Veneer trimming problem

[megamuel]

Hi guys,

I'm in the process of veneering my speakers and I've hit a few problems that didn't occur on my test pieces. I'm using raw mahogany veneer (could not find wide enough backed veneer in UK!) and I'm using a normal flush trim router bit to trim the edges. The bit is new so it will be sharp, however, after trimming with the router I noticed a small amount of chipping along the edges and especially in the corners. Any ideas why this might happen or how to avoid it? Luckily its only happened on the back panels but I wanted to find out how to avoid this happening before continuing. I had the router set to a slow speed, is that right? Could it be that there was too much of an overhang? Some pictures attached to show what I mean.

Cheers guys,

Sam.

[bonehead848]

were you making the cuts slow?

[megamuel]

With the router? Pretty slow yeah, I definately wasn't rushing....

[ColoradoTom]

Hi guys,

I'm in the process of veneering my speakers and I've hit a few problems that didn't occur on my test pieces. I'm using raw mahogany veneer (could not find wide enough backed veneer in UK!) and I'm using a normal flush trim router bit to trim the edges. The bit is new so it will be sharp, however, after trimming with the router I noticed a small amount of chipping along the edges and especially in the corners. Any ideas why this might happen or how to avoid it? Luckily its only happened on the back panels but I wanted to find out how to avoid this happening before continuing. I had the router set to a slow speed, is that right? Could it be that there was too much of an overhang? Some pictures attached to show what I mean.

Cheers guys,

Sam.

Make sure the direction of travel of the router is such that the router bit is spinning into your work (sometimes called a climb cut). Climb cuts require that you keep concentration on what you'e doing as the bit has a tendency to "pull" the router along.

here is a link:

http://waterfront-woods.home.att.net/Articles/Climb-Chip-Cutting.html

Tom

[Biff]

Normally, if you place a cover piece over the veneer, say, a sheet of 1/8" scrap sacrificial mdf or ply that slightly overhangs the face you are trimming the chip out will occur on that surface instead. If raw veneer is very dry it can sometimes split like your image shows and if that is the case a bit of veneer softener will help elasticize the fibers and reduce tearouts.

[Rolex]

What is your method of application? I am surpirsed you couldn't find backed wide enough. here in the US, we can buy 4'x8' sheets. That should be plenty wide, I haven't seen raw veneer that wide.

At any rate, the first thing that sticks out to me is that maybe the corners or areas of chip out are not adhered properly to the substrate. Even if your application method is iron on, you have to make sure and hit the edges and corners real well, or you can get router chip out exactly like you are showing..

[Martyn]

It's a good idea to rough-trim the surplus veneer with a utility knife before using your router. Just stand the veneered face on a slab of MDF to support the veneer. Use a steel rule or something similar to space the knife blade away from the adjacent face. As always, don't try to cut through in one pass.

[eddo]

When trimming veneer I always run the router full speed, and go rather fast around the workpiece. Granted I use paper-backed veneer, but I've never had an issue with chipping.

[megamuel]

What is your method of application? I am surpirsed you couldn't find backed wide enough. here in the US, we can buy 4'x8' sheets. That should be plenty wide, I haven't seen raw veneer that wide.

At any rate, the first thing that sticks out to me is that maybe the corners or areas of chip out are not adhered properly to the substrate. Even if your application method is iron on, you have to make sure and hit the edges and corners real well, or you can get router chip out exactly like you are showing..

I'm actually using a spray adhesive. This method was suggested to me by some guys on a woodworking forum here in the UK. It has bonded fine and I've not had any major problems with bubbling, but this could be the problem with the chipping if the bond isn't strong enough. As for the backed veneer, I struggled to find any at all never mind stuff wide enough. Maybe I didn't look hard enough! However this has been a problem with much of the parts I've needed for my speakers. All the things that best fit the job are in the US!

Tom, thanks for the link. I think I was actually using the chip cut as supposed to the climb cut. This might explain things. I will definately give that a go. I thought I was only supposed to use the router in one direction so I did not consider this. Thanks.

Eddo, I just assumed that a slower speed would be more suitable as the veneer shouldn't take too much effort to cut... Anyone els have any input on this, fast or slow? Thanks guys!!!

Sam.

[Carl V]

I run it reasonably fast
I also have used softener when using raw/unbacked veneer.
I have the bit running towards me---climb cut.
I also don't have large overhangs to trim off.

Good luck. if you apply a layer of tape for your roller guide
to run on this will give you a few mm. of leeway. The you
wil be able to sand back this last portion & threby eliminate
the chipping.

I've done this with burl veneer & unbacked.

