MDF Joinery

[Rick]

Hey all,

I have this question asked in my Project Thread (link in my sig) but figured the experts might see if better if it was here as well:

"If I am joining six pieces of MDF together to make a single 'sheet', using carpenter's yellow glue, do I absolutely need a good set of clamps across the 21 1/2" distance, or if I make sure they are straight and flat, with a good amount of glue on each of the adjoining faces, with 'weight' holding the left and right sides together (I have a bunch of house bricks - 400 actually - heh) on a sheet of newspaper, will this become 'secure and solid' when the glue has dried?"

More info - Because of the way I'm constructing my control panel, I need to join up six pieces of 3/4" MDF in the following manner:

Piece A and F measure 2" wide x 12" deep x 3/4" tall.  Piece B and E measure 2" wide x 10" deep (there's a 45 degree angle, but this makes little difference to the info) x 3/4" tall.  Piece C and D measure 6 1/2" wide x 10" deep x 3/4" tall.  I would like to join A-B-C-D-E-F together, and this face will have support running horizontally across the front and back, which (I believe - and I'm hoping/praying) will support the joined piece.  Once it's all joined up, I will be sanding it all flat, so that the seams are invisible, but obviously, I need it to be strong enough to not 'break apart' once I'm complete.  (Yes, I realize there's 1 1/2" missing - those are the end pieces, which will be attached later.)

Ideas?  Do I go out and buy different adhesive/Gorilla Glue?  Do I wait and buy/use proper clamps instead of my 'scapegoat' solution as above?

[The Lumberjackass]

its a bit late where i am at the mo , ( 2:46 am to be precise lol ) , but what i gather from your post by glancing at it, is that you want to join sheets of mdf together by butt joining them ?

the simple answer to this , is a yes , but it all depends on what kind of load the mdf has to bear,
and, what dimensions the sheets are. ( obviously you cant join 8 x 4 sheets , that'd be complete madness )

but , i would use dowels along with the glue if the panels arent too great in length or depth.
its not hard to do , you can buy a dowel kit which has the drillbit and the center pins. bosch make them
and i think they are priced under 10 euro.


it'd help if you dry assembled the mdf parts and posted a pic so i could get a better look at it or have a decent
idea of what you want to achieve

[BobA]

I like to use biscuits and a slot cutter as there is more leeway then using dowels.  A Kreg jig is also useful but not for this large a construct.  I would definitely get a couple of clamps that span your work. Yellow glue works well but do not overclamp.  I usually use Weldbond as it is more durable and has a better setup then reg yellow carp glue.

http://www.weldbond.com/

[Rick]

it'd help if you dry assembled the mdf parts and posted a pic so i could get a better look at it or have a decent idea of what you want to achieve

Here is the render of the present design.  This will be similar for both the top and bottom pieces of the control panel, and will bear normal load across the face.



The length of the control panel will be 21 1/2", the width will be 12", and the depth of the top will be 3/4".  (The depth of the bottom will be 5/8".)  For reference, the first piece is 1 1/4" in width, the second piece is 2" in width, the centre piece is 15" in width.  I am planning on building a simple dowel jig (similar to the one found here) based upon your recommendations of strengthening the pieces.  I figure that if I inset the dowels by approximately 1 1/4" inches from the sides, with one in the centre, that this will likely provide me with the strongest bond.  Now, considering that the top face will have the joystick and button holes cut into it, do I need to be more sensitive to the dowel location at all?  I figure that as long as I am careful with my cuts through, that it shouldn't make too much of a difference.

[EvilNuff]

Is there a reason you want to join the wood together as opposed to take one panel and cut the notch out?

[Rick]

Is there a reason you want to join the wood together as opposed to take one panel and cut the notch out?

Yes.  The entire top face slopes at a 15 degree angle, making the edge cuts possible (and very difficult) only with my jigsaw.  Here is a view from the left side to further illustrate.



If the front wasn't at a 90 degree angle straight down, then cutting a single piece would work perfectly.  Sadly, I opted for the 'omg, what the hell was I thinking?!' route.

 

[Rick]

I stand somewhat corrected! On my comment above, I mentioned that I needed multiple pieces - well, I still do, but not as many as first thought.

