Fixing Guillotine Knife Height

I finally had to replace a knife for my Challenge 193 19” guillotine, though it appears I’ll need to grind the top off for proper clearance. I don’t think it’s supposed to cut into the cutting stick by 1/4”, unless I’m missing something.

Does anyone know the dimensions of a new knife for the 193 as I can’t seem to find any info? The new knife measures 3.5” in height. I’ve installed it on the lower holes, backed up the adjustment screws on the knife bar, inserted it at it’s highest point (knife resting against knife bar). The manual says to lower the knife all the way down and turn adjustment screws until it cuts through paper cleanly, however the knife edge proceeds well below the surface of the cutting stick (by a 1/4”?) if allowed to fully travel. I had to remove the cutting stick to insert the knife, and I left the cutting stick out to see just how deep it would cut. This is my first brand new knife, but I’m guessing this is not normal.

Any knives selling new for this model list it at a knife height of 3.5”. One way I was thinking to remedy the issue is to have the knife material on the top ground down at the machine shop to just above the holes as this would allow the knife to seat higher in the guillotine assembly and have the proper clearance baseline (the older knives don’t extend higher than the top hole nearly as much as this new one, so it appears I could do without this headroom.) Any other solutions I’m not thinking of?
Any input would be much appreciated!

image: Challenge 193 Old Knife Holes vs. New Knife Holes

Challenge 193 Old Knife Holes vs. New Knife Holes

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Yes have the top ground off the new blade. I went thru the same thing recently and blade was cutting too deep into stick. After adjusting top screws I was able to get blade to cut bond sheet from side to side without cutting into stick. Cuts great and does not slam into the stick when adjusted properly. Kiss cut is what you want.

So, with these manual cutters- yours is indeed manual, no? - you can actually allow this to be the case and just get more use out of the knife blade, as you do not have to lower the handle to the bottom of the stroke in order to get the blade to cut through the pile.
What I am saying is that it will still cut fine likely, even if the handle may not go to the bottom of it’s stroke, and that is OK.
It isn’t a thing you have to necessarily set as if you were trying to make the knife kiss the cutting stick, like with a power cutter; ideally, yes, that would be the case, but not necessary.

As long as your cutter isn’t a hydraulic or power cutter, you can just try cutting a stack and see. It will possibly limit your pile height but I am going to guess here that you’re not filling the cutter with a high pile of stock up to the height limit, as is the case with most manual cutters.

Question though, when you do bring the knife up to the locked position, and then raise the clamp all the way, is the blade exposed below the clamp? Meaning, is that a safety hazard with clamp raised all the way?

If so, you might want to improvise a stop for the clamp, by introducing a 2-piece collar onto the threaded stud- like a spacer- to keep it from coming up so high that the blade is exposed. Any hands reaching under the clamp to grab stray pieces of paper could glance the blade and suffer a serious injury- that is one of the few limitations in this case worth looking into.

Another thing I would say is that you can actually continue using that old knife if you get a 1/4” strip of material and line the top of it. My cutter comes with spacers that you can bolt into it, for example, when the knife does wear down- allowing one to change the knife and add the spacer in above it and then the knife’s life is extended. If you make it the same height as your new second blade, with the right spacer, you can have a ‘spare’ blade for when you send yours out to be sharpened.

All you need is a piece of material the right thickness stock to be made up as a ‘shim’.

is there possibly a spacer stuck up in there?
new knife made to run without it?

Thanks for the great input everyone! Very helpful both for the long term and short term.

For the new blade, I’m going to have it top-ground to fit the cutter. Thanks for the suggestion Bob (Highlands Printing). There is no space in the machine like Ericm suggested might be possible.

HavenPress, thanks for taking the time to problem solve. My cutter is hydraulic with a manual clamp with two levers to control the knife. Using the two levers gives a fair amount of control the knife descent. The new knife doesn’t come down past the clamp at it’s highest point, so there’s no danger of injury there. If I had to, I think I could feather one or both handles to cut my stack without bitting too deeply into the cutting stick. Your suggestion of shimming the old knife worked very well for the short term or as a temp while the new blade is at the shop. The main reason I deemed the old knife unusable is the only way for the blade to fully reach the cutting stick was to use only the two slotted bolts as the non-slotted bolts would bottom out before the knife reached the cutting stick. This would leave nothing to hold the knife up if those two slotted bolts loosened, an obvious safety issue. To solve this, I secured two smaller bolts into the non-slotted bolt holes as a safety measure to keep the blade up in the unlikely event the slotted bolts failed. This in conjunction with adding two long strips of leading as a spacer above the knife made for a safe way to get more life out of the old knife.

Ah yes, all of my assumptions were based on the idea that you were using a manual cutter; definitely grinding it down is the way to go then!

Be safe!