Hi everyone,
I work as a 2D mechanical drafter at an equipment company, mainly responsible for converting engineers' 3D models into detailed 2D engineering drawings. In addition to that, I’ve created a set of standard timing pulley templates using parametric modeling. These templates allow engineers to select a pulley profile (based on tooth type), input the outer diameter (O.D.), and choose secondary parameters (such as set screw hole angle, thickness, etc.) to automatically generate a complete 3D model.
In the standardized design, the set screw holes are positioned approximately 120° apart, aligned with specific tooth roots to match actual machining practices. However, this approach ties the screw position to a specific tooth index rather than a fixed angle. As a result, some engineers (perhaps out of convenience or oversight) do not adjust the angle, leading to smaller angular spacing as pulley size increases.
I consulted AI tools and found that some suggest 180° as the optimal angle for two set screws, which contradicts my experience—where 120° seems best for balance, and 90° is often chosen for machining convenience.
So I’d like to ask:
Thanks in advance.
I work as a 2D mechanical drafter at an equipment company, mainly responsible for converting engineers' 3D models into detailed 2D engineering drawings. In addition to that, I’ve created a set of standard timing pulley templates using parametric modeling. These templates allow engineers to select a pulley profile (based on tooth type), input the outer diameter (O.D.), and choose secondary parameters (such as set screw hole angle, thickness, etc.) to automatically generate a complete 3D model.
In the standardized design, the set screw holes are positioned approximately 120° apart, aligned with specific tooth roots to match actual machining practices. However, this approach ties the screw position to a specific tooth index rather than a fixed angle. As a result, some engineers (perhaps out of convenience or oversight) do not adjust the angle, leading to smaller angular spacing as pulley size increases.
I consulted AI tools and found that some suggest 180° as the optimal angle for two set screws, which contradicts my experience—where 120° seems best for balance, and 90° is often chosen for machining convenience.
So I’d like to ask:
- Is 180° truly the optimal angle for two set screws on timing pulleys?
- What are the mechanical or practical reasons behind this recommendation?
- If 180° is indeed better, should I revise the template to default to 180° to reduce the risk of poor screw placement?
Thanks in advance.
