Mortises in red oak

Re: Mortises in red oak

Cameron

Scoring with a marking knife would help

need more information

Bill Tindall, E.Tn.

I don't understand exactly what you are trying to do, nor the problem doing it. I don't understand putting a dresser together with M&T joinery. I have never done mortise with a router so I don't understand how this part is done. And I don't understand what is "tearing" out. I have never had a defect with a router that I would call "tear out".

The chisel statement is unusual. I would have no problem with dulling a chisel while chiseling oak. In fact if I needed a mortise in oak I would be chiseling it.

There is something seriously defective about the chisel or how you are sharpening it.

Bottom line- I need more information to understand problems that I don't think should be occurring.

Re: Mortises in red oak

Derek Cohen (in Perth, Australia)

I am making a couple of dressers in red oak to match the bookcase headboard I made for the bed. The top and the bottom divider are connected to the sides with through mortise/tenon joint. The sides are 7/8 inch thick, so I have to rout out the mortises from both sides since I don't have a bit long enough to go all the way through (and, besides, that makes for cleaner joints).

I am having trouble with tearout. Blessedly, I made an extra side so right now I am working on the "spare". I am thinking that one solution might be to apply some thin superglue around the edges before I rout them. I am also trying to score around the edges, but that oak is so tough that I am dulling the chisel really quickly. Does anyone have a better idea?

Hi Johanna

First off, I would also have routed a through mortice from both sides. Trying to go through in one hit is not only hard on bits and routers, but likely to blow out the other side.

The router bit you are using may be relevant here. I suspect that you are using a common straight bit. I would rather use a spiral upcut. That is kinder on edges.

And most certainly knife the boundaries of the mortice. In fact you could go a step further if you were unhappy with the results of an upcut bit. Score the knife lines deeply, and then undercut the lines with a chisel.

One other thought: typically the mortice should taper outwards if you are using wedges in the through tenon. This allows you to widen the outside of the mortice, which would enable you to remove any chipping when you do this.

Regards from Perth

Derek

Re: Mortises in red oak

John McGaw

I've always gone with the scoring technique, either with super-sharp knife or chisel. With the chisel it is possible to go pretty deep and that is almost a certain cure for chipout in my experience. Hardest thing with either method is to "color inside the lines".

more going on here than meets the eye

Bill Tindall, E.Tn.

I presume we are talking about the edges of the resulting mortise is ragged from pieces of wood chipping out along the edge? with grain, cross grain?

Disclaimer...I have never cut a mortise with a router. But I have watched CNC machines cut them in oak, uneventfully. I have cut lots of hinge mortises and never had an edge tear-out. A solution to this problem may lie in determining why a CNC machine can route a mortise that is perfect every time and this operation can not. Ditto the hinge mortise difference.

Some factors to consider- speed of bit, dullness of bit, details of entry of bit into wood.

For those that cut mortises with a router, what about doing a mortise is any different than any other router operation? I find anything less than perfect when routing an edge rare. What could be different about the mortise vs an edge?

Re: Mortises in red oak

Lee Schierer in McKean, PA

I've made lots of mortises in red oak with no issue using my drill press mounted mortiser.

I have done a few mortises with a router using a Freud up spiral it. I don't recall having any tea rout issues. For deeper mortises you can use long end mills, but I would not recommend through cutting.

Can you clamp a block with a mortise over your piece of wood to hold down the surface fibers while you start the mortise? Once you get it started you can remove the guide.

Lee

Re: Mortises in red oak

AZ in Colorado Springs

In my experience, oak can act brittle and the fibers tend to split away ahead of the bit. I don't recall cutting mortices in oak, but when routing edges, such as around a picture frame, I push the stock into the bit (if on a router table) every other diameter of the bit. Then, when I run the piece along the bit, if the wood wants to split away, it'll be in short sections.

If I'm using a handheld router, that technique gets tedious, so I take small bites in several passes, or climb cut taking small bites in several passes.

Is this the kind of "tearout" you're seeing in the mortices?

Re: Mortises in red oak

Johanna Johanson

Yes, I am now scoring as deeply as possible and am also trying using some CA glue in the surrounding area. My first attempt with CA glue resulting in glue all over my hands - bummer!

Re: need more information

johannaj

The sides of the dresser are slabs 20” wide, 35” tall, and 7/8” thick. The tops and bottoms are attached to the sides with four through tenons. Because red oak is so hard and because there is a total of 32 mortises (8 on each side), using a chisel to cut them is not reasonable. So I have a template of ½” MDF I am using to cut them. (I have to rout from the outside first, then flip the piece over and rout from the inside due to the thickness of the sides.)

Once I rout the mortises I square up the corners with a chisel, but cutting the mortise completely with a chisel would take forever and require frequent sharpening.

Here is a photo of the headboard showing the same construction that I am using on the matching dressers. No ceramic dog will be included with the dressers.

Re: Mortises in red oak

johannaj

Yes, oak is really brittle. I am now scoring more deeply first with the marking knife and then with a chisel. I am also trying stabilizing the wood with CA glue. We'll see how it goes today.

Re: more going on here than meets the eye

johannaj

The mortises are cross grain, so oak, being very brittle, chips out occasionally. I'm using a spiral upcut bit and cutting first from the outside, then from the inside because the ends are so thick (7/8 inch). Today I will score the edges really deeply first with the marking knife and then with a chisel. That should take care of the problem. I am also drilling lots of holes in the waste area to give the bit some relief. Oak is tough stuff, and this batch seems tougher than most.

Bill, I am surprised that you have not cut mortises with a router. I rarely cut them by hand because using a template and router makes it easy to repeat the operation successfully.

