What tooling for a horizontal mortising machine

[Mike Kees]

Just purchased a horizontal mortising machine. It is an older machine with a cross slide table and a large Jacobs chuck. it is 3 phase and somewhere around 3h.p. powered by a flat belt. What would be the optimal tooling for mortises ? The guy I bought it from just used a brad point drill bit. I have seen suggestions in threads here ranging from end mills to birds mouth bits. What works well in solid woods (hardwood) and does it make a difference what size mortise I am milling ? I plan to use this mostly for mortising table legs and interior/exterior doors. So mostly 1/2'' and possibly 5/8'' mortises.

[Davis Young]

I have a Davis and Wells outfitted with a chuck and I use end mills. I have 1/4" to 1/2" sizes from JDS for their Multi-router, but ones from MSC and elsewhere are probably cheaper. The only thing with mine, and you can check with yours, is that the motor doesn't spin fast enough so going into end grain with a large bit can be rough going. This is not a big deal if you're mostly doing live tenons, but it's something you'll have to account for if you do slip tenons.

[Kevin Jenness]

If your machine has low friction linear bearing slides you may be limited to birdsmouth bits in the larger sizes as spiral bits over 3/8" tend to self feed, sometimes violently. If you have a machine like a Bini with dovetail ways, HSS center cutting spiral end mills are inexpensive and available in many sizes.

The key to using these machines is using the shortest bit that will do the job and a moderate, consistent feed rate. Long bits and a fast feed induce bit whip, which leads to tapered and inconsistently sized mortises. I have migrated to boring a series of overlapping holes and then sweeping away the waste, but you may find that sweeping side to side works better for you. The birdsmouth bits will not do boring.

I have a 5/8" spiral end mill with a 3 1/2" cut length that sits on the shelf since it tried to work its way out of my Westcott chuck in cherry. That might not have happened in pine or if I had a collet chuck, but you get the idea. I don't go deeper than 2 1/2" now, which seems fine for the doors I build with spline tenons.

My Westcott chuck has a maximum capacity of 16mm. It is hard to find reduced shank end mills, so when I wanted a 3/4" bit I bought a carbide birdsmouth bit from Rangate. Pricey at about $150 delivered, but it is a nicely made tool.

[Erik Loza]

Birdsmouths would be the common answer. I've never personally used an endmill bit in one, though many folks do. 100% agreement on using the shortest tool possible. Also, keep the inside of the chuck jaws clean. Rangate seems to be the go-to vendor for tooling.

Erik

[John TenEyck]

I use center cutting 2 and 3 flute spiral end mills in my MiniMax horizontal mortiser with Wescott chuck. I regularly cut 5/8" mortises for loose tenons to 2-3/4" with a bit that I think is 4-1/2" long overall. The chuck is the weak link in the system, for sure. I tried reduced shank 3/4" end mills but the chuck slips so I'm stuck at 5/&" max. As Kevin said, the shortest length bit that gets the job done is the best approach. I tried a long Amana mortising bit and it self fed and vibrated something terrible, very scary. Never used it again. I haven't tried birdsmouth bits yet because I'm cheap but they look like the optimal solution for deep mortises.

John

[Wes Grass]

If you want to use endmills and plunge, 4 flute center cut should be safer than 2 flute. They typically only center cut on 2 of the flutes, and there's a much larger web, and smaller gullets, to help hold them back. Which is why they basically suck in aluminum.

3 flute have only 1 center cut edge, so a better choice than 2 flute as well.

[Mike Kees]

What are some good sources to buy endmills or the birds mouth bits ?

[Jeff Duncan]

I'm in the endmill camp as well.... though I just sold my Bini so I guess I was previously in the endmill camp?? Anyway I found 4 flute center cutting roughing mills the way to go. The roughing mill is more aggressive so easier to feed into hardwood end grain. I bought mine through MSC, they have a pretty good selection for tooling in general.

good luck,
JeffD

[Bill Dufour]

Lots of new and used endmills on ebay. I find the used ones work well in my router. Solid carbide will be hard to grip in a three jaw chuck. Some thing like a ER25 chuck would be better and give you a good size range. What holds the chuck to the spindle. It should have a taper and a draw bolt.
Bill D

[Mike Kees]

Thanks for all the suggestions. I think I will try out endmills and see how that works.