[How do I?] Seeking Assistance With Jig-machine Build

auto.pilot

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As shown in the pictures, I am designing a dedicated machine (or jig) to cut the interior and exterior of drums. The drum shown was cut using a wood lathe and has a 14 inch diameter. It is approximately 6.5 inches deep and 1/2 inch thick. Note, this will NOT be a CNC machine. I'm simply attempting to make very accurate cuts that need to be parallel to each other (interior and exterior). I purchased 4 linear rails with bearing blocks and hope to use them as the basis for this jig. I am undecided if I will attach this to the lathe bed or build a dedicated machine. I am leaning towards a dedicated machine primarily because the lathe is in a maker space. A jig will require set up and removal for each work day.

A preliminary mock up is shown in the pictures. Could use some assistance to determine if anything is inherently wrong with my ideas (quite likely). Ideally, the machine should be able to cut drums of various diameters from 8 inches to perhaps 22 inches. The Y axis therefore needs travel of 15 inches. (22-8)/2. A hand crank lead screw is planned for the Y axis, since it needs to move in small increments for each shell. The raw shell starts at around 1 inch thick and ends around 0.5 inch. I am removing roughly 0.25 inch from the interior and exterior. This needs to be repeatable and accurate.

The X axis will also use a lead screw, likely powered with a DC gear motor and motor controller. Ideally, I'd like to cut deeper shells, as much as 16 inches. However, I'm resigned to the fact that this may not be possible.

Specific questions:
- There will be a plate between the upper and lower bearing blocks. Is 0.5 inch aluminum sufficient?
- As shown in pictures, the X axis uses only one linear rail and two bearing blocks. Would two rails and 4 blocks be a good idea?
- Obviously, I won't be using plywood for the boring bar! What material should I use?
- Should the boring bar be attached directly to the bearing blocks as shown, or should I use a base to which the boring bar is attached? I would appreciate any additional thoughts about the boring bar, since I know that there are many options.

Appreciate any and all replies.

Thanks

Jim



 
You just need a big old used lathe, since it is dedicated to only one type of work you may change it as needed without issues in the future, if only turning and facing tubular material it would not require a tail stock nor a bed longer then the work required.

Is the device with the square segments printed on it a machine vision target?
 
What material is the raw shell? Make the raw shell to size from the start and not oversize? Make the raw shell to ID size then mount in the lathe and turn/sand the OD? Get a lathe and dedicate it?
 
Is the device with the square segments printed on it a machine vision target?

No, it's just a small box that I made using a laser cutter.
 
What material is the raw shell? Make the raw shell to size from the start and not oversize? Make the raw shell to ID size then mount in the lathe and turn/sand the OD? Get a lathe and dedicate it?

Shell material might be maple, oak, ash. Many different species, including some multi species. The raw shell has 20 staves, so there is no opportunity to cut it to a perfect circle before glue-up.
 
That means instead of just rigidly held edged tools, such as a boring bar or turning tool, you would mount something like a laminate trim router on the bar and use it to do the cutting. Generally it is tricky to cut thin tubular objects to begin with and using the energy of a powered cutter will require less force on the part being made. You could also use a live tool on the OD. This also would allow you to use a slow speed on the spindle design, simplifying that aspect of the project.
 
That means instead of just rigidly held edged tools, such as a boring bar or turning tool, you would mount something like a laminate trim router on the bar and use it to do the cutting. Generally it is tricky to cut thin tubular objects to begin with and using the energy of a powered cutter will require less force on the part being made. You could also use a live tool on the OD. This also would allow you to use a slow speed on the spindle design, simplifying that aspect of the project.

I like the idea! Thanks
 
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