Mortices with a router

[David Starr]

I need to do about 16 mortises. I'd like them all to be the same size, so I thought I'd make a template for the router and use a router template guide (sleeve sort of thing around the cutter) to follow the template. Question. Where do I find a template guide to fit an elderly Craftsman router Model 315.17381? Sears part number 25973 (looks like a template guide set) "fits most current Craftsman routers". Does anyone know if "most" includes my old timer? Lee Valley has a set of 1 3/4" brass template guides, and the hole in my router's baseplate is 1 3/4". What are the chances of them actually fitting properly? Especially as the base plate hole is just a plain straight thru hole, no recess to take the lip of the template guide. Lee Valley also has a replacement router base plate with a 1 3/16" hole, and template guides to match. Do I need a replacement baseplate? If so, is it possible to drill it to fit the router and get it to line up properly (centered on the router chuck)? With just ordinary shop tools? Is there something else out there that was intended to fit this model router? While I'm on the subject, how deep a mortise can a 1/4" chuck router make? I have one bit that is 2 1/4" long. With 1/2" of the bit inside the chuck, that makes the mortise only 1 3/4" deep. Are there longer bits out there?

David Starr

[Morris Dovey]

| While I'm on the subject, how deep a mortise can a 1/4" chuck | router make? I have one bit that is 2 1/4" long. With 1/2" of the | bit inside the chuck, that makes the mortise only 1 3/4" deep.

At _least_ 1" of the bit needs to be in the collet for safe operation.

There /are/ longer bits; but keep in mind that with longer bits, the need for care and control increases significantly.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Teamcasa]

David, Making a mortise jig was not too much trouble. Look here for ideas. I made this in one afternoon.

[B A R R Y]

One of the easiest to make and use is here:

I've also made the Tage Frid version that looks like a miter box, and mortised on my table, and the simple jig above is my favorite.

Oddly enough, from a magazine known to me as the home of the "Rube Goldberg" device.

[David Starr]

That looks like a winner. Fits every router, and I have stock on hand to make it except maybe the carriage bolts, which Franconia Hardware is sure to have. I'll start making it tomorrow. And I don't have to scratch my head wondering which template guide bushing and or base plate will fit my old Craftsman router. I take it the jig keeps the router running straight alone the stock and you use pencil marks and the eye to control the length of the mortise? As a second issue. How deep a mortise is it possible to make with a 1/4" router? I'm making bookish type shelves that will have to carry some weight so strength is important. I'm thinking you get the strongest shelves if the mortises go clean thru the uprights, but that maybe one inch will give enough sheer strength to prevent the shelves from crashing to the floor when loaded with heavy stuff?

David Starr

[SonomaProducts.com]

Beautiful. I love simplicity. I had been considering several different ideas for a slat bed I am doing. It has nine slats at each end so 36 M&T's. I'll build and keep this baby for a long time. A good fixture is worth it's weight in gold.

I think I'll us 1/8 ply and scribe a center line along the bottom side parallel to the guides for easy centering. I'll measure and set one side guide then drop the fixture on the stock and snug up the other side.

I already got through the tough part of of this bed project putting a

5/4 x 7" mortise through (4) 3 3/4" posts for the through ten> One of the easiest to make and use is here:

[B A R R Y]

Did they ever replace Old Man on the Mountain?

My 1/4" wide (for 3/4" stock tenons) mortises are usually 3/4 to 7/8" deep, but I usually cut them with a Bosch 1617EVS. Remember, you don't cut full depth in one shot. All of my bits that are larger than

1/4" have 1/2" shanks, so I can't comment if you are making wider mortises. If in doubt, do it in more passes.

Don't forget to test the jig and methods on scrap.

How wide are the tenons? Total gluable area and a good fit are as important as the length.

[B A R R Y]

As do I!

This jig is so out of character for most "Shop Notes" and "Woodsmith" designs.

[pat]

[Lee Gordon]

Pat ...

Very nice looking jig. I don't generally comment on spelling but since you are hoping to sell some of these and, presumably, people find you through Google and other search engines, you might get more hits using "mortise" and "mortising," although it's probably not a bad idea to include both spellings in any keyword meta-tags.

Lee

[David Starr]

No. They have re lettered the highway signs to read "Old Man of the Mountain Historical Area".

My uprights are nominal 2" stock (1 1/2" actual). I assume the strongest joint is one where the mortise width is equal to 1/2 the width of the stock, in this case 3/4" wide. The router bits I have will easily make a mortise 3/4" deep. I was wondering if longer ones are made, and if made, do they cut well or do they start to bend and do bad things as they get longer? I'm beginning to think that 3/4" deep mortises are deep enough to prevent the tenons from popping out and dropping the shelf straight down under load. I'm not so sure that a 3/4" tenon has enough leverage to prevent racking from side to side, and perhaps I ought to add gussets or diagonal braces if 3/4" is the deepest mortise my 1/4" chuck router can do. I'd like to make the mortises 1 1/2" deep if they make bits that long.

