HELP! Problems with tear out

[relic_hunter]

Here’s my problem; I have many of the pieces pictured below to cut. Many of the corners are tearing out making them unusable. If you know how I can eliminate this problem I would greatly appreciate your assistance!

I have used a straight .25 end mill and an up-cut spiral bit. I have tried running at one and two inches per sec. Cut depths of .25 and .125 inches. The slower speeds have helped somewhat but the problem remains. Any Ideas?

http://i211.photobucket.com/albums/bb229/woodworks_az/IMG_6729.jpg

http://i211.photobucket.com/albums/bb229/woodworks_az/IMG_6726.jpg

http://i211.photobucket.com/albums/bb229/woodworks_az/IMG_6727.jpg

http://i211.photobucket.com/albums/bb229/woodworks_az/IMG_6728.jpg

[dlcw]

First thought would be to complete the milling operations on the smaller arches first then mill the longer arches.

This is kinda like doing a raised panel door - you first mill across the end grain then mill with the grain. Any chipout is removed when you cut with the grain.

I would also look into a downcut spiral bit for this type of work as it will shear the wood more so then cutting the wood. Should get cleaner milling operations.

[Gary Campbell]

If a downshear bit wont solve the problem, cut in the climb direction .015 offset to the outside (stepdown as per your normal) 3-4 ips and then do a full depth cleanup climb at 2 ips

[myxpykalix]

add some scrap to the end of the piece and extend your cut to end in the scrap that might help.

[LesLinton]

Don is correct. Common woodworking problem. using a hand held router, I always go across an end grain, down the long grain, across the end and back.

Just start across one end and proceed around. Should take care of it.

Good luck,

Les

[butch]

Like Don says, do the end grain cuts first, then have the machine do the 'with-grain' cuts. I do lots of cuts like this, and use a 1/4" down-spiral end mill. I either make a relief hole or cut end grain first.

[srwtlc]

To go with what the others are saying, change your start point to be somewhere on the downgrain portion so that you're not starting and finishing on the corner. Just add a node to that area if you don't have one and set it as the start point. Also, if you use a downcut or even a compression bit, instead of an upcut or straight, the bit will tend to deflect away from the cut not allowing subsequent passes to knock off the previous pass (conventional cut).

With the shape you have, even if you do the ends first, you may (most likely will) knock off the corner anyway.

Another thing that has always helped me is to unchceck "Sharp External Corners". The corners will still be sharp on your part, but the toolpath will round around the corner instead. Try it and look at the difference in the shape of the toopath. I had the same problem with this clover leaf shape and after changing that, no more problem. I use a 0.25" compression on them. I cut them 0.018" oversize in two 0.375" depth passes and then run a slow higher RPM finish pass at full depth through the onion skin. Cut starts/ends in the crook of the stem.

Scott

[feinddj]

You may have to split your vectors as well to cut with the grain on the arch

[gc3]

backing block. sometimes standard woodworking tools can do the job better and faster. this looks like a easy, faster one for the shaper