iPhone Screenshots


iOS 10 compatible!
Whether you use Metric taps and drills, US Standard taps and inch drills, or any combination of size types, this app has the answers. No typing required; just tap your thread type and spin the dials to find the correct size of drill for your thread tapping operation.

The interface allows for selection of the following variables to calculate your required drill size:
• Thread Type,
• Tap Size,
• Percentage Depth of Thread,
• Through Hole Clearance,
• Cutting or Forming Operation

The closest drill bits are given in Metric, Fractional Inch, and US No. / Letter sizes, making this the perfect tool for those using a mix of tap and drill types.

The app ensures complete control and accuracy of your operations by recalculating the actual percentage-depth-of-thread and through-hole clearance for each closest drill bit size.

Thread types include:
• US Standard UNC, UNF, UNEF
• ISO Metric coarse, fine
• National Pipe Thread - Tapered (NPT)
• National Pipe Thread - Straight (NPS/NPP)
• British Pipe Standard Thread - BSP (Parallel - G)
• British Pipe Standard Tapered Thread - BSPT (Parallel - R / Rp)

A helpful reference tool for engineers, machinists, trades-men, students, tool makers, DIYers, fitters and turners, and fabricators, etc.

What’s New

Version 4.0

- 64-bit compatibility added to allow app to function on future versions of iOS.
- Updated UI for devices with 4.7 inch, 5.5 inch screens.
- Fresh new app icon.

Ratings and Reviews

5.0 out of 5
1 Rating

1 Rating

Fernandco ,

Really good app. But Npt???


Griffon55 ,

Good drill app

Thank you so much.

Don Doucette ,

Handy, saves time.

Handy app to always have on hand!


Chewy Applications Ltd.
2.7 MB

Requires iOS 9.0 or later. Compatible with iPhone, iPad and iPod touch.



Age Rating


  • Family Sharing

    Up to six family members will be able to use this app with Family Sharing enabled.

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