# MDF advice



## basser (Sep 15, 2008)

Greetings from an newby to the forum. I am planning a built in wall/shelving unit which will be painted, so I am considering MDF and then hardwood face frames. The question is 2 fold: Should I be cutting any dado joints on my table saw or use a router set up ... and...presuming the MDF will eat up and dull the blade/bit, what types or makes are best suited for this task?
Thanks in advance,
Andy


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## Roy Harding (Jun 8, 2008)

Cut your dado's on either machine - whichever is easiest for you (I like the tablesaw, as I can go full depth in one pass - unlikely with a router, but that's just me). If you DO use a table saw, be aware that "wobble" dado blades do not cut a flat bottom - and this shows up when you glue in the mating piece of MDF. Also - depending upon your dado blade setup (shims, etcetera) the bottom of your dado may have small "ridges" - these need to be flattened either with a light pass with a router - or, if you only have a couple, a properly sized sanding block and 100 grit takes care of it in a hurry.

Use good quality carbide blades/bits. I have a "general purpose" (40 TPI, I think) carbide blade I use only for MDF.

I won't make a brand recommendation - any brand you're currently happy with will have such a "general purpose" blade.

Watch the span of your shelves - MDF (as with anything else) will sag over time if not properly supported (any purchaser of cheap MDF shelving will have discovered this).

Have fun


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## cabinetman (Jul 5, 2007)

Because of the weight and sizes of panels to be dadoed, I would prefer to use a hand router. I made this shop made jig, that makes dadoes very easy.


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## mmtools (Aug 21, 2008)

I agree with Roy, don't use a "wobble" dado. It leaves unsightly gaps in the joint. I use the Amana 8" dado set. If you have a small TS, you might look at the 6" for weght consideration. Also, some lighter weight saws do not have adequate arbor bolt length to allow you to mount a dado blade. Be CERTAIN the arbor nut is fully engaged on the bolt before proceeding!! You can add some rigidity to the shelves by including a 1/2" hardwood rabbeted nose piece on each shelf.


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## Tony B (Jul 30, 2008)

*Use router*

Since you will be putting your dado's across the small side of your end pieces, I would think the router will be much safer, both for you and your workpiece. MDF is heavy and a long heavy piece, presumably 2'X8' ( 2 pcs. 1'X8' each) would be very awkward to dado crosswise on a table saw. 
I have read much about MDF eating up blades, but I personally have not found this to be true. I have cut lots and lots of MDF, and oak and other hardwoods eat up my blades much faster.

I have used a jig similar to Cabinetman's jig and they work great. 
I would plan on dadoing the long pieces as one piece and slice it down the middle when you are done. If measurements are critical, make sure you leave enough width to account for the saw kerf and clean-up cut.

Tony B


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## basser (Sep 15, 2008)

*shelving unit advise*

Thanks for the advise gents. That router jig is a definate...and I will then use a router. My table saw is 10" and i just completed a 24" sled but I did not want to chew it up with the dado set(I have a Frued 8" dado set with chipppers) and I have wrestled with those full sheets enough to realize I am going to cut the panels oversized with a circular saw and trim down to size on the table saw. Current plans call for shelves 36" wide.... now honestly... should I be using 3/4" plywood?
Thanks again
Andy


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## Roy Harding (Jun 8, 2008)

basser said:


> Thanks for the advise gents. That router jig is a definate...and I will then use a router. My table saw is 10" and i just completed a 24" sled but I did not want to chew it up with the dado set(I have a Frued 8" dado set with chipppers) and I have wrestled with those full sheets enough to realize I am going to cut the panels oversized with a circular saw and trim down to size on the table saw. Current plans call for shelves 36" wide.... now honestly... should I be using 3/4" plywood?
> Thanks again
> Andy


You're spanning 36"? Check this link out:

http://www.woodbin.com/calcs/sagulator.htm


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## 97phatlady (Aug 16, 2008)

Advice on how to build this I'll leave to the experts (I'm a learner) but I had my first experience with MDF several weeks ago and I'll share my experiences. MDF - very, very heavy - very, very dusty when you cut it.


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## user4178 (Apr 18, 2008)

The quality of the cut at the bottom of the dado probably won't be a big issue if you are face frameing. Depending on how tall your sides will be, it would probably be the easiest and safest to use a router in a jig. If they are short managable sides and you have good dust collection on your tablesaw, from a dust stand point you'd probably be better off useing the tablesaw. I have a Freud 8" stack dado set also and I'm very happy with it. If you face your shelves front and back you might not get any saging.


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## Bob Willing (Jul 4, 2008)

Speaking of MDF. What is a good finish for this material? I am using MDF for drawer fronts that I have laminated (sides and front). I want to stain the back side that faces the drawer to match the laminate. I was thinking of using a polyurethane stain. There will be only about 2" or less that is exposed after I attach it to the drawer. I will put the finish on before I attach it to the drawer.


