Router bit for through mortise?

[Greg Guarino]

OK. Now I've got the plunge router. But can someone clue me in on upcut, downcut and compression?

I don't think I need the full primer; I get the basic concept of each. I assume I'll be cutting my through mortises from the side that will show. Thus I'll need the "up" side to be a clean cut. I read that that downcut is better for that, it doesn't have as much tendency to split the wood at the edge. But I'll be cutting through 1.5". It it "bad" to be pushing the chips down in that situation? Or perhaps there's plenty of chip room because of the oval hole? (Of course I won't attempt to go through the whole depth at once). And is there any need for a compression bit here?

One last thing. I haven't even settled on the type of wood yet, but it may end up being Oak. Can I assume that only Carbide is of any use? Can I further assume that only Carbide is of any use for *any* router task?

Ignorant minds want to know.

[Bob La Londe]

Would it be practical to thru drill first so chips from routing can be blow thru easier.

[dadiOH]

Upcut, with some woods (not oak,) can leave a fuzzy edge, never had it chip/spit anything. It helps hold wood to router but that can also pull the bit out of the collet a bit.

Downcut has to keep cutting the chips if not a through hole, clear them often.

Easiest/best(?) is to drill/saw ot most of the hole and clean it up with the router. spiral or straight bit.

[woodchucker]

There are no hard and fast rules. Sometimes you have to break the rules but here goes:

in plunge hand held:

upcut is for mortising drilling holes

down cut is for preventing tearout with a bearing for triming veneer

Compression For triming veneer on both sides when using a straight edge or pattern.

In table mounted router reverse the up and down..

There's more, but its really based on the task and the whether you are clearing chips, or protecting tear out.

[John McCoy]

Greg Guarino wrote in news:mgb1ld$eb$ [e-mail]:

Basically, yes. The advantage of the upcut bit is that it throws the chips out of the hole. Anything else, and you'll have to stop every so often and clear the chips out (which is how it was done in the old days, when we only had straight bits).

No - that's for when you need to cut both sides of an edge at the same time.

That would be my opinion. Can you even buy HSS bits now? I can't see any reason not to use carbide bits for all purposes.

John

[Leon]

Way back when, I used to make mouth blocks for Steven Knight. HE built wooden hand palnes and I manufactured that part for him by the thousands. They amounted to a piece if "Ipe" wood 3/8" thick, 2" widem

3.5" long and had 2 through 3/8" wide slots about 2" long and a 45 degree bevel on one end.

I Holding these pieces I plunged these down on to the router table and on to the router bit and slid the piece along the fence. I would do about 400 slots in one job.

Any way I burned through several carbide straight bits with each session. Then, one day a machinist neighbor brought me a 3/8" 4 flute HSS end mill bit. I never replaced a that bit and it cut probably 1200 slots with no indication of dulling. These things are designed to mill steel, Milling wood is childs play for these type bits.

Having said that there are regular plunge slot cutting bits that have a point on the end. These type bits will do a much better job of plunge cutting if all your slots will be through slots.

If you plunge deep holes you want as large of a bit as possible to prevent deflection. You also want up cut as a deep hole will clog and cause burning and smoking if you use a regular straight bit and or down cut.

If it were me I would get a HSS 4 flute end mill bit. Less expensive than a regular carbide router bit.

Keep in mind these often come in shank sizes like drill bits. You are going to need to buy a size that fits your collect. I used a 3/8" adapter in my 1/2" collect.

Here is a double ended end mill bit. Also keep in mind length...

[Electric Comet]

this is very useful info

also useful

so far everything you've said means that they should use a 4 flute end mill bit (not the pointed plunge slot bit)

i think they use a 1/2-inch shank 1/4-inch router bit but would benefit by using the 4 flute end mill bit

benefits are cheaper initial price plus ability perform a lot more work over its lifetime

all good things and maybe other benefits like better swath cleanout as it goes and improved accuracy at 60inch/minute cut rate

[dadiOH]

Sure.

I can think of some reasons... 1. Easy to sharpen, depending on profile. 2. Sharper than carbide 3. Cheaper than carbide? Used to be true, don't know about now but not a bif deal.

I have a few HSS bits, some more than 40 years old. Obviously, I don't use them all that often anymore. The exception is some HSS spiral bits...I use them when I want the very best cuts.

[Brewster]

Be aware that many (most?) 4-flute end mills are not designed for plunging (in metal). Their tips usually don't have cutting surfaces that meet at the center of the bit. Plunge cutting is typically done with a

2-flute bit. That aside, I have used a 4-flute end mill for cutting slots just like Leon describes. I have nowhere near the mileage so I can't vouch for the longevity, but the cuts were excellent and a price comparison between a HSS spiral end mill versus a solid carbide router bit (or end mill) is significant. I got burning if I tried to plunge straight (as expected), but by doing a sliding start, basically sliding the part sideways along the cut line as I plunged, solved that issue.

