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Post by johnboy on Jan 7, 2009 17:16:52 GMT
I have to make 6 of these  . I will be making a prototype out of softwood but the final items will be American black walnut. They are about 450mm square, 60mm at the thick ends and a radius of 700mm. Simple enough except for the large radius. I have thought of a few ways but am still undecided and thought it may provoke some discussion as to the best/easiest way to do it. John |
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Post by jasonb on Jan 7, 2009 17:37:10 GMT
Send the glued up blocks to your local CNC routing company. Many passes back and forth along the curve with a bull nosed bit should do it.
Jason
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Post by scraper on Jan 7, 2009 17:45:09 GMT
On page 360 of Patrick Spielmans Router Jigs and Techniques there are several illustrations of a home-made swinging router fixture which would do it. Ok, ok, I should post the pictures but I don't havea photo acount to link to!  Dave. |
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Post by cnc paul on Jan 7, 2009 17:49:49 GMT
John
CNC is the way to go
Paul
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Post by jake on Jan 7, 2009 17:59:19 GMT
Easy - find something like this:  And shove it across sideways. It's just big coving right*? *if this doesn't awake the ghost of Scrit, nothing ever will. |
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Post by mrgrimsdale on Jan 7, 2009 17:59:30 GMT
Chair bottom I presume. Presumably made up with 60mm square blanks spanning the width. In which case cut the curve on the bandsaw before gluing up, with margin for error. Glue up and then plane square bottom and edges. Mark up all round including the curve. Smooth the curve with whatever you have - compass plane, sanding drum, curved hand sanding block etc. etc. but working to the marks.
Or get hold of chair bottoming tools; adze, scorp etc there's plenty of sites.
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Post by jasonb on Jan 7, 2009 18:12:35 GMT
Would only work for blocks running side to side of the chair though.
If the grain did run the right way you could rough cut on the BS as you say then use a planer block in the spindle with a template or even router with bearing guided bit. Once glued up it should just need sanding ideally with a pad sander but a shaped block by hand would also do it.
Jason
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Post by mrgrimsdale on Jan 7, 2009 18:25:16 GMT
Would only work for blocks running side to side of the chair though. If the grain did run the right way you could rough cut on the BS as you say then use a planer block in the spindle with a template or even router with bearing guided bit. Once glued up it should just need sanding ideally with a pad sander but a shaped block by hand would also do it. Jason Isn't side to side the right way? It'd be stronger - esp at the weakest point i.e. the front edge where most weight is carried. |
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Post by cnc paul on Jan 7, 2009 18:47:32 GMT
It might not be a chair seat.
If it is, unless it is the choice of the designer, the grain normally runs front to back.
John, you have mail.
Paul
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Post by mrgrimsdale on Jan 7, 2009 19:15:48 GMT
It might not be a chair seat. If it is, unless it is the choice of the designer, the grain normally runs front to back. I'm sure it is! Grain goes sideways on older and simpler windsor chairs probably because it is stronger. But front to back on later ones perhaps because it makes bottom shaping easier i.e. the hollows also go front to back. In this case side to side would be easier if band sawing or fore and aft if doing it by hand IMHO PS come to think - sideways perhaps essential for weaker materials such as pine, but fore and aft for tougher stuff like the traditional elm? |
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stevep
Junior Member
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Post by stevep on Jan 7, 2009 19:55:20 GMT
? Needs a few refinements - something to hold the chair seat (?) in place and a couple of battens or something to stop the router swinging fore-and-aft, but constrain it to just swing from side to side. If you were really clever you could add a nifty little mechanism to advance the seat automatically at the end of each stroke, then set it swinging and go off and make a cup of tea.  |
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Post by mrgrimsdale on Jan 7, 2009 20:49:12 GMT
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Post by sainty on Jan 7, 2009 20:57:56 GMT
How about a sort of trammel arrangement like this...  rgds Stu |
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Post by jfc on Jan 7, 2009 21:07:32 GMT
Or you could just use the Legacy  |
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Post by engineerone on Jan 7, 2009 21:07:58 GMT
check out the jeremy broun series of router books, he made such a device in the 90's recently in the stobart sale. paul  |
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Post by colincott on Jan 7, 2009 22:18:50 GMT
I would do it the way saint said to do it as we use to do chair splats this way and it can be very quick and should need a little clean up after, as long as you keep an eye on it
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Post by modernist on Jan 7, 2009 22:51:44 GMT
If the grain runs back to front why not bandsaw out of slats and then plane with a either a wooden plane with curved sole or just a curved blade edge on a narrow plane . That should leave a fairly clean surface for final finishing.
Brian
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Post by nickw on Jan 8, 2009 9:03:58 GMT
I made a pair of those recently in pippy Oak - picture on my web site. I do hope there's no one nicking my designs   ;D I bandsawed roughly to shape then compass planed and finished with a ROS with a soft pad. |
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simuk
Full Member
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Post by simuk on Jan 8, 2009 10:03:01 GMT
Nick
Just looked at your bar stools on your site, very nice
Simon
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dunbarhamlin
Full Member
Lutherie with Luddite Tendancies
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Post by dunbarhamlin on Jan 8, 2009 10:05:40 GMT
Could do this with a long compass style jig - effectively use your router as the sharp end of a core box plane.
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Post by johnboy on Jan 8, 2009 17:12:41 GMT
Blimey, what a lot of ideas.
CNC is out as I want to make them myself.
I hadn't thought about grain direction, more to think about. If the grain goes side to side then I think I will bandsaw then template rout and glue up, shouldn't be to much clean up. If the grain goes front to back then a Sainty style router jig would probably be easiest.
They are chair seats, dining not bar stools though. I like the stools Nick but didn't steal my design from them. I have been playing around with designs for a dining table and chairs for ages and am finally going to get a prototype chair made soon (hopefully).
John
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Post by cnc paul on Jan 8, 2009 17:34:38 GMT
John,
Sainty's suggestion is the best way, my addition would be to make the guide base slightly wider than the router base and add some deeper sides to reduce any flexing of the guide base. The front to back end of the router guide will need some guide blocks to keep the router parallel to the seat.
Paul
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frank
New Member
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Post by frank on Jan 8, 2009 20:56:54 GMT
johnboy do as sainty says but use two steel bars in the router ,have them longer than you need ,then you can slide the router across the work as you cut it .i used this method when i made a dished jewelry box ,(you can see it on adels woodrat site)
frank
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Post by mrgrimsdale on Jan 8, 2009 22:53:09 GMT
Naah - . If you did them all by hand (or bandsaw + sanding etc) it'd be quicker than setting up all those complicated systems - you'd need several prototypes of prototypes! OK if you were doing a hundred. Sometimes it's easier to just resign yourself to having to do a bit of real hand & eye woodwork! |
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Post by wizer on Jan 9, 2009 17:32:23 GMT
or sometimes you require perfection
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;D
