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How to make tight inside curved corners?

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city17

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Hi, I'm working on the design for a bed, and I'd like to have legs that are very slightly angled, and have a nice subtle curve in the transition from the horizontal to the vertical part. See the example image below.

Schermafbeelding 2021-10-05 om 21.10.01.png

But I'm having a bit of trouble envisioning how to actually make the curved transition bit. Regular spokeshaves can't handle this kind of curve, maybe the cigar-type ones can? Would using a rasp be a better idea? Any specific type of rasp/file people would recommend? There seem to be a lot of variations out there.
 

D_W

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cut all of it in facets and then remove the lines between facets when done (scrape and sand).

make sure you do everything equally when creating the facets. Rasp, file or gouge would be fine in the transition assuming you either saw or drill the radius mostly into place at the corner.

I'm not sure I can think of a good reason to do something like that, though - is that leg some kind of moulded piece or is it actually wood? i"m guessing the former based on the location of the joint.
 

city17

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cut all of it in facets and then remove the lines between facets when done (scrape and sand).

make sure you do everything equally when creating the facets. Rasp, file or gouge would be fine in the transition assuming you either saw or drill the radius mostly into place at the corner.

I'm not sure I can think of a good reason to do something like that, though - is that leg some kind of moulded piece or is it actually wood? i"m guessing the former based on the location of the joint.
Not sure I understand 100% what you mean with cutting in facets? Do you mean just the leg and the frame, or dividing the leg in an upper and lower portion and cutting them separately, then joining them?

The bed in the image is probably metal or some composite material, not wood at least. For structural purposes this probably isn't the best joint in wood, will have to think about best how to make it in wood.
 

Adam W.

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Hi, I'm working on the design for a bed, and I'd like to have legs that are very slightly angled, and have a nice subtle curve in the transition from the horizontal to the vertical part. See the example image below.

View attachment 119231

But I'm having a bit of trouble envisioning how to actually make the curved transition bit. Regular spokeshaves can't handle this kind of curve, maybe the cigar-type ones can? Would using a rasp be a better idea? Any specific type of rasp/file people would recommend? There seem to be a lot of variations out there.
You'll need to carve it out with hand stitched rifflers and use a couple of gouges or a very sharp blade to finish it.

You can get the rifflers in Germany easily enough and I think they are made by Milani in Italy.

Here...

 

Jacob

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Or cheapo equivalent from B&Q 3 piece 8" Rasp set | DIY at B&Q followed by sandpaper on a piece of dowel
Get the thing joined and built before doing finished shaping at the critical points
There seem to be a lot of variations out there.
There are! You could build the thing flat faced , run a router around to start the curve and then refine that with rasps... etc.
 

Argus

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If that is done in wood, then you'll need a very wide piece - most of which will be cut away making that 'L' shaped profile on the top end of that leg.

Next, if it's wood, you'll need to carve it by hand, (unless you have some expensive profiling machines and cutters), which will need a succession of rifflers and rasps, completing with ever finer scrapers and abrasives. Not difficult for a carver.....

However, if it is made in wood, that leaves you with the dilemma of making a strong (M&T?) joint in what is, effectively, short grain on the 'L' shaped bit.

It may not pass the initial bonking test before it dumps you and your conquest on the deck.
 

city17

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If that is done in wood, then you'll need a very wide piece - most of which will be cut away making that 'L' shaped profile on the top end of that leg.

Next, if it's wood, you'll need to carve it by hand, (unless you have some expensive profiling machines and cutters), which will need a succession of rifflers and rasps, completing with ever finer scrapers and abrasives. Not difficult for a carver.....

However, if it is made in wood, that leaves you with the dilemma of making a strong (M&T?) joint in what is, effectively, short grain on the 'L' shaped bit.

It may not pass the initial bonking test before it dumps you and your conquest on the deck.
By moving the L-shaped bit to the horizontal frame, and not the leg (so the leg is only vertical), and using a mortise and tenon (or 2 dominos), I'd imagine it would be strong enough? At least you wouldn't have the short-grain issue.

Schermafbeelding 2021-10-05 om 21.10.01 2.png
 

Argus

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By moving the L-shaped bit to the horizontal frame, and not the leg (so the leg is only vertical), and using a mortise and tenon (or 2 dominos), I'd imagine it would be strong enough? At least you wouldn't have the short-grain issue.

View attachment 119253
Probably.... but I would expect that a commercially made version of that configuration would have some metal bracing - internal or external, or both in all the corners.
I think that whichever way the grain is oriented it will produce an inherently weak joint in a continually stressful position.
That joint - and its three comrades - will be under ergonomic stress for at least 8 hours of every day.

Finally, bed joints are generally de-moutable with metal brackets to allow the things to be taken apart to be carried up stairs and around corners...... You may be able to shimmy a one-piece single bed frame around corners, but it will be difficult with a double, a king..... super king or even an 'emperor' size.
Sorry to be negative on this, but these practicalities do exist.
 

city17

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Probably.... but I would expect that a commercially made version of that configuration would have some metal bracing - internal or external, or both in all the corners.
I think that whichever way the grain is oriented it will produce an inherently weak joint in a continually stressful position.
That joint - and its three comrades - will be under ergonomic stress for at least 8 hours of every day.

Finally, bed joints are generally de-moutable with metal brackets to allow the things to be taken apart to be carried up stairs and around corners...... You may be able to shimmy a one-piece single bed frame around corners, but it will be difficult with a double, a king..... super king or even an 'emperor' size.
Sorry to be negative on this, but these practicalities do exist.
Those are all definitely good points. It's still in early stages, so I'll have to do some thinking on how to make it practical and structurally sound.
 

D_W

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So, aside from the idea that this is difficult to make visually perfect by hand, I'll explain the facets:

If you have a curve that's either very steep or covers a large length, etc, and needs to be even from end to end, you can set out everything flat and then cut more or less tangents of the curves. That way, you get a good visual idea if each is the same on both ends (and you can key even the tangent planes by cutting ends to depth by marking the depth - and you can do it at steps between for a long span. This is the same idea as a violin maker drilling depth holes in a violin top and then carving to them to get approximate top thickness before tuning.

Once you have a bunch of facets, then to have an evenly faired curve, all you have to do is remove the facet junctions and round things over.

This is also a way to make a reasonably round handle without a lathe (start by making octagonal facets), and where I use it with some frequency is saw handles (which can look lumpy if the initial work is just done willy nilly). The faceting allows you to work quickly without checking too much, and then just blend the facets.
 

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