

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-16 12:56 PM
Post #33952 - In reply to #33951
Hi Bruce,
Thanks for the input. You're right that the backer is certainly part of the line I'm seeing. However, the line is quite dark - much darker and thicker than the backer. In fact, the color of the backer is close enough to the color of the actual veneer that if the line was only due to backer and not glue, I doubt I'd even see the line without looking very very closely. For that reason I've concluded it's the glue that is causing most of the visibility issue.

You mention plastic resin glue. Are you referring to urea glues like Unibond? I'm strongly considering that.

Veneering the panels prior to assembly is an approach I've given some thought to. It would solve the issue except for the top of the cabinet. I could probably live with that. One problem with that approach, though, is that it requires very close tolerances on the cuts coming out of the saws. Some of my cabinets are more than 60" tall. Getting a 60+ inch long 45 degree joint to match up precisely enough to make an invisible veneer seam sounds pretty difficult based on my experience with building these cabinets up to this point. The 45 degree joints are virtually impossible to clamp (at least as far as I know) so it's easy for them to come out with a less than perfect joint. I normally have to do some sanding and patching before they're completely flush. That said, I am working to improve my technique on those joints. If I can improve it enough, veneering prior to assembly will become a viable option for me. In the meantime, however, I'd like to explore all the options. Is that the only way to get an invisible corner seam with veneer?

Just thinking out loud a bit, I did a test a while back taking some scrap veneer, softening it, and pressing it over the 45 degree joint on one of my speakers. I then let it dry in that shape and it held the angle reasonably well. With the ability to reshape the veneer I'm thinking it might be possible with some work to get it to bend around the joint without tearing. Or maybe not - I haven't tried it yet. But one other thing I thought about was whether I could use two straightedges placed on the veneer on either side of the 45 degree bend to "sandwich" my utility knife blade and guide a cut down the ridge of the bend. Perhaps that cut would almost be like a miter cut with the two pieces able to butt together invisibly at the corner, hiding the glue line. I dunno, just thinking out loud here. That method seems like it'd be difficult to execute to me. But I'm new at this and still learning what I can and can't do.





 
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Bruce Berman

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-16 2:19 PM
Post #33953 - In reply to #33952
Dave
Carcass miters are a challenge on larger boxes. Here are some pointers.
The sides must be flat and straigt. The thicknesses of the panels must be consistant. Your cuts must be very square.

There are two miter joints that can be used for larger carcassses.

One is the "lock miter". This is a joint using a shaper or router bit that is designed for this joint specifically. It is widely used in the speaker industry. This bit is available in most full feature tool catalogues in the router and shaper bit section .
The second commom joint is the splined miter. It can be down on the table saw. You can look it up in most of the advanced woodworking texts. This is a good general miter joint for carcasses.
Both of these joionts allow you to clamp the corners allowing for a tight fit.

Try one of these out on a smaller box to get a feel for it. I think you might find your time better spent perfecting good miter joints that you will have to use in production anyway than trying to find rather labor intensive ways to make a joint that looks like a good miter joint. I think you will be pleased with the results.

Good Luck
Bruce Berman
The Miracle Veneer Trimmer






 
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Dave Peterschmidt

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-17 3:02 PM
Post #33954 - In reply to #33953
Bruce, thanks for the tips. I've already had some experience with a set of 45 degree lock miter bits. I bought them along with a small Rockler router table a while back with the intention of using them to create these joints. Unfortunately the router table was apparently a poor design, particularly the guide fence, and I was unable to use the bits to produce a straight, consistent cut. I don't have room in my shop for a large router table, so right now the lock miter concept isn't working for me. I did pick up another technique at another forum, though, which I think will be easy to execute and hopefully will produce a good joint. I'll be using that technique soon on my next cabinet. In any case, I can produce good solid joints. Improving my cabinet builds is not going to solve my need for a quality veneer finish.



 
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Don Stephan

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Location: Cincinnati, Ohio

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-17 9:03 PM
Post #33955 - In reply to #33944
Dave:

First, Brian is a terrible judge of character (but thanks for the kind comments BG).

And thank you Brian for the nice comments regarding the stands. First time I've known that anyone has seen them on the web site.

I made the carcases first, cutting 45 degree edges on the table saw. I then used an Inca 45 degree square to set the jointer fence and ran the edges through the jointer to get a more accurate angle. Finally, I ran the edges through the table saw again to cut a miter slot about 1/4" deep.