Piece 1 and 2 could be combined, as I could do the 15 degree cut of piece 1 AND the the ~10 degree cut of piece 2 using a mitre saw. Since I do already have most of the pieces cut, and I've read that butt joined and doweled pieces could be stronger than even a single piece, I shall stick with my original design.

[The Lumberjackass]

for what you want to do , dowels and glue would be my reccomendation.
and if anyone leans on the joined parts , at least the dowels could take a bit of pressure without caving in.

however , if i was going to do this myself , and once the finished panel was ready ,
i'd go as far as adding a top coat of fibreglass for strength . then bondo the finished piece
and sand the hell out of it to get a proper professional look.

but then again , thats just me being over cautious tbh
dowels and glue would be strong enough. ( dowel every 3 inches for maximum rigidity )

[drventure]

I think you'll have better results and a stronger cp if you cut the whole thing from one sheet and mitre the edges. The back and part of the front will be easy.

The angles won't be too bad with a skillsaw, the inside cut might be tricky, but worst case, you cut shallow and use a sander to true it up.

Heck, you could also cut just 3 pieces instead of 5 and simplify a bit, but I'm still not sure you'll get the result you want doing it that way. I pieced a keyboard tray together like that out of oak with biscuits, but I could run the whole thing through a planer to get it true once it was glued up. I don't think you'd want to try that with MDF 

[Rick]

Heck, you could also cut just 3 pieces instead of 5 and simplify a bit, but I'm still not sure you'll get the result you want doing it that way. I pieced a keyboard tray together like that out of oak with biscuits, but I could run the whole thing through a planer to get it true once it was glued up. I don't think you'd want to try that with MDF 

Hmm...  Now, you have me thinking.  No, not about redoing most of my cuts (ha) but about the biscuit thing.  Since I have my new router (see this thread) and table, I was wondering if I could just go buy a slot cutter bit and use it as a biscuit joiner?  MLCS Woodworking has a nice page on it.

From what I gather - and I have yet to hit up YouTube or other sites to check on this - I would assume the process should be as follows:

1.) Place the pieces of stock to be joined end-to-end at the joining point, and make a pencil mark on each where your slot cut is to be centered.
2.) Install the proper slot cutting bit, and set it's height appropriately.
3.) Set up your router table fence for the appropriate depth for your cut.
4.) Using a piece of scrap stock (that matches your good stock, of course!) test your cut.  Adjust the bit and/or fence accordingly.  Re-test until it's proper.
5.) With the mark on the stock centered in the bit, press the stock against the bit to make the cut.  Do the same with the other piece to be joined.
6.) Apply glue in each slot, fit your biscuit, and attach your pieces.
7.) Clamp and let dry.

Now, the only thing I can think of is that centering the bit could be a bit tricky, seeing as the table fence is used for managing the depth while the stock travels parallel down its face.  So, I was thinking that I might clamp a piece of stock perpendicular to the fence so that the centers of the biscuit cuts would match up a little better.  I'm not certain how necessary this might be, as I haven't worked with biscuits before, so I ask this: is there not a bit of 'play' in the slots whereby the biscuit cuts don't need to be 100% on each side?  (Of course, anything I can do to increase my success, I'll do.  That's the reason why I'm here, asking the Experts.)

I'm planning on hitting up Home Depot and Princess Auto on my lunch today, so any input you might have would be appreciated!

[drventure]

Now, the only thing I can think of is that centering the bit could be a bit tricky

Yeah, that's the risk I see there. You're idea of clamping a perpedicular piece to the table as a guide stop should work fine for that.

However, if you think you might do any other biscuit type joins, I'd scout CL for any deals. A real biscuit joiner makes that process REALLY easy! I picked up a makita of CL for 40$ a while back.

[Rick]

However, if you think you might do any other biscuit type joins, I'd scout CL for any deals. A real biscuit joiner makes that process REALLY easy! I picked up a makita of CL for 40$ a while back.

I agree - I could kick myself for missing out on the Ryobi Biscuit joiner that was on sale a couple of weeks ago at Home Depot.  It was regularly priced for $110 and on sale for $55.  Ah well.  I'll do my best!  (Actually, truth be told, I'm pretty excited about trying it.  I'm going to pick up a slot cutting bit and arbor - and, I guess, a bearing as well...  Sheez.)

