Weird joint triangle thing... beginners etc

[El Barto]

Ok sorry for the stupid post title but a while back I was in one of the workshops at Chichester college and they had these triangles which students had made to practice their joints. I think they were made up of a half lap dovetail, a halving joint and a mortise and tenon (might be wrong though, I didn't get a proper look). Students in their first year were made to do them over and over again, a great exercise I think.

A friend of mine wants to get into woodworking and I thought it'd be a cool way for him to start. Does anyone know the name of these things?

 

[memzey]

I don’t know about a triangle but there is something called the Gottshall block test which might fit the bill.

 

[Tasky]

Penrose Triangle :lol:

Is this a prism with a different joint in each face, or a triangular frame with a different joint at each corner?

 

[El Barto]

Penrose Triangle :lol:

Is this a prism with a different joint in each face, or a triangular frame with a different joint at each corner?

A triangular frame with a different joint at each corner! (I think...)

 

[adidat]

a remember doing an a shape thing with four joints, mitre halving joint, dovetail halving joint, bridle joint, cant remember the last corner?? perhaps a mortise and tennon?

adidat

 

[custard]

I'm familiar with the idea of a training piece which is just a random assortment of joinery, a great way of using up bits of scrap. But it's odd that it's in a triangle. That would mean jointing at an angle, which is usually something you'd save for later on in a woodworking career, because then you're wrestling with questions like, do you have an angled mortice or a short grained tenon? Consequently most of the exercises I've seen have been right angled joinery.

This is a Woodwork O-Level practical test, the wood is provided dimensioned but over-length, you've got three hours to mark up and make this using only hand tools,

 

[El Barto]

I'm familiar with the idea of a training piece which is just a random assortment of joinery, a great way of using up bits of scrap. But it's odd that it's in a triangle. That would mean jointing at an angle, which is usually something you'd save for later on in a woodworking career, because then you're wrestling with questions like, do you have an angled mortice or a short grained tenon? Consequently most of the exercises I've seen have been right angled joinery.

This is a Woodwork O-Level practical test, the wood is provided dimensioned but over-length, you've got three hours to mark up and make this using only hand tools,

Thanks Custard, that looks like a useful exercise too.

I know what you mean about the triangle, it's something I found odd at the time of seeing it and something I've also given thought to SINCE seeing it because, like you said, it adds a degree of complexity that wouldn't be there were it right angles.

 

[Sheffield Tony]

That looks pretty much as I remember from O-level, around 4 joints to cut, but when I did it (Joint Matriculation Board version, erm, 1980-something) the plan did not come with the joints drawn on ! Deciding what joints to use, drawing them on, and usually some other "decorative edge treatment" was your first job. So are these papers already dumbing down ?

 

[NazNomad]

Penrose Triangle

Made me chuckle.

:lol: :lol: I actually know what a Penrose triangle is, I made one from pallet wood recently.

 

[custard]

That looks pretty much as I remember from O-level, around 4 joints to cut, but when I did it (Joint Matriculation Board version, erm, 1980-something) the plan did not come with the joints drawn on ! Deciding what joints to use, drawing them on, and usually some other "decorative edge treatment" was your first job. So are these papers already dumbing down ?

I think that was the theory exam not the practical, that had furniture components where you had to draw in your choice of joint.

 

[Sgian Dubh]

This is a Woodwork O-Level practical test, the wood is provided dimensioned but over-length, you've got three hours to mark up and make this using only hand tools,

That test must have been after the time I took my woodwork O level, but the drawing puzzles me all the same. Do you know if the orthographic first angle projection in your post was deliberately drawn with missing and/or incorrect information? Was the intention that the examinee fill in the details, or perhaps in some way correct the projection, or even maybe ignore the drawing errors but make the piece correctly anyway? For example, the side 'elevation' is not an elevation, although it might be a section taken through the 1-3/8" square 'leg' piece, but even if that's the case there's still missing detail. And what are the extraneous heavy lines extending to the right of the 1-3/8" square 'leg' in the side elevation or is it section, or whatever it's meant to represent. Slainte.

 

[AndyT]

This is a Woodwork O-Level practical test, the wood is provided dimensioned but over-length, you've got three hours to mark up and make this using only hand tools,

That test must have been after the time I took my woodwork O level, but the drawing puzzles me all the same. Do you know if the orthographic first angle projection in your post was deliberately drawn with missing and/or incorrect information? Was the intention that the examinee fill in the details, or perhaps in some way correct the projection, or even maybe ignore the drawing errors but make the piece correctly anyway? For example, the side 'elevation' is not an elevation, although it might be a section taken through the 1-3/8" square 'leg' piece, but even if that's the case there's still missing detail. And what are the extraneous heavy lines extending to the right of the 1-3/8" square 'leg' in the side elevation or is it section, or whatever it's meant to represent. Slainte.

I wanted to take O-level but had to do Biology instead, much to my disappointment, so I may be totally wrong here. but I can't see any problems with those drawings! All the information needed seems to be there and I can't see any extraneous lines. Am I being thick? I know I'd struggle to make it in under three hours!