Re: Mortises in red oak

johannaj

Derek, I really like your idea of undercutting the lines with a chisel. I'll try that today.

Yes, I am routing from both sides - my bit is not long enough to go through a 7/8" board! I do use a spiral upcut - a new one. The mortise length is across the grain, so there would be no hiding tearout when angling the ends for the wedges. Too bad!

I'll post how the cutting goes today now that you have given the the idea of undercutting the lines.

Re: Mortises in red oak

johannaj

Lee, I've never had this problem before. I think this batch of oak is exceptionally brittle. Thanks to the ideas people have provided, I'm hoping to solve the problem. FYI - these are being done with an MDF template, so there is some pressure on the edges - not much.

Re: need more information

William Duffield

Mortise and Tenon joinery, and even through mortises with tusk tenons, is very common in Arts and Crafts furniture designs, though more typical of cabinets with shelves and glass doors, book cases, and open shelves than in cabinets with drawers.

There is something seriously defective about the chisel or how you are sharpening it.

It might be helpful here to provide an example or three of what could be wrong with the chisel.

- She may not have access to a CPM chisel like the ones you have made . Hers is probably much softer metal, maybe a Blue Chip or a home center Buck Bros. A better chisel is worth trying. She doesn't need a whole set; she can start with a singe chisel in a size she uses most often (e.g., 1/2" or 3'4").

- She might try to increase the bevel angle, or experiment by adding a secondary micro-bevel. Try adding 5° and see if that helps.

- If she is hollow grinding or trying to do the whole process on a grinder or belt sander, she may have overheated (blued) the edge and removed the hardness from the steel.

- A useful diagnostic tool for examining edge failure is a 10x loupe. With that, whether the failure mode is rolling over or micro-chipping should be visible.

Is an upcut bit a good idea?

Bill Tindall, E.Tn.

From the ignorant perspective of someone that never routed a mortise, except a hing mortise, an up cut would not be a choice I would consider. Wouldn't one expect it to lift fibers at the edge and yield the result you are seeing?

I route lots of dovetail waste. Straight solid carbide straight bit. Never had splintering at an edge.

Re: Mortises in red oak

jessecloud

Lots of good advice in this thread. If however, you are still seeking a solution, how about drilling pilot holes for a jig saw, then sawing close to the line on all sides to remove the bulk of the waste? All that needs chiseling now is the remaining thin edges inside the line.

Not elegant, but pretty sure to work....

Jesse

chisel preparation

Bill Tindall, E.Tn.

On a fine stone roll over a tiny portion of the chisel tip from whatever you have it to about 30-35 degrees. A chisel with good steel will not suffer from mortising oak providing the last bit of edge is ground at an angle that will support the chopping force. I chopped all these bench mortises, and others, with a chisel . (oops, picture reveals my daughter chopped them

Bash gently

A spiral twist, upcut bit is an excellent idea!

Bruce, a MN Galoot

I have cut mortises by hand and with a square mortiser but I get much better results with a jig and a plunge router. I have 1/4”, 3/8” and 1/2” spiral twist, upcut bits that produce mortises with really great sides, no tearout and predictable results every time.

Bill, I’m surprised you don’t have a plunge router.

Re: Mortises in red oak

Dick Coers

CA will wick into the pores of the wood and show as a stain when you put on any stains, dyes, or clear coat.

Re: need more information

Johanna Johanson

I am using Estwing chisels on the oak - not my good Japanese chisels (the only really cheap chisel I have is one used to scrape glue). I agree that a micro bevel might be useful. I do hollow grind initially, but I do have better sense than to overheat the steel. I have been woodworking for 40+ years and have made lots of furniture, so I am not all that inexperienced!

When I started on the second end piece, it was much easier to pare. The wood in the first panel may have been more dense and harder than usual.

The procedure I am using for these mortises is to drill holes in the waste area first, then use a spiral upcut bit in the router to take out most of the area on the outside of the piece then repeat from the inside. Finally, I chisel the corners square.

Re: need more information *LINK*

William Duffield

I suspect you know what you are doing. I do have a problem with one point, but this may be a failure to communicate (i.e., a nomenclature problem). Shouldn't you be using a spiral downcut bit?

The photo is from Infinity Tools' explanation of upcut vs. downcut spiral bits. Upcut bits are chosen for fast cutting because they tend to clear the cut faster by lifting the chips out of the hole (not an issue for through mortises, since the chips clear just as easily through the bottom of the mortise). Downcut bits, since they cut down into the material, are much less likely to chip out at top edges of the cuts.

BTW, I've been woodworking for at least 56 years, depending on how you count, so I think I can appreciate your experience. I appologize if I have insulted you by asking dumb questions. I have no experience with Estwing woodworking chisels, but I have one of their straight claw ripping hammers and a rock hammer that I like.


How To Choose Solid Carbide Spiral Router Bits

Re: Mortises in red oak - picture

johannaj

Here is a photo of a side:

I now have two sides done - two more to go.

Re: Mortises in red oak - picture *LINK*

Wiley Horne

Really interesting southwest look!

https://www.flickr.com/photos/78661951@N07/49885399171/in/dateposted-public/

Wiley


Southwest motif

Is that a Sorby chisel

Bill Tindall, E.Tn.

If so, you unfortunately own a chisel with the softest steel of any I evaluated. Unless sharpened at a steep angle they fold over when chopping out waste even in mild cherry and walnut.



This photomicrograph was taken of a Sorby chisel edge after 10 chops on walnut simulating removal of dovetail waste. The edge folds over because the hardness of the steel is inadequate for this task.

Weaver has found a partial fix for this deficiency. He rounds over the last tiny bit of the edge to create a "convex" edge. The knife people use this technique to strengthen edges.