Question about Mortising Machine and Bits

[phrog]

Are bits/chisels for different brands and models of mortising machines specific for a particular brand. I'm looking at a Delta Mortising Attachment for my 16" DP versus a HF or Sears or Delta Mortising Machine. Will a Delta bit fit the HF Machine and vice versa? In other words, are the bits/chisels a standard size and shape (at the attachment end)? For occasional use, would the Delta attachment suffice rather than a dedicated machine? Will be using on 5/4 oak. The Delta attachment is $75 vs $85 (on sale with coupon) for the HF Dedicated Machine. What brand of bits are considered good for these contraptions? Any info would be appreciated. Thanks.
Richard

[LarryG]

I last visited this issue a couple years ago, when I was shopping for a mortising machine (bought the Delta 14-651), and wondering what would happen if I needed a replacement bit, or one of a different size, etc. My impression was and is that the bits themselves, not only for the dedicated machines but also for the drill press attachments, are all the same. But that's not to say there's not an oddball or two out there.

Since you mentioned "for occasional use" ... have you considered using a router to cut the mortises, if this really is an operation you don't anticipate doing very often? (Actually, a router is a good alternative even if you DO cut a lot of mortises. David Marks on "WoodWorks" cuts almost all of his that way, FWIW.)

If you use a router, you have three basic alternatives:

1. Use loose tenons, shaped to fit the rounded ends of the mortises (note that twice as many mortises will be required)

2. Use integral tenons, and round off the sides by hand to fit the rounded ends of the mortises

3. Use either loose or integral tenons and cut the bulk of the mortises with the router and square up their ends with a chisel

Just a suggestion you might want to think about, if you've not already.

[LCHIEN]

All mortising chisels are not the same. There are two basic sizes of mortising chisels, they both attache the same way, by means of a round end fitting into a collar and held by a set screw. The two sizes are (I hope I have this correctly) 5/8 and 3/4" dia.
My jet came with both size adapters on the mortiser but I think that's the exception as most come wsith only one size. It's therefore important to know which one to get for your machine.

The bits, they usually come with the chisels, but most mortisers have a chuck which will adapt to most any sized bit shank.

As for chosing a $75 delta adapter vs a $85 HF mortiser, the adapter has a number of disadvantages,
the stroke of a mortiser is usually 4" but the stroke of the DP+adapt is limited to the DP stroke
The DP IMO does not have a strong enough arm since you have to supply the chisel driving power. The arm on the mortiser will be much beefier.

So in short, to me a real mortiser is much better, The HF one is really the very bottom end, so I don't know how well they work, the reviews i've seen said they are rated basically at the bottom but I can't imagine it being worse than the DP+adapter.

[LarryG]

Loring is, I suppose, technically correct; let me try again:

The chisels all attach using the same basic design, but there are indeed different sizes and the limiting factor will be the capacity of the machine's chuck. My understanding is that all chisel sizes up to 5/8" use the 5/8" bushing. Chisel sizes 3/4" and larger use the 3/4" bushing. There's also a 1-1/8" (or maybe it's 1-1/4"?) bushing size but I don't know how this relates to the cutting "diameter" of the chisels that would be used with it.

To my knowledge, none of the 1/2HP (or so) benchtop machines, including those mentioned in the OP, are supplied with chisels larger than 1/2". That is also the largest chisel included with the Delta drill press conversion kit. So my statement that they're all the same was meant in that context. Both Fisch and Lee Valley say their chisels will fit all the common brands of mortising machines, although LV does mention the larger bushing size of their 3/4" bit and advises checking the machine's chuck capacity.

I wasn't aware that the JET came with the larger adapter ... a 3/4" seems like a lot of chisel for that size of machine to drive. I thought the 3/4" and larger chisels were the province of those big floor-standing brutes that cost over a thousand bucks.

EDIT: As a clarification, when I say "chuck," I'm talking about the means by which both the round drill and the square chisel attach to the machine. If there's a more proper name for this dual-purpose assembly, I don't know what it is.

