Left hand cutters

[DAB_Design]

I've noticed I"ve never seen a reference to left hand cutters on this board. They are pretty common around our shop. Just wondering if it's due to the additional cost that they just aren't used in smaller/hobby shops.

What about reverse helix cutters? We use those every now and then also, but not nearly as common as the left handed cutters.

Is it just me or are the animated icons on the left moving alot faster than normal?

[mrainey]

What are the advantages of using left-hand cutters, except for specialized applications?

[DAB_Design]

One (usually why we used them) reason is that it's not as efficient to have programming program both a right and a left hand part (mirrored). So we invert the program at the machine. If you were to use right hand cutters on an inverted program then it would be conventional cutting. So we substitute the normal right hand cutters with left hand.

Also there are times when a left handed cutter will work in a certain condition better than right hand. For instance milling the end of a tall flange. A right hand cutter would be more likely to 'grab' (pull the flange into the cutter) the flange and either break the cutter, or worse yet, break the part. Thus a left hand cutter conventionally cutting would work better.

Reverse helix tools are used when milling the edge of a thin part. With normal cutter geometery, the cutting force pulls up on the part. If you are cutting a thin part, you take the chance of pulling the part up and undercutting it. With a reverse helix, the cutting force is in a downward direction. We use those on some .060 6-4 titanium sheet metal parts we do. If you don't have enough relief in the fixture, the chips seem to pack up and stick together. They also seem to leave more of a burr on the edge of the parts. But they do get the job done without pulling at the part.

[mrainey]

Do you have much trouble with operators trying to use the wrong tool? LH end mills are easier to spot than LH drills, but - you still have to look, and beyond that, know what you're looking at. A lot of the operators I deal with would never "get" it.

I prefer to do all the mirroring, etc. in the office, where I can be in control of the toolpath and climb/conventional mill as I see fit.

[E-Stop]

I use a Left-Hand endmill on one job only. I was having trouble with the part wanting to pull into the cutter because the set-up is not very rigid ( due to part geometry). The LH mill pushes the part down, which has proven to work really well on this one application.

I must agree with mrainey on the programming point. All of the programming should be done away from the machine and each part should have it's own unique program. Some try to run family of parts or similar parts with one program by changing a few variables or like DAB-Design, doing a mirror image. Even without a CAM program, a new program can be made for a similar part fairly easy just using Copy/Paste and Search/Replace functions. There are too many opportunities for mistakes and the people on the programming side should try to eliminate as many of those opportunities as possible for those on the machining side.

[DAB_Design]

mrainey, I'd be lieing if I said it never happens. In fact, I did it while I was training almost 9 years ago with a 6" facemill on titanium. Are those inserts supposed to glow orange? Hey, I was in training! But it doesn't happen too often. I honestly can't remember the last time I did it.

I'm not sure how, but in the past, I have caught endmills spinning the wrong direction at around 3000 RPM. I'm not sure why, but I can just tell that something just doesn't look right even when you can't see the individual flutes.

I would agree that it would be better to have seperate programs for each part in the majority of the cases. But it does cut alot of time. An average part in our shop, I would guess takes about 4 weeks to get from planning/programming to the shop floor.

E-Stop, as far as the copy/paste and search/replace. I wouldn't trust anyone, encluding myself, to do that. Most of the work we do is fairly complex, and thousands of lines of 5 axis code multiplied by multiple operations = way too much room for error. We don't actually do anything to the program when we run a mirrored part. We just invert whichever axis need to be inverted in the control(Y and A or X and B or all 4 if needed). Ok, we do edit the M03's to M04's. The same can be done in most control programs that people here use(Mach2 for instance), with just the click of a button.

There is one good thing about doing it that way....you only have to 'prove' the program once. But in the end, I'm not sure if the additional cost of cutters would justify not having programming take the extra time to do it right.

The problems I have with programming at the company I work at is a completely different subject. I could go on and on until I was red in the face, take a deep breath, and go on some more! Management knows about the problems we face on the shop floor, but refuse to solve them so to them I say ---->

[mrainey]

I could go on and on until I was red in the face, take a deep breath, and go on some more! Management knows about the problems we face on the shop floor, but refuse to solve them so to them I say

You've got lots of company.