Trepanning Job? Not sure

[Janderso]

Hey all,
I am making a small radial bender.
The outer ring needs to be 4 1/2” -as is, the ID is 3.750” (actually, i’ll take the OD to 4.250”)
The depth is 2 1/2”.
I would like to keep the inner part rather than making a pile of chips.
Can it be done?
What would you use?
I have a piece of 1” HSS. I could grind a trepanning tool. I may be done grinding it by Monday afternoon if I start now

 

[mmcmdl]

Trepanning that slug ?

 

[homebrewed]

I wanted to do something similar (the shape, not a bender). I used my rotary table and an end mill. It was a pretty deep circular slot so I continuously sucked the chips out with my shop vac. This approach is all about the kind of workholding stuff you've got lying around.

Even though I moved the end mill back & forth some to provide some clearance for chips, for much of the job both sides of the EM were cutting at the same time so my DOC's were pretty small. This was with a small benchtop mill so folks with a "real" mill could probably get the job done quicker than I could.

 

[DAT510]

I'd say take a swing. Nothing like trying and learning!

Here's how Paul Debolt does it.

 

[MrWhoopee]

Trying to trepan that deep is not for the faint-of-heart. If you do make it through, the slug will break your tool when it comes free and binds in the hole.

 

[pdentrem]

I would not attempt this. I have a trepanning tool that can reach 1" deep and it is tense to use. I have broken the insert and even the holder a few times. Lots of lube and repetitive clearing doesn't guarantee a successful job. With over 2.5" of stick out I would hand the job over to the EDM machine and have success which out the stress or find a guy with waterjet and pay the man.
Pierre

 

[rabler]

You could try a hole saw mount in your lathe tailstock. But I'd probably go online and find a piece of heavywall pipe,

 

[Janderso]

I wanted to do something similar (the shape, not a bender). I used my rotary table and an end mill. It was a pretty deep circular slot so I continuously sucked the chips out with my shop vac. This approach is all about the kind of workholding stuff you've got lying around.

Even though I moved the end mill back & forth some to provide some clearance for chips, for much of the job both sides of the EM were cutting at the same time so my DOC's were pretty small. This was with a small benchtop mill so folks with a "real" mill could probably get the job done quicker than I could.

I have a 10" rotary table. If I took <.050" depth of cut with a 3/8" end mill with an air charge blowing the chips that would work.
But now I'm thinking if the mess and time would be worth it.
I'm leaning toward boring it out. I have a 1 1/2" mt4 drill bit. That's a good start.
Had I thought about first I would have made this based on 4" pipe.
Live and learn....constantly

 

[Janderso]

You could try a hole saw mount in your lathe tailstock. But I'd probably go online and find a piece of heavy wall pipe,

I tried McMaster's for a piece of thick wall pipe. Nothing within my specs that I could find.
I assumed if they didn't offer it no one would?

 

[Janderso]

$63 plus shipping for this hunk of metal. I talked myself into ordering it as I was in the job nothing as I used my scrap pile.
Will a waterjet -EDM cost more than a 3 1/2" hunk of metal 3" long? See where I'm going.
I'm having a chip sale.....