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#33840 - 07/18/16 04:31 PM Re: Wedges [Re: TIMBEAL]
Dave Shepard Offline
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Registered: 02/19/06
Posts: 707
Loc: Alford, MA
A tapered peg is an inclined plane, i.e. wedge, until the taper runs out. When there is no taper, no work is being done, and it is just a means to hold the joint together. Trying to say that it isn't a wedge is just over thinking the situation, and adds unnecessary confusion to a simple concept.


Edited by Dave Shepard (07/18/16 04:32 PM)
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#33841 - 07/18/16 05:58 PM Re: Wedges [Re: TIMBEAL]
Jay White Cloud Offline
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Registered: 11/06/08
Posts: 480
Loc: Vermont
Dave...I agree completely that a "tapered peg" would be an inclined plane...Nevertheless...that is not what 99.9% of the "drawbore" pegged/trunneled joints are in Western timber framing...as the peg/trunnel does not possess and inclined plane for its entire length...

I don't think I (et al) are "over thinking" anything and more curious on accurate nomenclature (in English) for how this joint functions...That was the only goal, perhaps of this short section of the discussion...

Pegs/trunnel are not 'wedges' by any definition of the word or mechanical process...because...the "taper" does not run the length of the peg...ergo...there is no "wedging action of an inclined plane"...except, of course, in only a fraction of the overall length...

Further, there are round and square..."tapered pegs"...or..."pinned joints." These are indeed "wedged pins" but they are neither common nor found in Western framing (that I know of??) and only found in Japanese and other Asian joinery systems...

I don't believe (for the most part) that this is a very confusing concept or description at all? Other than defining more succinctly what other "mechanical process" is taking place in securing a "drawborn" joint.


Edited by Jay White Cloud (07/18/16 05:59 PM)
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#33842 - 07/18/16 08:03 PM Re: Wedges [Re: TIMBEAL]
TIMBEAL Offline
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Registered: 12/10/07
Posts: 1875
Loc: Maine
Well, humph, my pegs taper the whole length, therefore are wedges! As per the above comments.

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#33843 - 07/18/16 08:41 PM Re: Wedges [Re: TIMBEAL]
Dave Shepard Offline
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Registered: 02/19/06
Posts: 707
Loc: Alford, MA
If there is no taper, then nothing is happening when you drive the peg. Even if the taper is for a short part of the length, that is where the work is getting done. If you tried to drive a pure cylinder through a draw bored joint, you would destroy the tenon relish, not draw the joint tighter.
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#33844 - 07/18/16 10:03 PM Re: Wedges [Re: TIMBEAL]
Jay White Cloud Offline
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Registered: 11/06/08
Posts: 480
Loc: Vermont
Hey Tim B.,

If your pegs do indeed tapered the entire length...then I would agree completely that besides "drawing" the joint together, your approach to pegging a joint is a combination of a "draw and wedge."

I have seen this (rarely) in some barns, and old frames where pegs that seem to have more tapper from one end to the other. Thus far, this has always been in barns and older timber frames that have either been moved or modified and not the original work.

Further, when a Pe specs a "pegged joint" they will not allow (at least never in my experience) a cross sectional peg less than the full diameter of the hole that receives it. In ever frame I have had to meet there standards on, this is always the case.

Is the joints you are producing this way "strong enough?" I would think most likely they are...Nevertheless, they are not nearly as strong as if they are pegged with a full cross sectional peg, and there is a reasonable amount of academic study on this topic. I would love to see (or read) more PE studies that reflect the contrary and what "strong enough" may actually be in some joint configurations...

As I shared in my last comment we do use...".."tapered pegs"...or..."pinned joints" that is similar to what yours is in one respect...the peg (be it square or round) is tapered from end to end. However, traditionally (and the way we still employ this pinning system)...there is not only more "offset" than typically in the hole for the "tapered peg" (wedged if you will) There are also two of them driven from either side of the joint and driven home till they fully "seat" the hole, or square mortise that receives them...
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#33846 - 07/19/16 07:03 AM Re: Wedges [Re: TIMBEAL]
TIMBEAL Offline
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Registered: 12/10/07
Posts: 1875
Loc: Maine
My theory on this full tapered peg goes something like this, Jay.

When I have used a full sized peg that only has a short taper on the leading point, it has a high risk of blowing out the relish on the back of the peg hole. So I have adopted this longer tapered peg and am very happy with 20 years of use. All my pegs are hand made. Usually red oak. So, in the PE studies do they caculate the relish and the blow out that will happen if the peg is crammed into a drawn hole? Sure they do. You happened to leave out this factor in you strength calculations, it is not just the peg but the relish behind the peg and if that is compromised, the peg is of no use what so ever. By the time the joint is fully drawn and the peg comes to rest the cross section is withing specs of the hole. Also keep in mind there are many joints that are pegged that don't even need pegs, they are only used to wedge the joint together for assembly purposes.

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#33847 - 07/19/16 07:51 AM Re: Wedges [Re: TIMBEAL]
Hylandwoodcraft Offline
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Registered: 03/23/11
Posts: 141
Loc: Western NY
Personally, I thought it was a confusion of terms to refer to a pinned joint as being wedged. There are wedged TF frame joints, and I think that we all know what they are.
By the same token, a dovetail joint has a very definite wedging action, but we wound not say it is a wedged joint.

I think that as an overall concept, the majority of pegged joinery really isn't accurately described as wedged.

