Can you cut dadoes into 3/4" thich wood for shelves?

[LarryG]

Different kind of bit!

MLCS has a top-bearing flush trim bit that's 5/16" diameter, 1/4" shank.

That one won't work, though ... it produces a 3/32" lip which multiplied by two and added to the 5/16" large diameter equals 1/2" ... the same size bearing as on the smallest top-bearing template bits. I don't think there are top-bearing bits with pilot bearings smaller than 1/2" -- or at least I've never seen one.

[Tom Miller]

Here ya go:

Whiteside Bits at Routerbits.com




Also, "1/2 inch" baltic birch is actually 12mm (nominally), which is 0.47".


Oops, just realized these are all 1/2" diameter or greater -- just proves you need 3/4" thick shelves.
Regards,
Tom

[JonW]

Oh, in one mmagazine, I've seen an interesting variation on Larry's jig, that is fine-tuned to use either 1/4" or 1/2" straight no-bearing bit. Take 2 pieces of hardboard that are about 1" wider than your router base. On top, along its middle, attach a piece of wood 3/4 by 3/4". Now, using that piece as a fence for your router baseplate, trim one side of each with a 1/4" straight bit, and the other side with a 1/2" bit. mark which side is which. Now, orient the two pieces so that same width sides are facing each other, and on the bottom of hardboard along the edge coser to you and square to the top fence, attach another fence. Hope the illustration below makes things clear:
[ATTACH]605[/ATTACH]
It came out a bit skewed...
Viewed from top and from front. Clamp both pieces with bottom fence on same side of work, using shelf stock as spacer. For wider dadoes, put 1/2" marked sides facing each other, and chuck a 1/2" bit. For narrow ones, use 1/4" setup.

OK, that's very interesting. It might even work for me. I'd have to be careful about making the 3/4" x 3/4" part straight and all. But it just might work. I've already got 1/4" and 1/2" straight (no bearing) bits at home. So this might be something worth trying on some scrap.

Another question: For jigs, people often mention making them out of hardwood (or sometimes MDF). Is that because of humidity and temperature changes over the years? I've only got pine, MDF, and AC plywood scrap at home. Should I buy some hard wood for making jigs?

Oops, just realized these are all 1/2" diameter or greater -- just proves you need 3/4" thick shelves.
Regards,
Tom

Yeah, maybe I do need to make 3/4" shelves. Although I think it would look lighter with 1/2" and sag wouldn't be a problem. But if scorrpio's jig idea doesn't work, I may be buying a 1/2" pattern maker's bit and making 3/4" shelves.

[LarryG]

MDF is a good material for jigs, fixtures, and templates because it's dense, dimensionally stable, and dirt cheap. Its corners and edges will dent easily, though, so you have to use caution there. You also have to take care not to let it get wet. I don't finish my jigs with anything but probably should, since I have a very humid shop.

Baltic birch has similar characteristics and is more durable, but is not as cheap. I have been known to prototype a jig or fixture using MDF and, after tweaking the design based on what the prototype teaches me, build the actual jig out of Baltic birch.

Hardwood is better for fences and such because it is more durable and stable than softwoods like pine and fir. I mostly use red oak because it's cheap and readily available, but maple or beech would be better.

[JonW]

OK, thanks for the further education. Makes sense.

After buying my saw, I was disappointed to find out that there isn't really anywhere locally (Indiana corn fields) to buy hard woods. The local Menard's has a little precut (and shrink wrapped!) maple, oak, and cherry. But if I want decent quantities of such things or something thicker, I'll have to look beyond the area. A local place did just start carrying baltic ***** plywood last week. So maybe I can use that for making jigs. That will also be a good material to try building my first few projects, like those shelves.

[Tom Miller]

A local place did just start carrying baltic ***** plywood last week.

People, I can't stress this enough: you've got to be careful with your spelling. I don't even want to guess what those shelves are going to look like when you're done.