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## pianoman (Jan 16, 2008)

MDF, is less expensive than good quality vaneer core (cabinet grade) ply. MDF mills easily...but needs to be protected from moisture. I would say MDF is used more in commercial work than residential. Are you going to vaneer the visible faces? And with what? You`re right...hardwood facing should be dadoed to the MDF. Formica has a tendency to delaminate within 4 to 5 years in commercial application. I think this is due to the adhesive used today. I would use a good quality vaneer core ply to match the sizable wood being used. Others may disagree. Also ...I would use a stack dado set for the plow on the back side of the facing and a router for the toung on the ply or MDF. If your shelves span 3 ft., I would use a shelf noising for added strength. Depending on your design...this noising can be very usefull...front and back of the shelfs. Rick


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## joesdad (Nov 1, 2007)

With cases made from MDF I would forgo the dados and simply screw them together from the outside just leaving a dimple like you would sheetrock and then fill them with wood filler, sand, paint, veneer. It's not pretty, but neither is MDF, and will be just as strong, look as nice finished and cut your time in half. Save the nice craftsmanship skills for a stained piece. If your spanning 36" I'd definitely consider a fastner coming in from the back somewhere too to keep it from sagging.

-Armand


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## Tony B (Jul 30, 2008)

*The two advantages of Dado's*

are 1) Mechanical strength. The shelves inside the dado's 'lock' the unit into shape which makes it much much stronger and this will be immediately noticed when 2). the unit is assembled. There should be no alignment problems. Everything pops into place which makes assembly an easy one person job. 
I always use dado's and an air nailer. If it is a really fine piece of hardwood furniture, I will not use nails, just the joint. 
MDF takes to glueing real well. 

Tony B


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## cabinetman (Jul 5, 2007)

pianoman said:


> ...hardwood facing should be dadoed to the MDF.



Hardwood facing can be just glued and clamped to MDF...no need for dadoes. In an appropriate fabrication, dadoes and rabbets give more strength to a glue joint, but it's not always feasible.




pianoman said:


> Formica has a tendency to delaminate within 4 to 5 years in commercial application. I think this is due to the adhesive used today. Rick



I don't agree with a general statement like this. Is this statement based on any factual statistics? Properly executed, high pressure laminate like _Formica_®, or any equivalent laminate will not delaminate on its own unless subjected to heat sources, improper or insufficient gluing, or a lack of effective pressure during application. Those doing commercial work should be privy to suitable glues and procedures.


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## pianoman (Jan 16, 2008)

Walk into an Circle-K fast gas...fast food place and check out the cabinets. Production laminate proceedures are completly backwards in respect to the overlap methods. Ofcorse, they are used more than residential use...the glue used today is not as strong because of environmental regulations.


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## Tony B (Jul 30, 2008)

I agree with Cabinetman. Formica and any good HPL should last 30 years or more. If properly applied, the surface will wear out before it becomes delaminated. The adhesives today are as good as they have ever been.
As for production laminate procedures being backwards in respect to overlap methods, thare are standard ways of doing things, if their method is non-standard, then maybe a 'brother-in-law' got the contract. If it's backwards and the laminated product is failing and they did it in a non-standard way, then that supports the reasoning behind things being performed in a 'standard' fashion. Certain ways of doing things becomes universal because most people find it works best that way. 

IMHO

Tony B


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## pianoman (Jan 16, 2008)

The overlay doors on box cabinets are edge banded after being face laminated!!! This is a production method...the wrong way...I don`t like seeing the edge banding on the outside of the face laminate...just my opinion.


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## Tony B (Jul 30, 2008)

*OK......*

so who is disputing this?


Tony B


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## basser (Sep 15, 2008)

I think we got slightly off the original question, although I appreciate the discussion... the built in units are 36" wide X 8' (excluding a wider base) and will be PAINTED (no laminate). I am going to face frame the edges with hardwood and the back probably be painted bead board sheet material. There will be 2 of these units on either side of a center (high and narrow) window. Centered under the window is a TV cabnet unit(about 6' wide),with hardwood doors and face frame. The TV cabnet I planned to build using plywood. The entire unit will have a 3" thick hardwood counter top (natural finished but I am not sure wood type yet). SO the question is in reference to the shelving (bookcase) units... Am I asking for trouble with MDF? My thoughts were to save a few$$$ because these were to be painted, but I am getting the feeling that saging concerns will outweigh the cost differental.??
Andy


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## fanback (Mar 9, 2008)

Andy; Yes, you are asking for trouble. While this material certainly can be used (did you know they make a light weight MDF?)....it's not worthy of your good work. I recently saw some birch plywood that had come from China. A bit cheaper, and who could tell the difference. There's a whole different mindset when you approach a project with the proper materials. I have built similar shelving units to the ones you describe (earlier in my career) and they didn't last. I still remember the problems.

