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Couple more "technical questions"

Started by JoeyLowe, September 05, 2004, 03:21:24 PM

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JoeyLowe

Here is a couple more questions to ponder and prove my naivte'.  

1st.  When chiseling out a mortise with a hand chisel and mallet, what/how do you clear the bottom?  Do you use a swan necked chisel or is there a secret that I'm not aware of?

2nd.  When making octagonal pegs, what is the secret to making them all of the same size?  I saw the other posts and couldn't figure out how the jig works that Arkanasawyer was describing.  I squared up a peg after I rived it from a log and then I used my handplane to shave back the corners.  It made a pretty good peg, but they weren't standardized.

3rd.  How do you avoid tearout when drilling the peg holes?

Interesting side note:  I'm trying to get things ready for the upcoming seminar and I decided to make a couple sets of the saw horses that Jim described in another post.  First and foremost, laying out and cutting the tenons were easy enough.  Laying out the mortises were easy too.  Drilling the mortises was pretty straightforward.  Chiseling out the waste was a real pain and time eater.  I have very sharp chisels and a hefty mallet, but was still spending a lot of time hollowing out the square holes.  Not to mention, I felt like popeye when I was done. (Heavy arms)  Almost broke down and bought a chisel mortiser behind this experience but decided to wait and hear the error of my ways.

I won't be able to respond until Tuesday night, but rest assured I will take everyone's advice to heart.
 ;D
--
Joey Lowe

"Working towards perfection has to be a part of anything one does.  You've got to put yourself into it." ... Sam Maloof (chairmaker)

ScottAR

I know one of em... :D

When drilling, don't go all the way through on one side.  Drill till you see the point of the bit, remove, and finish on the other side.  Works for holesaws on doors too.  

Questions 1&2 are beyond me, sorry   :)
Scott
"There is much that I need to do, even more that I want to do, and even less that I can do."
[Magicman]

barn-apart

Hand made pegs can be driven through a metal plate with a series of diminising holes to reach the proper size, this will give you the same size pegs. My understanding is this was one of the old time tricks used.
 As for the bottom of mortise holes, I use a small chainsaw to sweep the bottom of the hole then simpl;y clean the cornners with chisels.
Hope any of this helps
Rick

beetle

Joey,

My question is why are you having to clear the bottoms? If you are drilling the mortises with the correct diameter bit ( same width as your joint) slightly overlapping each hole, and boring each hole to the same depth as the others you should really have no waste to remove from the bottom. You will have waste material in each corner that is easly removed with a SHARP corner chisel and a little bit of meat on the sides that is easily pared down with a SHARP paring chisel. When I say sharp, I mean the blade should shave hair from your arms. ( be careful here )

Although I am working Pine,  I can clear the waste wood from my 2" X 7.5" X 5" deep mortises in 5 min max.

As far as the Popeye arms....how heavy is your mallet? I am using a old vintage hardened leather mallet that weighs maybe 1.5 lbs. if that. I think the books say you should use 3 pounders but I think thats a little heavy unless your Arnold S.

SHARP, SHARP, SHARP Chisels is the key!... I dress the edge each day before I start, takes maybe 3 min. of time.
Too many hobbies...not enough time.

Jim_Rogers

Joey:
The first thing I do after I layout a mortise with pencil is to cut the lines or scribe the outline with a utility knife. This will cut the fibers several sixteenths of an inch deep. This will prevent some "tear out" at the surface when you bore a hole into your mortise with a boring machine or a power drill bit.
Once I have bored out my overlapping holes as Jeff has mentioned I then remove the wood along the sides of the mortise with a sharp chisel. I hold my chisel with the flat side towards the line or outside of the mortise and the bevel side towards the middle of the mortise, whether I'm doing the ends or the sides. Usually I use a chisel that is the size of the mortise in width. That is I use a 2" chisel to clean up a 2" mortise and 1 1/2" for 1 1/2". That way you can quickly change between cleaning the sides and cleaning the ends without having to set down the chisel and pick up another one.

Corner chisels are nice for doing these corners. Most corner chisels aren't truly 90°, they are more like 89° or less, so that they won't cut into both end or side at the same time. You have to clean one and then twist a little and clean the other.

If you have a lot of wood along the side of the mortise or at the end it's better to try and chisel off half or less than half of what's there first and then move closer to the line with the next cut. A good rule is to take half of what's there, then half of what's left and then half again, slowing working your way to the side or end of the mortise. That way you won't make it too big, because as you are trimming it to size you can check it with a framing square along the way.

And when cleaning out a mortise you always push the handle end of the chisel towards the center of the mortise to break the chips free from the timber. You do this when you are doing the sides or the ends. If you pull back on the chisel towards the outside of the timber you could break your chisel handle or bend your chisel shank or tip. These chisels are made to shave wood not pry it out.
As you get to the bottom of the mortise you might end up with a large chunk in the corner where the side face mets the bottom face or where the end face mets the bottom face. These chunks can be split up by chopping straight down with the chisel into the chunk by hitting the chisel with a mallet, but again you should plan on taking out smaller chunks each time. Just remember what the old timer said about moving a mountain with a bulldozer, "you can do it, but you have to do it a little bit at a time".
Another trick with using a chisel to clean out the bottom corners at the ends of the mortise is to put the chisel in with the bevel down and the handle touching the opposite end of the mortise. Cutting or chopping with the mallet with the chisel at a steep angle like this will usually loosen up a chunk of wood in a corner. But be careful not to drive you chisel in too deep and get it stuck in the beam. Because you're at such a steep angle you can't move your chisel handle end anyway other than towards the outside of the timber, to loosen the chip.
We frequently roll the timber over to have all chips fall out of the mortise to the ground.

