Sanding before router edge profiling?

[Tom Henderson2]

Greetings everyone.

In the past I have done the router corner roundovers after assembly but before doing any sanding.

I recently read that it may be beneficial to so some of the sanding *before* routering the corner round overs.

Anybody have any thoughts on the matter?

What grit do you stop at before adding the roundovers? I'm guessing 150 or 180, but wondering what others do.

Thanks in advance!

-T

[Andrew Seemann]

I try to do the roundovers prior to machine sanding if I can, but sometimes it works better afterwards. I know the grit is probably bad for the router bits, but I use the inexpensive Rockler brand ones for roundovers, so if I have to replace them a litter sooner, so be it.

I almost never sand past 180, so that is where I stop:) I normally use film finishes, so no need to go finer. I always do the final hand sanding after routing, so the whole surface is consistently abraded, especially if using any kind of stain or dye since their absorption is affected by surface roughness.

[Mel Fulks]

Making a round-over is sometimes spoiled by the router grabbing a “loose thread”, AKA sharp corner. A little sanding to remove the sharp
corners can prevent tear-out by the router. But that deposits grit into the wood dulling the bit. I prefer running the router backwards
( climb cutting) just some of the depth to remove the sharpness of wood corner. Then run full depth profile , with standard full forward .

That initial “safety “ cut is done with a round-over bit , regardless of what the finished profile will be.

[Edwin Santos]

I was taught to respect your cutting tools and sand last. The reason being that any cutting tool touching a sanded surface will be dulled by the sanding grit left behind.
Sanding grit will dull a cutting tool surprisingly quickly.

[Kurt Wyberanec]

I typically only do whatever flush triming and sanding I have to before putting profiles onto a piece and typically at 120. One reason is you will often get some marks from the bearing running on the wood... especially on softer materials, not to mention you might get handling marks from doing the work....I hate to sand twice!

That said, try it, might work for you... probably won't take long to see which you prefer.

[Frank Pratt]

If the edge has roughness to it, I'll sand that smooth before routing. I've had ripples transfer into the round over or chamfer otherwise.

[Robert Engel]

If the edge has roughness to it, I'll sand that smooth before routing. I've had ripples transfer into the round over or chamfer otherwise.

Same here. Often I clean up the edge with a hand plane. But it depends on how bad the saw marks are.

[johnny means]

I was taught to respect your cutting tools and sand last. The reason being that any cutting tool touching a sanded surface will be dulled by the sanding grit left behind.
Sanding grit will dull a cutting tool surprisingly quickly.

That's a fallacy. If abrasive grit is embedded in your workpiece, something has gone wrong. S
Sandpaper doesn't shed it's material like a brake pad. If that were true, you'd certainly see the embed abrasives in your finishes.

[Zachary Hoyt]

I almost always sand to shape with 80 grit on the 12" disk sander before routing, but that's because I'm not good enough on the bandsaw to leave a smooth edge that the guide bearing will follow nicely. If I routed first there would be a lot of chatter that would show up in the routed edge. Often I'm routing curved surfaces, so concave edges get sanded on the spindle sander first, then routed. Straight or convex on the disc.

[Jonathan Jung]

I sand everything, top and edges, to P150 or P180 with the RO, then roundover / edge treatment, then last pass with P220.

I've never heard that sanding will embed grit into the wood. Probably this is advice from before sanders hooked to dust extractors using abrasives with dust holes or mesh abrasives.

[Warren Lake]

accurate on the sanding grit. Lots of people in the trade know that and any sandpaper company that has anyone working there that knows their stuff will tell you as well. Nothing new.

Climb cut first before forward.

[Edwin Santos]

That's a fallacy. If abrasive grit is embedded in your workpiece, something has gone wrong. S
Sandpaper doesn't shed it's material like a brake pad. If that were true, you'd certainly see the embed abrasives in your finishes.

So then what is actually happening when sandpaper wears?
By design the grit is harder than the wood so it's not like the wood is abrading the silicon carbide.
The carbide grit must be breaking off with wear like the abrasive in a sharpening stone.
Or if it IS being abraded, the abrasive is then being turned into smaller microscopic abrasive particles in the same way that abrading wood turns it into dust particles.

