Compression Router Bits

[Julie Moriarty]

In the latest issue of FWW they have an article on pattern bits. There's the usual straight cutters, spiral cutters, upcut, downcut and compression. I had never heard of compression bits before. I learned compression bits cut down from the top and up from the bottom compressing the fibers in the middle. The result is a chip-free, no edge-fuzz finish. It looks like Whiteside is the only manufacturer of this type of bit. The ones that have bearings run between $100-$150 each. Ouch!

Has anyone tried these bits? If so, do they deliver what they say they do?

[Peter Quinn]

I haven't tried the router bits, but I have a shaper groover that is a 6z compression cutter and it delivers a very smooth cut in everything I've tried. Even where other cutters are tearing and would have to be run in climb fashion this one cuts smooth. IINM amana and infinity may also have compression spiral cutters, not sure about the pattern bits. I seem to recall Sam Layton had large custom compression router bit from Nordic tool he used in a door build thread some years ago here, it was a very cool looking cutter and performed great.

[Jerome Stanek]

I use them on my cnc I have some Whiteside, Onsrud, Centurion, and Freud bits mostly in the .5 size.

[Bill White]

Most CNC equipped cabinet shops use comp. bits. Smooth, clean cuts, minimize rework and waste.
Bill

[dan sherman]

I have a few, The one on the left is a compression flush trim bit that i use all the time while pattern routing. It's well worth its price if you do any amount of work in brittle woods.


276785

[Julie Moriarty]

I have a few, The one on the left is a compression flush trim bit that i use all the time while pattern routing. It's well worth its price if you do any amount of work in brittle woods.

I used a CMT flush cut bit that has a small shear built into it for a pattern cut in 8/4 high curl maple. It chattered like crazy and left a lot of sanding, and some chip filling, for me to do. I now have to make a similar cut in some 8/4 high figure sapele and just don't trust the CMT bit I have. I'm considering ordering the one in your pic on the left in the 1/2" D X 1-1/2" CL 1/2" SH 4-1/4" OL size. That's the largest cutting length I can find. I guess I'd have to cut the first 1/4"+ with a standard bottom-bearing pattern bit but if that chips the compression bit will just follow that. Hmmmmm.......

The fact that these bits seem so hard to find makes me think this is something relatively new to router bits.

[glenn bradley]

For us mere mortals, compression bits in the length you seek are a bit rare. Southeast tool (and others) make a 2-1/2" cutting length compression bit BUT, it has four flutes a 3/4" shank and costs over $300. They are readily available, just not where I usually shop ;-)

[Joe Scharle]

Wow, I got one from MLCS (not pattern)


#7425
1/2"
1-5/16"
3"
1/2"
$39.95
http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/graphics/orderbut.gif (http://www.mlcswoodworking.com/cgi-mlcswoodworking/sb/order.cgi?storeid=*128beabcdfa50a754e407f&dbname=products&sku=%237425&function=add)



I use mostly for through mortises and slots. Leaves a clean edge on both sides unless the bit goes too far on the other side.

[Stephen Cherry]

I have had pretty good luck with the whiteside spiral upcuts. One option would be to use a pin router attatchment:

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/daisypin.html

This has several plusses. First the bits are cheaper. Second, you can make the cut in a couple of steps, raising the bit each time around. Also, you can use different pins, or tape the pin, to allow a full length final cut to remove a small amount of wood.

Here is a part roughed out with a spiral upcut bit- it is slightly oversized and will be trimmed after it is assembled. The picture shows the non-compressed side of the cut:



276805

[Myk Rian]

A compression bit is most useful when routing plywood. It compresses both faces inward to prevent tearout.

[Jim Neeley]

While I'm sure this is as intuitively obvious as Myk's Sig line, when adjusting the bit, you want the place where the two spirals come together to be within the wood.

Howdy, Myk, greetings from RF!!

Jim in Alaska

[David L Morse]

Before I got a slider with a scoring saw I was unable to get two clean sides on Melamine using a table saw. I cut the panels a bit oversized and used a compression bit (MLCS #7425) in a router table set up like a jointer to clean up the edges.
http://www.dmorse.us/Cabs/slides/P1060159.jpg
The scoring saw is OK and I use it's cuts as-is but the compression bit cuts are nearly perfect.

[dan sherman]

I now have to make a similar cut in some 8/4 high figure sapele and just don't trust the CMT bit I have. I'm considering ordering the one in your pic on the left in the 1/2" D X 1-1/2" CL 1/2" SH 4-1/4" OL size. That's the largest cutting length I can find. I guess I'd have to cut the first 1/4"+ with a standard bottom-bearing pattern bit but if that chips the compression bit will just follow that. Hmmmmm.......


you can do it.

use one of these
http://www.hartvilletool.com/product/5849/up-down-compression-spiral-router-bits

and then either of these
http://www.hartvilletool.com/product/2980/spiral-router-bits
http://www.hartvilletool.com/product/2981/spiral-up-down-combo-flush-trim


all these bits can be had on Amazon, just take the part numbers and ignore the product images that are typically wrong. They are expensive bits, because they are solid carbide, not steel shanks with carbide brazed to them.

[Stew Hagerty]

I have the big Whiteside Ultimate bit with both top & bottom bearings and it is worth every single penny. I have a couple other bits too, but since I broke down and bought the Whiteside, I've never used anything else. It's so smooth and fast that I find I use patterns much more often.

[Myk Rian]

Howdy, Myk, greetings from RF!!
Hijack on.
Hi, Jim.
Hijack off.

[pat warner]

"Has anyone tried these bits? If so, do they deliver what they say they do? "
************************************
Yes.
But no free lunches at any price.
Whilst they (compression bits) have their place, in my view, they're just another pretty face. They do not prevent tearout but they are efficient.
Indeed they are a good choice in the CNC domain as finish cutters too.
That is, for the last operation of a panel e.g., one that does not have to joined.
They are thickness sensitive and the edges they produce are high centered, not square. As such, panels jointed with compression bits are not ideal for joining edge to edge.
A job specific cutter to be sure.
If tearout free cuttings are your goal I'd be thinking plunge routing in stages. There is always a plunge increment, albeit maybe thin, that will produce a teaout free edge. Moreover, that increment can be so slight that your cuts can be climb or anticlimb. = safety.
Taking one trim swipe on stock 1 -2" thick is an invitation to adversity. (Was an expert witness on just such a case.)
If thick full thickness cuts are garden variety for you I'd be thinkng shaper,
not skinny chippers like .500" D x long length trimmers.