If you are creating a threw mortise you draw the outline of the mortise on both sides of the timber, knife each outline, and then bore in half way from each side. This will insure you have your mortise in the correct location. And at the center if they don't completely or truly line up you can enlarge the side of the mortise so that they can, but you should check your layout first before you start to make sure you will line up when done.
You don't want to have a big belly in the side of the mortise right where you need wood for the peg.

About the pegs.
First I take a board and cut it into lengths of the intended length of the pegs.
Then I rip the board into squares, and if these pegs are to be 3/4" for example, I'll rip the 1" boards to 13/16" and then rip that square again by rolling it 90° and ripping it again. You should then have a square piece of stock that is the correct length and slightly over size.
Then using a shaving horse I clamp the square into the horse and trim it down using a draw knife. As you are trimming it you start by trimming the each of the square corners making it somewhat octagonal. As you are releasing the stock from the clamp head of the shaving horse to roll it over you can check it's size in a sample hole drilled into the shaving horse seat.
This way you can keep trimming away at it until it fits the hole.
We've found this works good for those who want to create their own pegs.
If you do this you have to closely inspect your stock that it is straight grained. Any cross grain stock can split as it is being driven into the timbers. If it does split inside the mortise you may not see it and think your peg is tightening up and really it's just passing by itself and not doing the job it needs to do.
So you have to be very careful and reject any wood that appears to be cross grain.
Here is a picture of the shaving horse:


here is a picture of the shaving horse:


Although this shot doesn't show the hole in the seat.

And the answer to number three was given above, you bore until you see the point coming threw and then stop, roll the timber over and finish from the other side. Some timber framers turn the bit and brace back-wards on the second side to score the surface of the wood before they turn it forward to make the cut. They seem to think this will help prevent the tear out. I've tried it and for some reason I don't seem to get it. Maybe I need to turn harder.

Good luck with your project and keep asking questions.
Jim Rogers

Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

JoeyLowe

Thanks for all of the replies.  Regarding drilling the peg holes, I understand that if I stop before getting all the way through and then drill from the other side, that will prevent tearout on the peg holes.  Guess what I was alluding to was the tearout you get when you first start drilling the peg hole from the original side.  Seems like there is a large amount of tearout when I first start to drill.

I must be doing something wrong with the boring machine, because it is very difficult to get an overlapping cut without the bit slipping out of place.  I'll keep practicing on that one.

I still have to make the shaving horse and I'm running out  of time (grin).  I leave for Colorado on Saturday and the guys just finished my dirt work this evening.  That means tomorrow that I will be out there re-forming the forms for the concrete to be poured on Friday if all goes well.
 ;D
--
Joey Lowe

"Working towards perfection has to be a part of anything one does.  You've got to put yourself into it." ... Sam Maloof (chairmaker)

beetle

Joey,
In referance to your machine slipping, a couple possibilities:

1)  The bit is not a true 90 degree's to the work?
2)  The bit is not cutting evenly, more on one side than the other?
3) Too much slop is in the carraige?
4) Too much over-hang?

No tear out = score with a knife as Jim describes.
Too many hobbies...not enough time.

beetle

Jim,

Nice horse!  Do you by chance have rough plans?

Jeff
Too many hobbies...not enough time.

JoeyLowe

Thanks for the tips Beetle.  I give a look at that today.  I'm beginning to get real excited.  Things are starting to come together.  I did go ahead and spend some more time on sharpening my chisels this morning and I plan to give a go at the saw horses again today.  I'll keep yall posted with my progress and maybe a pic or two.
--
Joey Lowe

"Working towards perfection has to be a part of anything one does.  You've got to put yourself into it." ... Sam Maloof (chairmaker)

Jim_Rogers

Beetle/Jeff:
Plans are available by private email, can't be posted on this forum.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Joey:
Jeff could be right about the amount of overlap of the holes.
Here is a drawing:



The first thing I do after I have drawn the outline of the mortise with a pencil is to score it with a knife. Then draw a center line down the middle of the mortise with a pencil. Knowing the width of the mortise is the same as the "D" diameter of my bit I know or can figure what 1/2 D is and then add 1/16th to it to get the distance from the end line of the mortise to the center point of the first hole. I add the 1/16th to insure that I don't drill my mortise to big, as sometimes this end is a bearing end and I don't want it too big.
Then I use this measurement to mark the hole location of the other end hole. The two end holes are always drilled first.
I then divide up the remain section into two or three equal size spaces where I can bore out the rest of the waste wood.
In the above drawing this could be a 1 1/2 inch wide mortise, 6" long or a 2" mortise 8" long.
You'll need to space your holes so that they bore out the most amount of waste wood with the fewest number of holes.
I hope this is helpful to you.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

beetle

I hade the same problem of tear-out when I start drilling the peg holes in my pine. I ended up using a gasket punch from my mechanic tool box, one good wack with a hammer. It helped a great deal, however, got to get it lined up on center which can be tricky. I am going to devise something to help with alignment, just have not got there yet.

Jeff
Too many hobbies...not enough time.

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