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Joint cutting - Process #34516 08/07/18 07:54 PM
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Jon Senior Offline OP
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OK. So time and again I've seen the same order of process for cutting a joint, in books, videos and descriptions online:

1. Cut tenon
2. Cut mortise (these two often reversed)
3. Drill peg hole in mortise
4. Drill peg hole in tenon.

Step 3 inevitable mentions that when the drill bit passes through the mortise you should take care to assure the alignment because the bit can move at this point.

This was the method I learnt from reading Tedd Benson's and from Jack Sobon's books and from countless videos on YouTube. And then I did my CAP here in France where we told to also drill the peg hole before cutting the mortise because otherwise the drill bit can wander as it passes though the already cut mortise. And this seems really obvious although I feel somewhat daft that I hadn't figured this out for myself while cutting the joints for our frame.

So I'm just putting this out there for those people who might (like me) have learnt one method and never questioned it. Drill your peg holes first. Then you don't have to work so hard to maintain the alignment and your draw bores will be smoother and more consistant (consistent difference in spacing on each side of the tenon.

Just my 2 c... it's been bugging me for a while.

Re: Joint cutting - Process [Re: Jon Senior] #34517 08/07/18 08:40 PM
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Jim Rogers Online Confused
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I have heard that some people bore the peg hole before hogging out the mortise wood.
However if the frame is going to sit for a while, as the joints are being cut part time, nights and weekends, it is possible that the hole will/may distort when it drys.
I usually cut all the joints and then during my fit up testing of the frame, bore the peg holes.
This works for me.
I feel that the peg hole beyond the second side of the mortise is not that critical and if it wanders off a little it's not the end of the world.
Jim Rogers


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Re: Joint cutting - Process [Re: Jon Senior] #34518 08/08/18 12:38 PM
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Will B Offline
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If using a boring machine or electric drill with feed screw I drill the pin hole after the mortise is cut, otherwise the mortising bit might lose its draw when it hits the pin hole. With a chain mortiser it doesn't matter and I'll usually drill the pin first, mainly to avoid a chip tearing out when I break through the first mortise wall with the pin bit. I don't think bit drift is a problem as long as you're reasonably careful to keep the bit square to the surface with a mirror or square. After all, the bit is straight and the pin is straight; its unlikely the bit will bend. If you're careful you shouldn't be that far off your drawbore on the tenon IF you're drilling from the reference face and your mortise is closer to that face (as in edge square rule). Actually, drilling the pin hole after the mortise gives you the opportunity to REsquare up the bit if you've drifted a bit at the start.

Re: Joint cutting - Process [Re: Jon Senior] #34519 08/08/18 11:03 PM
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Hi Jon,

There is logic (to a point) in your shared method. I would point out that Jim's point is very true from both a practical and historical perspective.

As to actually "worrying" about the drift of a trunnel bore going off track, it really isn't that big an issue all things considered.

From a contemporary approach, I agree with both Jim and Will on their reasonings.

I can also share from a "traditional approach" system prespective, that holes seldom to never got board first. The documentation evidence I have found hasn't suggested it (not to say that its not out there?) nor would tradtional logic support such an approach or worry about it drift that much.

Originally this kind of work was done with a T-Auger. As such, any extra wood to bore through would (and was!) avoided at all cost.

Most of my first frames and through my traditional apprenticeship, this was the tool of choice for creating the bore for trunnel and for hogging out mortise. With such a tool, the idea of drilling through extra wood just to avoid not paying attention to "bit drift" would be greatly outweighed by the extra labor. Paying attention to what I was doing was much easier than any extra labor of boring through more wood than I had to...

With the advent of a boring machine (miller falls is still my favorite!!) the worry of drift fell virtually by the wayside for the most part both in my personal world and from what I can ascertain historically, as any drift that would occur is negligible if everything is sharp and in operational order.

With our modern Mafell tool guides this is virtually not even something that is ever really thought about. I would also share that I do not peg most of the frames I design and/or are part of at all or very little. Often with square trunnel if it does occur. This is true for almost all contemporary frames I'm part of. Many of the traditional ones as well often don't have as many pegged joints as I see in contemporary frames. Especially braces which are seldom pegged in my experience, which seems to be a regional manifestation and mainly for the reason of raising...not joint structural integrity...

