Router Pattern Bits

[Gilmourisgod]

Another "What do to the Pros Use?" question from the Amateur Luthiery contingent:
I understand, and have used, several of the more common flush trim (top bearing) and pattern cutting (bottom bearing) router bits, upcut, downcut, etc, with varying degrees of success for body blanks, pickup routes, bridge recesses, etc. The standard straight cut pattern bits work well enough for template routing with the grain, but tend to tear out on figured woods or against the grain. This can be mitigated with careful use of "climb-cuts", but that makes me a bit nervous on long cuts. Most of the standard bits are two-bladed, so the bit kind of "hammers it's way through the wood, it's actually not in contact with the wood at all between blade cuts.

One solution seems to be the relatively new (to me, anyway) double bearing bits with shear-cut blades, like this one by CMT:
https://www.amazon.com/CMT-806-690-...8&keywords=top+and+bottom+bearing+pattern+bit
This one has a 2" cutting height with a 1/2" shank, which should handle any common bass body thickness. I've tried a cheap 1/4" shank version of this by Yonico, and it was a disaster, way too much vibration to yield good cuts. In theory, a double bearing bit can be used to cut everything "downhill" with respect to grain by simply flipping the work with attached template and raising or lowering the bit to have either top or bottom bearing in contact with the template. The shear-cut blades are supposed to "slice" the wood, like a skewed plane blade, rather than just hogging it out.

Another alternative is the Spiral Cut router bit, either upcut or downcut, like this one by Whiteside:
https://www.amazon.com/Whiteside-Ro...whiteside+spiral+pattern+bits#customerReviews
Based on Amazon reviews alone, this is an excellent bit. The theory here is that the spiral flute or flutes are in continuous contact with the wood, and always in a shear-cut orientation, so they cut more cleanly. These seem to be available in top-bearing only, so you would still have to deal with grain orientation.

Then you have so-called "compression" spiral bits, that have both up and down cut flutes on the same bit, in theory meaning they will cut cleanly regardless of grain orientation:
https://www.amazon.com/Whiteside-UD...rds=whiteside+spiral+pattern+bits+compression
Pricey!

Like most amateur builder on TB, I am on a limited tool budget, and looking the best Bang for the Buck. Suggestions, theories, or rants appreciated.

 

[rojo412]

[Invalid or Expired Link Removed] are amazingly good for the money. I've had a few for years and they perform better used and beaten up than just about any other bit I've had. They hold an edge almost too well, I've cut fingers with the slightest brush of them.

I've tried Freud, Diablo, Woodcraft, Bosch, Craftsman, Whiteside... and probably others. But MLCS smokes them all and does it with great prices and free fast shipping.

 

[Bruce Johnson]

Speaking as a working pro Luthier, I don't have the money to spare for expensive "boutique" router bits like those. They look nice and probably work well, but I can't afford them. I use straight cut 2-flute good quality (usually Freud or Amana) pattern cutting bits. I deal with tearout with refinements to my tooling and process.

 

[Means2nEnd]

Whiteside, Frued, MLCS, and my favorite best bits i have ever used Radian from the UK where even straight cut blade you can get with 3 blades and I have never had tearout and they are sooo smooth.

The main thing is they are sharp..plain and simple. Even the best get dull after a while and unless you can sharpen them it's best to just replace IMO.

 

[rudy4444]

In truth I only use a small number of bits in what I would consider "mission-critical" operations. The few things that I do where tear-out might be a problem I use solid carbide twin flute down cut spirals. The small amount that I've put out on a few specialty bits is money well spent in my mind. It takes the stress factor out.

I really dislike having to think about the possibility of canning a huge part of a project (like a body..) because I wasn't willing to put out $20 on a router bit.

 

[Gilmourisgod]

I’ve been leaning towards spiral, but most seem to come with cutting lengths less than 1-1/4”, so no good for 1-1/2” guitar bodies. Nobody seems to make a bottom bearing spiral bit.

 

[manupulated]

My freud bits had served me well , still with the original bearings , when I get close to tear out spots I stat away and use the drum sander or drill sander in tighter corners . At work our rep that sell us our cutters and blade always talks about freud in a bad way so I tried one of his brand top bearing cutter and the bearing exploded on my work piece , freud are inexpensive for the quality

 

[Bruce Johnson]

A general note about router bits:

In my experience, router bits really don't need to be sharpened very often. They just need to be cleaned. In use, wood resins and glue line residue builds up on the carbide edges and the heat cooks it on there like a hard varnish. You may not even notice it on there, but it builds up on the outer edge of the carbide chip, right behind the cutting edge. Even though the cutting edge itself is still sharp, the resin makes the cutter act dull and even scorch the wood.

I frequently clean the edges on mine. I use a small machinist's deburring scraper, dragging it gently along the back relief to peel off the layer of varnish. Being careful not to actually scrape the cutting edge. Then I use a small brass wire brush to scrub the varnish off of the front face of the chip. That's important for balance. Buildup of varnish on the faces of the chips can actually make the router bit vibrate at speed.

After cleaning off the varnish, if the edge feels a little dull to my finger, I touch it up lightly with a small diamond honing stick.

If you're not ploughing barrels of chips with big horsepower, the cutting edges actually last a long time. But you gotta keep them clean.

 

[Gilmourisgod]

That’s interesting, I was just looking at my straight cut pattern bit, it has that varnish you describe on the back sides of the blades. I have Some of that spray saw blade cleaner, would that work on a router bit?

 

[Bruce Johnson]

That’s interesting, I was just looking at my straight cut pattern bit, it has that varnish you describe on the back sides of the blades. I have Some of that spray saw blade cleaner, would that work on a router bit?

Sure those spray saw blade cleaners work fine, they're just messier and take longer. I do the scraper and brass brush thing because it just takes a minute. I often do it right on the router, without pulling the bit out of the collet.

By the way, table saw blades have the same problem. When they start cutting dull and burning the wood, usually they're just gummed up with resin. Look at the buildup on the back relief and sides of the teeth. The cutting edges are fine. With a saw blade, the spray cleaner helps. It would take a while to pick and scrape at every tooth.

 

[Bruce Johnson]

Here's what I'm talking about. A gummed up router bit right out of my rack.

This is the ridge of varnish on the back relief of the carbide chip that really makes the bit cut dull.

Here's the varnish on the front face. Not quite as important, but still should be cleaned off.

Here's the little machinist's scraper. I drag it gently along the back relief, barely grazing the edge,

...And peel off the little layer of varnish:

Do the same thing on the end relief:

Then scrape the rib of varnish on the face. Same thing, barely sliding on the edge.

And brush the excess off the face with a small brass brush. Not a steel brush.

That's the quick router bit cleanup. It makes for much happier routing.

 

[mark5009]

Here in Oz we have a local manufacturer called Carb-i-tool. Nice bits that aren't too expensive.

 

[Gilmourisgod]

Dang! I think ALL my router bits look like that. I gotta get to cleaning!