Rough edges on dado cut with router and miter fence moving

[JayStevans]

Hi,

I'm earning how to make a drawer, pretty basic I know but hey, it's the next thing I need to learn to do.

I saw an article in the November 2007 issue of "Wood" magazine on making super simple and very strong drawers - perfect, just what I needed. They use a lock-rabbet design, easy to understand and easy to set up. A picture is attached for reference.

To be clear - I'm much more of a fan of routers for cutting grooves and dadoes than using my saw. My logic is that if I put in a 1/4" router bit I get a 1/4" channel - period. But, my experience, and every article says more or less the same, has been that getting a dado set adjusted properly on the saw is often a lot of work. Being a fan of simplicity, I go with the router. And, thanks to the sliding miter table and fence on the BT3100 positioning the channel in the workpiece is easy.

So what's the problem? The edges of the channels I cut are very rough. A picture is attached with arrows showing where the rough edges occur.

I tried slow and high speeds on the router, sliding the wood over the bit slowly and quickly - no combination works. Even a new bit didn't help.

Any advice to offer (other than sanding every edge)? I'd welcome the help. Thanks.

Jay

[RodKirby]

In my experience, the ONLY (but not perfect) solution is a spiral bit.

An ordinary straight bit "scrapes", a spiral "slices". The difference is even more pronounced routing plywood!

Having said that, I think you will always need to sand. Not much required if you use a spiral upcut bit.

[Tamarack]

You might try a downcut spiral bit, it sounds like you are using a straight bit.
Paul

Edit- Rod, you beat me to it. Wouldn't a downcut spiral compress the suface as it cuts rather than pull it up, or do I have it backwards?

[LCHIEN]

I get the fuzzies too when cutting dados on the router with a straight bit.
I find I can cut faster and cleaner and very accurately using a good dado blade and table saw, but that's my preference.

You can either use a sanding block tilted a bit to clean up those edges or try a solid carbide spiral downcut bit or perhaps even a shear cutting bit... the spiral bit will be better of the two.

[LCHIEN]

oops you guys beat me to it.
Tamaracks right should be a downcut bit, not an upcut bit.
(direction refers to the router in the hand held position.)
upcut bit helps clear the groove of cuttings.
Use a combo upcut downcut bit if you need both.

[cabinetman]

Here's another one of those procedures that beg for multiple passes. Try a few depth passes, where the last one is just a skim pass. Your router speed should be fast (if you have a choice), and the movement speed comes with experience. But, as stated, there's always a little touch up sanding to do. That's why it's called "woodworking".
.

[JR]

Before I give my suggestion I'll say that I would learn to like it the way it is. It's the inside of a drawer and after sanding it's going to look fine.

You could use a jig to prevent tear out. A 1/4" top-bearing bit would be used, poking though a 1/4" groove in MDF. This would be a hand-held operation, with the drawer side on the bottom, the MDF above that, and router on top. Put a stop of some kind on the bottom of the MDF (located 1/4" from the groove), so the drawer side aligns perfectly every time and you could do repeat cuts to your hearts content.

It'd be pain to set up, but would give you the result you desire.

JR

[JayStevans]

Thank you all for the kind, and very speedy, input.

I realized after posting that I should have explained that when I cut the rabbet or a groove the edges are fine. It's only when doing a true dado, a cross-grain cut, that the edges come out fuzzy.

I will try out a spiral bit.

Thanks again.

Jay

[leehljp]

I have made numerous drawers in that exact layout. And I get the fuzzies too on the dado with my bits. To clean up, I use an ROS and a 60 / 80 grit pad and lightly over the dado edge. I always keep a razor knife around and use it if needed. It is a little time consuming but in the big scheme of things - no more than a minute or two per drawer to smooth out the edges.

It would be nice to have always smooth edges from the cut though.