Edit: Hmm.  I don't think I need the bearing yet.  These will be done on the table, so I can use the fence to set the depth.  Cool.  Money saved!

[The Lumberjackass]

im only giving my opinion here , but i personally wouldnt use biscuit joinery on a part which may eventually get a heavy
type dude leaning on it with his elbow.
i know most joinery is strong enough , but i dont reccomend biscuit joinery for something like this.
the only time i ever use biscuits is to help align a piece first . then i use screws and glue to fasten the joint.

its your choice at the end of the day with what you'd like to do , but if it were me , i'd test join other scrap parts
first  , and then add the type of pressure to the joint with which it may one day have to withstand from general use.


anyways, im usually very weary of biscuit joints . i always dowel when in doubt.

[Rick]

the only time i ever use biscuits is to help align a piece first . then i use screws and glue to fasten the joint.

So, how about this:



It's just rough, but because the first piece is 1 1/4" and the second is 2", I went with a 4" screw to check the depth if I drilled and went this route.  I didn't draw in the biscuits in this instance, but if I go with the screws in this case, I would likely do as you say - use them to align the piece first.

Now, here's one other thought for you.  I was only considering using the biscuits to join up the top and bottom pieces, as they will be supported by both front and rear supports.  The 'frame', so-to-speak, will all be glued in place, pre-drilled and set up with countersunk screws.  Do you think that the screws to attach the top and bottom pieces might be a bit of overkill, or would you still recommend them?  (I'm leaning towards them, but of course, my one concern is hitting any one of them when I have to drill for my joysticks and buttons.  Planning around that, of course, is still pretty easy.)

[The Lumberjackass]

hmmm,

you pose a good question.
but first , are these pieces , once they are attached , going to be flat ?
i.e , is the surface of the finished panel going to be completely flat along the entire surface ?

if so , cut out a full panel from mdf , it'll cut out the mess straight away.

but,
if the pieces are going to be added by means of using different angles , i.e - you want the edges to slant
downwards each side of the joysticks , then dowel and glue only . dont use screws as a form of dowel .
because as you say , cutting the panel for the joystick holes will pose problems if its located anywhere near the screw.
if you use dowels , at least it can be cut safely.

[Rick]

you pose a good question.  but first , are these pieces , once they are attached , going to be flat ?  i.e , is the surface of the finished panel going to be completely flat along the entire surface ?  if so , cut out a full panel from mdf , it'll cut out the mess straight away.

The entire face of the control panel is angled 15 degrees towards the player, with the flat pieces going 90 degrees straight down towards the floor.  (I'm hoping these reference views will tell the story better than I am...)



There's the top, front, left and isometric view of the completed control panel.

but, if the pieces are going to be added by means of using different angles , i.e - you want the edges to slant downwards each side of the joysticks , then dowel and glue only . dont use screws as a form of dowel.  because as you say , cutting the panel for the joystick holes will pose problems if its located anywhere near the screw.  if you use dowels , at least it can be cut safely.

I think that's what I mean - I did the joinery for the top yesterday (using the biscuits - it was my original plan) and everything is nicely clamped up...





The 'end pieces' are scrap stock, so I didn't marr the sides, and it's been clamped for the past 18 hours.  Everything seems pretty strong (so far) and I'm planning on doing the same for the bottom as well if everything is nice and tight as I hope it is.  I have some work to do evening up all of the cuts, but hope it will all turn out good.

[The Lumberjackass]

ok , i see what your trying to do now.
but i just cant understand why you didnt cut it out of a flat sheet to begin with. you've made things
alot harder on yourself overall. but hey , as long as it gets done , right ? hehe

but just as a sidenote , when you have everything clamped up and the glue has set , throw the panel
on a fresh sheet of mdf and use it as a template ( trace around the edges ). this way , if anything
should go wrong later , at least you'll have a full sized control panel , with no joints , ready and waiting to be cut out.

just an idea. better safe than sorry

[Rick]

ok , i see what your trying to do now.  but i just cant understand why you didnt cut it out of a flat sheet to begin with. you've made things alot harder on yourself overall. but hey , as long as it gets done , right ? hehe

but just as a sidenote , when you have everything clamped up and the glue has set , throw the panel on a fresh sheet of mdf and use it as a template ( trace around the edges ). this way , if anything
should go wrong later , at least you'll have a full sized control panel , with no joints , ready and waiting to be cut out.  just an idea. better safe than sorry

I appreciate the input!  My concern was the angles on the front.  How would you recommend cutting them, if I restart with a fresh, flat piece?  (I don't have a problem doing that - I'm not so far in that I can't redo it.)  Are you thinking jigsaw cuts would be as good, as long as I adjust for the various angles?

