High-Speed Router End Mills for Mortising

      Thoughts on end mill bits for high-speed mortise cutting. January 11, 2007

Those of you who use high speed routers for mortising, like the Multi-Router setup, or even a hand held router, what type and model of end mills have you had the best experience with?

Forum Responses
(Solid Wood MachiningForum)
From contributor R:
I use 2 flute spiral endmills in our commercial slot mortiser. I typically use high speed steel, as the rpms are around 4,000. I'd use carbide for a router. Endmills rated for aluminum would be a good match with machining wood. A spiral carbide router bit would be my first choice as router bits are with fixed arbor sizes. Endmills are typically the same size arbor as the tip, so you don't have as many options. Endmill collets come in a bigger range of sizes for milling machines. I wouldn't worry too much about the brand. A good reliable source will carry good tooling. The imports are fine for woodworking. mscdirect, wttool, use-enco, mcmaster, etc. Add the www.com to the above addresses. A number of folks are using the Grizzly G-0540 as a horizontal slot mortiser. Under $400.

From the original questioner:
Appreciate your feedback, but Iím looking for woodworkers who've had good or bad experience with high speed router end mills used for mortising. Horizontally set up like the Multi-Router, hand held or some other setup, as long as itís with a high speed router or spindle motor (over 15,000 rpm). I know about slow speed slot mortisers - I own one ( 400rpm max!) - and they're great. I can't find the Grizzly you mentioned when I search their site.

From contributor R:
HSS endmill are pretty cheap. Why not just buy a few and try them? The G-0540 is their horizontal borer/mortiser. I'd be willing to bet your mortiser runs at 4,000 rpm, not 400 rpm. Don't the regular or spiral bits do the job? They tend to get burned up a bit with the speed.

From the original questioner:
Found the Grizzly. Yep! Almost right for the RPMs, variable speed from 1500 to 4000 Ė oops!

As for the end mills, I just want some feedback on what others have tried. I just bought another horizontal slot mortiser, this one with high speed motor (up to 20,000 rpm) and need more info on end mills for high speed usage.

So far, Iíve tried a couple from Onsrud, but so many numbers to choose from. I'd like to see what others have tried before spending more time and money just to get frustrated!

From contributor R:
Your use of the term "endmills" was a bit confusing. Onsrud bits are not endmills at all. They are designed for routers at high speed. Also, they are carbide, not high speed steel. They are probably the best you can get. Endmills have a different geometry and do not do as well in the higher speeds in my experience, especially the hss ones. What brand is your low speed mortiser? Can't recall seeing any with that range of adjustability in speed and I've worked with many different brands over a 25 year period. Must have missed one somehow.

From contributor J:
What about a WoodRat? It is on my list of future purchases. Lee Valley now carries it so you can read about it in their catalog or online. It uses a plunge router mounted vertically above your stock. I was skeptical until I used one (through dovetails) at a show sometime back. It is very accurate and has some unique features.

From the original questioner:
My objective is to learn about others' experiences with different type and models of end mills for mortising, not jigs that can do mortising.

From contributor P:
I use solid carbide in my 625 plunge router for mortises, sometimes as deep as 2". The ones I use are made by West Coast Saws. I use the upcut 2 flute. They work great and they can resharpen them so you have essentially a brand new tool, except the diameter will be a few thousandths smaller. One big advantage with carbide is that you have a stiffer tool and you don't get the chattering that you would with hs running at the higher rpms, and chatter means less tool life.

From the original questioner:
Thank for this valuable information! Will definitively check it out.

From contributor P:
One thing I forgot to mention is that you can get 5/16", 3/8" diameter with 1/2" shanks from West Coast Saws as well as 1/2" diameter. They might tell you that their bits are made for just CNC and the feeds and speeds that are capable, but they work great in either a multi router application or in a hand held plunge application. I think that when they say that, they are worried about people trying to freehand the work through the bit and because of the geometry of the bit, it grabbing the work, but I have not noticed any more tendency to grab the work than other brands of spiral uncut bits. By the way, what I am talking about is spiral upcut 2 flute cutters.... Endmills are for metal working. These are for wood and wood composite materials.

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