Perfect Perforation!!??

I have a question reguarding perforation,
When a sheet is perforated should it NEED to be folded over to “tear off” or should it just “tear off” with out folding. My bigest problem is with 30T x .012” .030 microperf. Just how deep should a pref cut into 80# cougar cover stock?? We are using a Heidelburg 10x15 windmill with a die jacket.
Thank you for your help, this is a great site for letterpress help

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Hi, jfitz

Microperf is often unsatisfactory on cover-weight stocks unless the gaps between the teeth are quite deep. If enough impression is applied to perforate the paper with an ordinary microperf rule, the shallow relief has the effect of cutting the paper. Deep-relief microperf rule is available; or perhaps a 17-tooth rule would work.

I think perforating in general is a little touchier than commonly realized. If the piece is to be folded on its perfs for mailing, the end user will have less trouble tearing the perfs than if the paper is not folded, but the piece must not fall apart. Or, the end user may not think to fold the sheet (if flat) on its perf and reopen it before tearing, which can lead to tearing the sheet.

“Snap-out” rule is used frequently with multipart forms: the large teeth leave little paper holding the parts together, so it can be pulled apart without folding or tearing.

The direction of the paper grain and shorter fiber length due to recycled content can also be considerations. If the paper has to go through a printer, we ordinarily use microperf or 17-tooth. Clay-coated stock is often difficult to microperf.

In general, to test a perf I’m printing, I fold the sheet on the perf, impression side inside, and hold the sheet to the light, looking into the “V”. I expect to see clean cuts all along the perf. I then reopen the sheet and tug at it a little to make sure that it’s holding together. Watch for rules that have become dull in spots, and pack for an even impression all along the rule.

Hope this helps, Brian

Thought about it for another day and looked around our shop. The deepest serrations I seem to see are .012. So now I’m not sure there’s anything deeper made. If your stock is thicker than the depth of the tooth, I guess you’re cutting somewhat with the base of the rule.

And to answer your question, I say that a perf should be folded before tearing unless snap-out rule is used.

Brian

Not sure if you want a corner card to perf out of the cover stock or just a tear in half card. If the latter, getting a decent perf without having the card self-destruct at the post office may be impossible. If you are perfing out a corner, it will require fastidious makeready and an eagle eye on the form to prevent die “fade”.

Years ago I did a corner card perf out with micro-perf on Carolina 12 pt (I believe) using a Miehle Vertical and they came out great with the card snapping out if the card was bent more than 45 degrees at the perf. They may have been dogs at the post office, but I never heard anything further about them.

Cougar is kind of a cranky stock and may be too fibrous to perf cleanly, short of using too much perf (fall apart). A good way to tell if you have enough perf is to fold away from the perf side and look through the perf at a light, if you can see the light cleanly, you’ve got a good perf (provided it isn’t falling apart on you).

I need to create a “tic tac toe” pattern for some three up billing “postcards”

Customer specked 2 vertical perfs one with 30 teeth the other with 17 teeth.
The 2 horizontal perfs are 30 teeth.

Very difficult for us to provide sheets that will go through their printer and coe out still intact.

What prefs are available between 30 & 17 teeth? Maybe I can sell them on something different than 30 TPI.

Brian is right.