gibbongang
New member
So i work with 3"" oak and often make church doors and the like, does anyone know of any books that detail this kind of joint.
what are the correct proportions for hammerhead tenons?
- Thread starter gibbongang
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Steve Maskery
Established Member
If you often make church doors I think you are the right man to write it!
For more basic but sound joinery it is hard to beat Ellis.
Welcome to the forum, I don't think we have many church door specialists. Have a chat with Jacob...
S
For more basic but sound joinery it is hard to beat Ellis.
Welcome to the forum, I don't think we have many church door specialists. Have a chat with Jacob...
S
Jacob
What goes around comes around.
I did some on a circular window restoration, copying the original. They were loose tenons with a hammerhead at each end with wedges on the inside edge. Oak into redwood frames. I've got some snaps somewhere and a specimen. I'll see if I can find them tomorrow.
PS off the top of me head - the frames were ex 2 1/2" the tenons 1/2" with an extra 1/4" each side for the hammer heads making them 1".
PS off the top of me head - the frames were ex 2 1/2" the tenons 1/2" with an extra 1/4" each side for the hammer heads making them 1".
Phill05
Established Member
gibbongang":1srd57py said:
I have worked on church restoration and radius windows and used these type of tenons, rule of thumb is tenons should be no less than 1/3 the width of stock used, attached is an image of how I cut them, if you make a sawcut each side of tenon approx 20mm higher than shoulder this forms a grove for the next part to locate in and stop any lateral movement, self explanatory where to put wedges and how to cut cosponsoring mortice.
hope it helps
Phill
Attachments
Jacob
What goes around comes around.
In case it isn't obvious the point is to put wedges behind the hammer end to draw it up tight. Similar to draw boreing - useful for odd shapes difficult to clamp.
Having a loose tenon (hammer head each end) can make it easier if you are fiddling around with curved shapes and heavy timbers - you can get them aligned first and then fit the tenon.
Having a loose tenon (hammer head each end) can make it easier if you are fiddling around with curved shapes and heavy timbers - you can get them aligned first and then fit the tenon.
condeesteso
Established Member
Phill - sorry, what is the function of those 2 cuts either side of tenon into stock? Can't see how they help lateral location of morticed component.
Phill05
Established Member
Jacob
What goes around comes around.
Makes a bit of sense in that it's a bridle joint rather than a proper M&T but I've never seen them in the flesh myself.
The two slots are for slip or loose tennons to help stop any twist. I've also made arched windows in oak for a chapel. The dimensions appear to the rule of 1/3rds as already highlighted. The hammer is 1/3 the width of the stock, and the 'handle' or thin bit is 1/3 of the hammer width.
I would recommend using loose hammer heads, two reasons, it's blinking easy to snap off accidentally, and with two sides to wedge (each hammer head) it allows more opportunity to resolve any marking out issued. Equally, if you are too vigorous with the wedges / too much wedge, you can snap off the hammer head. Again, loose hammer head tennions are simple to replace.
The simplest way I have found of making them is
1. Square off the arch / curved frame so that both ends are square and parallel to each other ( I use a RAS with the arch mounted on a piece of MDF that runs against the fence - perfect results every time!) once cut square, and still mounted to the MDF I either turn the saw so that is running horizontally (not to be recommended - but very easy on the Wadkin RAS) or, use a wobble saw on a spindle moulder and cut two slots for the slip mortice slots
Mount / lay each style on the same thickness of MDF and cut the slip Mortice slots using the same method. These will now perfectly align with the arch.
Dry assemble the frame with the slip tennons and clamp everything square. A good tip depending on the size of the window is to use a sheet of MDF / sheeting ply etc to create a simple jig to hold it all together and square - I don't trust clamps for the next bit.
Mark out the Mortices for the hammer head tennons. Disassemble and cut the Mortices, they should be as deep as possible without breaking through on the other side.
When thinking about how big the space should be for the wedges, you are pulling along the grain, so they are not going to strectch that much before they break. Usually it's the hammer head flanges that snap off! I would recommend a quick try out on some scrap before deciding how far to drive in your wedges. Keep the wedges very thin.
The wedges and hammer heads should be cut from the same stuff to ensure they are of the same moisture content when first assembled. Oak moves a lot as it changes moisture content, so I cut the wedges and tennons together when I'm going to assemble. Never had a problem, just concerned that if I don't the change in moisture content will result in a failure of the tennon. Keeping the wedges thin also reduces the effects of changes in moisture.
I would recommend using loose hammer heads, two reasons, it's blinking easy to snap off accidentally, and with two sides to wedge (each hammer head) it allows more opportunity to resolve any marking out issued. Equally, if you are too vigorous with the wedges / too much wedge, you can snap off the hammer head. Again, loose hammer head tennions are simple to replace.
The simplest way I have found of making them is
1. Square off the arch / curved frame so that both ends are square and parallel to each other ( I use a RAS with the arch mounted on a piece of MDF that runs against the fence - perfect results every time!) once cut square, and still mounted to the MDF I either turn the saw so that is running horizontally (not to be recommended - but very easy on the Wadkin RAS) or, use a wobble saw on a spindle moulder and cut two slots for the slip mortice slots
Mount / lay each style on the same thickness of MDF and cut the slip Mortice slots using the same method. These will now perfectly align with the arch.
Dry assemble the frame with the slip tennons and clamp everything square. A good tip depending on the size of the window is to use a sheet of MDF / sheeting ply etc to create a simple jig to hold it all together and square - I don't trust clamps for the next bit.
Mark out the Mortices for the hammer head tennons. Disassemble and cut the Mortices, they should be as deep as possible without breaking through on the other side.
When thinking about how big the space should be for the wedges, you are pulling along the grain, so they are not going to strectch that much before they break. Usually it's the hammer head flanges that snap off! I would recommend a quick try out on some scrap before deciding how far to drive in your wedges. Keep the wedges very thin.
The wedges and hammer heads should be cut from the same stuff to ensure they are of the same moisture content when first assembled. Oak moves a lot as it changes moisture content, so I cut the wedges and tennons together when I'm going to assemble. Never had a problem, just concerned that if I don't the change in moisture content will result in a failure of the tennon. Keeping the wedges thin also reduces the effects of changes in moisture.
condeesteso
Established Member
all clear now Phill, many thanks. A really impressive joint - I'd imagine quite challenging to fit well and have the wedge working along whole length. I'll have to think of a place to try them, don't really do church doors!
