The kits used are PSI Trimlines and Woodturnningz Saturn style. I deburr immediately before assembling, after all sanding and polishing. I use a barrel trimmer to square the blanks. I drill the blanks slowly cooling the bit often. I start with a smaller size bit, the use the final size bit to finish. I use CA glue to glue in the tubes that have been thoroughly scuffed. The blanks are then set aside until the next day before squaring.
I just received a new order of these blanks and they seem to be a slightly different color,(darker), even though the name is the same, (Pink Sky). I have turned 2 of them so far and they seem almost softer, much less brittle than the previous ones.
One thing really stands out here. That is with the glue.
All to often you will see CA being the magic cure all, fix all glue to use. This is simply not true. Everything has limits, CA glue is no exception. Properties of glue/epoxy is that of flexibility, adhesion strength, debonding properties and others. Flexibility means how well the glue will handle the bonding materials moving. CA is not a flexible glue by no means.
A 'glue' joint bonds 2 materials together. In our case it bonds the tube (rigid, strength and support) to the blank (eye candy can range from soft to very hard). When it comes to brittle materials, esp
THIN brittle materials that bond becomes a very big issue.
Picture this. The brass tube is one size, you add a rigid glue and put a fragile blank on it. The more that tube expands/moves the more stress on the blank. Now replace that glue with a gap filling
FLEXIBLE glue (epoxy rather
) and now you have the glue dispersing the expansion stress in a larger area thus reducing the impact strength. Much of this motion is absorbed in the glue itself and not passed.
To further account for fragile materials you could drill ever so slight oversized and allow more room for flexibility via the glue joint. You must weigh the expanded drilling size with the amount of 'meat' you can get away with on the blank material.
Now couple what all I just said and throw it on the lathe, add
FRICTION HEAT via chisel, sandpaper and the like, you now have thermal expansion to contend with. That brass tube will expand differently than the blank material and all to often will act as another heat source. Before you know it you have material
FATIGUE.
Try this. Measure the thickness of the nib that you have problems with and write that down. Now check the thickness of all the other contact points and not the difference. You will find that the nib section you are dealing with the least space, generally.
Other red flags that I see is the barrel trimmer. Trimming afterwards, esp if the blank is thicker on one side than another, you have introduced a stress point and a future crack.
Also as previously mentioned pressing parts together when they are not properly lined up will cause some epic failures. Take note of using the drill press, lathe, bench vise and all sorts of other goodies to press (arbor press, mallet, etc)