David Starr

[Prometheus]

I don't know that that is necessarily the case. As a rule of thumb, it's fine- but you need to look at how much diagonal force is going to be put on the joint. The thickness of the tenon will support the downward pressure, and the shoulders will help prevent racking. If you think the piece is going to be especially prone to racking (for instance, if your shelf will not have an attached back,) then your rule of thumb is great. But if you're attaching a back or gussets to the unit, they'll take most of the racking force off the M&T joints for the shelves. In that case, you may as well make the tenons a little thicker, so they have more material holding up the stuff on the shelves.

It's still good practice to use mortise and tenon joints with the shelves, as the shoulders hide any imperfections in the mortise, and you don't need to worry about your stock being at a perfect thickness like you would with a shelf sliding into a dado, but the shoulders can be fairly narrow and still do the job.

If you are considering through mortises, as it sounds like you are, why not use a forsner bit in a drill press on the uprights to drill right through, then clean the mortises up with a chisel? (or even a drop cut on a table saw, if the shelves are deep enough for that) If I were doing that, I wouldn't even bother cutting full tenons on the shelves- just make the mortise the full width of the shelf thickness and cut rectangles out of the corners of each shelf to make one pair of shoulders on each side. If you do that, you may as well go all out, and run the shelves out past the uprights, and peg the tenons on the outside. The pegs will hold the single pair of shoulders tight against the upright, and that should resist an awful lot of racking- not to mention the fact that it can look really sharp, if you spend a little time making the pegs look nice.

If you're set on using the router, and it only cuts to 3/4" deep, why not just flip the upright over and do the second cut from the other side? Personally, I'd be more comfortable with that than putting a huge bit on a 1/4" shank in the router and hoping it will withstand any slop the router may have in it.

[David Starr]

I built my jig and it works nicely. Adjustment is straight forward. I didn't have any 1/4" hardboard or plywood so I used a scrap of 1/8" wood panel material. It's strong enough, but it isn't thick enough to sink the pan head screws down level with the surface. By the time you counter bore 1/8" material enough to swallow up a 10-32 pan head screw there isn't anything left under the screw heads. This isn't a real problem mortising narrow stock (like 3/4" or even 1 1/2"). However it won't like me sink a mortise into the side of a 2*4. I am going to try flat head screws tomorrow, and if that doesn't work, I'll round up a piece of 1/4" stock, make a new baseplate and recess the screw heads properly. I got the center 2 " hole matched up to the router nicely. I marked the baseplate screw holes by laying the plastic router baseplate onto the 1/8" stock and marking the three screw holes with a pencil. I drilled the holes, mounted the router and used the 1/4" router bit to drill the center hole. That got the center hole to line up perfectly with the router center. The I used a 2" holesaw in my drill press to enlarge the center hole from 1/4" to 2".

David Starr

[David Starr]

Probably a good idea. I just acquired the router (at auction, $30) and I'm looking for things to do with it. I just finished up mortising the first upright, and I find I can get a 1" deep mortise, and still have

3/4" of the bit inside the collet chuck.

(or even a

Another good idea. I'll try that next time. I've already cut the pieces for this design and I think I'll press on with it. I'm going to use some gussets or diagonal braces to stiffen it up against racking.

That also works but I'd have to be awfully careful to get the hole from one side to match the hole from the other side.

Personally, I'd be more comfortable with that than putting a

Aye. I'm able to get 1" of depth with the cutters I have and that is going to do, at least on this project.

David Starr

[David Starr]

Followup. I built the jig Barry recommended and put 16 mortises into

2*4 uprights. I was able to do the mortises into the edge of the 2*4 no sweat. I did the mortises into the wide side (the 31/2" side) by taking one of the guide bars off and using the jig as an edge guide. I had to make two passes to get the mortises to come out 3/4" wide. I was able to obtain 1 1/4" deep mortises with an ordinary 3/8" straight router bit and have the bit set 3/4" down into the router chuck. That seems to be about as deep as you can go with a 1/4" router and the assortment of bits in the local hardware store. This router isn't powerful enough to do the full depth in one pass. I made four passes, each time advancing depth of cut by about 1/4". I squared up the ends of the mortises with a 3/4" chisel rather than rounding off the tenons to fit the round cornered mortises. I used a "test tenon" (piece of 2*3/4" scrap) to check mortise fit. With just a little trimming with the chisel I obtained a good "spit tight" fit on all 16 mortises. Feel pretty good about that. At this point I have a few things on the wishlist when I decide to upgrade to a modern router.

1. I want a light built into the router to light up the bit.
2. I want a depth of cut adjustment that doesn't stick and has enough beef and mechanical advantage to allow smooth adjustment. Also want a lock that stays locked under the vibration of the router. My old timer has a simple screw with a knob that occasionally works loose, dropping the router bit deep into the wood. For extra class, a dependable and accurate depth of cut indicator.
3. Comes with a baseplate that accepts readily available router guide bushings, probably the 1 3/16" Porter Cable style.
4. Has the motor cooling fan arranged to blow chips away from the work and not into my eyes.
5. Has an edge guide.

