Author Topic: Fitting A Horn Inside The Base  (Read 5291 times)

Offline Tim Crosby

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Fitting A Horn Inside The Base
« on: July 17, 2010, 12:36:56 AM »
 
Sometimes based on the horn I have and the design I am looking for, instead of fitting the horn over the base I put the horn inside the base. Upfront let me say that you will need a lathe and a chuck for this.  It helps if the horn is fairly round to start with and the sides are close to the same thickness all around, a little thickness is a good thing. Drill the horn and start working it down. Using you choice of softening techniques round the base. Now you will need to even up the thickness of the base. You can do this by hand with files or chuck the horn up and turn the outside round. Using either method you will have to rework the body so it flows into the rounded area at the base. About ¼” or so of the horn will fit inside the base.
   You will need a base blank that will finish up about 1/8 or so larger than the horn opening. Start out by turning the blank round between centers. It should be at least ¼” bigger than the horn at this point. Leave it as big as possible, do not turn to shape yet. Turn a stepped neck on one end that will fit in your chuck, that end will also be the strap button. Put it in the chuck, measure the outside diameter of the horn. At this point the base should be round, of even thickness and parallel for about ¼” from the opening, that is the part that will fit inside the base. The center of the base should be marked from when you turned it between centers. Divide your diameter in half, that is your starting radii, set a divider a little LESS than the radii and make a mark on the base for the outside of the cut. Start SMALER than your mark, use a parting tool, maybe 3/16” thick (something close to the thickness of the part of the horn that will go in the groove) and make a very shallow cut, try the horn in it. It will probably not fit, to narrow is good. You have a taper inside the horn so the inside wall of your groove will have to have a slight taper. Widen the groove A LITTLE AT A TIME, remember you are taking off twice the width of your cut, don’t take too much off the inside wall either. Slow, with little cuts and test fits are the way to do this. Once it is close, fitting in the groove but not all the way in, DON”T force it or the wood will split, you may want to put a witness mark on horn and base and use some color on the base and take the horn down where the marks are. Once you have the horn fitting in the base the next step is to hollow out the center of it. It will make the horn lighter and increase the capacity slightly.  
 Once it is hollowed out to  a point you are comfortable with, turn the base around on the chuck. If everything went right you will have nicely spinning  cylinder, if not, that is why we left it a little larger to start with, turn it down until it is centered with no high spots. Turn it to shape, the step from base to horn should be  1/8” or less, round it or leave it square based on your design.
 Drill through the base into the horn and back through the horn into the hollow cavity and pin it.  

 If you have any questions let me know, I hope this is helpful, next is making a two part applied tip.  

 Tim C.
  
Notes:
1.   There are two different pieces of wood in the pics but they are in work order.    
2.   I didn’t think I had to show the between centers set up, what you see is the cylinder held in the chuck by the stepped neck.  

















« Last Edit: February 26, 2013, 09:25:35 PM by rich pierce »

Offline Mark Elliott

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Re: Fitting A Horn Inside The Base
« Reply #1 on: July 17, 2010, 03:54:20 AM »
Tim,

What chuck are you using and how slow do you set your lathe for turning the horns?

Mark E.

Offline Tim Crosby

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Re: Fitting A Horn Inside The Base
« Reply #2 on: July 17, 2010, 03:37:19 PM »
Tim,

What chuck are you using and how slow do you set your lathe for turning the horns?

Mark E.


 It is a Nova chuck, with a set of smaller jaws on it. I don't remember the the size but the largest it will take is about 1 1/4" the smallest about 3/8s".
 The lathe is running about 800, I know that is fast, I can slow down to 400 or so but the 800 has worked for me.  I work to the left side as much as possible.

 Tim C.