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#33848 - 07/19/16 08:20 AM Re: Wedges [Re: Dave Shepard]
Jay White Cloud Offline
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Registered: 11/06/08
Posts: 480
Loc: Vermont
Quote:
If there is no taper, then nothing is happening when you drive the peg. Even if the taper is for a short part of the length, that is where the work is getting done....


Sorry Dave...not only does that not make sense to me from an engineering or mechanical perspective it is not true historically in timber frames or furniture that I have read about, seen, restored, or studied...???

"Most"...(virtually all?) pegs/trunnel, be it in a chair, table, door, window...or...timber frame...are typically solid full cylinders (or squares) from end to end (once driven home.)

The..."happening"...is created by the "offset" between the hole (square mortise) in the tenon and that of the hole/mortise in the received member. It is the "offset" that creates the draw, and not the "taper."

Quote:
...If you tried to drive a pure cylinder through a draw bored joint, you would destroy the tenon relish, not draw the joint tighter.


Sorry again, but if that was the case, I would have destroyed thousands of joints at this point...and I haven't thus far...

Most "turned pegs" and riven...come as full cylinders and only have a slight "coving," "rondel" or "point" on one end that facilitates them properly engaging the "offset" and begins drawing the joint together...That is if the joint hasn't be "podgered" as I suggest is a much better practice...

There is no doubt that..."draw pins" (aka "timber framing "podgers")...be they for furniture or timber frames (we love them!!! and think they are a must have to draw these joints consistently and well...) are tapered for a portion of their length...Again...this is only to facilitate the ease of entry before driven home...it also is to facilitate their extraction once the proper..."draw"...is completed..

The following photos are PE approved pegs...Note that the pegs/trunnel are all full cylinders except for the very end...










Below is typical from a vintage frame that has not been moved and is original in materials and modality of construction...Note that few (if any) of the trunnel are tapered or "wedge shaped." These are full cylinder pegs and commonly found as such in most timber framing cultures whether "round peg/trunnel" or "square pin"...there is no inclined plane...


Classic Draw Pins and/or Podgers and a "offset Pricker"...





Anatomy of a well "drawn" furniture joint, a die plate or "peg shear"...Again the pegs produced are in a full cylindrical geometry...







Edited by Jay White Cloud (07/19/16 08:25 AM)
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#33849 - 07/19/16 08:35 AM Re: Wedges [Re: Hylandwoodcraft]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Quote:
Personally, I thought it was a confusion of terms to refer to a pinned joint as being wedged....


You are correct Sean, and it is not accurate in description of mechanical action taking place between peg and joint assembly...Except perhaps (as stated) only in the very beginning.

Quote:
There are wedged TF frame joints, and I think that we all know what they are...


Correct again, and for the clarification of nomenclature (at least in English) when we employ "wedges" in timber frames or furniture...these are typically referred to as... "keyed joints." The action of a "key joint" is a "wedging effect" that effectively and effecently draws the joint very tight, as well as, creates a method of additional tightening in the future and better joint flexiblity...

If any are interest, we can explore this topic as found in Asian timber framing systems as well, and the applicable nomenclature and joint descriptions...
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#33850 - 07/19/16 08:59 AM Re: Wedges [Re: TIMBEAL]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Hi Tim B.

All in all...the reasoning behind your system of pegging makes sense...

I would suggest that it is not the traditional nor standard practice for pegging or pinned joint systems...

"Offset" drawn joints are meant to be "pre loaded and drawn" before the peg or square pin is inserted and driven home.

In absence of a metal "podger"...a well seasoned and hardwood peg (undersized and tapered for 1/3 its length) of a wood species like Dogwood (aka "Dagger Wood") is fire tempered and case hardened. This is used in place of a metal podger or draw pin to "pre-draw" the joint and is driven from one side...and out the other. Then the final peg is driven in.

This would be time to note that pegged and pinned joints should also be wax and lubricated. This in turn diminishes greatly (if not arrests completely) the worry and/or risk..."...of blowing out the relish on the back of the peg hole..."

As suggested before Tim, such "tapered pegs" would not (most likely in many cases) meet PE specifications for a pegged or pinned joint. There is no need to..."calculate the relish and the blowout that will happen if the peg is crammed into a drawn hole..." because a peg or pin should never be "crammed into a draw hole" that isn't pre drawn and well lubricated...Which is a traditional practice in several timber framing cultures.

If your system works for you, and you do not have to meet PE mandates on frames, by all means do as you will. I only suggest that it is an "invented system" and not a standard nor traditional practice in common overall, but indicative of some of the post era and contemporary timber framing methods that have taken place in some areas of timber framing as reflected in relocated old barns and timber frame homes. In that regard, it is in practice...but not the original work.

In reference to your description of "cross section" a peg or pin (per numerous PE I have worked with over the decades suggest) must have a "full diameter" or "cross section from point of entry to exit...not just a portion thereof. So, to be clear, I did not "leave out this factor in...strength," as I understand the mechanics and reasoning behind why modern timber framing PE, and traditional Timberwrights did it the way I have described...more commonly than the method you have suggested and employ. Again, if you like what you do...by all means continue. I only suggest additional insight to the craft and meant no offense.

I also agree that many joints are pegged for the shear sake of raising the frame, and play little within the structural integrity of the joint. This is why (and in some areas quite common) oblique braces are never pegged. Instead they are "wedged" and sometime they are place after raising. Most "brace assembly" lack the proper relish on their tenons to ever have a peg driven through them, nor need it...Just to address one joint that is pegged that shouldn't be nor actually needs it as it works only in compression...


Edited by Jay White Cloud (07/19/16 09:12 AM)
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