Hammer A3-31 Slot Mortiser vs mortising methods

[Matt Kestenbaum]

I haven't posted in a while, but I have been a member for some time.

I have been making mortises with a jet bench-top hollow chisel mortiser for a few years -- it works okay and I have developed a few strategies to deal with the lousy clamp and fence. I don't intend to slight anyone who owns a JBM-5…I bought it from a fellow Creeker several years back and at the time it was a nice step up from making mortises with a drill press and chisel. But….

I am about to take delivery of a Hammer A3-31 J/P. I ordered the machine with the mortising chuck installed so that I'd have the option to add the slot mortiser. I have a few days to decide, but a few issues are on my mind and interested in the group's thoughts.

1) Tooling any owners of Euro combo machines with this type of attachment have a source for slot mortising bits? The bit turns left on these machines and and turn too slow for a router bit. Felder group seems to (oddly) only sell them in metric. Not interested converting all of my imperial ways.

2) The current price of adding the slot mortiser (considering that i am already covering installation for the J/P) is cheaper than a big PM or General hollow chisel machine (and uses less floor space and doesn't mean moving more cast iron). It is also a few hundred $ less expensive than the Festool domino XL…maybe is about in-line with the original domino.

3) I do sometimes cut mortises with a router, so the round ends on the slots are not my favorite…but I have no issues sharpening hand tools and know how to use a chisel to square 'em up. But I have not had to do a whole bunch of them. Too slow? Tedious?

If you have one do you use it for traditional Mortise and Tenon work? Loose tenon? Doweled door frames? What else? Would make a different decision given the choice to go back in time?

Thanks!

Matt

[Ryan Mooney]

Look for "birdsmouth mortising bits" a bunch of people sell them. For example: http://www.lagunatools.com/accessories/accessories-mortiser http://www.morriswoodtool.com/Tooling-Misc.htm http://www.rangate.com/specialtyproducts/rangate_mortiser_bits.php (claim "all sizes" but call), etc..

I can't answer the rest of your questions very clearly as I haven't used mine a whole lot. Honestly still end up cutting a lot of them by hand (clearly not the optimal strategy for large volume but for weird angles and small pieces..). I believe most folks end up using pre-cut loose tennons more like you would with a domino with this setup rather than trying to square up the holes (also allows you to make batch quantities of the tennons). The domino has some plausible advantage of being smaller/easier to use on partially assembled pieces whereas the hammer is arguably easier to jig up. I wasn't exceptionally pleased with the table/clamping setup, it worked but was harder to setup to index off of an end than I'd like and is a fairly small table (compare to how you would setup a floor or bench mortiser with offside support). I'm sure I'm missing some cleverness there, but have considered adding a slightly larger sub table with stops, quicker clamps, etc.. to make doing small things easier.

[Jeff Duncan]

A couple quick thoughts,

1st) does it really matter whether it's metric or standard? Unless your thinking of buying your tenon stock I can't see where it would matter? I mill the slots and then sand the tenon stock to size, so for me metric vs standard is not an issue.

2nd) you can use end mills to cut your mortises. There quite a bit cheaper than many of the router bits I've seen sold for the same purpose, and you have more options. I'm not sure but I think mine turns clockwise, or standard direction. If yours turns opposite you'll still find end mills for it, you may just have a smaller selection. Oh and FWIW I've found that a 4 flute roughing mill is about as good as it gets for fast mortises in hard woods.

3rd) one advantage to a slot mortiser is being able to use loose tenon construction which you can't do quite easily with a chisel mortiser. I don't know how the combination machine works but stand alone mortisers are a pleasure to use.

4th) I don't do any traditional M&T work with the slot mortiser. The rare time I need to do that type of work I have to dust off my old bench top mortiser. I do mostly faceframes and passage doors with it.

Lastly.....If I could go back in time I may have spent a bit more money and bought a new one that would have a few more features. At the time I needed it I had a short buying window and having a new one shipped from Europe didn't fit into it:(

good luck,
JeffD

[Chris Fournier]

I have had two machines with slot mortising attachments. They are very useful. Royce Ayr Carbide sells SAE left hand bits. There will be many other suppliers near you. The radiused ends of the mortises don't slow me down a bit. Get the unit and embrace floating tenons. This machine will make you think of all the time that you struggled with your hollow chisel mortiser.

