Corner round cut, how would you do it?

drcoelho · Dec 11, 2018

Presume the following:
- got a 10"x20"x1" sheet of mild steel
- need to cut 1/2" radius corners on all four corners, accuracy not critical, this is for aesthetics
- my mill is a Deckel FP1

My ideas:
- vertical head, corner rounding end mill, mount work on side in vice, use x-axis to move into work. Concerns: the 20" side exceeds my headroom and thus would have to remove my table and mount directly to z-axis, also concerned about having minimal contact with the work piece with a lot of it extended up without support

- vertical head, straight end mill, mount flat on rotary table, use rotary to move into work. Concerns: don't want to move that heavy rotary table on/off machine just for this little job

- horizontal, corner rounding end mill, mount work flat on table, use z-axis to move into work.

- horizontal with arbor and overarm, corner rounding cutter, mount work flat on table, use z-axis to move into work.

What approach would you take?

sfriedberg · Dec 11, 2018

Since the radius is non-critical, I would rough the corners out on a bandsaw or by chain drilling or just milling 45 degrees across the corners, then refine the curves on a good-sized belt sander. Actually, since the radius is only 1/2", I might just go directly to the belt sander. The time spent grinding might be less than the time spent on machine setup.

hanermo · Dec 11, 2018

Em..
this might be ghetto and politically incorrect, maybe, but either a big grinder or a good hacksaw would cut them in short order.
Finish with end mill, or belt sander if you can get access to an industrial one.

I did note the 1" thickness, and normal grinders and saws would struggle / fail with it.

A good plasma or laser would cut it to near-net by hand or machine and require dressing only.
Or waterjet.
The bigger/better tool will do in 60 secs what manual methods take 4 hours to do.

I would probably find a plasma/laser shop, and finish with a festool fs150 hand held sander.
Or a grinder with flap discs, depending.
The festo is very heavy (and noisy).

My expectation would be about 1000$ for the work- half a day and half to the laser shop.

Ries · Dec 11, 2018

this is why I built a table for the rotab, at about the same height as my mill table, just behind and to the left of my milling machine (not a deckel, but the same principles apply)

I never lift the rotary table. I crank my mill table to very slightly below the table holding the rotab, and slide it on. Reverse the height difference for removal.

Because the rotab seems to me the easiest tool for this job.

AlfaGTA · Dec 11, 2018

Mount on the table flat and use the horizontal spindle and a corner rounding cutter....

10 x 20 pretty large to camp on a rotab...unless you can drill holes in the plate....Not much room for clamps and the like.....Going to be a bit heavy and think
less moosing about is a good thing....On the table you can do it in two setups...using the horiz spindle....

Could draw it up .and calculate the "X" "Y" moves needed to do a profile in small steps cutting using the "Z" using a ball end mill.....Bit tedious, would need to finish by hand to blend the steps.

Cheers Ross

drcoelho · Dec 11, 2018

Ross, as usual you are very helpful, thanks!

thanvg · Dec 12, 2018

AlfaGTA said:
Mount on the table flat and use the horizontal spindle and a corner rounding cutter....

...

Hey Ross,

corner rounding cutter (like cutter for horizontal arbor) or corner rounding endmill? I can see how it can be done with a corner rounding endmill in the horizontal spindle with the part flat (working along Z) but you would have to fix it on its side for a cutter to do the job, no?

BR,
thanos

Edit: ok, now I see, you can use the horizontal cutter like the end mill, along Z....stupid me.

moonlight machine · Dec 12, 2018

I would just put it on the cnc and do it, easy peasy.

JCByrd24 · Dec 12, 2018

For a non-accurate radius of that size work scribe a nice radius and just work up to the line with an standard end mill and then file or belt sand the facets away.

drcoelho · Dec 12, 2018

moonlight machine said:
I would just put it on the cnc and do it, easy peasy.

Yes, but poor me...only little Deckel FP1, no CNC.....

CarbideBob · Dec 12, 2018

One piece or 1000 ??
Bob

thermite · Dec 12, 2018

AlfaGTA said:
Mount on the table flat and use the horizontal spindle and a corner rounding cutter....

THIS. On a Deckel. Cutter is a stock size, and I have them.

Challenge? I don't HAVE a Deckel!

Mounting a 10" X 20" up to present each corner off the Horizontal table I DO have is more "tedious", and I don't want to mess with the rotab or pivot and and endmill at a full one-inch, outside corner radius, not inside, of imperfectly predictable alloy, for a non-revenue tasking, either.

