Generally a stew cut tenderizes between 180-190 degrees F internal temperature. You want to take your time getting there so the connective tissue (collagen) that is tough, liquefies. As the collagen breaks down, it becomes tender. And what may have seemed dry and tough at 170 will be tender and moist at 190.
Elzon, welcome to Chef Talk. It's kind of hard to tell where you are going wrong without the full recipe you are following. Here are a few guesses though: 1. make sure you are cooking it long enough. I really cook a stew for any less than 2 hours and often 3 or more. 2. make sure it is at a simmer, not a boil which can dry out your meat and make it rubbery. 3. make sure you are using the proper cuts. I used to have a friend that thought that to make a good stew you needed good meat, meaning he used to use steak (NY Strip, sirloin, ribeye). These do not really make the best stews as they don't have enough marbling or connective tissue to stand up to long slow cooking. Instead I often use "chuck" which, IMHO is the best cut for general stew making.
As others have indicated, low and slow is the secret of stewing and potting. That and the choice of meat.
Less than an hour won't make it, no matter what the cut. So that's your major problem for sure.
By and large, you want what used to be the "cheap" cuts for stewing. Chuck is, as others have pointed out, ideal. Another is bottom round---although not as fatty as chuck it still tenderizes very nicely. In fact, I used some tonight for a Boef Bourgignon and it came out terrific.
Next time you make a stew, try this. Instead of cooking it on the stovetop, pop it in the oven at about 250 degrees. Leave it in there until the meat is tender---which could be anywhere from 1 1/2 to 3 hours. But remember; at very low temps you cannot overcook it. After oven stewing you'll have a better idea of how low the stovetop should be.
The upside to all this is that there's a very shallow learning curve. Soon as you make the first stew correctly you'll never have this problem again.