Thanks for sharing Jon...Great topic!

j

Last edited by Jay White Cloud; 08/08/18 11:06 PM.
Re: Joint cutting - Process [Re: Jon Senior] #34520 08/10/18 08:20 PM
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Drilling the peg hole before boring the mortise can cause the boring bit to jam. I bore all peg holes, both mortise and tenon, at the same time I cut the joinery. I have had no problems, even if the timbers are stored. If there is a storage problem, the timber has usually destroyed itself in some other way.


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Re: Joint cutting - Process [Re: Jon Senior] #34521 08/15/18 07:15 AM
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Cecile en Don Wa Offline
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Some responses make the point that 100% accuracy in this matter (meaning a perfectly perpendicular peg hole in the mortise) is fine but not so critical and this is my experience in practical terms also as long as the peg goes in one side, passes through the tenon hole and then out the other side. Maybe this idea of perpendicular has some relation to wood movement in the interim between cutting joints and assembly, or maybe it is just a matter of neat working.

Re: Joint cutting - Process [Re: Jon Senior] #34522 08/15/18 10:35 AM
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Another factor to add is the effect of drawboring the joint. The draw bore not only pulls the joint together during assembly and as drying occurs, it also puts you on the side of correcting error. If you mark out your holes exactly and one is off one way or the other it can in effect push the joint apart, so we ensure a correct pull to the joint by forcing the joint to come together with a draw bore. Even if the mortice hole is bored a little off the draw more often than not, I don't think I have ever had one push the joint apart when done correctly, will allow the joint to come full together. Preassembly and pricking the tenon through the mortice peg hole will give very accurate peg location regardless of the angle of the mortice peg hole. Why do we feel the need to be so exact in some small aspects of our work? There are many ways to over come such hang ups. I never bore the peg hole before mortice work. Maybe if I was using a chain morticer, but even then I wouldn't.

Re: Joint cutting - Process [Re: Jon Senior] #34523 08/16/18 01:24 PM
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An interesting range of responses. There are perhaps 2/3 factors at work here. The first is that boring machines are non-existant here. Those of us without chain mortisers are boring out our mortises with a power drill, often with no stand. Drilling guides can be found in some shops but in the 5 places I worked during my course I only ever saw one drill guide (A really nice Mafell with matching carpentry drill). I do notice when the bit passes through my pre-drilled mortises, but it's never posed a problem. Obviously with a boring machine losing the lead thread might be more of an issue.

Secondly, I was taught "standard practice" here and a standard roof truss here is made from 8x23 (75mm x 225mm) timbers. A 30mm wide mortise in a 75mm wide timber leaves you with ~20mm each side of the mortise. An alignment issue will blow out the fibres as the peg exits the tenon. I've seen it done a few times.

Tim: I wouldn't call it a hang-up. My post stemmed from the fact that my personal experience led me to find this to be a better system. And having a routine is not a hang-up. Your routine is to bore peg holes after. Jim does it just before raising.

Don: It's not necessarily about being perpendicular. It's about alignment. A mis-aligned peg hole can put more pressure on one side of the tenon than the other, or cause blow out of fibres on the exit side. But in large timbers this is rarely an issue (the peg just gets stuck).

What I really find interesting about this is that each person seems to have their own reason for drilling pegs holes after cutting the mortise. Which suggests that it's not a universal system because it's taught that way, or at least everyone has found their own justification.

Re: Joint cutting - Process [Re: Jon Senior] #34524 08/16/18 04:26 PM
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If your anything like they are in Germany using what I consider real short and blunt pegs couldn't a solution to blow-out or getting stumped against the far side of the mortise as a consequence of less than perfect alignment be more peg length and bevel it over the first 1/3 of that length? This is sort of the standard of practice as you call it here in my area. That's a good point about uneven stress on the tenon in the case of an angled peg hole.

Re: Joint cutting - Process [Re: Jon Senior] #34525 08/16/18 06:31 PM
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Jon Senior Offline OP
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That's how we do pegs here (mostly). 3 cuts with a bisaigue. The first makes a large flat that cuts across about 60% of the diameter. The next 2 make shorter flats at 90 to the first to make a flattened off-centre point.

Some of us then make one final short cut opposite the first one, this helps with extreme draw bores or narrow timbers to prevent blowout.

Personally I like to have long enough pegs to drive them until they bind and then cut them off on both sides to clean up.

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