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Printable Hobby Knife - Number 11 X-Acto Blade Size

by pggibson Dec 8, 2016
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Just to say, I love reading peoples comments on how their designs have been updated overtime with experience. Nice work :)

Thank you! Much appreciated!

Man, I just could not fit the blade base into the holder. I forced it wider to fit it and it snapped. I might try again, but maybe scale it up a few percent. I could also not get the blade holder top all the way down to the threads. I figure maybe some working it, but since I broke it... well, I'll try again. I hope I get it to work because I like this.

Hey Chris,
I'm sorry it is giving you issues! You may want to check the comment thread here between myself and CharmPeddler as it has some troubleshooting steps for when you're running into things being too tight on this. The threads on the base are undersized by 0.325mm from the top, so if they are super super tight, you most likely have an over extrusion issue going on. Were you printing in PLA?

HI there, I printed this and visually it looks great! The threads seem to be too tight. I had to go in with some files and grind down the topmost points of the threads on the collet and the nut and also the bottom of the threads. As I'm new to 3d printing do you have any suggestions on what I can adjust on my next print of this? I plan on printing 4-5 total.

My setup:
1.75mm PLA
Prusa i3 MK3
Cura w/ official Prusa Profiles. Using the 0.2 layer height.
I did go in and adjust the Shell wall line count to 4 and bumped the infill to 70%.


Hey CharmPeddler! This is probably more detail than you wanted, but here goes:

There are a few things that can cause the threads to be too tight, but usually screwing the top on and off a few times clearances things well and they work more smoothly. Here are some things to check if that doesn't do it for you:

  1. Make sure your extrusion settings are correct for the particular roll of filament you are using. If the filament is out of spec a bit (just a bit on the thick side, for example) the result will be over extrusion. If you can, get a good pair of digital calipers and sample about 20 points along about a meter length of the filament you are using and average them together. In Cura, you can update the process and edit your filament diameter to reflect its real-world diameter. It is a pain in the butt, but it really can make a difference. I've printed tons of these things in all sorts of filaments, and any time I have a fitment issue, it almost always turns out I have an over extrusion problem that needs to be adjusted out.

  2. Does the cap snap on well? If the cap is way too tight too, there is definitely a print setting issue - probably over extrusion. For the cap, you should be able to snap it on and off without having to sand anything. If the cap fits ok, it is probably a problem other than over extrusion.

  3. Make sure you aren't using supports. The model is designed so that it can print without supports. If supports are left on, sometimes it will put a few artifacts inside the thread area which can cause issues. If you are using PLA and your part cooling settings are working on other prints, it should give you no trouble.

  4. Check the very base of the top (the part that screws down onto the collet to grip the blade) Make sure there is no flange or boogers right on that edge as sometimes that will cause issues. This can happen especially if you have your first layer squished a lot.

  5. The shell thickness is a good call - if you have it bumped up to 5 or above, you can get away with a lot less infill (I need to update my instructions to reflect that). That shell increase shouldn't cause any thread issues.

  6. I don't know for sure if Cura has the setting (probably) but check if there is a "inside-out" vs. "outside-in" setting for your outer perimeters. You want to be printing "inside-out". This allows more accurate overhangs without using supports. It can sometimes cause some surface defects, but they won't impact this print. If you are trying to print outside-in on this model, it may cause some sagging on some of the thread overhangs and cause you some issues.

  7. If all else fails, you can print the top part at slightly higher percentage (like just 0.5% to 1%) larger in the X and Y and then test that out and see if it screws on well.

Let me know how it goes! I'd love to see one come off a legit MK3!

Thanks for the huge reply! I'm all for the extra details! I'm trying to learn as much, and as fast as I can.

Before any sanding/grinding, I test fit the screws and it only screwed on about 1/2 of a thread. I'm a big guy and but there was NO budging after that. I had to get pliers to unscrew it. Just FYI. I've ground everything down so the screw comes within about 1/4" from bottoming out.