[Dennis H]

Make sure the direction of travel of the router is such that the router bit is spinning into your work (sometimes called a climb cut). Climb cuts require that you keep concentration on what you'e doing as the bit has a tendency to "pull" the router along.

here is a link:

http://waterfront-woods.home.att.net/Articles/Climb-Chip-Cutting.html

Tom

+1 on what Tom said. Remove most of the material with a climb cut to avoid blowouts and then do a finishing pass the other way to clean it up. That said, if you have more than 1/8" or so hanging over, it makes sense to trim some of it off with a knife/saw/scissors before you start with the router.

[Rolex]

One way that has worked for me is to cut the veneer witin an 1/8" all the way arround. Then I just sand off the excess (hand sanding only) and forget the router all together. Not my first choice, but I needed to do that with the heavliy figured project I just finished.

I also think your choice of bonding is not the best.

[megamuel]

Cheers guys, I turned the speed up a bit on the router and change my direction of cut and this has worked fine, no chips! Rolex, I know there are better methods but this seems to be bonding fine and is a lot less labour intensive than some methods. I'll post my results when I'm done and then I'll let you judge! Thanks again,

Sam.

[CupCak3]

I don't want to put words in Rolex's mouth but I'd be concerned about long term bonding & bubbling... though spray adhesives have come a long way in past years

[JonP]

I run it reasonably fast
I also have used softener when using raw/unbacked veneer.
I have the bit running towards me---climb cut.
I also don't have large overhangs to trim off.

Good luck. if you apply a layer of tape for your roller guide
to run on this will give you a few mm. of leeway. The you
wil be able to sand back this last portion & threby eliminate
the chipping.

I've done this with burl veneer & unbacked.

Sounds like most of what I was going to add, though my variation was to have a layer of easy release tape on the veneer face where the bearing would hit. Mainly I was thinking to protect the other face from marking with the bearing, but the good side effect is that you space the flush trimmer away from the surface, and the cut portion sticks out a bit.

I haven't tried the tape on the bearing, I guess one could go either way... as long as it's not easy to lose the tape. I had a bit of grain lifting when peeling the tape off the veneer... when you do that, always pull cross grain!

FWIW... I didn't use climb cut on most of my cuts, sometimes right near a corner. I had pretty good result on the African Mahogany, your wood may vary...

[Rolex]

I don't want to put words in Rolex's mouth but I'd be concerned about long term bonding & bubbling... though spray adhesives have come a long way in past years

Agreed. Spray adhesives are okay if you use the commercial variety in a pot. Out of the can, I would never trust it.

I know there are better methods but this seems to be bonding fine and is a lot less labour intensive than some methods

I agree it is a lot less labor intensive. What you may find though, is that it doesn't hold up over time. In fact, depending on your method of finishing, it may not hold up to the moisture you apply in the finishing process.

[megamuel]

Guess I'll have to wait and see how it holds. In the mean time, any advice on how to best fill those chips? I intend on finishing up with Danish Oil. So I need something I can use with that. Thanks again,

Sam.

[Martyn]

Oil finishes are rather unforgiving of surface blemishes like chips and scratches. Unless you're a fussy bugger like me, remember that no-one is likely to look at your speakers from less than a metre away. Your alternative is to let some edging or stringing into the corners in the same or a contrasting species. More work...

[megamuel]

Yes I am a fussy bugger! I'm having sleepless nights over these chips I tell you! I've ordered some strong 2 part filler in mahogany so hopefully that will vaguelly match the colour, then I'll just touch it up with some pencils or something. Luckily they are only on the underside and back as I found out the proper way to do it before doing the important parts!

[Dennis H]

For big chips like this one, I'd try to glue in a veneer patch with matching grain and just use the filler, if at all, on any crack between the patch and the main veneer. Try to straighten out that ragged edge with a razor knife and a straightedge before you patch.

[Martyn]

Try your mahogany filler on a piece of scrap first - your Danish oil will almost certainly "take" differently on the filler than on the veneer. In the past I've tried mixing mahogany sanding dust with wood glue and using it as a filler, but without much success. I've also used a grain filler and coloured it with mahogany stain, but you'd still want to try a test piece first. For your test piece, use a piece of veneer bonded to a substrate - it you use just raw veneer you probably won't get the same result.

[megamuel]

I did think about the dust and glue thing, done that with MDF before but wasn't sure about doing it with mahogany. I guess I'll wait until this filler arrives and try it on some test pieces. Whatever happens a different coloured filled gap will look better than a gap I guess. Anyway, I used to do a bit of art I should be able to get it looking something like the grain with paint or pencils or something... Cheers Martyn et al,

Sam.

[Hank]

I recently found spiral flush trim bits - haven't tried my new one yet, but I think the concept is spot on. The #5089 in your hand-held routher should do the trick:

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_solid.html

[Martyn]

Great idea - I'll look out for those.