Newbie- First Tooling Question

[HMB3000]

scrap wood is cheap

[thackman]

I've been going down the CNC path for 3 years and I've got a big box of unused endmills to prove it. Maybe you can learn from my mistakes. I had an X3 for a year and I've had my Tormach for about 6 months.

My vote would be for you to pickup a relatively small selection of HSS cutters and buy two of each. One to learn with and one to finish up the rest of the night once you learn what not to do. When I was starting out my carbide endmills only lasted one or two nights. Carbide is great but it's real easy for a beginner to chip the corners off a carbide endmill. Rough handling, errors while zeroing, and some interesting revelations with the wizards (one of them defaults to CCW), incorrect speeds and feeds all took their toll quickly. I picked up two full sets of HSS endmills and assorted ones every other month as the usual sales rolled around and I ended up with a big bin of endmills that I never use. The biggest issue is usually length of cut or odd diameters. I would often pick up a range of sizes which I later realized relatively pointless w/ CNC. You can skip a lot of the intermediate diameters since they just cause needless tool changes. I also noticed that I was picking up too many stub endmills. Everyone was recommends the shortest possible endmill to maximize rigidity and stub endmills are always on sale somewhere so that's what I was buying to build up stock. Once I started using the mill frequently it dawned on me that .25" endmill w/ .25" DOC isn't ever going to be used when I'm always working on 1/2" and 3/4" 6061 plate. And then I realized that all my standard length cutters were only occassionaly being used. You really need to consider how thick your stock is and how large of an endmill you can get away with. I now use my overstock of endmills when I'm experimenting and I have a very small set of production cutters. For any of the softer materials I'd recommed starting with all Long or Extra long cutters and then later pick up some shorter ones if you need to improve your surface finish. Just look at the parts you want to make and pick a large endmill for roughing out the part, and intermediate endmill for cleaning up internal corners etc, and a small endmill only if you can't get away without it. Larger endmills are much more productive than the little ones. I try to get at least 80% of the material removed with the largest endmill. All of this seems like common sense but for some reason it's wasn't obvious when I was starting out.

Since I made it out of the beginner stage and graduated to novice (about 4 months) I've gotten along fine with just these 7 endmills. Once I wear out the High Speed Steel cutters I'll replace them w/ carbide.

(SL standard length, EL Extra Long)
For UHMW I use :
1/2" SL HHS 4FL
5/16" SL HSS 4FL
1/4" EL Carbide 2FL
3/16" EL Carbide 2FL

For 6061 I use :
1/2" SL HSS 2FL
1/4" EL HSS 2FL
3/16" EL HSS 2FL

[sharpshooter90]

Originally Posted by justgary ... And I get an image of that guy with the lawyers and the rag in his ball screw from early December. I looked through the back posts and couldn't find where hsm had promised him anything about Tormach. Of course, a good portion of that thread is gone now. Maybe I'm wrong. Either way, perhaps we all get a rag in our ball screws every now and again. How we handle it is a good portion of who we are. Remember, character is what you do when no one is looking. - Just Gary

That whole thread disappeared with a promise from the moderator to post the outcome of the dispute. That promise never came through- maybe the troll was that same guy under a different name.

[thackman]

I re-read your first post and had forgotten that you had a manual mill. Understanding manual milling is a big bonus that I didn't have when I jumped into it but CNC is very unforgiving. Tool life and surface finish are important but only after you get to a point were your G-CODE is telling the machine to perform reasonabe actions. At 60ipm the Tormach is very slow compaired with full size production machine but that's 1 inch per second. I don't have the TTS and had a couple of instances where I forgot to re-zero after a tool change. In one case I was doing a tool change and I was above a strap clamp. When I pressed go it was supposed to go to a save Z of 1" but instead rapided straight down into the clamps. It put a 3/8" deep hole in the clamp before I got to the e-stop. It often takes about 0.5 to 1 second for the machine to get it trouble and about 2-3 seconds for you to react. After a few of those your reaction times will begin to improve and you'll realize the true value in air-cutting the first part and maintaining absolute focus during tool changes and zeroing. I've been around tools my whole life and approched CNC milling with confidence but when you tell a computer to shove this spinning piece of metal into that one over there it's becomes a whole new ballgame. Once you become confident that what you tell it to do and what you expect it to do are reasonably close then you can start experimenting with the fancy endmills. A $50-$100 uber endmill rated for 1000's of hours lasts about .001 seconds when it hits a vice. I started off with CAD experience and had far more confidence in my newly acquired CAM skills than was warrented. After I got over that disappointment and learned a bit more CNC became fun again instead of just expensive. My solid models and toolpaths were looked great until I took them to the mill and realized that you have to plan for clamps . Someone forgot to tell me that efficent fixturing is an art until itself . Now I try and keep things simple.

[philbur]

Looks like it is time you got a T&CG and learned how to use it.

Used machines can be surprisingly cheap.

Phil

Originally Posted by thackman I've been going down the CNC path for 3 years and I've got a big box of unused endmills to prove it. Maybe you can learn from my mistakes. I had an X3 for a year and I've had my Tormach for about 6 months. My vote would be for you to pickup a relatively small selection of HSS cutters and buy two of each. One to learn with and one to finish up the rest of the night once you learn what not to do. When I was starting out my carbide endmills only lasted one or two nights. Carbide is great but it's real easy for a beginner to chip the corners off a carbide endmill. Rough handling, errors while zeroing, and some interesting revelations with the wizards (one of them defaults to CCW), incorrect speeds and feeds all took their toll quickly. I picked up two full sets of HSS endmills and assorted ones every other month as the usual sales rolled around and I ended up with a big bin of endmills that I never use. The biggest issue is usually length of cut or odd diameters. I would often pick up a range of sizes which I later realized relatively pointless w/ CNC. You can skip a lot of the intermediate diameters since they just cause needless tool changes. I also noticed that I was picking up too many stub endmills. Everyone was recommends the shortest possible endmill to maximize rigidity and stub endmills are always on sale somewhere so that's what I was buying to build up stock. Once I started using the mill frequently it dawned on me that .25" endmill w/ .25" DOC isn't ever going to be used when I'm always working on 1/2" and 3/4" 6061 plate. And then I realized that all my standard length cutters were only occassionaly being used. You really need to consider how thick your stock is and how large of an endmill you can get away with. I now use my overstock of endmills when I'm experimenting and I have a very small set of production cutters. For any of the softer materials I'd recommed starting with all Long or Extra long cutters and then later pick up some shorter ones if you need to improve your surface finish. Just look at the parts you want to make and pick a large endmill for roughing out the part, and intermediate endmill for cleaning up internal corners etc, and a small endmill only if you can't get away without it. Larger endmills are much more productive than the little ones. I try to get at least 80% of the material removed with the largest endmill. All of this seems like common sense but for some reason it's wasn't obvious when I was starting out. Since I made it out of the beginner stage and graduated to novice (about 4 months) I've gotten along fine with just these 7 endmills. Once I wear out the High Speed Steel cutters I'll replace them w/ carbide. (SL standard length, EL Extra Long) For UHMW I use : 1/2" SL HHS 4FL 5/16" SL HSS 4FL 1/4" EL Carbide 2FL 3/16" EL Carbide 2FL For 6061 I use : 1/2" SL HSS 2FL 1/4" EL HSS 2FL 3/16" EL HSS 2FL