I work for a manufacturer of cutting tools.  One of the departments I work in is the special tool quoting department.   I see a lot of requests for special tools everyday.  Most of these requests have tolerances called out on various dimensions of the tool (diameter, width, flute length, shank diameter, radius, chamfers, etc).   Sometimes the tolerances called out are extremely tight; other times they are wide open.  Each tool is different but frequently the tight tolerance called out on a tool causes the price to go up and some of these price increases are unnecessary.  So, when requesting special tools do not put tolerances that are unnecessary on the request.  If a dimension is not critical consider having it quoted to the manufacturer’s shop standards rather than putting a tolerance on the request.  The more information that can be provided about the application and the tool the better.  This information includes the material being machined, the material hardness, or even a part print.  This will allow the manufacturer to determine the most economical tool design for your application (and your pocketbook).  Even when a tool is quoted properly generally speaking the more complex a tool is the less likely it is for the manufacturer to make money when making the tool and the more likely it is for the tool to be more expensive for the end user.  It’s a lose-lose for the manufacturer and the end user when unnecessary tolerances are called out.

 Below is an unofficial list of tolerances that may cause a price increase to a special tool if held too tight.  The list is geared towards carbide tipped tooling but a lot of the tolerances will hold true for solid carbide and high speed steel tools because the manufacturing processes are similar.  This is by no means all encompassing and there are exceptions to every rule.  They are sorted by tool type.  Feel free to leave a comment if you have other tolerances that I didn’t list.

Tolerances that may cause a price increase 
Reamers    
Diameter Tighter than 0.0003″
TIR (Total Indicated Runout) Tighter than 0.0005″
OAL Tighter than +/- 0.015″
     
Milling Cutters (Arbor Hole Type)  
Diameter Tighter than 0.005″
Width Tighter than 0.001″
Arbor Hole Tighter than 0.001″
     
Keyseat Cutters    
Diameter Tighter than 0.005″
Width Tighter than 0.0005″
Shank Diameter Tighter than 0.0004″
OAL Tighter than +/- 0.015″
     
Dovetail Cutters    
Diameter Tighter than 0.005″
Width Tighter than 0.010″
Shank Diameter Tighter than 0.0004″
OAL Tighter than +/- 0.015″
     
T-Slot Cutters    
Diameter Tighter than 0.005″
Width Tighter than 0.002″
Shank Diameter Tighter than 0.0004″
OAL Tighter than +/- 0.015″
     
End Mills    
Diameter Tighter than 0.002″
Shank Diameter Tighter than 0.0004″
OAL Tighter than +/- 0.015″
     
Counterbores    
Diameter Tighter than 0.001″
Shank Diameter Tighter than 0.0004″
OAL Tighter than +/- 0.015″
     
Drill Bits    
Diameter Tighter than 0.0005″
Shank Diameter Tighter than 0.001″
OAL Tighter than 1/16″
TIR (Total Indicated Runout) Tighter than 0.005″
     
Other Miscellaneous Cutting Tool Features  
Radii Tighter than +/-0.003″
Angles Tighter than +/- 15′ (15 minutes)

As always if you have any questions about tolerances or special tooling (or any other cutting tool questions) feel free to leave us a comment here on our blog or fill out the form on Super Tool’s Contact Us Page.

Bryan Enander
Super Tool, Inc.
941-751-9677

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