Rounding over ?

[d-m]

Is there a member out there that would show the proper use and set up of rounding over end mills I could sure use the advise.I see so many examples of bases with a nice rounded over edges and playing with the tools I can't seem to find the right height and depth to set the cutter.
Thanks Dave:wall:

 

[kvom]

Generally I try to "calibrate" these end mills on some scrap. I "zero" the tool by touching the flat bottom to the top of stock and the round shaft to the side. Then I move the tool down and in in small increments, Once you see a ridge being cut on either end of the arc then you know that's the limit for that axis. Write down how much you had to move each axis, and it should then work on the actual workpiece.

 

[Mainer]

There may be a clever way to adjust a corner rounding end mill, but if so I don't know what it is. Like KVOM I do it by trial and error. Since they are used strictly for appearance in most cases, "if it looks right it is right" is close enough.

On one occasion I solved the problem by advancing the cutter beyond the point of just cutting a radius and cut a step as well. Doing so makes a more interesting molding look for the edges, sort of like a strip of quarter round.

 

[d-m]

Thanks guys I will give this a try next weekend
Dave

 

[MachineTom]

Sometimes we can't see the tree's because we are on the beach. Take a 1/4" rounding bit, assume it is a full 90°, because it should be, measure the OD, mine is 1.002", there are 2, 1/4" flutes on the OD line so they add up to 1/2", if you subtract from the 1.002"D, the .5" of the flutes, the center diameter should be .502" and measurment proves to that result.

Measurement of the height of the flute was .250". So if you set the bottom and the side of the cutter as KVOM stated, then move down and in .250" you wil be there for the full radius.

I find the a less than full radius appeals to my eye, so I would move it .200 down and .200 in. If it was a large but thin plate then .250 in and .150 down would look better.

I came upon this at one of lifes 'DUH' moments, so after missing up a piece with the wrong eyeball setting, I measured the bits and then said 'DUH' of course.

 

[Ken I]

I normally start wide and guess to depth until a ridge appears - mark that position for later and work a thou or two shy. Then come out and go high - repeat to get that position.
Any ridges made during the trial and error phase are removed during subsequent machining.

Alternatively as suggested overdo it for an interesting edge - particularly a wooden base moulding.

I don't know of any reliable way to simply "go there" given the vargaries of cutters.

Ken

 

[ShopShoe]

Slight diversion of this thread:

Pretty much what is said above works for me. In addition, I sometimes actually like the look from using only part of the cut from a larger roundover (an idea stolen from woodworking and Norm Abram,)

What I can't sort out is whether normal or reverse feed (climb cutting) provides better results with these tools. I'm using a Grizzly GO4063 (X3).

--ShopShoe

 

[rkepler]

There is a spec for these (ANSI B94.19-1985), you can find it in Machinery's Handbook and in other sources. It will serve as a decent starting point for setting up as it has the diameter of the center. I usually have a zero at the edge so I drop the cutter on the top for the tool bottom zero (set the knee to zero, drop the tool onto the work and lock the quill), lower the table a bit and move away from the work to the radius of the tool tip. I typically feed down until I have passed the zero by the radius of the cutter. This way you can see the ridge that'll remain at the bottom before you do that finish cut - moving out a little bit early in the cutting process means that the ridge will go in the next pass.

Sadly I've never found a happy cut with a corner rounding endmill, they just bang like crap no matter if you take light passes, deep passes, climb passes, whatever. They're the most likely tool to pull work out of the vise I've ever seen. Cutting 440 stainless with one is not for the chicken hearted.

 

[aliva]

http://tomstechniques.com/portfolio-items/how-to-use-the-corner-rounding-end-mill/
Everything you want to know

 

[tornitore45]

If you are feeding DOC in one direction the portion of tool cutting gets larger and larger leading to stress and banging, even a light cut has a considerable width of the tool engaged. The trick is advance alternatively on both axes with lighter passes as you get close to full 1/4 circle. Naturally you have used the techniques described ti set your dials so you know when you are close to tangent.