I found urea formaldehyde glue, such as Unibond, the ideal glue for assembling the cabinets because of the long open time. Most of the carcases are MDF, and I applied the glue with a squeeze bottle for speed and then brushed with a glue brush. I applied two coats as the first penetrated quite a bit. I held the joints closed with Collins spring clamps about every 5 inches.

The next day, I carefully sanded with a strip of sanding belt on a 4" x 12" piece of MDF, trying to avoid rounding the edges. VERY occasionally, I had a gap that required filling with Minwax two part filler or something similar.

After those steps, I veneered one pair of opposing sides. It took some time to learn how to carefully sand the edges flush (again with the 4" x 12" board) without chipping. Then I veneered the other pair of opposing sides. Last, I veneered the top.

For maple, I used another brand of urea formaldehyde (Pro-Glue) which seemed lighter in color, but Unibond is also a great product that has never failed me.

Especially for smaller carcases, one can press veneer with cauls and hand clamps, but if the plan is to produce any volume at all a vacuum press is a lifesaver.

My immediate sugestion would be to get some raw maple veneer and make a test pressing with your same adhesive and process. My understanding is that one of the differences between paper backed and raw is that the wood veneer on the paperbacked is so thin that any sanding at all beyond light 220 or so would sand through. I have sanded veneer with 6-8 passes of 80 grit, 6-8 of 150, and 6-8 of 220 before without sanding through.

If the Heatlock adhesive dries dark, you can also try using white PVA adhesive, using the exact same iron-on approach to see if that would lighten the edges.

Now you have me curious to look closely at the edges of the maple stand, but I don't recall that the glue line was at all noticeable.

Keep posting questions - looking through the archives you'll see I have pestered the forum innumerable times, and will continue to do so.

Have fun with the veneering, and hope you hear some big band & swing through the speakers...

Don


 
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Dave Peterschmidt

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-18 8:55 PM
Post #33957 - In reply to #33955
Don, I appreciate the detailed response. If anything it has reassured me that my basic approach was the right one. I'm starting to think I've simply used a dark glue on a light wood, which wasn't a particularly good match. Perhaps I'll try to come up with a way to darken this particular cabinet to make the glue lines less visible. I'll definitely try some white glue with the maple and see how that works out.

Was there a particular reason you veneered pairs of opposing sides vs just working your way around the cabinet?

The veneer I was using was 10mil thickness. I've been using 120 grit with a sanding block to flush the edges and clean up the seams. I haven't really hit the veneer with much of a sanding effort as yet so I don't know how quickly they'll sand through, but I have done some spot sanding as needed and haven't gone through yet. Nothing like what you described, though. I'm pretty sure the sanding schedule you described would remove the veneer completely.

Back on the subject of glue lines, one thing I noticed was that if I sand the veneer edges such that the visible glue line falls exactly on the corner it's much less visible to the eye. I think it kind of tricks the eye into thinking it's seeing a shadow or something. Anyway, to get that effect I had to carefully sand down the visible edge grain of the seam. It seems to work well on some of the seams but not so well on others. For example, for some reason it's been quite effective at hiding the glue line along the top and bottom corners, but not so much on the body panel corners.

Another thing I'm curious about is that I recently picked up some matching edging from the same company that made the veneer (Cedan). The interesting thing is that this edging comes pre-glued with a white, heat-activated adhesive of some kind. I'm betting this adhesive will probably not leave much of a visible glue line, although I haven't tested this assumption yet. I've been trying to find out what kind of adhesive it is so I could look into using it on future maple veneering projects, but so far no luck. However, maybe the regular white PVA will work just as well.

BTW, using the Collins clamps do you ever have to repair the divot the clamp makes, or does it disappear after the clamp is removed? Like you, I use MDF, and I've been wondering how well the Collins clamps would work with it.

As for the speakers, I've definitely listened to some big band and swing on them. I used big band music fairly often for listening tests during crossover development. Brass instruments have a way of making crossover flaws audible...



 
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Don Stephan

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Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : RE: Outside corners without visible glue line?
Posted : 2007-07-21 8:42 AM
Post #33967 - In reply to #33957
I veneer opposing sides at once for efficiency whenever possible.

I've used iron-on melamine edge banding for shop cabinets, and find the adhesive is rather thick, leaving a dark line. You'll have to try your product and see if it is acceptable to you.

Unless I do a lot of trial clamping before glueup, the Collins clamp dimples generally are small enough to ignore, especially on substrates.

Good luck!
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