Hello,
I’m about the purchase a Grizzly GO540 horizontal mortiser for drilling dowels and mortises but I could use some advice from people who have a similar set-up about specifically which brand and type of end mill you use. There are way too many choices out there!
I know that I want a spiral up-cut bit – and from my own research it seems 2 flutes are better than 4 for waste removal on mortises with these types of machines. But where I’m getting lost (especially in that MSC catalog) is with the length of cut of the bit. Most of the bits out there have very short (1″ or less) lengths of cut that taper to a wider shaft, which wouldn’t work for cutting deeper mortises. So I’m looking for something with a longer cutting surface.
I have found one type in the MSC catalog described as a center cutting bit (not sure what that means) which seems to fit the bill: http://tinyurl.com/2ahnfua But I’m just not sure about it. What do you guys use? Any links or catalog info would be much appreciated as each brand/type seems to have about 20 variations….
Also, when buying drill bits, I usually go with HSS over Carbide cause I can sharpen my own, but these look too complex to do on a grinder, so I’m thinking I’ll go with Carbide. Does anyone have experience sharpening these by hand with a baldor-type low rpm bench grinder? Seems really difficult to impossible.
Thanks for your advice!
Replies
The machine you are looking at is a drill, not a mortiser. There are 2 dead giveaway features: 1) The 3 jaw chuck. This will grip a drill but doesn't have enough holding power to deal with the radial loads on a mortising cutter. These require a collet if they are not going to wander out. 2) The spindle. The chuck is mounted right on the end on the motor. You have 3600 rpm, which is way slow for a mortising cut, and probably a single row ball bearing at the front end which is ok for the axial load on a drill but will chatter under the radial load of a mortising cut.
There's a lot to be said for the conventional wisdom that mortising is done with router cutters spinning at 9,000 rpm plus with super precision bearings.
Unconventionally, James Krenov in "The Fine Art of Cabintmaking" describes mortising with 4 flute, upcut hss end mills mounted on a saw arbor. This is well worth reading.
No one can sharpen spiral flute carbide router bits. I don't care what equipment they have. In production mills these are used once and thrown out. Stick with 2 flute straight router bits. I sharpen these all the time with a hand held diamond hone. Count your strokes on each flute and hone them often.
Thanks for getting back to me. People do use this for mortising, although you're right, it's designed for drilling holes -- and is actually called a boring machine. There are some other threads by people who use it as a mortiser -- you need to take very light passes cause the chuck's not designed for side to side motion. But people do it without incident. Speed shouldn't be a problem -- I previously used a larger sized machine originally designed for metal that ran at @ 1700 rpm and it worked great. Much more solid than this one, but 4x the money.
Thanks for the tip about the diamond hone. I found some 2 flute bits through MSC and will try it.
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