Ok as promised this is the method I was taught to straighten a shaft, be prepared it's long post:
“How to straighten a pool cue shaft”
First let me say all warped shafts can not be straightened, the following points of interest are things that may point to internal stress in the wood that has not been relieved, or methods of poor handling that can result in a shaft causing stress to wood objects. However, all or none of what I have listed below could have been the cause of a shaft warping. Shafts warp due to wood that has not been properly stress relieved. Now this internal stress can be natural which is normal for all wood once it is cut and when it is being processed. Or it can be man made by abuse or by improper handling / treatment of the wood by some one using one of the following methods.
1. Turned to finished size to fast. (Such as taking a 1 inch dowel and turning it to finished size in a afternoon)
2. Shafts that have excessive non-straight grain. (Sometimes this can be used to identify a problem and sometimes shafts like this will stay straight forever)
3. Shafts that have been exposed to unstable conditions such as, high temperatures or low temperatures. ( Leaving your cue in your automobile summer and winter can cause a shaft to warp, along with many other problems, but wood is wood and sometimes this will not have an effect concerning a shaft warping. However, it will cause expanding and contraction that will cause inlays to pop, materials to expand or to shrink which will cause many types of damage.)
4. Shafts that were exposed to excessive amounts of moisture for extended periods of time. (This is very easy to understand keep all items that are made from wood dry, moisture will cause swelling and as it dries shrinkage which in most cases will damage any pool cue.)
Things you will need to straighten a shaft:
1. Lead Pencil
2. Flat Surface
3. A single burner Electric Stove
4. A method to hang the shaft with the cues butt attached
5. A method or device that you can use to bend the shaft
The first step to making a warped shaft straight again is finding the highest point of the warp. Now keep this in mind, in some cases when a shaft warps the internal stress will cause it to bend at more than a single location, so you will have to fix one bend at a time. I have seen and fixed shafts that had multiple bends ( 3 or 4) and while this seems like a situation where a shaft can not be fixed that is not always the case, so the key is patients, this is something you will need a lot of LOL. The best way to find the high point is to roll the shaft on a flat level surface such as a pool table, but any flat surface will work. Now this is not the method I would use to check a shaft for straightness, I would recommend placing the shaft between centers on a lathe and spinning it, then using a dial indicator to determine how much movement there is. But most do not have a lathe so rolling the shaft on a flat surface is an alternate method that anyone can do to find the high point of the warp. Next mark the high point of the warp with a pencil so that you can find it before you make your first bend of the shaft ( The first bend should be done without heat so I call it a Cold Bend)
Once you have found the high point of the shaft and marked it you are ready to make your first bend. Hold the shaft flat to the surface you are bending it upon and lift up on the joint side of the shaft, holding the marked area flat to the table. Then roll the shaft and see if the marked high point is still the high point. In many cases it will move a little because what you thought was the high point may not have been, or there may have been more than a single area that warped. It may take a couple of bends until you get the shaft as straight as possible bending it cold, then hang the shaft with or without the butt attached for 24 to 48 hour’s.
After it has hung for one of the times listed above check the shaft for straightness and to see if any of the original warp may have returned. Either way it is time to roll the shaft and again find the high point and mark it with a pencil. Then heat up your single burner electric stove, when it is fully heated holding the shaft about 2 to 3 inches from the mark on both sides place the marked area above the coil of the electric single burner stove, and keep the shaft a good distance away from burner so that it does not mark the shaft. If you are too close you will know it because it will burn your hands, that is why you are holding it two to three inches on either side of the mark. When the wood and your hands start to get warm place the shaft on the flat surface and bend it again. Again this may take a couple of times but the shaft should straighten out for the most part at this time then hang it again for 24 to 48 hour’s. After that time has passed again check the shaft by rolling it on the same flat surface you have been using to check and see if the warp has returned.
If there has been any movement, again mark the high point and get out your Electric stove and heat the shaft as mentioned before, At this point after a few bends along with heating the shaft it should be straight, but to be on the safe side again hang it for a minimum of 24 hour’s. If the wood doesn’t move your good to go, if it moves at this point it is most likely the best it will ever get and to my knowledge there is nothing else that can be done to correct the problem.
I hope this helps