Assembling machinery is always a game of chance. Most of the time you can get all of the parts together, and none of the parts give you any trouble. Then there are the other times, when "tab A" does not fit "slot B." No matter how hard you try, or what angle you come from, two parts do not fit together, even though the directions say they should. What do you do then? Try one of the following options.
Contact the Manufacturer
This is supposed to solve all problems. However, there is the possibility that the manufacturer sends you new parts that are supposed to work, but then those parts have the exact same problem. Once in a while, the manufacturer understands the problem, and sends a replacement part that actually works, but it takes weeks or months to get it. Still, this is an option.
Hire a Machinist or Welder to Alter the Parts
A machinist can cut the part so that it fits with the other parts. That is what machinists do. In most cases, you would be able to find and hire a machinist for this one-time job, and you could have parts that fit together in two weeks or less.
A welder can help, too. He or she can add something extra to the parts if the problem is that the parts will not stay connected. While these alterations may void the warranty on the machine, at least you will not be frustrated by the problems at hand.
Custom Machine Parts
Finally, you could try custom machine parts. Clearly, the designer of the dysfunctional parts you have in your hand did not do a good job. Taking the instructions, the diagram of the machine, a picture of the machine assembled thus far, and the messed up parts to a manufacturer of machine parts, you should get two parts that will not only work in the machine, but also work together as they were meant to. These are custom parts, and they may or may not resemble the originals. However, they will fit in your machine, you will finish its assembly, and the machine will work.
If you need to learn more about your options in order to make the decision that is best for you in regards to your machine's parts, it may be helpful to get in touch with a business such as C & C Machine Works