Yet another slot mortising question......

[Rob Will]

Thanks to all who provided advice on mortising machines. For right now I am leaning toward a horizontal slot mortiser and floating tenons.

Here's the question: Grizzly sells a lightweight horizontal boring machine ($300, shown below). I'm trying to get it in my pea brain as to how these things can cut a mortise.

When machining out a slot mortise does one first drill several adjacent holes to full depth.....or do you make several sideways cuts, each time plunging the bit a little deeper?

Is this rather light Grizzly machine capable of machining out a mortise?

TIA
Rob

[Roy Wall]

Rob,

Normally, mortising bits are NOT made for plunging......they will burn.

Just dig in a 1/8" or so and begin the side to side motion. As you get the hang of it, you will learn to control the depth in small increments while sweeping from side to side. Both arms working together and eventually you'll reach your depth. Then make a few more sweeps side to side to "clean out" any misses.....

[Rob Will]

So has anyone actually used one of these Grizzly machines?
Are they rigid enough for the task at hand?

Rob

[Dewayne Baker]

I didn't know grizzly made such a machine. If it does work the price is right. The key to accuracy is the method of table travel and how much play or slop does it have. I am currently pondering building my own horizontal mortiser featured in Shop notes magazine issue # 68. The plan calls for drawer slides but I'll be playing with a more accurate way of travel.

[Alan Turner]

On another forum, a fellow reviewed the Grizzly for use as a slot mortiser, and had a video clip or 2 as well. His conclusion was that it was OK at this task for light work if one proceeded slowly.

One uses an end mill on these guys, not a router bit. Plunge in a bit, perhaps 1/8" on the Grizz, or 1/4" or slighly more on a true slot mortiser, and having set your side to side stops, go back and forth, advancing the bit for each pass, until the limit stop you have set is reached. Quick and easy. There is debate on the best endmills; I use a 2 flute, center cutting one from Bentz tooling of California. Solid carbide.

[Gary Sutherland]

FWIW, while Grizzly only lists this as a horizontal boring machine, Leda (Australia, I think), sells the same machine under their label as a horizontal slot mortiser.

Haven't used one myself.

Gary

LEDACRAFT BM-01 BORER & SLOT MORTISER

[Cliff Rohrabacher]

I use a center cutting end mill ( I like OSG) .

[Rob Will]

What do you guys think of a two-flute upcut cutter for mortising?

Rob

[Mark Singer]

What do you guys think of a two-flute upcut cutter for mortising?

Rob

That is the bit I use for mortising with a router...the chips need to be free to get out though... So a template bushing is not a good way to go

[Joe Chritz]

What do you guys think of a two-flute upcut cutter for mortising?

Rob

Should work well. I have cut a few mortises with endmills either in a vertical mill or CNC router and the straight center cutting two flutes work great.

No comment on the Grizzly machine as I have not used one. Looks to be a decent price if M&T joints are you thing. Last project I used a lot of M&T joints was a mission style bed and I did them with a plunge router, 1/4 upcut bit and a jig.

Joe

[Rob Will]

What sort of jig do you use for router mortising?

Rob

[Dino Drosas]

I don't know about the Grizly but it is sure priced well. I use a Felder slot mortising table that is an accessory for the J/P. As for bits, I use the "birds mouth" bits that are designed solely for this purpose (shallow plunges, then side to side until propper depth is reached). Last project was heavy heart pine doors - floating tennons 3/4" X 4" long.

[Joe Chritz]

I don't current have the one I was using for the bed. It was basically a box that was the same width as the router base. (I was using 1/4" tenons and a 1/4" upcut bit) It was long enough so that when move from end to end it cut the mortise the correct length. The rail of the bed slid under the "box" and a mark aligned to the jig positioned the mortises. The plunge stop set the depth.

It was a simple as align the marks, clamp the board, router the mortise from end to end. Unclamp, move to the next mark and do it again.

It is truely much easier than I make it sound. I will get to my buddy's shop and grab a picture of it. It didn't fit my router so I left it there.

Joe

[Rob Will]

I don't current have the one I was using for the bed. It was basically a box that was the same width as the router base. (I was using 1/4" tenons and a 1/4" upcut bit) It was long enough so that when move from end to end it cut the mortise the correct length. The rail of the bed slid under the "box" and a mark aligned to the jig positioned the mortises. The plunge stop set the depth.

It was a simple as align the marks, clamp the board, router the mortise from end to end. Unclamp, move to the next mark and do it again.

It is truely much easier than I make it sound. I will get to my buddy's shop and grab a picture of it. It didn't fit my router so I left it there.

Joe

Sounds interesting,
Was the "box" set up for a certain width / thickness board?

Rob