Drag Knife allowable cutting depth

So I’ve used the drag knife a couple times and it mostly worked but I’m confused on the length.

From the picture linked below, there is a decent amount of blade (a few mm?) that sticks out from the bottom when the stopper nut is fully threaded to the blade holder. However, mine only allows for <1 mm (barely enough for card stock in 2 passes) to stick out. the blades are juuust under 23.3mm - 23.4 mm in length. Is there a mystery here?

For stickers and such you tend to only want to cut through the sticker and not the backer, so that tends to be rather thin. A lot leas than a mm.

@Ryguy13 I’m still building my Primo so I haven’t been able to try mine out yet but I was also looking at a couple designs on Thingiverse that use box cutter blades. That style may give you a little more depth of cut than the one you have now.

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@Bigchepin I’ll look into that, thanks, I’m still curious as why I don’t have the depth in the pictures.

@Tuco it’s hard to measure, but its around .2-.3 mm max. I’d like to cut thicker objects as well and not have to maintain more tools than necessary. It’s also so close to the end that making those final fine tuning adjustments is difficult.

@Ryguy13 I recently came across this thread on a tangential cutter that may be of interest to you.

Thanks for that, it looks really neat. I need to try my current one on vinyl and see if there’s enough, I’m also still curious as to why I barely have a few tenths of a mm when the images show multiple mms.

The photo at the top of this topic shows pieces well for promotional purposes but may be misleading as a setup instruction. Some additional photos may be helpful.

Here’s the cutter I purchased from the V1 shop with the blade installed and adjusted to maximum extension:

Here it is roughly adjusted (by eye)for cutting through paper:

I was aiming for cutting one sheet but this cut through the top four layers of my legal pad.

This is what it looks like at 5x magnification when tuned to cut one sheet and just crease the next:

Sorry for the hand-held iPhone focus issues - the cat was helping me.

The cutting edge on the blades I received are only about 1mm long so that’s my expectation of the thickest materials I’d try to cut. Other blades may be available, I haven’t looked into that myself.

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@ttraband Thanks for the pictures. My drag knife is totally different. I also purchased it from the shop about a year ago maybe. Here are pictures:

It appears @vicious1 had some slight variance from his supplier since we both got them from the V1 shop. I think the only difference is the color of the outer casing, and that mine doesn’t have an o-ring in the slot.

I’m guessing the o- ring provides a bit of resistance so the outer shell doesn’t turn too easily when making adjustments.

I adjust the cutting depth by turning the outer shell until the shell rides the surface of the material to be cut and the knife dents but doesn’t cut the backing material, then use the brass knurled ring to lock the position. The printed tool holder for the MPCNC has a bit of springiness to keep the cutter in contact with the material while cutting.

I hope that’s the proper technique.

Some instructions.


Thank you @vicious1. I have read those instructions. In this picture, the blade sticks out beyond the case a few mm. The form factor and length appears the same as the blade holder and blade I have. However, the maximum blade length that comes out of the case of mine is <.5mm. The case is tightened all the way down, and the blade is engaging with the magnet. I can also measure from the pictures that the difference in length of my caseing and @ttraband 's casing is ~10mm. Is my plunger/magnet potentially too short?

Yeah, that is perfect. Most vinyl is about 0.086mm

That picture is with the button pushed in (I wedged it so it would stay out). The button is for taking the blade out.