Smooth cutout technique

[DickB]

My usual technique for doing cutouts on a 3/4" board is to simply set the Maximum Pass Depth to .25". It works, but usually leaves faint lines at .25" and .5" deep all around the cutout that can require a good deal of sanding to remove. I tried a new (at least to me) technique to combat this today and it worked quite well.

Once I had drawn my vector cut path, I duplicated it and left the duplicate in place, on top of the original. To one vector path, I assigned the 1/8" Straight Bit, set to a depth of .5" with a Maximum Pass Depth of .25". But, I set the offset to just past the path where a cut out would have taken place. In other words, when you assign a Cut Out or a flip cut, the bit will be offset .063" inside or outside the vector path. I set this first two-pass vector cut to .073" offset, just a bit larger than desired. Next, I set the second, duplicate vector with the Cut Out tool to full depth with no Maximum Pass Depth restriction. Because vectors are cut before cut outs, the vector cut was done first, in two passes, to .05" deep. Then, the full cutout took place, at full depth. But because of the earlier vector cut, the bit was really only cutting .25" of material, like a third pass, and taking of a fraction of an inch from the earlier two-pass cut, cleaning it up. No lines at .25" and .5".

I will probably make this standard operating procedure going forward.

62367 62366

[Digitalwoodshop]

I LIKE IT !!!!

Pretty Slick !!!!

AL

[bergerud]

I remember discussing that technique before and using a similar trick to beat the scalloping of the 1.186 cut outs. Now that the scalloping has been fixed, the "clean up" pass makes sense again.

I wonder if there is a danger to watch for - climb milling. I broke my first (and only) genuine CW cutting bit because of climb milling. It may be important to control the cutting direction.

[mikemi]

I have always disliked the 2 lines that it left, but this way sounds so simple.
Thanks for the tip. :-)

Mike

[brdad]

I've been using the 3/16" bit for cutouts and on the last few projects forgot to set the max pass and it's done fine on 3"4" oak and maple. I don't think there's any problem of the bit handling it, but there seems to be no mention in the manual or the forums from LHR as to whether they think the machine can handle it.

I also wonder if climb milling as bergerud mentioned would be an issue. It may actually be easier on the bit and machine to be cutting on both sides of the bit.

[DickB]

Something to consider, but since on the cutout the bottom third of the bit is cutting both sides, and the top shaving off only a hundreth, I wonder if climb milling is really a problem.

[bergerud]

Something to consider, but since on the cutout the bottom third of the bit is cutting both sides, and the top shaving off only a hundreth, I wonder if climb milling is really a problem.

You are probably right. Also since the last cut is full depth, the machine is going slower than it would if it was the last cut of a mult-pass. It would still be nice to able to control the cutting direction.

[spalted]

My gut feeling is climb cutting shouldn't be an issue.
Climb cutting is common in power feed situation. Like a shaper with a power feeder. The only issue with climb cutting it when doing it free hand and you are not able to control the feed rate. Then it becomes a safety issue.

[bergerud]

If you do a full depth climb mill with the 1/8 cutting bit, it will break. I know!

[spalted]

If you do a full depth climb mill with the 1/8 cutting bit, it will break. I know!

You know after I posted I was thinking about it more.
The climb is not the real problem.It's the fact that with a CW, it is a controlled cut in one sense, but we still don't have control over the feed rate.
That's what happens when I talk without thinking.....lol

[DickB]

Also since the last cut is full depth, the machine is going slower than it would if it was the last cut of a mult-pass.Hadn't thought of that.


It would still be nice to able to control the cutting direction.Then we'd start complaining about breaking bits 'caused we chose the wrong feed rate!

[mtylerfl]

...

Then we'd start complaining about breaking bits 'caused we chose the wrong feed rate!

Probably so. Plus, depending on the grain direction of the board placement in the machine, you have to figure out whether Climb or Conventional cutting direction would yield the cleanest cut on the majority of the parts being cut out. I go through this decision-making process all the time for material placement/grain direction on the ShopBot...and...sometimes I'm wrong. (Thank goodness for sandpaper.)

[DickB]

(Thank goodness for sandpaper.)Amen to that!