In this post, we are sharing tips on how you can be a better CAD designer specifically when it comes to knives.
We have created a checklist to make sure there are no geometry errors in your file before it is sent to us for cutting. Keep reading for more things you should know when designing and exporting a knife in CAD.
Tips for designing knives in CAD:
Degree of Splines
CAD must be designed in degree 3 geometry, not 5​. Degree 5 causes designs to be exported as polylines instead of smooth splines. Click here for details on how to change this.
Cleanup Allowances
CAD files should show the part as you want it cut from the raw material, not the finished knife dimensions. Depending on the cutting machine and your process of secondary operations, you may leave more or less wiggle room for finishing.
Guidelines for allowances:
Waterjet and Fiber Laser: cleanup by hand (.005-.010") cleanup by mill (.020")
Undersize holes (.015-.020") for additional machining
Wire EDM: Very little cleanup if any. This is ideal for folder knives that require repeatable precision in the locking mechanism or other tight tolerance features.
Tolerances
When designing, do not tolerance anything that does not require a tolerance. The more critical tolerances, the more the part will cost.
Typically only the finished diameter of holes, a profile fit, detents, pivot holes, counterbores, and the locking mechanism for folder knives might require tolerances.
What to Include
1. Any hardware that will be used in the finished knife.
2. Separate dimensioned PDF drawings for each CAD design, see below for examples.
Example of supporting documents and hardware provided with CAD files.
Include design name, dimensions, material, hole diameters, finish thicknesses, surface and edge finishes, secondary operations, quantity, tolerances, and notes.
Another example of a supporting document that we would receive with CAD for lockside handle machining.
Include design name, material, dimensions, hole diameters, tolerances, secondary operations, finish thicknesses, surface and edge finishes, quantity, and notes.
How should my CAD be exported?
In .DXF, .DWG, .STP/ .STEP, or parasolid formats
2D (.dxf, .dwg) is preferred for shape cutting
3D (.stp, .step, parasolid) is ideal for models of folding knife designs and CNC milled components
Name files with identifying design names and material being used.
examples: CPM154_BladeDesign.dxf
titanium_pocketclip_design1.dxf
Software
"Free CAD"
For anyone looking for free CAD, there is no shortage of examples of "you get what you pay for." Even for experienced CAD designers, free CAD software can be difficult to use. If you are someone new to CAD, this is not a good place to start.
No one wants to waste their time trying to learn a program that may not even produce a machinable file, so send us a template and we can create the file and cut the parts for you.
Here's an example of what you might get from a machine shop that isn't experienced with cutting knives.
If you have questions about how to get the end product that is ideal for your custom knifemaking project- contact us!
Leave additional topics or questions in the comments here or on Instagram.
Check out this video if you are interested in more detailed design tutorials.