Order of machining and assembling parts?

[dansawyer]

This is what I think I learned:
The project is to build a clutch assemble to hold a ring gear. The project is made up 4 parts from left to right a clutch disc, a ring gear, a clutch disc, and a collar. The assembly is all bored to fit on a shaft. The primary alignment between the assembly and the shaft is through the collar. The objective is to hold the bore tolerance to a tight slip fit.
I learned that machining parts independently and then assembling them and expecting independently bored holes to align is a high bar, i.e. risky.

I believe the optimal order would have been to machine the disc to gear to disc to collar interfaces first and then to bore the center. I tried fully machine the parts independently and then assemble them. The shafts were out of alignment by offset by a couple of thou. The bores also were out alignment by axis by just enough to cause binding. If the machining had been to complete the interfaces and assembly machining first and then bore the center the alignment issue would have been avoided.
Thank you - Dan

 

[RJSakowski]

There are a bunch of unknowns here and seeing your design would probably clear most of them up. Also what machines are at your disposal? Machining the parts except for the bore and boring the assembly as a unit will require concentrically aligning all four parts. I see that as a difficult task. The simplest alignment feature would be the central bore.

 

[dansawyer]

The key take away for me was when machining two parts that require multiple mounts don't create a dependency on two independent surfaces. In this case I was creating a disc and a collar. The disc was the critical part to hold the gear. The collar was the critical part to mount the assembly on a shaft. The order of machining should have been first, the square surface between the disc and the collar. I should have created that first, permanently joined them and then bored the hole for the shaft, and then mount the assembly via the shaft and machine the disc to gear surface.

 

[dbb-the-bruce]

I agree with @RJSakowski, drawing or at least a sketch would help. I don't have nearly as much experience as some of the folks here, but have been hobby machining for 5 or more years, starting with a lathe.

From your description, sounds like a bunch of round(ish) parts aligned axially, so start on a lathe. Add features (holes?) that you can use to align on the mill if it makes sense.

Without knowing what the parts look like, how they are arranged and what operations need to be performed, it's hard to offer useful suggestions.

 

[RJSakowski]

The key take away for me was when machining two parts that require multiple mounts don't create a dependency on two independent surfaces. In this case I was creating a disc and a collar. The disc was the critical part to hold the gear. The collar was the critical part to mount the assembly on a shaft. The order of machining should have been first, the square surface between the disc and the collar. I should have created that first, permanently joined them and then bored the hole for the shaft, and then mount the assembly via the shaft and machine the disc to gear surface.

You have to realize that determining the best order of operations based on a rough description of the parts and without some idea of purpose is difficult at best. Additionally, not knowing what tools are availabe complicates matters further.