Cutting A Ring From A Plate

[pineyfolks]

I'd cut the slug out with a bi-metal hole saw then turn the outside diameter, but I do have a good selection of hole saws. Probably wouldn't be cost effective for one part but it is another way of doing it.

 

[tomw]

If you don't have a hole saw that large, perhaps:
1) machine the outside diameter
2) If necessary, drill large enough hole in center for aluminum cutting jigsaw blade
3) use a handheld jigsaw to carefully cut close to your final id
4) mount in chuck and clean up id.

You will have a lot less swarf laying around.

Cheers,

Tom

 

[ch2co]

Well guys, thanks for all the input. Since starting this venture, I have learned how to grind a Trepanning lathe tool, and it worked beautifully.
It took a few experimental trials and reforming of the tool as I saw how it cut and how to get the part of the tool that wasn't cutting out of the
way of the under the tool radius of the groove that the top of the blade was cutting out of the way while at the same time leaving as much meat
as possible for strength and rigidity. Still had a little bit of a problem with the gummy aluminum building up on the lower sides of the blade,
but in the future I will give a little more attention to putting a radius on this area and better polishing out on the grinder marks. I'm still in
kindergarten when it comes to this stuff.
As for holding the part in the lathe, I pulled the jaws off my chuck (Chuck's chuck) and applied several strips of double sided masking tape
to the chuck face. The aluminum part was held against the chuck face with a live center held in the tailstock. No lubrication was necessary.
The aluminum was 6061-T6 from a piece of scrap bought from the local aluminum recycler. Two previous rings cut for this pre trepanning
projects produced one and a half five gallon buckets full of turnings. The trepanning reduced this to about a gallon can's worth, took much
less time and provided two additional disks that will be use for parts being made for the telescope mount. I've included 6 photos of the process
and usage of these parts. The rings, with octagonal faces are used to hold accessories on the back of the telescope. The problem that I had
previously was that I couldn't adjust the position of these accessories for easy access. Now the accessory stages can be easily moved radially
and forward or backwards on the 'scope tube by loosening four allen screws pressing against little nylon rods that then press against the
'scope tube. The inside of the rings themselves are lined with 3M polyethylene tape to help preserve the tubes finish.

Chuck the Thankful Grumpy Old Guy

 

[joshua43214]

Wow! Great work!

You need to add some unsightly dents and a sloppy paint job.
If you take that out in public, everyone will be asking for one

-Josh