I'm building a pair of cabinets out of MDF right now and am wondering about the edges. The original plan was to miter the edges so that there are no visible seams, but now I'm wondering if mitering the edges is actually necessary for this.
Would it be just as possible to get as nice of a flush edge (so that the speaker appears to be one solid piece of wood) by just using normal butt joints and and then using a liberal amount of filler in the gaps, sanding, reapplying, and so forth? Or is a miter joint really the only way to go?
Would it be just as possible to get as nice of a flush edge (so that the speaker appears to be one solid piece of wood) by just using normal butt joints and and then using a liberal amount of filler in the gaps, sanding, reapplying, and so forth? Or is a miter joint really the only way to go?
The seems showing is because MDF expands primarily in the thickness direction. Butt joints will always show. I've read that another solution is to use butt joints and cover them (and the rest of the box) with 2 mm MDF.
...cut a wide and shallow V-groove along the butt joint (it's easiest to do on the T-saw before you glue up), fill with Bondo and sand it smooth with a block.
Alternatively ....
... you can 'celebrate' the joint with a kerf.
Consider round-over of enclosure edges for acoustical reasons.
2" x "2" Stock can be used for this purpose.
Also you can strengthen panel assembly by using spline & grove, rabbet or dado joinery.
Regards,
WHG
... you can 'celebrate' the joint with a kerf.
Consider round-over of enclosure edges for acoustical reasons.
2" x "2" Stock can be used for this purpose.
Also you can strengthen panel assembly by using spline & grove, rabbet or dado joinery.
Regards,
WHG
Long miters suck to cut and assemble. How about a butt joint in 3/4" material and then round over the corner with a 3/4" radius bit. The roundover ends right where the joint is and does a decent job hiding the joint. Add batons or tongue and groove or whatever to reinforce the assembly.
Yes, the edges will be rounded over with a router.
Have you tried and/or seen this or is this an idea to try?
Thanks, after you posted this I saw a thread where someone did this and it seemed to turn out well. Do you know how well this holds up over time?
I'm not sure I understand what you mean. I do know what a kerf is but not sure how it'd work in this context. Do you mean something similar to the v-groove suggested by tommus, except with a kerf rather than a v-groove? And how would the 2"x2" stock be used?
Also, has anyone tried using butt joints, then roundover, then a veneer and painting over the whole veneer? Or would the butt joint still start to show over time?
Thanks guys!
evanc said:
Have you tried and/or seen this or is this an idea to try?
tommus said:
Thanks, after you posted this I saw a thread where someone did this and it seemed to turn out well. Do you know how well this holds up over time?
whgeiger said:
I'm not sure I understand what you mean. I do know what a kerf is but not sure how it'd work in this context. Do you mean something similar to the v-groove suggested by tommus, except with a kerf rather than a v-groove? And how would the 2"x2" stock be used?
Also, has anyone tried using butt joints, then roundover, then a veneer and painting over the whole veneer? Or would the butt joint still start to show over time?
Thanks guys!
Main problem is finishing the exposed MDF ends.
As well, with 45 degree mitres, the joint is longer and the glue area longer.
Another option is to use square stock at the edges and butt them MDF to that.
J.
As well, with 45 degree mitres, the joint is longer and the glue area longer.
Another option is to use square stock at the edges and butt them MDF to that.
J.
Check out Lock Miter bits if you have a router table.
They are a bit of a pain but they work well.
When I have to do a butt joint I will seal the exposed MDF with slightly diluted wood glue and then a couple coats of dewaxed shellac after sanding the diluted wood glue.
Dewaxed Shellac will help to seal the MDF and allow for equal expansion/contraction across the entire cabinet.
They are a bit of a pain but they work well.
When I have to do a butt joint I will seal the exposed MDF with slightly diluted wood glue and then a couple coats of dewaxed shellac after sanding the diluted wood glue.
Dewaxed Shellac will help to seal the MDF and allow for equal expansion/contraction across the entire cabinet.
Lock miters are nice if you have the equipment. A butt joint will always show through paint after some time. 16 years of professional experience tells me this.