[thiggy]

I originally had a mortising attachment for my drill press which worked adequately for the infrequent use I made of it. However, it was a nuisance to set up and remove, and the hold-down was not easily adjusted. I retired it a few years ago and purchased the Delta 14-651 and have not been disappointed. I have just cut a bunch of mortises this week while building a reproduction pierced tin pie safe.

[AlanWS]

A router quickly cuts mortises with very smooth walls. Where a router falls short, so to speak, is in mortise depth.

For deep mortises, don't discount a simple mortising chisel and a mallet, or a drill press and then a bevel-edged chisel.

[LCHIEN]

Loring is, I suppose, technically correct; let me try again:

The chisels all attach using the same basic design, but there are indeed different sizes and the limiting factor will be the capacity of the machine's chuck. My understanding is that all chisel sizes up to 5/8" use the 5/8" bushing. Chisel sizes 3/4" and larger use the 3/4" bushing. There's also a 1-1/8" (or maybe it's 1-1/4"?) bushing size but I don't know how this relates to the cutting "diameter" of the chisels that would be used with it.

To my knowledge, none of the 1/2HP (or so) benchtop machines, including those mentioned in the OP, are supplied with chisels larger than 1/2". That is also the largest chisel included with the Delta drill press conversion kit. So my statement that they're all the same was meant in that context. Both Fisch and Lee Valley say their chisels will fit all the common brands of mortising machines, although LV does mention the larger bushing size of their 3/4" bit and advises checking the machine's chuck capacity.

I wasn't aware that the JET came with the larger adapter ... a 3/4" seems like a lot of chisel for that size of machine to drive. I thought the 3/4" and larger chisels were the province of those big floor-standing brutes that cost over a thousand bucks.

EDIT: As a clarification, when I say "chuck," I'm talking about the means by which both the round drill and the square chisel attach to the machine. If there's a more proper name for this dual-purpose assembly, I don't know what it is.

Chuck: theres a chuck for the rotating bit. Theres a collar to attach the non rotating chisel. It fits closely and is held by a set screw. (Collar is my terminology).

The Collars, it's my recollection they come in two sizes (3/4" and 5/8"), they differ by like 1/8" and its not related to the cutting size of the chisel - they're just different standards. So most machines take one or the other. AND you have to buy chisels to match. Its not often clear which one you are buying as most catalogs don't specify the collar size. E.g. a given machine will take chisels with the 3/4 collar in all sizes. or with a 5/8" collar in all sizes. Most benchtop mortisers in the Jet and Delta size only come with chisels 1/4" to 1/2". I don't think they are recommended for any larger than that.

There's of course no real limit on the chisel size a machine can take assuming you don't break the handle driving it. Most people don't realize that most of the work is done by manual force driving the chisel down. The auger bit merely clears the center of the cut but the walls of the mortise are basically hand cut but guided by the machine.

[LarryG]

The Collars, it's my recollection they come in two sizes (3/4" and 5/8"), they differ by like 1/8" and its not related to the cutting size of the chisel - they're just different standards.

Could be. I'll put it this way: I'm 99.44% certain all the little benchtop machines we're talking about here are supplied with the 5/8" shanks; both Fisch and LV say their 5/8" shank chisels will fit the Delta, JET, Powermatic, etc. Perhaps the assumption that chisels below a certain size *all* use a 5/8" collar is just that, an assumption (on my part).

Also, I know for a fact there's at least one additional, larger size collar, although as stated I don't recall exactly what it is. Although I tend to doubt there are any benchtops that would use anything larger than the 3/4" size. EDIT: Just found it, Powermatic (for one) has a 1-1/8" size on their floor-standing mortiser.

There's of course no real limit on the chisel size a machine can take assuming you don't break the handle driving it. Most people don't realize that most of the work is done by manual force driving the chisel down.

That's what I was getting at. The big benchtop machines typically have longer handles and beefier frames, in addition to more powerful motors.

[LCHIEN]

... Perhaps the assumption that chisels below a certain size *all* use a 5/8" collar is just that, an assumption (on my part).

...

I'm sure that's an assumption on your part.

I do know there are two sizes in common use on benchtop sized machines (the big powermatic does not count!) - 5/8 and 3/4"

I do not know the fraction split, you may be right that the 5/8 is more popular and I do know that is Delta's favored size, but I'm sure the 3/4" are much, much more prevalent than 0.6%. I did find in my research when I bought my Jet that there were these two sizes floating around.

