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

This app has been updated by Apple to use the latest Apple signing certificate.

- 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

4.5 out of 5
13 Ratings

13 Ratings

DigitalBman ,

Best tap drill app

I use this app daily when setting up new jobs and converting older jobs from cut tap to form tap sizes. Often multiple times per job and per day.

Having tried many machinists related apps, I find the information in this one very well presented and accurate. The ability to adjust tap hole size for difficult materials or deep threads and know what percentage of thread engagement should be created if the tools cut properly is very nice. Easy to play "what if."

Tap charts usually give drill sizes based on 65 or 75 percent engagement. When a form tap doesn't meet minor diameter requirements, using this app can help quickly determine if a smaller drill will be risky by showing what percentage thread the new hole size should generate.

Sometimes drills don't drill to size for various reasons, tools wear, and materials can be difficult. When troubleshooting I find myself pulling up this app to verify drill size and then check the drill being used and resulting hole diameter.

From a long time user of this app,
It's easy, accurate, and far more useful than a simple tap chart.
Thank you for a wonderful tool and please keep it future proof.

patmasterdigital ,

Awesome app

Awesome app would love to see clearance hole drill bits.

Alyanes ,

Great Application

I usually don't write any reviews but this application deserves one. It is very useful for my type of work, very simple to use and complete. Customer service is also great. They responded to my request in less than 24 hours. I surely will buy more applications from this developer.

App Privacy

The developer, Chewy Applications, has not provided details about its privacy practices and handling of data to Apple.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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