Thread: How do you cleanup a mortice roughed out by drill?

Take a seat.
Mark out your mortice a fraction wider than the chisel you intend to use to hog it out. Mark the ends with a marking knife and the sides using a marking gauge. Drill as much waste as possible out. Use a drill that's 0.5-1.0mm less than the width of the mortice. Mark the centre of the mortice and the centre of the holes, or you'll drill outside the mortice. Leave a bit of wood between the holes, or the drill will slide into the hole next to it, and also leave about 1mm between the holes and the ends of the mortice. Drill 1-2mm deeper than the tenon. If you have a drill press, use it so that the holes are parallel to the sides.
Drilling mortices 1.jpg
Use your chisel to make cuts across the mortice, on the circumference of the drill holes. This is to stop splits when you are paring the sides of the mortice. The don't have to be deep but they extend the full width of the mortice.

Chisel out the wood between the holes. You can start by cutting from the top, but if the mortices are deep, it helps to have a narrow mortice chisel to lever out the wood at the bottom.

Pare the wood from the sides. Don't try to do it in all one go, and if possible, don't finish to the sides until you have nearly all the wood out of the centre.

Pare the last of the wood away from the ends of the mortice, working to the cut line. Test fit the tenons.

Hope this is clear.

Fuzzie,
No shame at all. Our hardwoods are hard and ironbark is one of the hardest. UK and American woods seldom go harder than oak or beech. They seem soft to us. Woodworking methods come from Europe or America and reflect the woods they work with. I have just had the same problem as you with my bench build using blue gum (well I think it is). Recycled and very hard. I tried the first through mortice with mortice chisels. Took ages so I used the drill press to remove most of the waste for the rest. Cut half the time off the job. The inside of a mortice will not be seen so dont get hung up on perfection. Good marking out is the key and cut lines with a marking guage or marking knife define the limits of the opening. Another trick is clamp a squared bit of wood along the line as a guide to keep the chisel perpendicular. If the opening is kept to the marked lines and reasonably clean an square then it will work ok. When working real hard wood take your time and shallower cuts than in softer wood. Dont pound the chisel so hard it binds in the wood. The job is just going to take longer so be happy with that. You will have to sharpen the chisels more often and perhaps have higher bevel angle too. One last trick to save work i picked up on this forum is it is quicker to round the corners of the tenon with a rasp than it is to square the corners of a mortice so just leave the drill hole at each end round. One final cheat is epoxy glue as it is a gap filler so if the inside of the mortice looks like a rat chewed it out well only you will know.
Regards
John
PS fostner bits are the best for drilling out the waste and I use bits the width of the mortice.

Excellent advice above. I'll add that a fence set up on the drill press makes things much easier. It's not often that you do only one mortice so a fence set the correct distance to the centre of the mortice will speed things along and ensure your series of holes are parallel to the edge of the timber. If doing a number of identical mortices i.e. table legs, you can also set up end stops so you only have to carefully position the first leg.

Thanks for the input guys. Glad to know I'm on the right track!

I'm working on my bench legs 125x70x855 and aiming for 15mm mortices for the 110x45mm rails. The holes are already drilled. Not having a decent table on my drill press I first routed a 1/2" slot between the layout lines then used a 1/2" spade bit as I don't have any forstners, but it was easy to start them accurately enough in the slot and using the depth stop to make sure the point didn't push through the other side. I started with the 15mm chisel on the first mortice but downsized to a 1/2" chisel on the second one. It looks like that fits in with Alex's description which is encouraging.

One leg down, 3 to go!

Having done my first trade as a carriage builder, I am familiar with the vagueries of trying to cut mortices into hardwood. Many are they that try to speed up the process by drilling holes in the mortise only to find the chisel developing a mind of its own and going in all directions. Here are are a few hard-found suggestions for retaining your sanity:
1 Drill only one hole in centre of mortice.
2 Use only sharp firmer chisel no greater in width than width of mortice.
3 Work progressively from each side of hole taking small bites.
4 Stop short of mortise end line to allow a leverage shoulder for waste
removal.
5 Clean bottom of mortice before chiseling mortice ends to line.
6 Use a wide paring chisel to clean sides of mortise if required.

Having already drilled out the waste and therefore not able to apply Rustynail's method, I found the most effective way of cleaning up for me was:

Using three chisels, a full width mortice, a slightly undersize mortice and a wide bevel edge.

1. Using the full width mortice chisel, starting at one end of the mortice with the chisel held vertical, make small cuts all the way to the other end of the mortice. This traverse can start and finish on the line.
2. Turn the chisel around and this time keeping the bevel vertical (not the chisel), make deeper cuts back to the other end of the mortice, gently levering out a little waste with each blow away from the direction of travel.
3. This establishes a reasonably deep and well formed starter mortice.
4. Swap to the slightly undersize chisel and with somewhat more force break out the web remaining between holes, pretty much using the same traverse method as before, one or more times depending on the finished mortice depth. (In my case I'm working from one side only as I do not want a through mortice)
5. Next use the sides of the starter mortice as a reference face for the wide bevel edge chisel to pare down the full depth of the mortice to the correct width.
6. Now use the undersize mortice chisel to cut the mortice ends exactly to the line. (The shoulders of the end drill holes being too resistant to allow good control for finishing directly with the full width chisel)
7. Use the full width mortice chisel to cut down what remains of the shoulders to the line or alternatively they can be pared back with the bevel edge chisel.

Without a forstner bit ... I think someone wrote on here about grinding off the centre spike of a spade bit ... or making it smaller ... so you can get closer to a flat-bottomed hole.

Don't quote me.
Paul

I used spade bits for years and in a drill press they can be resonably accurate. Get the point in the right place and it is quite good. I would be wary of grinding back the point as any inaccuracy will make for a rough hole. When I got fostner bits a couple of years back I was hooked. So much better for things like mortices. Very short spike and a flat bottomed hole. I use them on the lathe also. I still use spade bits for quick holes where near enough is good enough but fosteners are the next step up.
Get a set. Well worth it.
Regards
John

Excellent thread - many thanks guys

Chisel work has always been a mystery to me, and this helps solve some of it. Will have to get in a give it a go

Dengy, if you want to see it made look easy watch this..
Cutting a Mortise - Mortise chisel vs bevel edge chisel - with Paul Sellers - YouTube

Hi, you seem to have plenty of answers, but one idea that might help: Use your drill press to cut the waste out after you've done the drilling. Take an old chisel. Cut off the handle and turn/grind the tang to fit your drill chuck. Now you can use the feed levers to press the chisel vertically down into your work. Lock the drill so it can't turn on you and grind/sharpen the chisel end to say a 30° angle so it slices when pressed down. A bit of experiment and you have a really cool morticer.

Hello corieltauvus and welcome to the forum. Sounds like the poor mans version of an antique foot operated machine I once saw that I think came out of a door and window factory. That was a brute with a heavy counter weight to give the chisel some push.

I think I'd be forever checking the switch to make sure I had unplugged the drill if I ever tried to use the idea.