I am trying to use a portable rotary tool but i can't remove the drill bit that's already on it, there isn't a reverse button on the tool so i am at a loss for how to remove it. can you help me?

Before the invention of the hammer drill, people face a lot of trouble drilling in the tight spaces. They had to break down the parts in smaller units in order to drill it properly. But, now the time has changed and the users can easily drill on a portable manner. But, one might wonder, what makes the best hammer drill
? The answer is being more and more complicated each year with so many brands on the market.

The market offering is huge and most of the brands are continuously reinventing their products. We have analyzed many different drills from cordless hammer drill to a corded hammer drill, to hammer drill machine to cordless hammer drill drivers. Thus, we have come up with these top picks.

For a tool like the dremel you push down the shaft lock button on the side of the bit and use the small wrench to unthread the collet nut.
basic manual, others on page: http://mdm.boschwebservices.com/files/05-11%20100-3000%20r37449v3.pdf

Lock the spindle (small chrome button near the tool's nose or lever at the power switch). You'll probably need to rotate the spindle by hand as much as one full turn as you do this, to get the lock to drop into place.

With the spindle locked, use your supplied wrench to turn the collet nut counter-clockwise (as seen from the cutter end) about one full turn. The collet should now be plenty loose enough to release the cutter / wheel / drill.

Push the rubber sleve off the drill bit and up the drill bit then the plastic ring. release the clip around the spindle. Slide the clip and chuck sleve forward and remove the ball sitting in the spindle. You should then be able to pull the bit from the machine. If it does not want to come hold the bit in a vice and tap the spindle off the end of the bit using a suitable punch. Rebuild chuck in reverse.

The button is only to keep the shaft from turning while you loosen the collet (the nut) with the little wrench. THEN the tool comes out.

what you need to do is twist the collar of the chuck to remove bit and reverse the procedure to lock it into place.

The SDS designation relates more to the type of chuck on the tool for the bits than to the tool/drill itself. There are both chisels and drill bits with SDS-Plus and SDS-Max shanks, SDS-Max being the the larger of the two. As far as the tools go: Demolition hammers will only hammer and can only use pointed chisels, scaling chisels, scrapers, etc, not anything like a drill bit that requires spinning to work. Rotary hammers can hammer and rotate the bits. Rotary hammers have a selector switch with two or three positions; one for hammer only for the above demolition bits, one for rotary hammer for use with carbite tipped drill bits, and some have a position for rotation only. The rotary hammer is a more versitile tool but more expensive because of extra workings inside.

possible if you have a drill bit smaller than the screw and you can try drilling in reverse. Might be better just to replace the mandrel though.

This is not an ordinary chuck like on a drill. It will only adjust a little bit.

Basically yes. Lower power units are usually titled as "hammer drills." Higher power units, usually labeled "rotary hammers," tend to be larger and provide bigger impact forces. But there are a few differences that are worth knowing: The rotary hammer usually have a chisel only feature, for light chiseling and masonry removal. Rotary hammers also have specially designed chucks that only accept bits specifically designed to fit their chuck. The special chuck on a rotary hammer helps hold the drill bit and prevents it from slipping during use.