Well I just drilled a piece of mine with a carbide bit and it will get the job done just slooowly. I'd recommend drilling maybe a 1/3 at a time if your drilling it dry and letting it cool just a minute cause it will get hot. I had a small blowout at the end of that piece but luckily I can still use it this will be my personal pen so If it's not perfect that's ok. Still need advice on turning and finishing.
The finish is not as critical as the temps it will be around. In following this forum for a number of years, and the dozen or so times I have read about those who have problems - is with mammoth tooth cracking. Not in the building process but in the long run.
Snake wood, some ebonies and mammoth tooth seem to crack from heat, not humidity swings as most woods can do.
I don't know if this is the answer or not, but if I were to use an expensive or rare material that is temperature sensitive, I would use a chart to find out the next size up for drill bit, one maybe .003 larger than the one recommended for the pen. Drill the mammoth tooth out and use a rubber epoxy to allow for contraction/expansion in heat and stress situations.
Some people have trouble with cross cut blanks, which is where wood expands and contracts the greatest. This happens with humidity swings. But very hard woods and some materials such as mammoth tusk/tooth and ebonies and snakewood are more sensitive to heat swings, especially if expansion is not allowed.
People (me included) have had some of these sensitive material/wood pen blanks for several years and nothing happens. These blanks go through humidity swings and temp swings in unheated and un air conditioned shops. No cracks! But after making a pen out of them - within 6 months to a year cracks develop. WHY? They are locked into position by unmoving glue. Try some rubber epoxy. Most rubber epoxies that I have seen are whitish in color after mixing. Rubber CA is black and I don't think I would use that. Also, remember to use a chart to find the next size up (but not too large) drill bit.
For the sake of discussion only... I'm not trying to argue, rather make couple points...
Such a pen made of rare material can crack. Mammoth tooth is very brittle and can crack at any stage of pen making, such as cutting a blank, drilling, squaring, turning, sanding, polishing and setting blanks on pen kit. If everything went well and you finally made a pen I would consider this a collectible item which should be take care as such. Such a care should involve preventing this item go through rapid temperature changes which are able to cause cracks etc. But these points could and should be explained to owner.
In regards of above mentioned suggestion to use bigger size drills to drill slightly bigger holes and use glue which can be a "buffer" for size changes during temperature changes... I agree with principle and idea, but wanted to bring to your attention 2 more consideration...
First is that you want to try to use that material on the pen which allows the thickest blank walls possible and in some cases if you gonna make walls too thin it will not be possible to turn that material.
Second... I have never used rubber epoxy, so I do not know how it holds material on the tube during turning. If that glue will not hold well you might ruin your blank on turning stage.
And if we take both moments into consideration - thin walls ans blank which is not hold "dead" on tube it could be a recipe for disaster on turning stage.
Having said that I think that it make sense to try that rubber glue with bigger holes on some other material first and see how it holds and how thick resulted walls will be and in case of success it could be applied to pen kits with the thickest possible walls which kit will allow.
Just a thought.