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How to make your own wooden sash cramps

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How to make your own wooden sash cramps

Postby AndyT » 27 Jul 2021, 17:55

Regular readers with long memories might recognise the title of this thread. I started a thread on another forum about it once - over four years ago now. In that thread, I showed photos of some wooden cramps that I had bought and liked, plus some pictures from old catalogues. (Have a look here if you can tame the onslaught of adverts that corral the content there now.)

What I skated over in that thread was that although I really like these two little lightweight wooden cramps,

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one of them is not as straight as it was when Mr Fennimore finished it. :cry:

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I decided to make a new one. What with wood being expensive nowadays, and with me having one or two useful bits squirrelled away just in case, I had a look for suitably sized bits of hardwood, good enough for this but not up to anything finer. Before I get on to that, let's have a closer look at what makes these nice.

At the business end, a wooden screw pushes against a captive pad, which is free to slide along as required - there is no need to find a third hand or tape pieces of scrap in position.

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The threaded hole for the screw is fixed with a strong joint which is a sort of composite bridle joint / through mortise and tenon, with wedges. (Does anyone know a name for this joint? I can't recall reading a description of it anywhere.)

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At the other end, a loose stop is held on brass straps, which have a bar that sits in a notch.

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The stop is kept in line by a tongue and groove.

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I found these bits and pieces which should be ok. A lump of walnut and some mahogany-like wood from a thrown away table. Plus some offcuts of brass.

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The walnut has a bit of sapwood on the corner and isn't straight, so I took it to meet my trusty old three wheeler bandsaw, which enjoys this sort of thing.

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Then I did some planing,

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and so on, and found a little bit more walnut, until I had this kit of parts:

It's nice having a 3D example to copy - I can set a gauge off it and hardly need to bother with numerical measurements at all.

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Looking at it on screen, I do wonder about this piece. It's far from being straight-grained, but walnut is fairly well behaved, isn't it? Or will I have to do this all over again in fifty years time? ;)

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Whatever the case, I won't be rushing this project - family and other stuff means I shan't be in the workshop again for at least a week - but I did just make a start on the threaded handle. I make no claims to be a turner, but I can manage something serviceable like this.

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I made the stem slightly oversized, so I could regularise it with a dowel plate:

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Whatever this wood is, it takes a nice thread, even with a cheap Chinese cutter. (The original rod was 5/8" and I'm upsizing to 3/4" rather than going down to 1/2". Making a thread box would be too much of a digression!)

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The last bit needs the cover to be removed:

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That's all for now.

I'd be very interested if anyone has experience of the bridle/M&T joint and any tips on how to set it out and make it.

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Re: How to make your own wooden sash cramps

Postby Cabinetman » 28 Jul 2021, 21:43

An interesting joint, can’t say I’ve seen one before, it’s strange that the wedges don’t go into the tenon and I can’t really see how they work except that they are probably just glued to the sides of the tenon which stops it coming out again I suppose, and obviously the mortise is shaped more like a dovetail.
The original has a wonderful colour, – it’s a nice little piece and you should have a fun time recreating it.
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Re: How to make your own wooden sash cramps

Postby AndyT » 29 Jul 2021, 19:14

Thanks. I suspect that how to wedge your tenons might be a bit like whether to cut dovetails pins first or tails first. I thought wedges outside were normal, but it looks like you prefer to split your tenons with wedges, is that what you mean?
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Re: How to make your own wooden sash cramps

Postby Andyp » 29 Jul 2021, 19:55

Without questioning the challenge of recreating the original and without the knowledge of others here I am left asking myself why the maker ( I assume this is a one off & not mass produced) used a joint that nobody can put a name too nor find another example of, I have tried too. A bridle joint with wedged tenon perhaps?

Is it the right joint for the job? Would it be any stronger than a bridle joint with a couple of dowels to strengthen?
I do not think therefore I do not am.

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Re: How to make your own wooden sash cramps

Postby Trevanion » 29 Jul 2021, 20:13

I'm not sure exactly what you would call that joint, possibly a comb joint but it doesn't seem the right term. It does make a lot of sense though, for a clamp you need to have resistance to the clamping force from opening up the clamp which the M+T does amply, but also twisting which a single M+T in the middle might struggle with and end up cracking the end of the clamp by twisting tenon in its mortice and splitting the grain along it's length, by having a larger head you can put shallow bridles on either side which will help prevent twisting and bears the force across the whole section of the clamping rail rather than right in the middle, also, once glued this joint is incredibly strong because of all the long-grain gluing surface.