Michael


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## Tony B (Jul 30, 2008)

*I wouldnt do it.*

Nailing/screwing from the back of the cabinet and face framing it will help but not solve the problem of sagging. 36" is a long span for lots of materials especially MDF. The weight of the MDF alone will make it sag not to mention anything you put on it. 

Maybe if you submit a simple hand drawn sketch, we can be of more help as to what materials to use.

Tony B


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## basser (Sep 15, 2008)

good idea and thanks again for the interest. I will take a pict of the room and send along my drawing later this afternoon.
Andy


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## basser (Sep 15, 2008)

Ok here are the images. rec room as it stands now, drawings show plan for units. Currently the trim is an off white and the walls a light green, flooring is non existant. Our idea was to use the off white trim on the shelving but face frame them and the doors on the center cabnet with hardwood. counter top would be about 3" thich hardwood.








Our wood choices are white oak, sycamore, brown oak.









the smallish shelves on the outside of each wall unit are 12" wide free floating shelves(for lighter art work, no books)... the drawing makes them look like they are enclosed with an outside walled edge, but they are attached only on the inside and rear.
thanks again for any imput.


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## John in Tennessee (Jun 11, 2008)

I assuming the outlets on each side are for speakers. What about if you decide to get a big screen later? Can your unit be expanded?


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## basser (Sep 15, 2008)

I do not have any outlets pictured...the center base cabnet is 6' wide and 21" deep(actual counter top is 24" deep)... and 36" below the window... isn't that big enough for a tv? The counter top on either side of center...ie. under the wall units is 4' wide but only 21" deep...they step back but are at the same height as the center counter top.


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## pianoman (Jan 16, 2008)

After seeing the picture...I`m trying to imagine the size of the TV. It would be nice to have an area in front of the window to display the birds...above the TV. Use the TV and the window as the focal point. As far as contrasting the TV area with hardwood...that could be done ...but should be accented in other areas of the cabinet to maintain a single theme. Just my opinion...Oh, sorry if I distracted from your thread earlier. Rick


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## Tony B (Jul 30, 2008)

Ok, now i see what you are doing. 
36" shelves are still quite long. It is do-able though, if you dado the shelf into a faceing, just keep in mind not to put anything heavy on the shelves. 
I also dont know why you want a 3" thick counter top. It is not necesary for strength so you can use 3/4" stock and face it to look like 3" thick. 
And lastly, Unless you need the shelf space, I would space them more than12" apart, just for looks. The unit risks looking too busy. As an experiment, get some cardboard and make a simple mock-up of the 12" spaced shelves and make sure that is what you want. 

Tony B


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## basser (Sep 15, 2008)

I have access to a local hardwood mill yard, he owes me money so the hardwoods are part of a trade off. The materials he has are all rough cut 5/4 and thicker. I will be ablt to cut/plane down the face frames and smooth out the counter top materials but not resaw it myself( i could get another mill shop to do this). some of his selection goes up to 3" thick. I like the idea of contrasting the tone of the wood with the off white painted shelves (the brown oak has really neat tones and pattern in it) and the same wood could be used as a contrasting face frame material.??
re. shelve spacing... great point and it DOES look too busy and symetrical... I will design it with some deeper shelves at lower levels and smaller ones near the top.
The outlets in the picture (not on the plan) are cable and AC.


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## Tony B (Jul 30, 2008)

*Sounds like*

you got it together now

Have Fun

Tony B


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## pianoman (Jan 16, 2008)

OK, and back to the question Basser...I don`t think you`re asking for trouble with a 3` opening using MDF. Some will disagree...If it was ever in question...it would be a good idea to (if they are adjustable shelves) add a build-up to the front and back edges...1" to 1and 1/2"s. A three foot opening is user friendly. Fixed shelving should have a build-up on the front only...but ...secured from the back through the bead pannel. On the two side units...is there going to be an area 30" to 36"s up for a fixed counter area? Rick


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## basser (Sep 15, 2008)

the counter top will run the width of the wall unit and at the same height accross...(30")... it will be wider in the center...24" (over the center cabnet) than on either side...21" (inder each shelf unit.
Andy


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## pianoman (Jan 16, 2008)

Andy, the transition of 3" to 1" or 1and 1/2" for the rail... to me is in question...how is it going to look? Rick


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## basser (Sep 15, 2008)

I am not sure what you are referring to. The Counter top will be the same thickness over the entire width of the room... it just will step back under the shelve units, so in essence the width from the back wall out to the front edge will be narrower under the shelve units. I probably will NOT go with a 3" thick top either. The face frame around the cabnet and shelves will be identical in thickness and width.
Andy


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