[Steve Rozmiarek]

I have the Felder version, I think it's the same as the Hammer pretty much. Felder's birdmouth bits work very well. Like Ryan said, just mill up several feet of tenon stock periodically. I resaw, plane, and roundover the edges, then cut it to length as needed.

[Frank Drew]

I'm completely with the pro-slot mortiser crowd here; it's, by far, the fastest, most efficient and most accurate method of mortising I've used. I agree with Jeff that you cut your mortise then make the tenon to fit, either integral or loose. I also mostly used end mills, specifically double flute upcut style. And having done both, IMO it's much faster to round the tenon ends than to chop the ends of the mortises square.

An oscillating slot mortiser or a swing chisel mortiser would be even better!

[Frank Drew]

I'm completely with the pro-slot mortiser crowd here; it's, by far, the fastest, most efficient and most accurate method of mortising I've used. I agree with Jeff that you cut your mortise then make the tenon to fit, either integral or loose. I also mostly used end mills, specifically double flute upcut style. And having done both, IMO it's much faster to round the tenon ends than to chop the ends of the mortises square.

An oscillating slot mortiser or a swing chisel mortiser would be even better!

[Sam Babbage]

I started my apprenticeship pre-domino, used to use a slot mortiser a lot. With domino: not very much. For very high volume or unusual setups (that would require jigging to locate the domino) they are better. But for run of the mill work a domino is much more convenient with the whole take the tool to the work idea. My current work ripped their scm slot mortiser off the jointer to reclaim the (admittedly smallish) amount of floor space. I tend to think a domino (whichever size suits) and a hollow chisel mortiser is a good combo. Domino for general joinery, hollow chisel for when you need square corners, slats etc.

Edit: domino also has the advantage of being able to put a mortise anywhere on a component (with suitable jigging/fixturing), slot mortiser not so much. Don't get me wrong, slot mortisers are awesome, when they are in their element, but I tend to think their element is more in a large commercial shop. If I were you I would get the chuck installed with your machine as sort of insurance (moderate cost); buy a domino (probably the 500, if the scale of your work is regular scale), worst case scenario you sell the domino (small loss) and buy the table for the combo. Best case scenario you end up with the trifecta of domino/chisel/slot!

[Kevin Jenness]

Slot mortisers are great machines, especially for inserted tenons. For true mortise&tenon work, I find rounding the tenons a little faster. For tooling, I prefer end mills as you can drill as well as ramp/sweep, whereas the birdsmouth bits will not bore. I like to drill multiple overlapping holes in edge grain mortises, then sweep gradually in to clean up. The shorter and stouter the bit the better to eliminate bit whip. One weakness of slot mortisers is that too long a bit or too fast a feed can produce mortises that are tighter at the bottom than the entry point- I think the bit whip is restrained as it gets farther into the mortise. That's why I use the drill/sweep technique on big mortises. Otherwise, I take light cuts, boring in 1 or 2 mm, then sweeping across slowly enough not to force the bit to deflect. I usually cut lengths of tenon stock, round over the edges while leaving a small flat at the edge to allow for glue squeezeout. Some people groove the tenons for the same reason.

I don't know where Hammer mounts their auxiliary slot mortiser. If it's on the operator side of the jointer, you will probably find it in the way most of the time. If it's meant to be removed, it needs to go back on with no adjustments/tuneup, or you will rue the day you bought it.

Re the Domino, they are great tools, and add the capability of mortise/tenoned case partitions as with biscuit joinery. We have both sizes at my workplace, and they get a workout, but we still use the slot mortiser for large doors. There's no way, though, that they will have the longevity of a good slot mortiser. The brass slide bushings need to be replaced periodically, and I don't know what happens when the oscillating mechanism wears out. Still, for hobbyist use, you could buy both size Dominos for the price of a good used slot mortiser and probably never wear them out.

[Erik Loza]

.....That's why I use the drill/sweep technique on big mortises....