Solution? Just de-burr and sorta chamfer them with an angle-grinder and leave them "square-ish" with an eyeballed-on facet or an eyeball-grade much smaller radius.

You DID say it was only for looks, yah? Reducing "sharps" as might crunch flesh more my goal.

Gots to have SOMETHING in the shop uglier than me and less expensive!

RC Mech · Dec 12, 2018

hanermo said:
My expectation would be about 1000$ for the work- half a day and half to the laser shop.

You charge $1000/day? ie per 8 hours?

That’s a $270 plasma cut 44W plate with 0.5 hrs of “hand finishing” at $75/hr...

thermite · Dec 12, 2018

RC Mech said:
You charge $1000/day? ie per 8 hours?

That’s a $270 plasma cut 44W plate with 0.5 hrs of “hand finishing” at $75/hr...

And no go-order, go-fetch, go-drop, go-recover, nor paperwork, nor burden, nor GST nor VAT taxes?

That's not a $1,000 job. That's a lose-lose AKA "no-bid" time and potential credibility-waster.

AKA "Just go and DIY it THIS way, good luck!" brush-off.

Spruewell · Dec 12, 2018

Just lay that thing down flat on the table. Set up a couple stop points to locate it and clamp it down. Put the radius cutter in the horizontal spinner and set your x,y to hit the corner how you want and run the z to cut it. Then rotate the workpiece 90 deg., set it up against the stop points and run the z. Repeat and repeat. All done. Shouldn’t take more than an hour. 1/2 hour or less if you are good

drcoelho · Dec 12, 2018

CarbideBob said:
One piece or 1000 ??
Bob

About 20 pieces, for my own use.

drcoelho · Dec 13, 2018

Spruewell said:
Just lay that thing down flat on the table. Set up a couple stop points to locate it and clamp it down. Put the radius cutter in the horizontal spinner and set your x,y to hit the corner how you want and run the z to cut it. Then rotate the workpiece 90 deg., set it up against the stop points and run the z. Repeat and repeat. All done. Shouldn’t take more than an hour. 1/2 hour or less if you are good

You confirmed an idea I was thinking but didn't mention, e.g. the use of stop points, very helpful suggestion, thx.

thermite · Dec 13, 2018

drcoelho said:
About 20 pieces, for my own use.

Yah need to SAY SO "right up front", 'coz THAT makes a difference, actually!

Stacked and clamped or temp-welded you now have a nice 20" long + get-clear pass done just four times. Easier yet if the plates are first drilled for some grid or other form of mounting holes. One can use those holes.

Separate the 20 sub-plates and the de-burr isn't even as much work. THIS way, the Deckel prolly can't stand the mass of 20 at a go, but my mill can do.

Or two runs of ten. Or however many - at least in fours or fives - yah can manage.

You get the idea. Reducing the monkey-motion so the horizontal just "eats" off fewer, simpler, set-up and clamping steps instead of needing all the tedious foreplay, minding the cut, and post-op asiding, one plate at a time, twenty times, and Oh, BTW, don't get tired or distracted and enter into a trial marriage with the shop dog for even one go, yah?

Goal is to work the mill, not have the mill work YOU!

Wannabee jugglers should just run-off and join the circus.

drcoelho · Dec 13, 2018

Ah, well maybe a little MORE information...not actually 20 identical plates, but a variety of plates that vary in size from one to the next.....

BUT, I do like your idea of stacking when the plates match in size.....

thermite · Dec 13, 2018

drcoelho said:
Ah, well maybe a little MORE information...not actually 20 identical plates, but a variety of plates that vary in size from one to the next.....

BUT, I do like your idea of stacking when the plates match in size.....

Stacking is the sort of thing adding a 7+ HP Alzmettal AB5/S drillpress with over nine inches of travel and selectable power-downfeed and coolants to the poor struggling Walker-Turner engenders.

Keep that in mind if the plates are also to be grid-drilled for tapping.

My "way" was to do the first two holes a tad undersize as extremes on the diagonal, upset steel drill rod into those as rivets, do all the other holes, drill those locating master/clamps back out at the end and ream up to the same size as the others.

There are MANY things in this world where as good a match as can be had is crucial, but the absolute hole position is much less-so.

Corner round cut, how would you do it?

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