Swiss Mode v Chucker Mode

Over the recent years, the CNC Swiss machine manufacturers have been making advances by leaps and bounds to make parts better and faster than ever before. Even the most complicated parts, which we couldn’t make five or ten years ago are now a possibility. One of my favorite capabilities is the machine ‘hybrids’, which means you can remove the guide bushing and use the main spindle and tools like a conventional lathe. This is known as the “chucker mode” as opposed to the using the guiding bushing in “Swiss mode”. Each way has its own advantages and disadvantages. You’ll soon be able to see that I am a big supporter of chucker mode because it has more upside in most cases.

I’m going to start out by explaining the conventional way with guide bushings on, which is the Swiss mode. In this mode, you can make long parts (as long as your bar stock anywhere from 12 to 20-foot-long cord). The guide bushing allows you to machine your part with your tool right next to the bushing, which allows you to have less tool deflection, better support from the collet and bushing on bent bars.

Some of the items I see as disadvantages are:

• parts only as good as your material
• if the bar is out of round it shows up on the parts as out of round
• the bar remnants are normally longer
• no material grinding cost

In some cases, on longer turns it’s a one and done cut. You can have chatter issue with out of round materials.

Non-guide bushing or hybrid mode (every machine manufacturer calls it differently). I call it “chucker mode”, as we are using the Swiss type machine like you would a chucker lathe. I see more pros to running in chuckler mode, such as shorter bar remnants if you’re running an expensive material because this could add up on profits by making more parts per bar.  You can also run material that is not ground (still has to be good material can’t be more than +/- .015”). Also, you can rough and finish better as you won’t fall out of the guide bushing. The OD’s have better concentricity like in a standard chucker lathe.

I’ve found in some cases it’s easier to remove bars too in chucker mode. Once part is made, I can go back in and redo a feature, that normally you couldn’t in Swiss mode. With the material hanging out and away from the guide bushing there is more room to get oil to the cutting tools, increasing tool life.

A few disadvantages are normally you can only run parts that are 2-3 length to diameter ratio. You can make longer parts, but you would have tune out and tool deflection issues. (If possible, in certain situations, you could run longer part and add rechucks). In most cases the stock is hanging out and stock is not supported while turning.

Changing the machine from Swiss to chucker mode and vice versa first couple times might take 45 minutes to an hour but can easily be done in 20 minutes once you get used to it after doing it a few times. It will also have to be a consideration on how to run a certain job.

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