Ceramic or glass bowls are the safest. I would err on the side of caution when using aluminium (aluminum in the US), even if it is anodised, as there is evidence that aluminium plays a role in alzheimers disease.
Brass is fairly inert (hence they make screens out of brass). I dont really like smoking out of anything but glass however the only aluminum bowl I have right now is attached to some weird bong that has internal led's so it lights up. That's really the only metallic bowl I will smoke out of and even then it's not too often.
i've made quite a few pipes using brass. actually spent shell casings set into deer antler so that you don't burn and inhale the antler. they looked really nice if i say so myself. gotta make some again.
i would just select the part of the antler that appeals to you and cut that out.
do you have a dremel tool?
the bowl part is obvious.
the stem is trickier. what i did was cut a piece of metal clothes hanger and after starting a small hole with the dremel i then used the piece of clothes hanger to bore the rest of the stem. YOU MUST REMBER....
DO NOT PULL THE HANGER OUT UNTIL THE TOOL HAS STOPPED TURNING. If you remove the piece of hanger while the dremel is spinning it will bend 180 degrees and slice you up. usually near your wrist. it works good but can be dangerous if your not careful. i learned this the hard way. you can make them in pieces also. a stem that fits into the bowl piece. i would also use smaller shell casings for the joiner. i love the look of antler pipes but you don't want to smoke the antler, i've been told thats not good for you, hence the brass.
if you start getting a bunch of antler dust in the air you might wanna use a mask bro. that stuff is not good in your lungs. i have made them with an extreme curve in them like you've got there. if you accidentily drill to far and come out the side just save some of the antler dust and mix it with some clear drying glue and patch. sand and it will not show. its a nice piece of antler for a pipe. can't wait to see the finished product.