Yes, I have done it many times when making counter tops out of plywood with a solid edge. Routing a detail in the solid edge that ends right at the joint helps hide the inevitable.
A v groove right on the joint makes it look like you meant it to show. When flush trimming the parts use a router bit like this with the v running down the joint is an easy way. Whiteside V-Groove Flush Trim Router Bits
Yes, I have done it many times when making counter tops out of plywood with a solid edge. Routing a detail in the solid edge that ends right at the joint helps hide the inevitable.
A v groove right on the joint makes it look like you meant it to show. When flush trimming the parts use a router bit like this with the v running down the joint is an easy way. Whiteside V-Groove Flush Trim Router Bits
Attachments
aye, the trick to concealing a panel joint in MDF is not to try - as WGH put it rather poetically - "celebrate" it, laddie
sorry, just watched the 2 hr finale of "Outlander" on Showcase, and was feeling a bit o' it, then
sorry, just watched the 2 hr finale of "Outlander" on Showcase, and was feeling a bit o' it, then
Cabinet Joinery II
The attached sketch is exemplarily of the joinery methods I described earlier.
You can also use pocket hole screws (avoids clamping during glue set) but this requires application of a veneer after assembly.
Regards,
WHG
The attached sketch is exemplarily of the joinery methods I described earlier.
You can also use pocket hole screws (avoids clamping during glue set) but this requires application of a veneer after assembly.
Regards,
WHG
Dave Pellegrene does this thing with a routed groove along the joint using a type of wide, shallow, crown molding router bit. I can't find the link right now but the photos of the results (even after time) are flawless.
Sorry to revive this old topic, but it's been about a year and I've had a lot more experience and I'm running into this question again.
I've been cutting mitered rabbet joints on a CNC router and they work well when they work but they're very sensitive to tolerances (the CNC router I use has a very weak vacuum table, which can be a problem) and generally take a long time to cut due to switching bits, having to slow down the feed rate with chamfer bits, etc.
I'm leaning towards switching to regular double rabbet joints with large roundovers but am concerned about seams showing. If tolerances are tight, the seams are completely flush, and the radius of the roundover is large enough to make the exposed seam lie within the roundover (much like how it falls within the radius when using a mitered edge, except with a rabbet it'll be a bit off-center), do you think this would be resistant to exposing seams? I know that the separation along seams occurs because of the tendency for MDF to expand in thickness as moisture is absorbed, but shouldn't a solid double rabbet joint greatly stabilize the seams compared to a butt joint? (I should also note that I'm using Duratex on the whole box and I doubt much moisture will enter.)
The obvious answer is to give it a try (which I'm going to do later this week) but if anyone has any firsthand experience with this then I'd love to hear it.
Thanks!
I've been cutting mitered rabbet joints on a CNC router and they work well when they work but they're very sensitive to tolerances (the CNC router I use has a very weak vacuum table, which can be a problem) and generally take a long time to cut due to switching bits, having to slow down the feed rate with chamfer bits, etc.
I'm leaning towards switching to regular double rabbet joints with large roundovers but am concerned about seams showing. If tolerances are tight, the seams are completely flush, and the radius of the roundover is large enough to make the exposed seam lie within the roundover (much like how it falls within the radius when using a mitered edge, except with a rabbet it'll be a bit off-center), do you think this would be resistant to exposing seams? I know that the separation along seams occurs because of the tendency for MDF to expand in thickness as moisture is absorbed, but shouldn't a solid double rabbet joint greatly stabilize the seams compared to a butt joint? (I should also note that I'm using Duratex on the whole box and I doubt much moisture will enter.)
The obvious answer is to give it a try (which I'm going to do later this week) but if anyone has any firsthand experience with this then I'd love to hear it.
Thanks!
Possibly removing the hard MDF surface from the immediate joint area will work, exposing the softer and more flexible(?!?) core MDF. It's a thought.
The other is idea is reverse rabbet the joint making the join offset from the edge. Then groove or otherwise hide the joint.
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