Wedges on the outside of the tenon like on those clamps is a common practice in door and sash construction to secure the joint, I'm not sure how old the practice is exactly but I've seen it on practically every very old piece of joinery I've pulled out. The technique of wedging on the inside of the tenon seems to be a more modern technique (as in I only see it on work less than 30 years old) possibly stemming from furniture-making practices, making the joinery look prettier and flashier than the other method which tends to squash the fibres of the tenon and stile as it's driven in.

I used to it the flashy way with cutting slots in the tenons, drilling holes in the ends of the slots, and driving the wedges in, until I had to take apart a stable door as I had made a cock-up on the stile measurement not allowing for the overlap (schoolboy error!) and I wanted to salvage the rails. Once I got the stiles off I realised just how much the wedge actually cracks the rail on the inside when they're driven into the tenon, which can't be good for its structural integrity, since then I've wedged on the outside of the tenon.

Probably with modern glues you could do away with wedges completely, I know some people do actually but I can't bring myself not the have the wedges as it just seems proper.
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Re: How to make your own wooden sash cramps

Postby Just4fun » 29 Jul 2021, 20:59

AndyT wrote:I thought wedges outside were normal, but it looks like you prefer to split your tenons with wedges, is that what you mean?

Whenever I have used wedged tenons I have cut a saw kerf down the tenon and inserted the wedge there. I feel that is stronger and would be stronger in this joint also ... but how would you cut the saw kerf? The outside parts of the bridle joint mean your saw could not get at the tenon. So it seems to me that the wedges have to be outside the tenon, but I don't really see why the wedges are needed at all if the M&T are properly cut.
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Re: How to make your own wooden sash cramps

Postby AndyT » 29 Jul 2021, 21:47

Interesting, thanks. I think Just4fun is right though, in this case, the wedges have to go on the outside. Inside the tenon would be impractical to cut.
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Re: How to make your own wooden sash cramps

Postby Cabinetman » 30 Jul 2021, 17:34

Just4fun wrote:
AndyT wrote:I thought wedges outside were normal, but it looks like you prefer to split your tenons with wedges, is that what you mean?

Whenever I have used wedged tenons I have cut a saw kerf down the tenon and inserted the wedge there. I feel that is stronger and would be stronger in this joint also ... but how would you cut the saw kerf? The outside parts of the bridle joint mean your saw could not get at the tenon. So it seems to me that the wedges have to be outside the tenon, but I don't really see why the wedges are needed at all if the M&T are properly cut.

Absolutely right of course, hadn’t occurred to me, I have always put a sawcut into the tenon, just seemed the right way to do it but after what Trevanian said I may just change my methods except of course when I’m fox wedging. Ian
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Re: How to make your own wooden sash cramps

Postby spb » 31 Jul 2021, 23:24

AndyT wrote:I'd be very interested if anyone has experience of the bridle/M&T joint and any tips on how to set it out and make it.


I can't claim experience, but I did notice this video posted today:



A slightly simpler version of the design, but it has the same type of bridle-M&T hybrid joint, albeit without the wedge.
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Re: How to make your own wooden sash cramps

Postby Trevanion » 31 Jul 2021, 23:29

I was today years old when I learned AndyT was a moniker for James Wright :lol:
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Re: How to make your own wooden sash cramps

Postby AndyT » 01 Aug 2021, 11:17

Good spot, spb. The question is, do I cut the joint the way I think* or watch the video first?

*Shim the thin piece so it lines up with the thick one and mark with two settings of a mortice gauge. Once for the inner M&T and once for the outer bridle cheeks.

Trevanion, I wonder if autocorrect has mangled your post somehow?
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Re: How to make your own wooden sash cramps

Postby Trevanion » 01 Aug 2021, 11:25

AndyT wrote:Trevanion, I wonder if autocorrect has mangled your post somehow?


I don't think so? :eusa-think:

It is a bit of a millennial joke, if someone tells you something fairly mundane that you didn't know before, a reply can be "I was today years old when I learned X,Y,Z."
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Re: How to make your own wooden sash cramps

Postby AndyT » 01 Aug 2021, 11:48

I guess we're both showing our ages! :)
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Re: How to make your own wooden sash cramps

Postby AndyT » 03 Aug 2021, 21:13

I've now watched the video that spb found, and skimmed through the longer version with the commentary. I can't fault him for his level of enthusiasm and I certainly agree with him that lightweight wooden cramps like this definitely still deserve a place in the workshop. This one will take me longer than 21 minutes though!

