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Dish/Hollow form construction question
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=15244		 Page 1 of 1
Author:  canegri [ Thu Jan 03, 2008 2:58 pm ]
Post subject: 
Hello All,

I'm preparing to build my first guitar. The budget is tight and I need to
find as many ways to save money as possible. That said, I'd like to build
my own dish forms. Would anyone be able to post some guidance on
how this is done using mdf and a router?

I combed through the archives, and there's ton's of great info. I wasn't
able to find a description of creating the profile in MDF using a router,
though. Excuse my ignorance, but I'm new to using routers (don't even
own one yet). I've only used one (fixed base) to round over some edges
on a bench I built. I'm planning on buying a small laminate trimmer
(probably a PC 309); but i'm guessing this won't be up to this job?

I have the Cimpiano book and could go the route of creating curved
clamping cauls, but I'd prefer the benefits of using the form.

Thanks!
Author:  TommyC [ Thu Jan 03, 2008 3:39 pm ]
Post subject: 
Hey Chris! Welcome to the OLF.  First of all, be forewarned that what you are proposing will create an unholy amount of fine dust!  That being said, here is a picture by Stuart Ketchin (from MIMF) that I based my dish making jig on.  Basically, make a bridge that has rails with the corresponding radius you are trying to achieve on which your router rides on ( 15', 25' etc).  Make a pass, rotate a little, make a pass, rotate a little, choke on dust, make a pass, .... you get the pic.  I used plexiglass templates (from LMI) and a pattern bit to make the rails.  Attach walls adjacent to your rails and set the width to match your router base.  Hope you can understand my explanation.  Anyway here is the pic and I am sure others will chime in.
Author:  TommyC [ Thu Jan 03, 2008 3:43 pm ]
Post subject: 
I guess I should've added that I made mine out of two pieces (laminated) of  3/4" particleboard but wish I had used MDF ( although that would make even more fine dust). I used a straight router bit.  
Author:  LuthierSupplier [ Thu Jan 03, 2008 4:30 pm ]
Post subject: 
Chris,
I think Tommy is giving you good advice. That is probably the simplest way to
make dishes. You will need a jigsaw or bandsaw to cut the circle, or I think you
can buy 24" diameter mdf circles. Don't know if you know that I sell the radius
gauges that are used to draw your rails. I'm about $5 cheaper than LMI, and my
gauges are also convex and concave on each side. Good luck, and if you get
tired of making the dish, you can always purchase from me(ours are made on a
CNC machine). Best of luck!
Tracy
Author:  Michael Dale Payne [ Fri Jan 04, 2008 2:01 am ]
Post subject: 
I have a set of plans for a dish routing form in the Library of Plans.

A bit of warning this is a task you will rather do outdoors.. If you make them from MDF you will be come Granolaman
Author:  Brad Way [ Fri Jan 04, 2008 2:24 am ]
Post subject: 
When I made my dishes I made sure that I had a shop vac hose as close to the router bit as possible. I had minimal dust and was able to make them in my shop.
Author:  canegri [ Fri Jan 04, 2008 5:40 am ]
Post subject: 
Huge thanks to all who responded! Very helpful.

I'll have access to a shop with a really good dust collection system next
month. Sounds like I'd better wait and do this one there!
Author:  erikbojerik [ Fri Jan 04, 2008 6:01 am ]
Post subject: 
I do it in a similar way to Tommy, except that I drill a hole in the
center for a dowel, and spin the dish with one hand while holding down
the router and moving it slowly down the track with the other.
Author:  J.R. Hunter [ Fri Jan 04, 2008 8:05 am ]
Post subject: 

Chris,


I'm in process of making the jig that TommyC showed. I hear you on the tight budget issue. 


The biggest concern is getting the correct radius. To do that I took some 1/4" hardboard, drew a straight line about 30" long to give breathing room. At the center I drove a small finish nail then two more an equal distance apart from the first one on that straight line.I then took a 30" steel rule and flexed it slightly so that it was in front of the midddle nail and behind the others. I then traced it and compared the curve to that of my plans(carefullly trace the top and back radius onto tracing paper). It wasn't right the first few times but after pulling out and re-nailing the outside nails closer or farther from the middle nail I finally got the curve to match perfectly. I did this for the top and back radii. I then cut them to within 1/16" lf the line and then hand sanded it the rest of the way careful not to obliterate the line. These will be my templates to make the "rails" for my router to ride on.


I'll trace the template onto 3/4" plywood and cut to 1/16" of the line with a jigsaw. Next,I'll tape the template to the plywood with double sided carpet tape and and run it through my homemade overhead pin router on my router table. You could do the same thing with a ball bearing pilot bit.  


I would advise against using a laminate trimmer to cut your dishes. I would use a full size router for that.


Since you're new to the router I also highly reccomend the books Router Jigs and Techniques and Router Basics byPatrickSpielman. They're a great resource for anyone that wants to get their money's worth out their router. I made my own router table and many of the jigs in these books and learn something new every time I read them.


J.R.


Oh yeah, welcome to the OLF!    
Author:  Brad Way [ Fri Jan 04, 2008 10:46 am ]
Post subject: 
Just remember that if you are using a router to make your dishes that you figure out the distance from the router base to the end of the router bit. This distance (probably and inch or two) must be added to the router jig radius to get the dish to come out perfect. Yes...this is probably only a very small amount but it is worth getting it correct if you are going to take the trouble to lay things out.

Of course I didn't figure this out until after I finished my first set of dishes.
Author:  psl53 [ Fri Jan 04, 2008 2:44 pm ]
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I used a screw in the middle and cut both sides and finished it off when I was done.
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