1: EASY No real is construction is required. Any tools needed are common household items. There may be a very simple cut or some washing or removing of parts/labels involved but this is an easy project that anyone can do with minimal effort.
2: BASIC Fairly simple construction technique. Tools are common household items like scissors, razors, etc. Those with no prior experience making their own gear should be able to accomplish this project without difficulty.
3: MODERATE May require some special tools, but nothing that is too difficult to obtain and substitutions could be made. Some experience with making gear would be helpful but is not necessary. Those without prior experience may have to make a few attempts before getting it right.
4: SOMEWHAT DIFFICULT Specialized tools and more obscure materials are be required and can't be substituted. This may entail ordering from specialty shops or borrowing a blow torch or sewing machine from a friend. Those less skilled might find this type of project a little frustrating but it is doeable with enough resolve.
5: DIFFICULT If you have your own machine shop, you're set! Otherwise, you might want to consider another project. This one is going to involve a substantial amount of time investment and skill.