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undersized dowels - Building a new bender
http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=5129		 Page 1 of 1
Author:  Scott Thompson [ Thu Feb 16, 2006 10:20 am ]
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I'm building a new bender with wooden dowels instead of pipe. The dowels are all under sized and I can't find any locally that are the correct sized to use with a forstner bit. How do others handle this? Are there dowels available that are the actuall size that they are marked?
Author:  Michael Dale Payne [ Thu Feb 16, 2006 11:01 am ]
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manufacturing tolerance has bit yet another. yes but with wood dowels the issue is going to be swell or srink. All depends on the moisture state of the wood when turned or extruded. take a caliper with you on your next shopping trip and pick by meassured od not by basic od. Also hardwood dowels will be truer than softwood. other option is to shim on the underside of the dowl and fill the gap with hardwood inpregnated epoxy. only the portion of the dowel that is tangent to the outside of the form is relavent. I may be mistaken but I assume you are refering to the cross struts on the 1/2 half guitar shaped form that you bend around. if so next time use aluminum or stainless steel tubing instead of wood dowels. Many use aluminum flat bar on edge instead of tubing, pipe or dowels. Typicaly 1/8" x 1" because it is somewhat easer to slot to the right depth than drill perfectly tangent to the edge through two sides. No matter what you use they need to be matched drill to assure alignment.MichaelP38764.793599537
Author:  Scott Thompson [ Thu Feb 16, 2006 2:24 pm ]
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Thanks, Michael. Yes, I'm talking about the cross struts. My bending forms now have the steel tubing, but I was going to try the wood dowels just for a change. I did take my calipers around with me the second time and nothing came close. The closest I came for a 1 1/8" marked dowel was 1.098!

I've never tried the flat bars. Do you slot them so they are flush to the bending surface and exposed? How would you cut the slots?


Author:  Michael Dale Payne [ Thu Feb 16, 2006 2:59 pm ]
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Yes tangent to the arcs and flush. I built my first four froms this way and aluminum flatbar is a good heat sink if you are using bulbs for heat. I slotted mine on the band saw. spaces about every 1 1/2 to 2" helps with an even heat dispersment. I think I still have a autocad drawing of the plan for my OM If you like I can post it in the morning.

by the way the manufacturing tolerance for 1 1/8 dowels is more than likly + 1/16 -1/16 so 1.09 is in the acceptable tolerance.MichaelP38764.9656828704
Author:  Scott Thompson [ Thu Feb 16, 2006 6:17 pm ]
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That would be great. Thanks.
Author:  Colin S [ Thu Feb 16, 2006 9:03 pm ]
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I just built a new side bending form at the weekend for a new body shape (a classical FE19) that I'm starting to put together. I have never used wooded dowels or metal rods for my bending forms as I use a blanket and the metal rods were originally used as heat sinks when using light bulbs. I always use flat stock instead.






Alignment is assured by drilling the connecting bolt holes together, I then install threaded inserts and the rods are screwed through and held with nylock nuts. The top slats are then just screwed in place and profiled to the required curves.

Just another way.

Colin

Heh, I just noticed when I put the picture up that I've left a screw out! A lot of people say I've got a screw loose! Colin S38765.2118402778
Author:  Serge Poirier [ Thu Feb 16, 2006 11:20 pm ]
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Colin, your design looks quite similar to mine ! Just a few differences. it looks great!
Author:  Michael Dale Payne [ Fri Feb 17, 2006 1:59 am ]
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Ok Scott here it is the slots are 1/8 x 1 for 1/8 x 1 aluminum flat bar

Author:  Scott Thompson [ Fri Feb 17, 2006 5:30 am ]
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Ahh... Now I understand. In my mind I had the slat lying perpendicular to this. Got it now. Thank Michael!

Colin - thanks. Never thought of flat stock. I don't know why everyone uses dowels when yours seems simpler.
Author:  Arnt Rian [ Fri Feb 17, 2006 6:00 am ]
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I use flat steel bars and saw the kerfs out with the band saw, wedge the bars in with wood scraps if necessary.
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