I noticed that the threaded handle part I made last time didn't have the decorative lines on it that the others have, so put it back on the lathe. It's the perfect time to use one of the simple cup chucks I bought some time ago, paired with a little leather pad that fits over the live centre. I wouldn't attempt to turn a whole handle fixed as loosely as this but it was fine to cut in some grooves and then scorch them. I used an old guitar string.

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I added some oil while it was on the lathe. Here it is - a better match than before.

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On to marking out. First I marked the tenon on the upright part in the usual way.

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And then I marked for the mortice on the beam. I had already found that the difference in thickness between the two parts was equal to four of these handy thin strips, so putting two of them alongside gave me the right position. (The strips are bits of someone's old wooden venetian blind and have been useful for all sorts of odd jobs, being straight and accurately thicknessed.)

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For the other lines, I set a gauge from the original cramp.

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and marked all the waste very clearly.

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Some time later, I realised that there was no benefit in using the shims - all I needed to do was to re-set the fence so the marks were centred on the wood. Never mind!

For the bridle joint, I decided to try the method where you drill a hole at the bottom of the slot, then saw up to it. Here's my bread and cheese powered drilling machine:

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and a posed shot of sawing, which is just like you do for cutting a tenon:

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I cut the mortice with a nice old chisel - if that trademark belonged to FG Pearson and Co, it's somewhere between 1854 and 1958, probably on the early end of that span as it's the sort with a thin layer of hard steel welded on to a wrought iron body.

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I freely admit that, despite trying, the joint did not fit straight away but needed some adjustment with chisels and rasps. I also admit to not being the tidiest woodworker...

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Nevertheless, I cracked on and cut the stopped groove on the top of the beam. A little chiselling at the end, then a Record 043, with a short skate, ideal for this scale of work.

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I also made the slots where the metal strap goes, by drilling small holes near the edge, then sawing into them and filing them out a bit. This walnut may not be the ideal choice for the job - it's a bit brittle and with the wavy grain it's easy to let bits chip off the edges.

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I drilled a 5/8" hole in the upright using a relatively recent brace, probably from the 1960s

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and tapped it

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Assembly time! Liquid hide glue - nice and runny, long open time and much stronger than people think.

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It's also very easy to clean up...

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which is just as well!

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That's all for now - I'll be on to some of the metalwork next time.
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Re: How to make your own wooden sash cramps

Postby Cabinetman » 03 Aug 2021, 23:43

Crikey Andy, I haven’t seen one of those cramps in ....well since I was at school! But they obviously do the business.
Coming on nicely.
I have a supply of Venetian blind slats – white ones made in wood and like you I find them incredibly useful for all sorts of things.
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Re: How to make your own wooden sash cramps

Postby AndyT » 04 Aug 2021, 07:46

Cabinetman wrote:Crikey Andy, I haven’t seen one of those cramps in ....well since I was at school! But they obviously do the business.
Coming on nicely.
I have a supply of Venetian blind slats – white ones made in wood and like you I find them incredibly useful for all sorts of things.


I'm guessing you mean the big Woden one in the last two pictures. As you say, they work just as well now as they ever did. I rather like tools that are more useful than they are fashionable.
Maybe that's because I see myself that way!
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Re: How to make your own wooden sash cramps

Postby Mike G » 04 Aug 2021, 09:16

My dad had a set of clamps similar to these, but I have a feeling that the head end was removable. I think it had similar straps on the head, but a fat pin which passed through a hole in the bar of the clamp. This meant he could interchange the mechanisms between longer and shorter bars as needed.

Anyway, nice little project, Andy, and as always, a really nice write-up.
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Re: How to make your own wooden sash cramps

Postby PeteW » 04 Aug 2021, 12:19

AndyT wrote:I also admit to not being the tidiest woodworker...


I believe that's what is known as a "trustworthy" bench :)

I have a few of the handscrew clamps in various sizes and find them useful in all sorts of ways, but i've never seen one that size. A trip to the auction site might be called for.

And many thanks for the time and effort you put into these project threads. Always a pleasure to watch a craftsman at work.
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Re: How to make your own wooden sash cramps

Postby AndyT » 04 Aug 2021, 14:10

Thanks guys. A little flattery is always welcome!