-BR

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[Greg Guarino]

I've heard this before and am looking into it, especially as I may have outsmarted myself a bit with the jig I built. (it's 3/4" thick) I'm going to need a longer bit for the through holes; that, or a separate jig for that purpose.

But I read things that confuse me about the ends of these bits; specifically that they are not designed to cut "forward", only sideways. Some of those accounts say they cut "forward" OK in wood, just not in the metal they were designed for.

Did the bit you got have a different sort of end? Or does the relative ease of cutting wood render the subject moot?

One more thing: The 3/8" adapter you used worked well? Is it just a split tube or something like that? No worries about a secure grip on an object spinning so fast?

OK, one more, more thing. I have done the very tiniest bit of metal milling in the distant past. In those applications (aluminum) the speed was lower. What speed did you use for wood routing?

[Swingman]

Been using these extra long end mills from Travers Tools for routing mortises over ten years.

The price will scare you, but you get what you pay for. I have cut literally thousands of mortises with these, haven't had to buy but once, and use them on both my Multi-Router, and plunge routers, at high speed, and with Porter Cable collets:

Photo is so you can get the part numbers, otherwise it would take a while to find the correct ones.

[Greg Guarino]

I see that those are center-cutting. I'm trying to determine if that's necessary for wood use. And the price for 1/2" is pretty eye-popping. Do you use an adapter for the 3/8" shank, or have you got a 3/8" chuck?

[Leon]

I have to wonder what the difference between forward and sideways is.

The neighbor that gave me the bit knew what I was looking for an brought me this bit.

I will say this however the piece of Ipe that I was holding and plunging was trapped so that it could not go too far in either direction against the router table fence. I also had the bit about 1/2" above the table. I put one end of the wood against one stop and pressed the opposite end down onto the spinning bit. So, the bit engaged the wood at a slight angle until the wood was all the way down on the table top and then I pushed the piece towards the other stop. Going in at a slight angle may have aided the plunge. As the bit was about to penetrate the top surface of the wood it would often throw out a 3/8" round plug of smoking wood. ;~) While the bit would look charred after a run of dado's, 200+, it would always clean up except for the slight tarnish that you see in the picture. The bit pretty much shows no signs of wear.

Yes it worked well, it was a slip in adapter, 1/2" down to 3/8" I even have a similar adapter to go to 1/4" and us that one pretty often.

I do not recall but it was not slow. May have been wide open as smaller bits need to run faster.

[Leon]

FWIW "I don't think" normal straight cut bits are centering... I'm not so sure how important that is, if I have an understanding of the centering function. Maybe center cut means you can cut with the side of the bit vs. just the tip.

Also the bit on the second link above is carbide. Mine is HSS and has held up far better than any carbide bit I have had and it has only been used on Ipe. Ipe is about 2.5 times harder than oak.

[Greg Guarino]

Here's what I found, which seems to mirror my (slight) understanding of it:

"An end mill?s end cut type is either center cutting or non-center cutting. Center-cutting end mills can create three-dimensional shapes and profiles, and make plunge cuts similar to a drill bit. Non-center-cutting end mills are suitable for peripheral milling and finishing, but cannot make plunge cuts."

In other words, "non-center-cutting" can cut by plunging into the material, like a drill bit. It can also cut by moving the bit from side to side. "Non-center-cutting" is intended to cut ONLY on the sides, with "X-Y" motions, no up and down plunging. At least that's the case for metal.

[Leon]

That is how I would understand it and makes sense.

[Swingman]

Does that sentence not contradict what you just said in the first above, or did I miss something?

In any even, IME, all this is basically irrelevant to the woodworking application for routing mortises.

Years ago I switched to "end mills" for routing mortises for one reason, and one reason only:

_there were no router bits made, at the time, long enough to do many of the mortises I wanted to do_

I called Travers and asked to talk to one of their engineers, not a salesman.

The upshot is I've been following Traver's expert advice on which end mills to use for over a decade of cutting mortises, with both various jigs and plunge router, and later the Multi-Router.

Real life experience, thousands of mortises, no problems, and no one else's GoogleFu to have to rely on ... the one's in the photo work, and I have yet to have to buy another in all that time. ;)

3/8" router collets are readily available and easy to find.

For the 5/16" end mills, I use an 8mm collet, which are also easy to find.

[John McCoy]

Leon wrote in news: [e-mail]:

In a metal working context, "forward" is into the work, and "sideways" is across the work.

It comes from lathe work, but machinests seem to use the same wording for mill work too.

John

[Greg Guarino]

Oops. Yup, that should have read:

I found a good diagram that shows the difference: