Router and dadoes

[NCPete]

I have had my DW621 and a Milwaukee 5615-29 for little more than a year now, and have used them to make rounded and chamfered edges on minor projects since then. My wife has recently given me the mission of building a rather large built-in bookcase, and she has seen plans for one calling for MDF as the major construction material(the bookcase will be painted). Dusty, maybe I can make some good stew.

my question is this, Not yet having permission to get a table saw (drool over the Jet at the local Lowe's) and everything associated with it (Dado set, etc) what is the best way to get dead straight dadoes? My straightcutting bits are all 1/4 inch, the Milwaukee only has its 1/2 collet. The 621 likes to turn ever so slightly. I have a good clamping straight edge. Should I bild a jig to fit the dewalt? Or just practice more with it?

TIA,
Pete

 

[Steve D]

Here is a great thread that you should find helpful. Several jigs and techniques are discussed. MDF is a full 3/4" so you wouldn't need an undersized bit. One of the versions of the "two sided" jig should do well for your application. Let me know if you have any questions.

 

[NCPete]

Thank you Steve, for the link. Where was I on the 3rd? And why did I not think to do a search??? :slap: time to go play some more on in the garage.

 

[McRabbet]

Peter,

Before you head for the garage... consider some other aspects of MDF before you start:
(1) Because of high glue content, MDF is very tough on router bits, so only use cardide (AND WEAR A DUST MASK);
(2) Joints need fasteners as well as glue for strength (books are heavy), and drywall or wood screws do not hold well in MDF (check Woodworker's Supply http://woodworker.com/cgi-bin/FULLPRES.exe?PARTNUM=128-183 or McFeelys (http://www.mcfeeleys.com/subcat.asp?subcat=20.1.1.2) for Confirmat screws, which are made for MDF and particle board).
(3) You need to add a strengthening edge band for shelves of MDF because they will sag (I would add a 1/2-3/4" thick x 1" wide x full shelf length strip to cover the MDF edge and to prevent sag)
(4) Some people are sensitive to the urea-formaldehyde glues in making MDF and particle board and they will "outgas" for an extended period. (See sources like MDF FAQs at http://www.lungster.com/l/speakers/mdffaq/mdf.shtml or do a Google search yourself).

My $0.02 -- I'd rather use 3/4" shop grade Birch plywood and pay a few dollars more for a better result.

Rob

 

[NCPete]

Rob,

thanks, I was testing out my ability to cut straight dado's tonight, and the possibility of building a jig with the scraps I have in the garage. I work an odd schedule, which will keep me from actually doing too much of this for a few more weeks at least, so right now it is all prep.

FWIW, I hunted out my dust mask before cutting into the MDF scraps tonight, and the bits are carbide. I was toying with the idea of using the birch, being aware of strength/rigidity issues with the MDF. LOML likes the cost of MDF, had seen this plan suggesting it was possible to do and have turn out well, so....

more FWIW, I am an old (Ok, not so old, maybe it should be former) hardwood flooring guy.... What on earth am I doing thinking about building something that goes vertical????

 

[D L Ames]

My $0.02 -- I'd rather use 3/4" shop grade Birch plywood and pay a few dollars more for a better result.

Rob

Pete, Check out HD over on Skibo (401 by-pass). I was in there last week and they had 3/4 shop grade birch for about $25 a sheet if I remember correctly. It looks like it offered a nice smooth paintable surface and might be an alternative for you instead of MDF.

D L