Mike, I wonder if you are thinking of the pairs of cast iron cramp heads - they are really useful too, and I have a few pairs, just in case. ;)
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Re: How to make your own wooden sash cramps

Postby AndyT » 05 Aug 2021, 17:39

With the glue dry, I could trim the wedges and the other bits flush. I'd left off shaping the end of the upright, thinking that it might need some persuasion during assembly, so I drew round the end of the old one and turned my chair to face the fretsaw for a few minutes.

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This was a little awkward at full length of the beam, but does let you see the fancy foliage casting again, which I hope makes it all worthwhile.

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Getting there!

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Here's the bit of walnut that will be the sliding stop, marked out from the old one and for the tongue.

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I have so many options for cutting the rebates to form the tongue that it was hard to choose. Because I had just matched the groove on the old cramp, a dedicated tonguing plane was not quite right. I could have set up a moving fillister, but it's such a short piece it's hardly worth it. So I just used the 'freehand' method where you rest the edge of a shoulder/rebate plane in the gauge line, at an angle; take a few strokes, bring it upright, then work down. For the bulk of the cut, I used a wooden rebate set fairly coarse, and I finished with a heavier metal plane set very fine.

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I don't see anything wrong with using three different planes on a job like this; more minimalist workers may use their own methods.

For the curve, I turned back to the fretsaw

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which gave a reasonable finish straight off the blade, needing only a little sanding.

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The moveable pad needs a strip of brass to hold it in place. Looking again at the original and the brass I found earlier, I decided to use a thinner piece, 1/32" thick. This was just thin enough to cut with aviation snips, which was much quicker and straighter than sawing. First mark a line

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then cut

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To straighten the edge, I used a "dreadnought" file, which is good on brass, with less tendency to clog. (One of the many tips I learned from Richard Tomes.)

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Bending the brass round the wood made me realize that I should have done it before I cut the notch out, but I managed it without breaking anything or needing too much force. I'm glad I chose the thinner material though.

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To hold the brass in place, I went carefully, drilling the brass,

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then using steel screws, then taking each one out, countersinking

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then cleaning up, in that nice stage where it starts to look like an object rather than raw materials.

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This pad needs a little dimple where the tip of the threaded rod will go. I just carved this freehand.

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That's all for now.
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Re: How to make your own wooden sash cramps

Postby Mike G » 05 Aug 2021, 17:57

AndyT wrote:.........Mike, I wonder if you are thinking of the pairs of cast iron cramp heads - they are really useful too, and I have a few pairs, just in case. ;)


No, no, they were all wooden, with steel straps.
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Re: How to make your own wooden sash cramps

Postby AndyT » 05 Aug 2021, 18:06

Mike G wrote:
AndyT wrote:.........Mike, I wonder if you are thinking of the pairs of cast iron cramp heads - they are really useful too, and I have a few pairs, just in case. ;)


No, no, they were all wooden, with steel straps.


That sounds like something that could be easily made - were they like this at all (but with a wooden threaded part)?

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That's from a 1929 French catalogue - https://archive.org/details/auxminesdes ... loguea1929 - page 26 and they just need a beam with some notches underneath. If not, any chance of a diagram, when you have a minute?
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Re: How to make your own wooden sash cramps

Postby Trevanion » 05 Aug 2021, 18:27

Nice to see the political name brother's Fret Saw in action! 8-)
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Re: How to make your own wooden sash cramps

Postby Mike G » 05 Aug 2021, 18:44

AndyT wrote:
Mike G wrote:
AndyT wrote:.........Mike, I wonder if you are thinking of the pairs of cast iron cramp heads - they are really useful too, and I have a few pairs, just in case. ;)


No, no, they were all wooden, with steel straps.


That sounds like something that could be easily made - were they like this at all (but with a wooden threaded part)?

tete et mentonnet.png


That's from a 1929 French catalogue - https://archive.org/details/auxminesdes ... loguea1929 - page 26 and they just need a beam with some notches underneath. If not, any chance of a diagram, when you have a minute?


Yes, very much like that. I'm not at all sure that they had wooden threads, either.
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Re: How to make your own wooden sash cramps

Postby AndyT » 05 Aug 2021, 19:18

Trevanion wrote:Nice to see the political name brother's Fret Saw in action! 8-)


Just testing... You mean the Trump Brothers?

Ah, freedom of speech! :)
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