# End Mills vs.Rrouter Bits For Mortising.



## Gaia (Feb 20, 2010)

Hello all,
I'm learning, teaching myself to make internal and external house doors.
I came across this article the otherday. I was wondering what other forum members opinions were?
Ta,
Peter.

"My choice: end mills. Here’s why.

I do most mortising with my trusty Elu 3338 plunge router, currently available as the DeWalt 625, with various jigs and methods, most involving a template guide riding in a slot. I formerly used solid carbide upcut spiral router bits with generally good results, though I often encountered two problems.

First, 1/4" and 3/8" spiral bits are usually sold with cutting lengths of 1" and 1 1/4", respectively. I often want to make mortises deeper than that. Second, 1/4" and 5/16" diameter bits, especially some long HSS versions, will sometimes vibrate in the cut and produce steps on the mortise walls. Even a 3/8" bit may be made with a surprisingly thin web at the core of the spiral which can cause the bit to flutter when cutting dense woods.

My preference now is a standard, four-flute, center-cutting, single end mill in uncoated solid carbide with a plain shank and a 30-degree helix. These are available in longer overall lengths with longer cutting lengths than router bits, thus allowing deeper mortising. The core of this type of end mill is more substantial than that of the same diameter spiral router bit. I find the cutting action of these four-flute end mills has less vibration and is smoother and more balanced than that of router bits. This results in cleaner mortises. Furthermore, these end mills are generally less expensive than comparable router bits.
I usually run the end mills at 18-20,000 rpm. Some cautions that I employ are:

* chuck at least 1" of the 3/8" bit into a clean, top quality collet such in the DW625
* cut the mortise in small depth increments (e.g., 1/8" in a dense wood)
* use a vacuum to frequently clear chips that may build up in the jig apparatus
* do not mortise deeper than the flute length
* use a steady, reliable jig setup

I always listen and feel for signs of strain from the router or bit and adjust the depth of cut and feed rate accordingly. I have read of mostly speculative concerns regarding burning and chip congestion in the mortise, but I have not had either problem.

The disadvantage of an end mill is that the cutting diameter equals the shank diameter. Therefore, I usually mortise with a 1/4" or 3/8" end mill using a router collet of the same size for each. A 5/16" end mill can be used with a shank adapter though I prefer to avoid these adapters.

This is what works for me in my shop using these specific end mill specifications with the mortising tools and techniques described.
ources for end mills are industrial supply houses such as MSC, Enco, McMaster-Carr, and Grizzly. It will take a while to go through their catalog algorithms or directly study their catalog pages but these are good ways to learn about this type of tooling."


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## istracpsboss (Sep 14, 2008)

Hi Peter

It's not a bad idea. I might try it as I've plenty of 1/2" spiral milling cutters and I think even a 3/8" one with a 1/2" shank. They are a good length too. Given that mortices are never very long, the concern about using HSS instead of carbide because of overheating issues might not matter too much. Obviously use your slowest speed, although it is still way above normal speeds for milling cutters and you can't use coolant with wood, but for brief usage, allowing the bit to cool before it gets too hot, it could work.

Woodrat do actually sell HSS bits for use in routers. Just bear in mind the heat limitations.

Just reread the article and realised the guy is actually talking about solid carbide bits. OK. They would be better. You could still try HSS ones which are usually available s/h very cheaply at model engineering exhibitions/rallies. I'm talking £3-4 each.

Cheers

Peter


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## RJM (Apr 11, 2010)

I've read that new HSS cutters can provide a better finish than carbide cutters because the HSS holds a better edge, making the HSS bits are sharper. Of course, the HSS also dulls quicker. Comments?


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## Gaia (Feb 20, 2010)

Thanks for the 2nd hand tip.


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## Gaia (Feb 20, 2010)

RJM60 said:


> I've read that new HSS cutters can provide a better finish than carbide cutters because the HSS holds a better edge, making the HSS bits are sharper. Of course, the HSS also dulls quicker. Comments?


Thanks for the input


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## bobj3 (Jan 17, 2006)

Hi Robert

Carbide cutters hold the edge much better than HSS it's true you can resharpen HSS easy but it will not hold the profile/edge or to say every time you play with them it will change the profile not to say anything about strait cutter bits they will become junk most of the time and once they become blue that's it most of the time ,,,,junk router bits.. heat is real killer for router bits..

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RJM60 said:


> I've read that new HSS cutters can provide a better finish than carbide cutters because the HSS holds a better edge, making the HSS bits are sharper. Of course, the HSS also dulls quicker. Comments?


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## istracpsboss (Sep 14, 2008)

RJM60 said:


> I've read that new HSS cutters can provide a better finish than carbide cutters because the HSS holds a better edge, making the HSS bits are sharper. Of course, the HSS also dulls quicker. Comments?


I think for sheer durability, carbide will always win. However, it is more brittle and I think part of the reason Woodrat go for them is that they can make slimmer dovetail bits that are relatively strong, offering a profile nearer to a hand cut dovetail, which is less easy with the carbide tipped steel bits, as they are of necessity more beefy.
HSS can also be ground more sharply, so that it cuts rather than bashes its way through the wood.
If I ever finish my Quorn and Stent T&C grinders, I'll even be able to sharpen them properly !

Cheers

Peter


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## BigJimAK (Mar 13, 2009)

HSS might just have a bigger percent $$$ markup too, eh Peter? 

Call me a cynic..


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## istracpsboss (Sep 14, 2008)

Now that _is_ cynical ! Certainly, it is difficult to find any alternative source for them to get comparable HSS cutter prices. It may be that the relatively high price on them is because they are getting them made specially in small batches. 
However, I think their point about getting skinnier dovetails is valid. All the other (TCT)dovetail bits I've got are much wider in the neck.

Cheers

Peter


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