This is probably the most common technique for mortising attachments on combo machines ^^^^

Birdsmouth bits are probably your best choice, pick your brand (Royce, Onsrud, et al). If someone already owns a Domino, then it may not make sense to pay extra for a mortising attachment but that is their call, of course. That being said, the fact that you have a 5hp slot mortiser which weighs several thousand pounds make doing some projects a lot easier. My colleague, Sam, uses the attachent quite a bit on his combos...

Erik Loza
Minimax USA

http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/CU410Elitemortisertable.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/MiniMaxmortisingbits2.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/Installingauxiliarymortisingtable.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/Mortisingtableoperatorview.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/Mortisingtabletopview.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/Mortisingsetup.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/Preparingtomortise.jpg
http://i75.photobucket.com/albums/i315/erikloza/Mini%20Max%20Combo%20Seminars/Slotmortising.jpg

[Peter Quinn]

I run an older Laguna stand alone slot mortiser that is left rotation only in my home shop. I get birds mouths from Onsrud in HSS from Morris wood tool, and long two flute solid carbide made by Leitz from Laguna for deeper stuff or things like teak. As Jeff noted with any mortising operation you make a whole, fit the tenon (integral or loose) to that hole....it doesn't matter at all what the actual size of that hole is, metric or sae. I don't even know what size my tooling is other than relatively in proportion to stock thickness. Square holes? Who cares. It really only matters to me on window bars and through tenons, window bars i punch with a drill press chisel attachment, through tenons are not my thing so it doesn't matter. I love the speed and easy set up of the slot mortiser, and even my cheepo Chinese version is very accurate.

[Frank Drew]

Another great advantage to horizontal slot mortisers is that it's as easy to mortise into end grain as into side grain, no matter how long the piece is; try that with hollow chisel mortisers.

I've never used a domino, but from everything I've read here they sound pretty handy.

[Robert LaPlaca]

Another happy slot mortiser user here, mine is on my Minimax FS-41E J/P. Hopefully the mortiser on the Hammer J/P attaches to the back of the machine like it does on my MM, that way it doesn't get in the way of the J/P functions of the machine. I know I wouldn't want to have to keep attaching and removing the slot mortiser to the J/P.

As others have stated, the best thing about the slot mortiser is how accurate, fast and most importantly how quietly one can excavate a mortise.

For the 18th century furniture I build, I excavate round end mortises and use standard tendons with the tendon ends rounded over, just couldn't bring myself to use loose tendons, although for non 18th century furniture I have used loose tendons..

So far I have only used birdsmouth bits that I think are either sourced from Onsrud or Clico, been pretty happy with the results.

[Bob Falk]

I have a Robland mortising attachment and I think it works great. I periodically make tenons using the tablesaw, then planer, then router table to round edges (I use bullnose bits to do each tenon side in one pass).

[Ryan Mooney]

Another happy slot mortiser user here, mine is on my Minimax FS-41E J/P. Hopefully the mortiser on the Hammer J/P attaches to the back of the machine like it does on my MM, that way it doesn't get in the way of the J/P functions of the machine. I know I wouldn't want to have to keep attaching and removing the slot mortiser to the J/P.

Its on the front and yes it does get in the way. Its not as heavy as a lot of them though, I think the MM has quite a bit more cast iron in it so it would be more painful. It also re-references back to the same location fairly well (although I haven't put it on/off a lot so I can't say how well that holds true over long periods of use).

[Matt Kestenbaum]

Thanks for all great response! I have been a little insistent on SAE bits for the simple reason i just think in term of SAE when it comes to design and layout…1/4 tenon centered on a 3/4 apron, 1/8" filet from leg to apron, and so on. (Not really the actual fitting of tenons to mortise). Metric and undersized plywood gives me enough grief already.

I was already leaning towards getting the unit, but the feedback here has been various levels of endorsement. Helpful in making up my mind.

[Rod Sheridan]

Hi Matt, I finally went metric awhile ago.

Far simpler designing and building in the metric system

Make pieces 20mm instead of 3/4", 50mm instead of 2".

Makes calculations and measurement much easier.........Rod.