My advice is DONT DO IT! Sound post fitting is ounce for ounce one of the most difficult acts in lutherie. I dont mean the act of getting the right sound-I simply mean just getting it to fit properly with no obvious gaps. Its much more challenging than what is commonly believed. The interior contours of the plates are complex in their relationship. A well fit post moved a degree or two in its horizontal plane or vertical axis will then only be fitting on a point. Heres where the danger is. [BTW-anyone who has read my SP rant may notice a bit of Department of Redundancy Dept. here-my apologies] Everyone always rails about the dangers of a tight post. [Partially to get you to come in every season!] I am not advocating a tightly fit post here but mind you, once the tension goes up-all posts are unbelievably tight-just try to move even a loose post under tension! A well fit post never damages the top but a poorly fit one does every time. Dents. [at least] It happens each time the post is moved-eventually leading to a generalized depression in the top plate which as it grows, makes each successive fitting more difficult.
Fitting a post is so hard that many professional luthiers cant seem to do it right. My bud Arnold and I regularly see horribly fit posts come in that were fit by pros in 5 minutes. So no offense guys- but how can we expect players with minimal experience to get it right when it is such a crucial element to a basses health? That being said I know youre prolly gonna do it anyway, so I should stop ranting and put in my two cents. Previous advice from Bob and Samuel was good-mebbe I can add to it.
As always the right tools are crucial. Believe it or not the most important tool is your lighting. For years I used a simple 15 watt bulb on the end of a wire---totally inadequate. You really need a lot of light in there-the difference between a shadow and a gap is quite hard to see. I use two lights. One, my favorite is called the sitelite and it was actually developed as a music stand light. It has a clip, a gooseneck, and a hooded halogen bulb. Take the hood off and drop it in a bass and its Yankee Stadium at night. It is available here-
Link Removed The other light is more directional and is like a very long flexible rod with a bulb at the end. I forget the name but it is available at
www.garrettwade.com . Using two lights may seem anal but it really is difficult to see inside a bass-especially while using a mirror.
Samuel recommended the standard soundpost tools and these really are the best. Anyone who needs to know where to get these please let me know[just dont have those addresses at hand right now]. But those tools are somewhat expensive and there are cheaper alternatives more commonly available.[though not as good] A telescoping mirror and a retractor[for grabbing the post] are available at any auto parts store. The retractor will need to be bent gently along its length in order for it to manipulate the post through the f-hole properly. You will also need something that can put leverage on the bottom of the post to help pull it up. A 3/8 in steel rod mebbe 15-20 inches long can be used here. Bend a small L into the bottom and curve the long length-you will need to experiment to get the right curve. This rod can also bang the post around handily. BTW it is a good idea to cover these tools with shrinktube or rubber paint in order to cut down on f-hole erosion. Another necessary tool is a feeler gauge to tell you exactly where the post is on the top. Most luthiers make these and they are quite simple. You will need a flexible piece of steel banding about 8 in. long. Bend it in half so it resembles your index finger touching the tip of your thumb. This can be inserted into the f-hole and as the bottom of the gauge corresponds to the top the soundpost can be traced revealing its position. Watch the varnish!
The basic process to stand a fallen post would be as follows-stab the post with the standard post tool or grab it with the retractor about ¾ of the way to the top of the post. Remember to orient it so that when you stand the post the grain is perpendicular to the grain of the top plate. Put the post through the f-hole and place it so the bottom of the post is touching the back where you feel it should be and the top of the post is angled out towards the center of the bass. From this position you can lever the post up by pulling it towards you. Unfortunately, this basic process is somewhat akin to describing a heart transplant as first cut open the chest and cut the old heart out. Then put in the new one and sew it to all the places you cut before. Sew up the chest and apply electricity. That may be an exaggeration but not by too much.
Fitting a new post is a whole nother order of difficulty. First, youve got to get your blank down to fitting size. Use your old post length and cut the blank oversized from this 5-10 mm. The first tool I use in fitting after rough cutting is a small 4 in. stationary disk grinder. This is for gross fitting only. Use this to get the post to the point where you feel you could pull it upright with some muscle[dont, of course]. Now it is time for fine fitting. The proper tools for this job are either a very sharp chisel or knife. Thats not a problem if you are adept at sharpening, but if you are not there is no way you can cut end-grain spruce with a dull tool. Sanding and filing tend to be very inaccurate and accuracy is crucial here. Perhaps the least of evils here would be a very fine diskgrinder-lets say 180 grit or above. [better to learn to sharpen]
Take the final fitting process very slowly. You may have to put the post in scores of times so try to be patient. BTW another trick to keep down the f-hole erosion is to take safe-release masking tape and line the hot parts of the f-hole with it. As far as where the post should go-generally it should stand centered with the treble foot and a little less than the diameter of the post back from it. The bassbar also should be centered on the bass foot but sometimes this is not the case. It should be checked and the post should reflect its symmetry[re centering]. The vertical angle of the post should be 90 degrees to the flat plane of the top plate-but this is not crucial. It could be off a few degrees and it wouldnt matter-what does matter is that it fits. How far can you go in terms of varying from this position? Only so far before you start to compromise the structure of the top. I would say no further than two diameters of the post back from the bridge. As far as moving the post towards the f-hole-dont let more than a ¼ of the post diameter travel past the outside edge of the treble bridge foot. Both these positions are extreme and I would never put a post in them-they just represent where I think structural problems[sinkage] may begin to occur.
Well, this is very long but it is by no means comprehensive. It is just a hipshot of trying to cover all the bases here. If anyone has read this far and wishes for more detail please feel free to ask a detailed question. Hope this helps somebody-I know it did me [I had a need to be long winded].
jeff