 

[custard]

Do you know if the orthographic first angle projection in your post was deliberately drawn with missing and/or incorrect information?

It's from "Woodwork For GCE and CSE" by J.N. Green, he also wrote "Technical Drawing For GCE and CSE". Maybe that explains Britain's industrial decline?

 

[El Barto]

This is a Woodwork O-Level practical test, the wood is provided dimensioned but over-length, you've got three hours to mark up and make this using only hand tools,

That test must have been after the time I took my woodwork O level, but the drawing puzzles me all the same. Do you know if the orthographic first angle projection in your post was deliberately drawn with missing and/or incorrect information? Was the intention that the examinee fill in the details, or perhaps in some way correct the projection, or even maybe ignore the drawing errors but make the piece correctly anyway? For example, the side 'elevation' is not an elevation, although it might be a section taken through the 1-3/8" square 'leg' piece, but even if that's the case there's still missing detail. And what are the extraneous heavy lines extending to the right of the 1-3/8" square 'leg' in the side elevation or is it section, or whatever it's meant to represent. Slainte.

I wanted to take O-level but had to do Biology instead, much to my disappointment, so I may be totally wrong here. but I can't see any problems with those drawings! All the information needed seems to be there and I can't see any extraneous lines. Am I being thick? I know I'd struggle to make it in under three hours!

I can't see any problem with them either :/

Anything we're missing Custard?!

 

[Sgian Dubh]

I can't see any problems with those drawings! All the information needed seems to be there and I can't see any extraneous lines.

The top orthographic drawing in custard's post is laid out using (essentially) first angle projection, although the standard first angle projection symbol is missing that would immediately tell the viewer that's the convention in use.

Therefore the top left hand drawing is the front elevation. Dashed lines indicate hidden detail. Conventionally in first angle projection the drawing to the right of the front elevation is the side elevation, and the drawing below the front elevation is the plan view. To get the side elevation the drafter pivots the front elevation bringing its furthest left side towards the viewer using the furthest right position as a pivot. Similarly, to draw the plan, raise the topmost point of the front elevation towards the viewer using the bottommost point of the front elevation as the pivot.

In this case, the plan is correct, but the side 'elevation' omits details. For instance, where is the L shaped piece as seen in plan with its dovetailed corner? Who knows because it's omitted? If this top right hand drawing is actually a section there should be section indication lines and direction of view letters on the front elevation drawing, but none of these indicators or pointers exist. The side 'elevation' also isn't a section because if it was a section drawing the 1-3/8" square 'leg' would include lines 3/8" apart where the bridle joint passes through, and hidden detail lines to indicate there's a 5/8" thick piece of wood on the far side of the leg. That detail is omitted too, so it's not a section of the piece. Finally, to the right of the 1-3/8" square leg in the sort of side elevation, sort of not a section drawing there are two short heavy lines indicating that they are either something, or perhaps just a couple of random lines for no good reason.

True, there's more than enough information to make the piece from the drawings provided, including the isometric projection, but sloppy drawing practice doesn't make for clear communication, and can lead to errors. I've had to deal from time to time with sloppy drawings for longer than I care to remember, and drafts people who nowadays are a whizz with all the functions of things like 3ds Studio Max, AutoCAD and Rhino, but they have no real idea of how to set out orthographic projections in both the common drawing convention, i.e., first angle projection or third angle projection. I have sometimes received drawings that are copper bottom guaranteed (sic) to be set out in third angle projection, for instance, but in reality the drawings on the page are a mixture of third angle and first angle, with the added complication that the various elevations, sections, detail drawings, etc are set out randomly on the page or pages. It's no wonder that some complex jobs can sometimes end up made seriously out of whack. Slainte.

 

[MusicMan]

Took me a while as the projection is so confusing, but I agree with Richard. It's sort of a messy first angle projection but the side view (let's not dignify it with the term 'projection') is missing a bunch of both dotted and solid lines, and has those weird short heavy lines.

Fully agree that if drawings are taught and used, they should be accurate and stick to convention.

Cheers, Keith

 

[Sgian Dubh]

Do you know if the orthographic first angle projection in your post was deliberately drawn with missing and/or incorrect information?

It's from "Woodwork For GCE and CSE" by J.N. Green, he also wrote "Technical Drawing For GCE and CSE". Maybe that explains Britain's industrial decline?

I'd not come across the book until your mention in your earlier post, although I see from doing a bit of searching the book was around in the 1990s, if not before. I don't think it necessarily explains the UK's industrial decline which I think has more to do with market forces, cheaper labour elsewhere, cost of bulk transport, the changing nature of work and perhaps the value of intellectual property along with needs of a service economy. Slainte.

 

[custard]

I see now why they say humour and the internet don't mix.

 

[Phil Pascoe]

It must have been pre '88, that's when they ceased to exist.

 

[Sheffield Tony]

Older than that - it is in Imperial. In 1983 my exam was in metric. But we definitely did have to decide the joints ourselves, perhaps it varied by exam board. I recall clearly discussing my choice of joint with the teacher after the exam; I used a single bare faced M&T where he thought it ought to be a twin. I still think I was right :wink: