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

[JimDawson]

-Can I put the bearing blocks closer together on the top platform to get more reach? Any minimum distance between the blocks?

I would think 3 or 4 inches apart would be OK if the platform is strong enough.

-Each axis will have a metal plate/platform. What thickness should they be? Should I use aluminum or steel?

In this case mass is your friend to reduce vibration. I would use steel 3/4 to 1 inch thick for the plates.

 

[John Hasler]

The OD can't deviate from 13.875 inches. In my experience, best results are achieved with a very fine final cut. This will minimize sanding. Also, the thickness may differ from one shell to the next.

I think that argues for Wreck's solution. You still might want to use live tooling.

 

[chips&more]

Here's a raw shell before cutting. Both interior and exterior need to be smooth and flat.


View attachment 139414

Sorry, but that is not the strongest approach and very easy for it to split and unstable. Have you considered wrapping a mold with veneer wood. Then you would have a plywood type of end result and very strong and durable. If you insist on using the method you have. You can easily pre-arc the staves on the ID before gluing. Then glue it all together on the mold for a finished ID. Now just thinking, you could then on a stationary belt sander with fixture, finish up the OD. No need for a lathe or rail contraption.

 

[chips&more]

Not trying to hijack. Just trying show going outside the box in thinking. I made the corner block in the pic without a lathe. I actually made about 300 of them. I did not use a lathe. I went outside the box. Made all the wood you see in the pic(s). I could have filled up a truck with jigs and fixtures when the whole project was done. Yes, you can glue wood together in the form of a rough circle. But is that the best? What is the best? Is using wood necessary? Are you making a percussion drum?

 

[auto.pilot]

Sorry, but that is not the strongest approach and very easy for it to split and unstable. Have you considered wrapping a mold with veneer wood. Then you would have a plywood type of end result and very strong and durable. If you insist on using the method you have. You can easily pre-arc the staves on the ID before gluing. Then glue it all together on the mold for a finished ID. Now just thinking, you could then on a stationary belt sander with fixture, finish up the OD. No need for a lathe or rail contraption.

Plywood shells are sort of nondescript and are used by most low end manufacturers. Stave drum shells are preferred by many drummers and custom drum builders because the amount of glue is limited which makes for a more sesonant shell. stave shells may be made up of many different species and patterns, as with segmented turning.

 

[auto.pilot]

Not trying to hijack. Just trying show going outside the box in thinking. I made the corner block in the pic without a lathe. I actually made about 300 of them. I did not use a lathe. I went outside the box. Made all the wood you see in the pic(s). I could have filled up a truck with jigs and fixtures when the whole project was done. Yes, you can glue wood together in the form of a rough circle. But is that the best? What is the best? Is using wood necessary? Are you making a percussion drum?
View attachment 139439
View attachment 139441

Beautiful work! these are indeed percussion drum shells, which need to be precisely 13.875 inches in diameter. smooth, flat and of uniform thickness.

 

[John Hasler]

You can easily pre-arc the staves on the ID before gluing.

I like that. He could even machine both ID and OD of the staves to the proper shape and just slightly over target thickness so that minimal sanding would finish the part. If the OD is more critical than the ID perhaps an external mold might be better.

 

[auto.pilot]

I like that. He could even machine both ID and OD of the staves to the proper shape and just slightly over target thickness so that minimal sanding would finish the part. If the OD is more critical than the ID perhaps an external mold might be better.

Very interesting concept, which had never occurred to me.

 

[chips&more]

I have no direct knowledge with a large thin shell made out of segmented wood. But I would suspect that changes in ambient humidity would play a large roll in trying to mess with that 13.875 critical dimension, even if the wood was sealed. You have that dimension carried out to the 0.001”. That would be an interesting challenge if made out of any type of material! And using the most elaborate machinery. And metrology standards to trace your findings. I commend your efforts.

 

[chips&more]

Plywood shells are sort of nondescript and are used by most low end manufacturers. Stave drum shells are preferred by many drummers and custom drum builders because the amount of glue is limited which makes for a more sesonant shell. stave shells may be made up of many different species and patterns, as with segmented turning.

There are also some VERY beautiful burl veneers and rare exotics too that could be your last layer