cut-off width

how wide should my cut-off be for parting off .125 dia barstock, but the part off side is turned down to .112 dia. i dont have a right hand cutoff (we are using a left hand), and no extended nose collet. i just started here and am implementing these things. i am currently using a .094 wide insert. i think i ned a right hand cutoff, an extended nose collet, and a .061 wide cutoff.

i have ordered this tooling, but this job turned into an expedite so im stuck with what i have. any help would be appreciated

We used exclusively RH cutoff tools and extend nose collets on jobs below 5/16" diameter. I use .039 wide cutoff tools for 5/16" and smaller diameters, but I do not do my back chamfers with the cutoff tools. I'll use a back turn or groove tool for those.

I run a lot of short parts, so using wider tools adds up to a lot of wasted stock and more tool pressure on the part in the sub collet.

I used left hand cutoffs and .098 wide inserts above 1/2" diameter stock.

Use the smallest width you can get away with and still have tool rigidity and good wear characteristics and strength. Probably an 0.040" would work well in this application.

WHen I started with cam machines years ago, Bechler had a guide you could follow to make the proper width cut-off tools based on the material diameter. Well, now we come into the modern age, and I no longer make any tools I don't need to. It is so much better just taking them off the shelf and using them. With that said, we use three different width cut-off tools in our Swiss machines, 1mm, 2mm and 3mm. We make plenty of parts up to 20 mm in A-286, 304SS, Kovar, 15-5, 17-4, etc, etc, etc, and I could never imagine using anything over 3mm for parting off. Most of our cut-off tools are neutral rake, so they can be used right or left. In your application I would use the 1mm (.039"), right hand with an extended nose pick-off.

Considering you have to produce the parts now and you cannot wait for the EN collet & RH c/o...the .040 to .060 wide for LH c/o and regular pick off collet should be fine.

Only thing to be concerned with is the safety cut-off process when you're cutting off the face of the bar during bar change. Depending on the material, sometimes small diameter bars deflect (due to the distance away from the guide bush) and cause chatter which may chip the tip of your cut-off tool.

When I encounter those conditions, I'll "manually" cut-off a new bar via the override and reduce my feed rate for that one time only.

Once you're in production, the support of the sub-spindle is more than sufficient to provide rigidity during the part off process.

Quote:

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Originally Posted by DCogswell

Considering you have to produce the parts now and you cannot wait for the EN collet & RH c/o...the .040 to .060 wide for LH c/o and regular pick off collet should be fine.

Only thing to be concerned with is the safety cut-off process when you're cutting off the face of the bar during bar change. Depending on the material, sometimes small diameter bars deflect (due to the distance away from the guide bush) and cause chatter which may chip the tip of your cut-off tool.

When I encounter those conditions, I'll "manually" cut-off a new bar via the override and reduce my feed rate for that one time only.

Once you're in production, the support of the sub-spindle is more than sufficient to provide rigidity during the part off process.

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Slow and low is the way to go. When the bar is changing every hour and you're running 24/7 its quite inefficient to manually load bars, especially if you run lights out and don't have capable night operators to be trusted to do such a thing.

Perhaps you're talking about even smaller diameters, but Ive run 3/16 brass and 303,304,416 stainless with a 12mm left hand cutoff without any issues.

Extended nose collets cost an arm and a leg and take quite a while to deliver, arent as accurate, and dont evenly clamp the part which produces a push on the part on pick off. I ordered up one collet I absolutely needed for a job that required a lot of mill work on a K16 and I needed the length simply because I had to support the part while milling and if I didnt have the EN I would have run the machine into itself. The collet took over a month to get to me after their quoted "2 weeks" Boss was not happy, and he had given me substantial lead time.

If you have to get the job up, you gotta do what you gotta do. Thats the biggest folly in machining if you ask me. Everyone only thinks of ideal situations which is more often than not not possible and you have to learn to work with what you have

Cheers

Quote:

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Originally Posted by SirDenisNayland

Slow and low is the way to go. When the bar is changing every hour and you're running 24/7 its quite inefficient to manually load bars, especially if you run lights out and don't have capable night operators to be trusted to do such a thing.

Perhaps you're talking about even smaller diameters, but Ive run 3/16 brass and 303,304,416 stainless with a 12mm left hand cutoff without any issues.

Extended nose collets cost an arm and a leg and take quite a while to deliver, arent as accurate, and dont evenly clamp the part which produces a push on the part on pick off. I ordered up one collet I absolutely needed for a job that required a lot of mill work on a K16 and I needed the length simply because I had to support the part while milling and if I didnt have the EN I would have run the machine into itself. The collet took over a month to get to me after their quoted "2 weeks" Boss was not happy, and he had given me substantial lead time.

If you have to get the job up, you gotta do what you gotta do. Thats the biggest folly in machining if you ask me. Everyone only thinks of ideal situations which is more often than not not possible and you have to learn to work with what you have

Cheers

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I hear what you're saying...most likely this job is not high volume, just an estimation on my part because it's on a "must-run-now" basis. Most jobs I've come across that are of any significant volume will at least give you some lead time to navigate through.

Even if someone had to start "now" and had to wait 2 weeks for the correct tooling, they'll just have to deal with the early inefficiencies. Many high volume jobs have a life-cycle of early inefficiencies corrected through experience on that particular job.

I would never suggest that doing anything manually on an automatic machine would be the norm. It was simply a work-around until the correct tooling could be obtained.