I installed a new bottom BB (square tapered) on a single speed conversion (old 10-speed frame). I'm now about to install a new crank, but I noticed that it does not come with crank bolts so I guess I reuse the old bolts? However, the bolts off the old BB/crank are the two piece type (threaded bolt in spindle and separate nut). Does this mean that I need to take the threaded bolt out of the old BB spindle? If so, any good way to do this since there is nothing to grab on to (it's just threaded on both ends)? Is the bolt reverse threaded into the spindle? Or, do I need to just buy new crank bolts?

Thanks for the help.

No, that won't work. Apparently the OP has a "nutted" bottom bracket spindle, that is the spindle has threaded extensions built in (not removable) and the crank is held in place with nuts, not bolts.

You can get the proper nuts at an LBS, possibly for no cost. This type of bottom bracet was usually a very low cost one but functional.

Well, I'm not using the old BB, so it looks like I just need to get new crank bolts for the new BB. Don't cranks usually come with crank bolts included?

Thanks.

Bolts usually come with the crank but they may come with the bottom bracket. I've seen it both ways. In this case, since the bb didn't include, them I hope they will come with the crank.

Your LBS will have them. I had the same problem when replacing a cup and cone with a cartridge. They will probably give them to you for free.