Please Help! My cast iron cutter won’t cut straight

If the cut is straight, I would check for an adjustment of the top brass ruler. If the cut is curved. you may be able to adjust the attached cutting blade (screwed to the iron surface)
I had a similar problem with and Ingento cutter, and eventually shimmed the attached cutter to straighten it.

One of the weaknesses of this kind of cutter is that there is no mechanism to hold the sheet down while you are cutting. In my own experience the scissoring action tends to pull the sheet in toward the blade while cutting, creating the problem you describe. Try holding one sheet very firmly with your left hand and cutting slowly with your right, checking to see if the sheet is moving against the back gauge. If the blade is at all dull this problem will be magnified. You can always check the cutter for squareness with a carpenter’s square. I can’t imagine that a cast iron cutter would be that far off. Even when I use a guillotine cutter with a hold down bar I never cut more than 5 sheets at a time (even tho’ they say you can cut 40 or 50). A cutter such as yours I would only cut one sheet at a time.

Paul

Appreciated for all the advices, I will check those issues that you both mentioned above.