  1. Filament thickness: I checked 15-20 spots. Four of the spots were 1.75 and the rest of them were right at 1.74. I'll go in and adjust the material settings to match this. Haven't done it before (this is only my 4th print), but I'm pretty sure I know where its at. Thanks!
  2. Cap does not fit anywhere near enough to get it to snap.
  3. No supports used.
  4. Couple boogers when first printed. but like I said, I ground the heck out it, and its still not going down all the way. and when I say that "I ground it", I mean that I ground down directly onto the crest of the threads, I also ground the lower roots and the flanks. Still hella tight.
  5. Thanks for the confirmation. that helps with a few questions I had on that.
  6. It looks like they do. I'll set this as "inside > out" when I print again. Thank you.
  7. When you say "Top" you do mean the Nut right? And if so, the two pieces are a solid unit in the STL file. I know the STL can be edited via my Fusion 360 program, but I just haven't had time to learn how to do that just yet. I'll learn that (or if you can share out original model file?) and then test it along with the "Inside > Out" setting.

Thanks for the detailed response. I'll be sure to let you know what happens.


Yup, if the cap is no where near fitting I can almost guarantee you have an over extrusion issue. That can be from the filament diameter being wrong, the extrusion multiplier being wrong, or the extrusion width being wrong. What I would start with is checking out some videos on dialing in your extrusion multiplier. Makers Muse has some great info on this along with some "tolerance" test models so you can dial things in. It is worth getting it dialed in - if not for this, for your future prints! (https://www.youtube.com/watch?v=XnJBpCWf9Mc)

Also double check the measurements on that filament and see how close it is to spec. Is it the Prusa PLA, or another brand? Sometimes they will list the tolerance on there (like + or - 0.03) but if it is way outside that range, be suspicious.

As for printing the separate parts: from what I understand, in Cura you can just right click on the objects and click "Split object into parts".

If you can't get that to work, let me know and I'll post that part of the model as a separate piece!

Good luck!

I'll check that all out for sure!

" It is worth getting it dialed in - if not for this, for your future prints! " Absolutely. I've noted down MANY of things you've said in my "Diagnosing Issues" notes. So thank for the help on this print, and the (HOPEFULLY!) many more to come!

UPDATE: It looks like the extrusion was right on. I did adjust everything else. But I'm still getting the same issues. I've included a picture of the 2nd print as tight as I can get everything together.

I'm having a hard time setting time aside to learn how to split the file. IF its not too much trouble could you upload the parts individually? I'd love to get this working.


I edited my last message with this info, but I'm thinking you might now get the "an edit has been made" notifications, so I'll post a separate reply now:

UPDATE: It looks like the extrusion was right on. I did adjust everything else. But I'm still getting the same issues. I've included a picture of the 2nd print as tight as I can get everything together.

I'm having a hard time setting time aside to learn how to split the file. IF it's not too much trouble could you upload the parts individually? I'd love to get this working.


Sure thing! I've uploaded them separately. Looking at the image you posted, I'd still hazard a guess that you have some over-extrusion taking place. One other thing to check is to use "random start locations" in your settings and take a look at your coast and retraction settings. That should help with some of the zitting you are seeing and avoid having the line of artifacts where the layer is starting being as noticeable. Hope you get it working!

Thanks for the reply mate, they are totally awesome, i fell in love with them as soon as i see them in your post here lol, shame i cant seem to find a UK source :-(

If you're looking for a good inexpensive set that you can get in the UK, check out the iGaging OriginCal. They aren't quite as nice as the Aventors, but they are much much better than the typical imports. You can get them through Amazon.

thanks buddy ill have a look, cheers :)

Nice design, also that looks like one bloody nice calliper... you got a link to it please mate?

The calipers are Aventor 8" from Shars - they are incredible, especially for the price. Always return to zero, wonderful fit and finish. I got them here: http://www.shars.com/products/measuring/caliper/aventor-8-dps-ip54-electronic-caliper