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Context: I have a paper roll of about 8 in (20 cm) diameter mounted in a 3 inches core (7.62cm). Its length is about 1.2 m. The paper is bond of 95 g/m2. I have to cut slices of it of about 10-18 cm in length, down to the paper core.

As this is a very eventual task, I can't afford a log slitter, which is the right tool for the task, so I'm trying to do it in either a lathe or a cutoff machine.

What I've tried: In the lathe I've tested with two different options: a fixed blade (a knife and a machete) and a rotating one (a lightweight circular saw with wich I've used ceramic and wood cutting discs). The machete produces the best cut, but as it's fixed, it dulls very quickly. The circular saw produces a lot of small paper chips that cause problems in the process that follows after the cutting.

I've experimented with different RPMs in the lathe, specially in the trials with the fixed blade, but haven't quite controlled for the feed of the blade into the roll. With the circular saw the RPMs of it are so high (5800), that I'm afraid the relative speeds (even if I have rotation of both pieces in the same direction) are too high (diameter of the cutting disc is about 19cm or 7.5 inches). In the lathe I've mounted the roll both between points (as standard steel would be) and on a central bar (a core inside the core) to avoid tightening of the cutting area.

In the cutoff machine I've tried with discs of different tooth sizes, but all of them end up burning the paper in the cutting face (I don't have the RPM of the cutoff machine, but I can provide it in a few hours).

I have searched for available information on speeds and feeds for paper in log-slitting operations, but have found nothing so far, and the available tables of speeds and feeds are just for metals and some plastics.

What my expected result is: I'll appreciate if someone can provide an adequate speed and feed value for cutting paper, or if can point me in the right direction.

Regarding the cut of the paper roll: I need a cut that is as clean as possible, without significant burning, that requires as less sharpening of the tool as possible, and that can be considered safe for the operator.

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If a knife is working but has poor edge retention your bet bet might be to look at a harder blade.

It is also possible that, if you are getting hot enough to scorch the paper, the temper of the blade is being affected. Similarly applying a dry lubricant (eg PTFE spray) to the blade may also help if that if compatible with the rest of the process.

It might be worth trying High Speed Steel for the blade, something like a parting tool blank may work as they are already a suitably flat, relatively narrow section. With care you should be able to grind it to a cutting edge without needing to heat treat it afterwards. Alternatively a section of a scrap HHS disc saw may work.

The edge geometry will also be crucial. I woudl suggest that something similar to a wood chisel would be a good starting point ie a fairly acute angle on one side only with a small secondary bevel. Even a slight hollow grind on the primary bevel may help and give some clearance to help reduce heat from friction.

Other Tools steels may also work, something like D2 is an obvious contender, also O1 and A2. there woudl probably need to be custom made and heat treated but of you can find a small knife-maker (of which there are many) you might be able to get a simple utilitarian blade fairly cheaply.

Something else whcih might be worth trying is a chainsaw chain., Set the work up in the lathe and mount the chain so it wraps around part of the circumference with something to apply a bit of tension. Just draping it over teh top with a weight on one end may work.

you can get 'pocket chainsaws' whcih should be cheap enough to at least test the idea.

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  • $\begingroup$ Thanks for your input. I'll work on your ideas, and come back and share here the learnings. I had't thought of the chainsaw, but someone in the team suggested using a wire. What do you think of such idea? What specs for the wire would you suggest? $\endgroup$ – PavoDive Oct 9 '18 at 9:37

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