Edit: I am the "Master of Second Guessing Myself", and I am completely leaning towards trying this.  If I can recreate the top with the appropriate angles and a jigsaw, likely requiring less sanding and significantly less filler, I think you're right.  As it is, I've made awesome progress on something that I could have made significantly greater progress if I had thought about it more ahead of time.

Damn.  I hate when that happens.

 

[The Lumberjackass]

all you need is a router with a bearing guided cutter a to cut an exact replica of the template.
place the template on the new sheet of mdf , clamp it , and use the router to produce a clone.
and , stay away from the jigsaw , they are designed for cutting curves and circles only.

[Rick]

all you need is a router with a bearing guided cutter a to cut an exact replica of the template.  place the template on the new sheet of mdf , clamp it , and use the router to produce a clone.  and , stay away from the jigsaw , they are designed for cutting curves and circles only.

Ok, two questions I have.  One, using the router, I won't get a crisp corner on the internal angles, will I?  I don't have an issue using it to get close, and then cleaning up the internal corner later.  Two, how would I create the 15 and 9 degree angles on the front of the top, if not with a jigsaw?  Maybe there's a cutting tool I'm not privy to?

[The Lumberjackass]

there are alot of router bits available with many different cutting angles.
you can buy them with or without a guided bearing , so any cut is possible with them.
if your looking to bevel edges at any degree , or cut slots at any degree , a router with the proper bit
will make short work of anything you need to do, regardless of the cut type or location.

as for making clone cuts , or copying a template with a bearing guided cutter , the edges will come out
100% the same as the original , provided the bearing can fit into any intricate / detailed shapes or edges.

something tells me you dont have much experience with a router . trust me , get to use one more often and
alot of your work will be better , easier and faster to make. they really are the best and most versatile machines
anyone could own.

[Rick]

You're absolutely right - I'm a router newbie.  I'm learning, and it's a fantastic tool. (I'm loving the biscuit joinery.)

I actually went ahead and rebuilt my top, although I didn't do it as I had originally intended as one piece. I thought "what is the best way to minimize the number of joins, while still getting the crisp cuts with the tools I have?" - those tools being a router with 'common bits', a table saw and a mitre saw.

So, I figured it out - I cut a rectangle with the 15 degree bevels front and back, and built the front 'wings' from separate pieces of stock!  Now, I have two, small, 3" seams to fill, instead of the five large ones on my original attempt!

It was all a matter of thinking through the compromise. I couldn't afford all the bits required to make the cuts I need, so improvisation saved the day. I joined the pieces using biscuits, and the actual face spans the entire length, so I'm calling this a win. Not to mention that this piece looks so much nicer than my first try.

Thanks again for all the advice! It has really come in handy.

[The Lumberjackass]

no probs dude, glad your happy with your finished piece.

sidenote :
did i read correctly that your using your router for biscuit joinery ?
please dont try cutting slots with your router , thats what the biscuit jointer is for.

[Rick]

sidenote : did i read correctly that your using your router for biscuit joinery ?  please dont try cutting slots with your router , thats what the biscuit jointer is for.

The 'bad news' is I don't own a biscuit joiner. The 'good news' is, I seem to have a lot of skill in biscuit joinery on the router!  I used scrap stock, setup a couple pieces of wood with clamps as a stop guide, and marked the width of the biscuits on the stock before cutting with a 5/32" slot cutting bit for the number 20 biscuits. Everything worked really well.

Maybe I was lucky.

[The Lumberjackass]

i suppose you could get away with doing it that way alright

its just i had a horrible vision of a router newbie using an ordinary straight bit on the edge
of a 3/4" board.

phew , thank god your using a slot cutter , hehe lol.

[Rick]

Found the info on YouTube, and verified it at Home Depot! Worked a charm.