[Sentinel]

I am new to CNC, and very new to woodworking, and have been having newbie troubles for past few weeks.

Today I've tried cutting a piece of oak, and ended up with damaged work.

Here is the picture:



What puzzles me is that other side of the same piece ended up perfect, like this (sorry for the blur):




Area I was cutting was 20 x 20cm.

I am not sure if this (breakage and 'hairy edges') happened because of wood, or because of something else.

Any pointers that could help this newbie are much appreciated

Thanks.

[rustamd]

I believe climb/conventional milling has something to do with that. Not sure which one should be used on wood

[Glidergider]

May I suggest trying this pattern on a piece of MDF. MDF is very stable and has no grain. Then, if it is the wood, try cutting with a reduced depth per pass.

Your photo is difficult to see, but it looks like you have either chips missing or your cutter moved out of its defined path. Either of those two conditions can be fixed if you reduce your depth per pass.

[ger21]

Looks like it's due to the grain of the wood and the cut direction. As was mentioned, lighter cuts can help, as well as using very sharp tools.

[spoiledbrat]

Try searching for MSC industrial supply for some good cutters. Sold under the guise of "Solid Carbide Aluminum cutting 2-fluted end mills", my cutters have remained sharp after 100's of hours of use. I only cut hardwood, and try to stay away from MDF and pine. I believe that the glue in the mdf and the resin in pine dull cutters quickly. The 1/2" endmills can be found on sale for around $30, and the smaller endmills can be found for less than $10. Compared to a harbor freight or Home Depot purchase router bits, these are more economical when you consider not having to sharpen or replace as often. The advanced precision and superior geometry of these helix-shaped cutters make easy work of wood.

Solid carbide, baby!

Rob

p.s. I have never tried the Onsrud wood router bits. I did hear they were expensive, though.

[Sentinel]

Thanks for the answers.

Cutter is brand new solid carbide 2-flute end mill (of the expensive type, not the cheapo stuff ). It cut other piece of oak before, and it turned out ok, so that's why I asked if wood grain can be the problem.

Wood got broken (and edges got screwed up) only on 1 side of the wood, so I will still presume it was the problem with wood piece.

It was 6mm end mill, I used 3mm pass depth, might be that I'll need to reduce it next time.

Thanks again.

[turmite]

This photo shows what the problem is. The grain enclosed in the green oval is from a crotch, or a fork between the trunk of the tree and a limb. Though the wood right at the crotch did not break as bad, all the wood surrounding the crotch is much harder and more brittle than the rest of the board. About the only way to keep this from happening is two fold. First it has already suggested to make shallow cuts, but there is also another step needed. Offset your tool path by about .75 of a mm to the outside. Cut to full depth less .5 mm and then let the last pass be full depth on your original toolpath. This means the bit is only shearing away .5 mm and there is less load on the cutter creating less heat, vibration and general stress! The cut should also be in a clock wise direction for a climbing cut, especially in this type grain structure.

Mike

edit: I just saw your depth of cut. I would reduce it to 2mm but still follow the offset toolpath example I gave you.

[jabguit]

Turmite is correct. When you have figure in the wood, such as the crotch's curly figure, the wood's grain direction changes wildly, as well as it's density. The best things to do are reduce the depth of cut and feed rate slightly. Too slow and you'll have to deal with burning. Wood is a natural material that contains resins which vary from species to species. Another idea would be climb cutting. Since wood grain changes relative to the feed direction of the tool, this is a solution for only a percentage of the work.

[nosplinters]

All great answers to help solve the problem. I'd also like to add that white oak can be quite fussy due to the nature of the gain. White Oak has a very open grain and can cause some headaches even with the sharpest of tools. Of course, being so hard, it will produce a rock solid sign with little chance of edge errotion. I've been working with White Oak for quite a while and had to purchase a Tormek sharpener in order to keep my edges razor sharp. I tend to go shuffle through a few 100B/F until I find a plank that has a crotch, curl and lots and lots of ray flake. Like mentioned before, make sure your bits are super sharp and minimize your depth of cut and you should be able to get past the tearout. I would try and avoid the highly figure wood though unless you're customer has requested it.

Now if you want the grain to really pop when you're all done, apply a few coats of boiled lind seed oil, some bison wax and a few coats of poly.

Good luck!
-Ed

[turmite]

Of course Ed, he could just cut all that bad, nasty ugly grain out of the boards and send the stuff to me! Of course I would take walnut, maple, cherry, mahogany............well the list could be endless, of all that "bad stuff"!

I make rifle stocks and pistol grips and you would be surprised how beautiful a very small crotch of oak can be when whittled down to a thin set of grips for a hand gun or knife!

Mike

All great answers to help solve the problem. I'd also like to add that white oak can be quite fussy due to the nature of the gain. White Oak has a very open grain and can cause some headaches even with the sharpest of tools. Of course, being so hard, it will produce a rock solid sign with little chance of edge errotion. I've been working with White Oak for quite a while and had to purchase a Tormek sharpener in order to keep my edges razor sharp. I tend to go shuffle through a few 100B/F until I find a plank that has a crotch, curl and lots and lots of ray flake. Like mentioned before, make sure your bits are super sharp and minimize your depth of cut and you should be able to get past the tearout. I would try and avoid the highly figure wood though unless you're customer has requested it.

Now if you want the grain to really pop when you're all done, apply a few coats of boiled lind seed oil, some bison wax and a few coats of poly.

Good luck!
-Ed

[turmite]

Jack I just visited your site......impressive. Now if you need an unbiased "permanent" tester of new products.......just let me know. I don't play too well, but I admire beauty and workmanship with the best!!!

Mike

Turmite is correct. When you have figure in the wood, such as the crotch's curly figure, the wood's grain direction changes wildly, as well as it's density. The best things to do are reduce the depth of cut and feed rate slightly. Too slow and you'll have to deal with burning. Wood is a natural material that contains resins which vary from species to species. Another idea would be climb cutting. Since wood grain changes relative to the feed direction of the tool, this is a solution for only a percentage of the work.

[nosplinters]

Ok, I had to check out Jack's website as well. Beautiful guitars I must day, even though I'm a percussionist I still appreciate fine craftsmanship. If you ever need some custom laser work, don't hesitate to give me a shout.

Mike: Got any pics of your gun stocks. I know my father is always looking to add new items to his gun collection. I'd like to have a nice figured grip on my . 44 V Dragoon too, but the one that's on it now, makes a nice impression on my hand after firing off a couple rounds.

-Ed

[cpsheets]

I'm no expert but I have to tell you that when you reverse the side of the grain that you cut on the first side the grain reverses direction on the other side when it is flipped over ,reverse the direction of your code will probably solve your problem./;

[turmite]

I hate to hijack this thread but you can check out my url

www.turnercustoms.com

I need a major overhaul of the web site and someday maybe I can get it done!

Mike

btw to keep this on topic in machining my gunstocks I have to deal with tear out all the time. Since most of my tool paths are created via cam it's hard for me to edit them like I would like to. Climb cut and sharp tools are the best you can do for the most part, but like Jack said the grain is always changing and it is hard to keep this problem totally at bay.

Ok, I had to check out Jack's website as well. Beautiful guitars I must day, even though I'm a percussionist I still appreciate fine craftsmanship. If you ever need some custom laser work, don't hesitate to give me a shout.

Mike: Got any pics of your gun stocks. I know my father is always looking to add new items to his gun collection. I'd like to have a nice figured grip on my . 44 V Dragoon too, but the one that's on it now, makes a nice impression on my hand after firing off a couple rounds.

-Ed