In either case, where does this grit go?

[Zachary Hoyt]

The same arguments can be applied to metal too. If your saw blade becomes dull the sharp corner at the cutting edge has worn away, and where did it go? Is a smaller amount of carbide embedded in the wood better or worse for a router bit than a potentially larger (but still small) amount of aluminum oxide or ceramic?

Also, I don't see any reason to suppose that much of the grit that comes off the sandpaper would be embedded in the wood. It seems more probable to my uneducated mind that it would fly off into the dust stream.

[Warren Lake]

sandpaper is engineered to break down in some fashion. Id think so it keeps opening up a new sharp surfaces. Some amount of that break down gets pushed into the wood. Id think a wide belt would leave more grit in wood as its a constant pressure compared to a stroke sander where your pressure is only what you need.

Ask your sandpaper company, if nothing else you will see what they know. In some companies older employees are gone or retired and the new ones dont have the same knowledge or history.

[johnny means]

So then what is actually happening when sandpaper wears?
By design the grit is harder than the wood so it's not like the wood is abrading the silicon carbide.
The carbide grit must be breaking off with wear like the abrasive in a sharpening stone.
Or if it IS being abraded, the abrasive is then being turned into smaller microscopic abrasive particles in the same way that abrading wood turns it into dust particles.

In either case, where does this grit go?

Your supposition that the abrasive must be continually breaking down is erroneous. I use large abrasive belts every day, creating trailer loads of sawdust every week. I've never seen an abrasive belt from a wide belt sander wear out due to mileage. With regular cleaning and a little care, the inside of the belt will fail before the abrasive wears out.

[Warren Lake]

grit breaks as you use it, some falls off.

You should ask your sandpaper company instead of always claiming fake news. At least two very top sandpaper companies confirmed that to me over the years and probably knew the cabinetmaker that taught me that in the first place. He ran a very large shop.

[Tom Bender]

The minimal amount of grit doesn't seem to cause a problem but working with unhanded wood does cause problems, at least fir me.

I sand early and often. It makes measuring and marking easier and more accurate. It makes the routing smoother. It makes prefinishing possible. And it is much easier to sand and finish prior to assembly.

476966

One has 80 grit, the other has 320. Nothing else needed in hardwood or soft.

[Edwin Santos]

Your supposition that the abrasive must be continually breaking down is erroneous. I use large abrasive belts every day, creating trailer loads of sawdust every week. I've never seen an abrasive belt from a wide belt sander wear out due to mileage. With regular cleaning and a little care, the inside of the belt will fail before the abrasive wears out.

Not trying to be argumentative here but you got me curious enough to go do some research. I will share what I found.
Source is an article from FWW #178 Jul/Aug 2005 Choosing Sandpaper by Scott Gibson:

Manufacturers have concentrated their research on aluminum oxide and newer ceramic abrasives, designing abrasive grains that are friable or semifriable, meaning they break down to expose fresh cutting edges as the sandpaper wears.“Friability is an excellent thing,” says ChrisMinick, an advanced product development specialist at 3M and a consulting editor toFine Woodworking. “What it does is rejuvenate the points, so it extends the life of thesandpaper. Second, it gives you a much,much more consistent scratch pattern than you'd get with a nonfriable material.”

Similar information from FWW #125 Jul/Aug 1997 Making Sense of Sandpaper by Strother Purdy:

Aluminum oxide is a sharp and blocky mineral. It is the most common, all-purpose woodworking abrasive, and for good reason. It is the only abrasive mineral that fragments under the heat and pressure generated by sanding wood. This characteristic is called friability and is highly desirable. As you sand,aluminum oxide renews its cutting edges constantly, staying sharp and cutting much longer than other minerals.Aluminum oxide is also a relatively tough abrasive,which means that its edges won't dull much before they fragment. Its friability and toughness make aluminum oxide the longest lasting and the most economical mineral.

If you have access to the FWW archive the latter article is interesting because it includes super magnified photos of grit and swarf.