Horizontal Mortiser Cutters (Bits)

[John Renzetti]

Hey Floyd,
Mini Max stocks more than two sizes, but at the time you called there were probably on two sizes in stock. The reason stock is low at this moment is that I have been working on changing suppliers for more variety, and as of yesterday I shook hands with and Onsrud rep, who will now be supplying us with mortise cutters -- Off the shelf 4 flutes, similar to what you've shown, but with 4 flutes instead of two. And they will be making some specialty spirals for horizontal mortisers (both left and right) to the specs I gave them. They will be longer than off the shelf spirals and the shaft will shrink by .002" behind the cutter to prevent any undo friction on deeper mortises, yet allow for more bit strength because you won't have to have a longer cutting edge or spiral.

What you picture is a cutter for an oscillating mortiser (no plunging) that can cut in either direction of rotation. If you tried to plunge more than 1/16" you probablly didn't like the results. With that type of cutter the mortise is made moving side to side only, and will yeild very clean mortises quite quickly. If you want to plunge for doweling, use drill bits or router bits, but make sure and determine whether your mortise attachment is on the back side of the J/P (right hand rotation) or the front side of your J/P (left hand rotation) and get the appropriately oriented cutter. I doubt you will find the "birdsmouth" cutters like the one you have in solid carbide, and if you do, I don't recommend getting any sized 3/8" or less - they will tend to snap. Also keep in mind that with solid carbide, expect to pay premium prices, while sacrificing cut quality a bit (not that this will matter that much for a mortise). High speed steel, in this application, still offers the best bang for the buck.
Hope this helps,
sam

Hi Sam, Felder has them in carbide but they are much more expensive. I've not used the carbide as I've found the HSS work great. I've been able to get about 1/8" cut on mine and then just continually move back and forth as moving in about an eighth on each side pass. Works real good. I've got a variable speed on my mortiser and that helps to adjust the speed to the cutter.
take care,
John

[Steve Rowe]

The four flutes are in and I've been using them for a little over a month now. They aren't quite as fast as the two flutes, but the mortises are cleaner and a bit more consistent (though, the difference is very marginal). They haven't got me the spiral they were going to work up for me. Could be a time for a call to see what's going on. What depth are you looking for? and in what diameter?

Sam - I usually use the 1/4" and 5/16" bits.
Thanks,
Steve