David Starr

[Charley]

David,

That's some wish list. I don't think there's a router on the market that can satisfy ALL of them, but there are a bunch of features that aren't on your list that I think should be. You should also be looking for the most versatile, powerful, lightest router you can find with soft start, accurate adjustment capability, comfortable balance and handle grips, convenient switch location, 1/4 - 1/2 collet capability.

I've been quite pleased with my latest router purchase and think it's one of the most versatile routers on the market today. It is a DeWalt 618 and I got the 3 base kit plus the edge guide. It comes with one wrench and a shaft lock, but I bought another wrench because I found that the shaft lock wasn't convenient to use sometimes and I found that it's possible to use both wrenches with the shaft lock still in place. It doesn't satisfy all of your wishes as it has no light, but I think it meets all of your other wishes, and then some, and the base openings are wide enough to easily let in enough light to see where you are cutting. One of it's features that I really like is a detachable power cord with a twist lock connector at the router end. This makes it easier to store the router and it's very convenient to disconnect the power at the router end of the cord when I'm changing router bits. Having the 3 bases and 2 1/4 hp with variable speed and soft start makes it a router that can do almost any routing chore easily. I own 6 other routers of various styles and brands, but find myself reaching for this one most of the time now.

[David Starr]

Tell me about soft start. My old medium size/power 1/4" Craftsman wants its handles gripped with authority before pulling the trigger. Do the more powerful ones need soft start to avoid the router torquing itself right out of your hands? How much of a weight and size penalty do you have to pay to get a

1/2" collet? Do 1/4" bits center up and run without wobble in the 1/4" adaptor?

I'll certainly look for a 618 when I get into the "buy-another-router" mood. The shaft lock is something I forgot to put on my wish list. Ideally you ought to able to change bits without any tools at all. As a step in that direction, you ought to be able to change bits with only one wrench rather than two wrenches. Wrenches, chuck keys and the like are never around when you need 'em unless you tie 'em to the cord. The pair of 11/16 and 9/16 combination wrenches I need for the Craftsman are a little too big to tiewrap onto the cord.

It doesn't satisfy all of your

I like that too. I am a believer that routers should always be unplugged when changing bits. The trigger is just too easy to press by accident. Them bits feel sharp and I'll bet they hurt when they chew into your hand.

Tell me about variable speed. Don't the bits cut best when turning as fast as possible?

David Starr

[J. Clarke]

Depends on the router, but when a 3 horse router with a large bit in it cranks up at full torque you really want to have it controlled--soft-start reduces the tendency for the thing to take off and start chasing you across the shop.

None to speak of. The very smallest models won't take a half inch collet but most models from 1 horsepower or so on up that aren't specifically designed either to be lightweight or trimmers will take half inch these days.

There's no "adaptor", it's a 1/4 inch collet that replaces the 1/2" collet.

Small ones do. Above a certain size though pieces can start coming off them at high speed. You do _not_ want to try to run a 3 inch panel raising bit at 25,000 RPM. At least not unless it's on the other side of a very solid wall.

[Charley]

Soft start is something that you have to experience to appreciate. It makes a relatively tame animal out of even the biggest routers. If I had my way I would have it in all of my power tools.

There isn't much, if any, weight or size penalty for routers with 1/2 inch collets but the 1/2 inch bits hold up better and cut better because the shaft doesn't bend even slightly under load. With 1/2 inch capacity routers many router manufacturers supply 8 mm and 3/8 collets as accessories so you can use end mills and European size bits as well. With a proper size collet there's no wobble. There are sleeve adapters to make smaller shank bits fit in 1/2 inch collets, but I prefer to use the proper size collet for the job. They just seem to work better.

There are tool free router bit collets on the market now, but I'm not comfortable using a very sharp router bit spinning at 20,000 rpm unless I know that it's well secured in place. If it takes one wrench or two to be sure that it won't come out, then so be it. I keep my tools in their boxes along with all of their accessories, so I don't have a problem finding them when I need them.

Bits that are larger in diameter than about 3/4 inch should not be run at full speed because of the centrifical forces that are present in the larger bits when they are turning at those speeds. There is also an optimum cutting speed and it is possible to cut at too high of speed. Generally, the larger the diameter of the bit above 3/4 inch , the slower it should be run. When you put larger bits in your drill do you run them at full speed? I certainly don't. They cut better at slower speeds, and they don't burn as easily.

Charley

[J. Clarke]

I have some of the Sears tool-free collets--I hardly ever use them unless I'm working with matched pairs of bits--for that they're _very_ handy because the cutting height stays put across bit changes--I don't even have to raise the router in the lift. Getting them adjusted in the first place is a pain though. Looking at the things doesn't inspire confidence but in practice they work fine.