Newbie: Particle Board, blades and joints

[Brian Grimm]

Greetings all. I'm attempting my first project other than minor framing-type stuff, and I'm looking for advice.

I'm building a bookcase for storing video tapes, dvds, and such. I'm putting it into a small walk-in closet, so I'm not looking for beauty. I've decided to use bullnose particle board shelves for the uprights, and pre-made laminate covered shelves, which will pretty much match the closet organizer that's already there.

After dulling a couple of inexpensive circular saw blades and making a mess out of a couple of long cuts (I know I was weaving officer, but I'm not drunk!) I did a little research and discovered the recommendation to use carbide tipped blades. For occasional use, how are the inexpensive ($10-20 each) blades? Do they have enough carbide to bother having them sharpened? And which would be better - 24T, 40T or higher?

Now for the router. I've got a pretty good router, and a good set of carbide bits. However, I don't understand the difference between a straight cutting bit and a mortise bit. To my obviously untrained eye they look the same, except the straight bit is 'longer' than the mortise bit. Am I going to bring an end to the world by using the wrong bit?

Finally, what is a good joint to use for the fixed shelves? I'm looking at the top, bottom, and one in the middle for a little stability. I've looked at putting a 3/8 dado in the upright, and a 3/8 x 3/8 rabbet in the shelf, or just a 3/4 dado in the upright. Which of these would be best, or is there a better joint?

Thanks for your time, Brian

[Stephen M]

We really need to know what type of saw. I *assume* that you are using a 10" blade in some type of table saw.

With tooth count, more is not necessarily better.... count and geometry depends on use (rip, crosscut, laminate). Your best bet is to start with a

40 tooth combination blade. I picked up some *really* cheap blades once. Once I have tried them they kind of freighten me. I would aim for $40-50 for a respectable medium quality blade.

No. I suspect that a mortise bit is just straight bit that does not have a guide bearing on the bottom.

Go for the 3/4" dado. It's equally effective and requires a single cut. Do

*not* assume that your stock is 3/4" thick. Most plywoods are *almost* - stated thickness.

Cheers,

Steve

[dadiOH]

Personally, I like a 1/2" tongue into a 1/2" dado. The shoulders top and bottom on the shelf hide all of the dado and align it exactly.

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dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[gw]

Circular saw blades are typically marked for the materials they are designed to cut. Look for one specifically for particleboard and laminates. More teeth are better, but slow the cut. Use a long straight edge to keep the saw straight. The factory edge of your sheet goods should be good enought to use as a straight edge on your other pieces.

A mortise bit has cutting edges on the bottom of the bit to smooth the bottom of the groove. It can also be used in a plunge cut. A straight cutting bit does not necessarily have cutters that will leave a smooth-bottom dado. They also don't plunge very well without bottom cutters.

With bullnose shelves, I would cut a 3/4 dado in the upright, but cut the shelves long to leave the bullnose proud of the edge of the upright. You could also cut a 1/2 dado in the upright, and 1/4 off each side of the bullnose edge, but leave an inch or so in the front so the bullnose is not cut.

[Patrick Conroy]

"Brian Grimm" wrote in news:1120643297.9dc377098a4d7555268fe829bb996d7a@teranews:

Assuming you're using a 7 1/4" Circular saw, I'd go for a 30 or 40T count to minimize chipping.

For Particle Board, I go even *cheaper* on TS and Circ Saw blades. Particle Board is reputed to be tough on blades so, I usually throw the Black and Decker, Harbor Freight blades at them.

Don't think I ever paid over $10 for a Circ Saw blade so I'm no help here. (The blades on the Table Saw and Miter Saw are another matter.)

Yeah - the world will end, the G-8 summit will collapse, that Comet Busting probe will miss...

Again, if the reputation is true and PB is hard on bits, then pick an inexpensive one. If you want to use the router to cut dado's then there are dado bits: flat bottom, bearing etc.

I use biscuits and butt joints when I do PB projects.

If you don't have a biscuit joiner, are you aware of the "New Project, New Tool" rule???

[mac davis]

Steve... he mentioned "circular saw blades"... don't know if in a skillsaw or TS... or even in a RAS or CMS??

mac

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[mac davis]

If you're using a skillsaw (TM?) or the like, you need to use cutting guides, either a straight board or a metal strip... best method is to measure the distance between the side of the saw foot that will be against the guide/fence and the blade, and clamp the guide that distance from where you want your cut... If possible, practice a bit on scrap first...

Use a plywood or composition blade, best bet is to hit a saw shop or borg and tell them what you're cutting and what type of saw (circular, table, miter, etc.) you're using.. generally, for sheet goods, you want a lot of little teeth, as opposed to a few large ones, for a smoother cut... WEAR A MASK!

Joints are simple, just don't get caught smoking one... *groan*

My non-tech version of your router bits:

Straight bits are long and narrow, compared to fly cutter/mortice bits and are used to cut grooves and dados in wood...

Fly cutter/mortice bits are wider and made to do edge treatment...

IMHO, unless you're using really thick particle board shelves for the uprights, you don't have enough "meat" for a 3/4" dado... I think that I'd cut "cleats" to go under the shelf edges, maybe 3/4" - 1" by the thickness of your particle board, and about 1/3 the depth of the shelves... glue to the sides and then glue the shelves to them... If you want it really strong and don't care how it looks, put a cleat above each shelf, also, like building a dado.. YMMV and probably will..

mac

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