Smoothing curves

[transatlantic]

I'm making some shelf brackets like below and am having a little trouble smoothing out the tight curves marked by the boxes. I cut them out using the bandsaw but my curves aren't the greatest and don't flow as nicely as they could (more experience needed with bandsaw!). Am I right in thinking a card scraper would be good here?

I also thought about the spokeshave, but I don't think I'd be very good at keep the curves 90 degrees to the edge.

I ended up using a file, but I want a more finer finish.

 

[monkeybiter]

For concave curves at 90 degrees to the flat plane I use a drum sander in the pillar drill, there are different diameters and it works well. e.g. :
http://www.screwfix.com/p/rubber-drum-sanding-kit-25pcs/19906?_requestid=350639

http://www.axminster.co.uk/axminster-sleeveless-sanding-drums-ax896201

 

[Beau]

Yep as said drum sander is your friend for small little concaves. Got a couple of Carol ones myself and cant fault them.

 

[transatlantic]

These aren't just concave though?

 

[marcros]

router, guide bush/bearing and template?

 

[monkeybiter]

Drum sanding works for the convex curves too, just needs IMHO a little more care, probably best to do a couple of practise curves on a piece of scrap to get your eye in.
For the 'V notches' or whatever the correct term is I'd make an appropriately sized and shaped block, again of scrap, and glue a piece of abrasive paper to one face with the abrasive right up to [but not overhanging] the edge which will go into the corner of the notch.
HTH

 

[Bm101]

dave-s-wooden-stuff-t99301-30.html

Dave (DTR) just posted up a similar project in the detail at least. Might generate some ideas/methods?

 

[oakmitre]

If its only a small number, just glue various grades of sandpaper to lollypop sticks.

No pressure applied , sand it crossgain.

 

[Sheffield Tony]

I'd use chisels, gouges, card scraper and possibly an Iwasaki rasp. But I have luddite tendancies :wink:

 

[custard]

A card scraper is not a good beginner's tool for cleaning up curves, it's hard to enter and exit the cut cleanly, plus it's hard to achieve a really fair curve by scraping as unless you're pretty slick it'll tend to dig in.

A bobbin sander is an interesting one, it's one of those machines that delivers a reasonable-ish result with very little practise, but achieving a really fair curve is trickier than you'd think. If you "dwell" in one spot for even a moment then you'll cut a small depression, and they're really hard to remove with a bobbin sander. If you use a bobbin sander day-in day-out you'll become a real maestro with it, most of us however do passable work (if we're lucky) but no better.

The best tool for this job is a spoke shave. The workshop where I trained was so convinced of the value of spokeshaves that each apprentice had to make these lamp stands with little else other than a spokeshave,

It's worth putting some real time and effort into mastering a spokeshave, for most shaping jobs it's hard to beat.

 

[Beau]

A card scraper is not a good beginner's tool for cleaning up curves, it's hard to enter and exit the cut cleanly, plus it's hard to achieve a really fair curve by scraping as unless you're pretty slick it'll tend to dig in.

A bobbin sander is an interesting one, it's one of those machines that delivers a reasonable-ish result with very little practise, but achieving a really fair curve is trickier than you'd think. If you "dwell" in one spot for even a moment then you'll cut a small depression, and they're really hard to remove with a bobbin sander. If you use a bobbin sander day-in day-out you'll become a real maestro with it, most of us however do passable work (if we're lucky) but no better.

The best tool for this job is a spoke shave. The workshop where I trained was so convinced of the value of spokeshaves that each apprentice had to make these lamp stands with little else other than a spokeshave,





It's worth putting some real time and effort into mastering a spokeshave, for most shaping jobs it's hard to beat.

I would agree on a spoke shave or compass plane for long shallow curves but tight ones like the OP has highlighted?

 

[mbartlett99]

Spokeshave for me - they're really not all that difficult to use, one of favourite tools. Could use a decent rasp.

 

[sunnybob]

If the curves are that small, just wrap sandpaper around a drill bit to make a miniature hand held bobbin sander

 

[ED65]

I also thought about the spokeshave, but I don't think I'd be very good at keep the curves 90 degrees to the edge.

Marking out and practice! No doubt shaving in the right direction relative to the grain would present a challenge, but the gross shaping is right in the spokeshave's wheelhouse. I don't have a cigar shave so I wouldn't be able to do all of it with a spokeshave though, so I'd have no choice but to switch to rasps and files to finish the profile.

I ended up using a file, but I want a more finer finish.

A file would be my weapon of choice to smooth the tighter curves certainly and for a smoother finish I'd simply switch to a finer file after the large round had done all it could. A rat-tail needle file can leave a surprisingly good surface, even working across the grain, although you can switch to drawfiling at the end to reduce cross-grain scratches.

If I needed a really top-class finish I'd probably end up finishing off using fine sandpaper wrapped around a bit of dowel or another rod of suitable diameter. The whole smoothing operation could be done this way if need be, it is surprisingly effective, and if you work along the curve instead of across gives a much better change of a creating or retaining a fair curve.

 

[Mr T]

I think it would be difficult to spoke shave those short curves, especially if you lack experience with a spoke shave, I find the round bottom ones harder to control than the flat ones. For the convex curvesand into the notches I would pare with a sharp chisel across the grain, The concave curves you could try an initial clean up with a chisel working along the grain according to grain direction then followed by sanding with the paper on a suitable diameter round block. Somehow I can't findit in myself to use a file on wood!

chris

 

[bugbear]

If you can't (or haven't) mastered using a round bottomed spokeshave on tight curves, I'd use REALLY coarse sand paper, probably cloth backed, wrapped round "something" of the right diameter.

By REALLY coarse I mean 40 or 60 grit to start with.

Then work through the grades as normal.

BugBear

 

[custard]

A spokeshave is the right tool for the shallow curve in that bracket, for the tight curves I'd chop them with in-cannel and out-cannel gouges. You only need two or at the most three matching pairs of gouges and then you can amend designs to fit your tooling. Any 90 degrees corners, internal or external, are chopped with a chisel.

I agree with BB, if you're going the "sandpaper around a dowel" route, then don't mess around with finer grits, get the shaping job done with something really course before you think about refining the surface with higher grits.

 

[bugbear]

... you can amend designs to fit your tooling ...

Topic drift. When my Joiner friend made an oak porch, the (large) moulding
at the top was designed (on a computer) using tracings of all the spindle moulding
tooling he happened to own as the starting point.

BugBear

 

[Phil Pascoe]

If you can't (or haven't) mastered using a round bottomed spokeshave on tight curves, I'd use REALLY coarse sand paper, probably cloth backed, wrapped round "something" of the right diameter.

By REALLY coarse I mean 40 or 60 grit to start with.

Then work through the grades as normal.

BugBear

And if you have trouble finding it (especially cloth backed) tool hire places stock it for floor sanders.

 

[transatlantic]

Thanks for the replies guys, some interesting ideas. I'm surprised by the lack of support for the scraper approach, I'd have thought thats what everyone would be suggesting.

I think I'll go with the sand paper approach though as I have the materials to hand (don't have a spokeshave)