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Strategies for large holes in 304

T

Tichy

Aluminum
Joined
Jan 1, 2019
I need to make some 52mm diameter holes through 304 stainless steel in my VMC.

The material is a 250mm radius 20mm thick disc.

The fixture is untested (custom-built jaw expansion for the vise) so stability may be suboptimal. I may have some ideas how to make it better.

I have at my disposal a 52mm Trigon insert drill. I have also considered ramping with a Seco 32mm high feed face mill and spiraling with an Iscar 16mm 7 flute endmill (which I don't have at the moment.)

Other than that I have a pretty wide assortment of solid end mills though none really perfect for the job.

We're talking 5 discs and then 200 more if we get the contract. If we do these will probably be a mainstay.

What would you suggest? Namely: How slow can you go with a 52mm insert drill? Tips for combating poor stability and reducing vibrations?
 
Tichy said:
I need to make some 52mm diameter holes through 304 stainless steel in my VMC.

The material is a 250mm radius 20mm thick disc.

The fixture is untested (custom-built jaw expansion for the vise) so stability may be suboptimal. I may have some ideas how to make it better.

I have at my disposal a 52mm Trigon insert drill. I have also considered ramping with a Seco 32mm high feed face mill and spiraling with an Iscar 16mm 7 flute endmill (which I don't have at the moment.)

Other than that I have a pretty wide assortment of solid end mills though none really perfect for the job.

We're talking 5 discs and then 200 more if we get the contract. If we do these will probably be a mainstay.

What would you suggest? Namely: How slow can you go with a 52mm insert drill? Tips for combating poor stability and reducing vibrations?
Click to expand...

Stock thickness is less than HALF the hole diameter?

I'd want to annulur cut / trepan, or a reasonable facsimile thereof. Not full-diameter "drill" nor plunge-mill, either one.

The drill seems unwise, what with "breakout" & c.

Got a powered rotab? Can your VMC not interpolate?

Could was, ROUND "disk" stock, ROUND bore, a lathe could do the better job?

Don't HAVE a lathe? Get quotes. Round stuff, rings and flanges, is their ordinary rice-bowl- nuthin' special.

"Diamond" shape? Rectangular, rounded corners? Other odd shapes?

NOW you need a mill! (EDM Waterjet, plasma...) .. but "classically", simply STACKED and pre-drilled on an ignorant drill-press, three to five or so, each go.

:D
 
To clarify there are six 52mm holes at different positions. The material is a disc but one side is shaved off leaving a ~160mm straight line, I use this for fastening the piece.
 
Tichy said:
Not an option, we don't have one and I'm not high up on the food chain to suggest to outsource.
Click to expand...

Hem's sake. Newest flunky on the floor makes a common-sense suggestion to a foreman, and it DOES make sense?

Foreman carries the idea up the "food chain" until the Chairman of the Board thinks it was HIS idea.

Everyone gets to live longer and eat better, who cares where a better idea originated? They'll either know your name "someday". Or never.

BFD, so long as yer paycheck doesn't bounce off the back of a team doing stuff the hard and expensive way so damned often they lose their economic and AVAILABLE TIME ass, whilst wiser competition gets all the work and even makes MONEY at it!
 
I'd support it clamped to a piece of MIC-6 on the table and get after it with an inserted high feed mill. I don't like drilling in a setup like that where you've got flex of the workpiece lowering the clamping force, not to mention the inwards pressure of the jaws will make the material move around as you remove parts of it.
 
Tichy said:
Oh hell why not, here you have a pic so you know what I'm talking about.

View attachment 276932
Click to expand...
If it was me think I'd ditch the vise and clamp the part down to a 1" plate with some locating pins. That would put some support under the cut.

If I was hitting my tolerance and finish requirements with the insert drill, that would be my tool of choice, maybe follow with a chamfer mill to break the edge.
 
I think I'd try to hold onto that thing just a little bit better and rock that Trigon drill. I love my Trigons. You can't stack drill with them but if you had a Komet Duon you certainly can. Pentron too but not as stable. Even if you don't have coolant thru, at that plate thickness the Trigon will work perfectly fine with a good blasting flood coolant. I did hundreds of holes in 3/4" CRS at 7/8" and 1 5/16" with flood before I had the thru coolant working. Zero problems. Not 52mm I know, but that should allow even more coolant ingress with all the chip room in the flutes.
 
Personally, I think Thermite gave you the best answer in post #2. Annular cutter. You'd have the holes done already and with a decent tolerance. I don't know how common 52mm cutters are, but 2" is everywhere and you could finish with any number of methods.

Quick look shows 2", 50mm and 53mm under $100 ea.
 
Well, update:

The fixture worked. Ran the drill slow (Vc100 F.08) and there were no stability issues. That said I realize I could've done this a ton better. I should've put two vises together in order to get the required width and then placed the custom jaws at the bottom of them. (And they should've been wider.) I also think that yes an annular cutter would be better.

Bottom line it worked but for safer and faster machining a fixture update is needed.
 
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