As I said the Jet is equipped to handle both sizes (you can see the specs here - look at Chisel shank capacity and bushing sizes)
http://www.woodquip.com/jettools/jbm_5.htm

[LarryG]

I'm sure the 3/4" are much, much more prevalent than 0.6%.

That's NOT what I said, but enough, I give up.

[onedash]

I have the delta deluxe and with the huge arm I still have to apply decent pressure...I would never use the DP attachment. I dont think it (DP) would last very long with that kind of abuse. I even snapped the arm of my mortiser. Had to replace the pin.

[phrog]

Thanks

Thanks to all who have posted in response to this question. A special thanks to Larry and Loring for all their posts. ( I hope they are still friends.) In any case, I think I got the picture. Unfortunately, no one around here except HF sells a dedicated machine. (and, I forgot, Sears - Don't know who made it) Once again, thanks. I think you'all have talked me outta the Delta attachment.
Richard

[paintandbodtman]

As I said the Jet is equipped to handle both sizes (you can see the specs here - look at Chisel shank capacity and bushing sizes)
http://www.woodquip.com/jettools/jbm_5.htm
Today 04:20 PM


Trying to follow this thread and from what I gather from both loring's and larry's disscussion the chisel shanks are diffirent sizes which I totally agree with but loring I don't see what having the capicity to use both size chisel shanks with the jet makes it any more desireable than the other benchtops out there because you still are limited to mortise size based on the chuck size, according to the specs on the jet 3/8 inch bit is the largest drill bit that it will accept unless someone makes bit and chisel combo with a stepped drill bit which if they do than the mortise size exceeds the practical use of the benchtop tool, however I guess that could give you a better price range of chisels.

[LCHIEN]

P&B man,
One point i was trying to make is that having the ability to use either shank size eliminates the problmes in buying the right chisels. I pointed out that chisels are often not indicated what size shank thay have.
There are 3 or 4 confusing but separate measurements:
Bit or auger cutting diameter (bit is wider at the cutting tip)
Bit or auger shank diameter (fits up to the maximum chuck size)
Chisel dimension (square profile)
Chisel Shank dia. (either 5/8" or 3/4")

3/8" bit limit you refer to is the chuck size and thus the bit shank limit.
But the bits cutting diameter can go up to near 1/2" for a 1/2" chisel, they're stepped and expanded at the tip.

its all independent of each other, more or less (obviously you won't have vastly different measures for these).

[LarryG]

Yes, Loring and I are still friends, no worries there.

But at the risk of needlessly flogging a thoroughly dead horse, I do have to say that I don't understand his continuing insistence that there are only two sizes of chisel shanks, 5/8" and 3/4". The larger Powermatic mortisers (and there may be other brands too, I don't know) will accept either a 5/8", 3/4", or 1-1/8" bushing. His JET mortiser came with the smallest two sizes of these; the big Powermatic comes with all three. The small benchtop mortisers like his JET mortiser or my Delta may not accept a 1-1/8" shank chisel, but the issue, raised by Loring himself, is the available sizes of chisels. As he himself has stated at least twice, the chisel manufacturers don't always specify (at least in a way that is easy to find) what size shanks their chisels have. My point is that the size choices are not limited to just two: there are at least three.

My error, for which I apologize, was in assuming, incorrectly I now realize, that the chisel shank size was a function of the chisel's cutting size, rather than being differering standards as Loring has explained. This assumption stems in part from reading a comparison test of six or eight benchtop mortisers. I don't recall all of the brands included in the test but I do know that it included both Deltas, the JET, the tilting-head General, the Fisch, and a couple-three others. I remember reading that in order to more accurately gauge the relative performance of the various machines, the tester/author used the same chisel in all of them, to eliminate the variable of this chisel itself. Since this same chisel had to be installed into every machine tested, and since my Delta mortiser comes with 5/8" shank chisels, I made the assumption that this was the typically-supplied size for these benchtop machines. Perhaps it is, perhaps it isn't: at this point, I still don't know. (Loring, your JET came with both size bushings, but what size are the chisels themselves?)