Regards,
Tom
I'm not sure I'm gonna make it to quittin' time today....

[scorrpio]

To clarify a possible misconception: hardboard is NOT hardwood! It is more like MDF, usually brown in color, and comes in either 1/8" or 1/4" thickness. Common variations include regular, tempered(more durable but hard to work with), melamine-faced(usually white), and perforated(also known as 'pegboard').

On the jig I pictured, no need to use exactly 3/4 x 3/4 - in fact, standard 2x1 lumber should work just fine for this.

[greencat]

OK, thanks for the further education. Makes sense.

So maybe I can use that for making jigs. That will also be a good material to try building my first few projects, like those shelves.

Maybe you already thought of this but the order of your cuts and dados can increase your accuracy and save time.

For example - If your legs are 3" wide then I would cut the dado on a sheet 48" x 13" and then rip all 3" pieces at once. If you plan ahead with the cuts you will save yourself a lot of time trying to match a previous cut. If you want the shelves 22 1/2 wide then if you cut all 5 at once and they end up at 22 3/8 it does not really matter.

[JonW]

People, I can't stress this enough: you've got to be careful with your spelling. I don't even want to guess what those shelves are going to look like when you're done.




Regards,
Tom
I'm not sure I'm gonna make it to quittin' time today....

Woops! Umm, sorry about that, ladies.

[JonW]

To clarify a possible misconception: hardboard is NOT hardwood! It is more like MDF, usually brown in color, and comes in either 1/8" or 1/4" thickness. Common variations include regular, tempered(more durable but hard to work with), melamine-faced(usually white), and perforated(also known as 'pegboard').

On the jig I pictured, no need to use exactly 3/4 x 3/4 - in fact, standard 2x1 lumber should work just fine for this.

Thanks for the clarification. I know what hardboard is- like peg board without the holes. But that doesn't mean I didn't misread any of these posts.

Right. For your jig the strip could be about any size. I've got some scrap 1x2 at home and that's what I was thinking about. However, getting 1x2 that is really straight is another matter.

If I have a chance to get into the woodshop, I'll try your jig out this weekend. But this pesky job keeps getting in the way.

[cjupdike]

JonW,

The jig I used to rout my dadoes was just a piece of masonite with two slim hardwood boards on either side wide enough for my router base plate to slide straight in. Then I routed a groove down the masonite and that's my jig. It helps keep tearout on the ply to a minimum and wherever I put the goove that's where my dado goes. The edge banding is birch ply banding you can buy off ebay. it's thin strips of veneeer with an adhesive backing that you iron on the the edge of your plywood for a better appearance. The bracing isn't there to support my shelves, those are plenty stong on their own. They're only there to keep the whole unit square and I needed something for attaching the unit to the wall and it will be hung.

Greencat,
The ply isn't oak ply I'm afraid. This was a pretty newbie project for me and I made the mistake of buying third-rate play, I'm not even sure it's birch. So that brings me to a good TIP: Use quality plywood if you want to be able to get clean edges and not have voids and delamination.

[JonW]

cjupdike-

So does that mean that your whole jig is just one piece? When you cut the groove in the jig with the router, you do not go all the way to both ends. And so it's like a one piece template you just lay over the desired dado location? Seems to make sense. But maybe I'd want to add a piece to help square the jig to the work piece. Thanks.

[cjupdike]

JonW,

Yes, the whole jig ends up as one piece but it's large enough to go from end to end. the grove in the masonite where the dado will be doesn't go to the end of the masonite. This is a good picture of what I mean (not my jig, more fancy, but you get the idea). http://www.davehylands.com/Wood-Work.../04-Router.jpg
I made it sized enough to do quite large pieces if I need to. I used a square to square it up to the sides but you could always add a piece underneath to set the jig square. In fact, the last episode of NYWS with Norm, his router 101 episode, did make this exact jig. I couldn't to this because I was working on the ground because I have no workbench yet (next project).