This adapter is being updated to the new Mk.II version. Orders placed now will ship starting in the second half of January 2026. While it’s out of stock, all pre-orders will receive a 10% discount at checkout.

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DRO for Milling Machines
4-Axis with RPM and Touch Probe Inputs

DRO for Milling Machines
4-Axis with RPM and Touch Probe Inputs

Wireless 4-axis DRO interface box for milling machines. Reads optical, magnetic, and supported capacitive scales and sends position data to the TouchDRO Android app. Mill-ready features include quill/knee summing, touch probe or tool setter input, RPM display, and indexing head support.
$299.00 USD
$299.00 USD
Sale Sold out
  • Backordered until Jan 2026 – 10% off pre-orders.
  • Free domestic shipping on orders over $200
  • 5 year warranty
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Add a 4-axis digital readout to your manual milling machine with the TouchDRO DRO interface box. It reads your scales and sends position data to the TouchDRO Android app over Bluetooth for a large, responsive touchscreen readout. Mill-ready features include quill/knee summing, touch probe or tool setter input, RPM display, and indexing head support.

 

What is This?

This is a wireless-first 4-axis DRO interface box for manual milling machines. It connects to the TouchDRO Android app via Bluetooth, and can also stream data over USB. USB is used for power and is the primary method for firmware updates.

Compatibility:

  • Works with most modern optical and magnetic DRO scales (TTL 5V or RS-422, single-ended or differential)
  • Supports capacitive scales, calipers, and micrometers via Mitutoyo SPC or BIN6 protocol (converters sold separately)

To complete your setup you will need:

  • A set of compatible DRO scales (supported pinouts are listed further down)
  • An Android tablet that meets TouchDRO system requirements
  • A 5V USB power supply (1A or higher — an old phone charger works)

* Android tablet and DRO scales not included.

Why Choose TouchDRO?

  • For Beginners

    TouchDRO's clean, intuitive interface helps you work more accurately and make fewer mistakes. Real-time position readouts, built-in calculators for bolt circles and hole patterns, and simple zero-setting let you focus on learning the craft instead of second-guessing your measurements.

  • For Seasoned Hobbyists

    TouchDRO adds capabilities that go well beyond a basic DRO. The graphical projection view simplifies complex parts, and the reference drawing overlay lets you cut intricate shapes without needing a CNC.

  • For Professional Machinists

    TouchDRO streamlines setup and keeps your spindle running. Touch probe and tool setter inputs speed up workpiece location and tool offsets. Sub-datum import supports offline job prep, and the reference drawing overlay reduces errors and rework.

Specifications

TouchDRO TDA-420 Plus is a 4-axis DRO interface box for milling machines. It can be used with the majority of modern optical and magnetic DRO scales, and many common capacitive scales.

  • Up to four 5V TTL/RS-422 scale inputs (differential or single ended)
  • Tachometer/RPM input
  • Two touch probe/tool height setter inputs.
  • Compatible with DRO scales and rotary encoders (NPN, PNP, and Push-Pull) with and without reference track support
  • Support for Mitutoyo SPC and BIN6 data protocol (adapters sold separately)
  • Axis summing (combine any two inputs, e.g., quill + knee)
  • Bluetooth and USB connectivity
  • Position retention during power loss
  • Access to TouchDRO Plus application
  • Support for over-the-air firmware update

Please refer to the TDA-4xx User Manual and Adapter Feature Comparison for more details.

Supported DRO Scales

The adapters support DRO scales and rotary encoders that output 5V quadrature signal. This includes:

  • Majority of modern optical, magnetic, and inductive scales. Learn more
  • Mitutoyo DigiMatic scales with SPC output  - requires a SIC-5V-MIT-A input converter (sold separately)
  • iGaging Absolute DRO Plus scales  - requires a SIC-3V3-IG-A input converter (sold separately)

Pinout Options

TouchDRO TDA-420 scale inputs use female DB-9 (D-Sub 9) connectors. The adapter can be purchased with several different pinouts to suit some of the most common scale brands:

Brand 1 2 3 4 5 6 7 8 9
Acu-Rite SENC Scales   A A' B B' OV/Gnd Vcc/5V R R'
Electronica/EMS, PM MagExact +Z Z' Vcc/5V Shield OV/Gnd A A' B' B
Ditron, Sino, Aikron, Easson, Vevor A' 0V B' Shield R'/Z' A +5V B R/Z
Generic Chinese Pinout (ToAuto, etc.)  5V 0V  A  B  


If you intend to use a mix of the above pinouts, choose the "Mixed". Please use the "Order Instructions" field in the shopping cart to tell us the pinout options for each axis. Alternatively, you can purchase one of the pin mapping boards and change the pinout yourself.

Frequently Asked Questions

Can TouchDRO display combined readings from both the knee and the quill?

Yes, TouchDRO supports axis summing on any of the three primary inputs. You can easily configure the Z-axis to combine readings from two scales, even if they have different resolutions.

I only have 2 scales on my mill. Can I still use this adapter?

Yes, TouchDRO works perfectly with just two axes connected. You can always add additional scales later if your needs change.

Can I use this adapter for a lathe?

Yes, you can. Besides the touch probe inputs, this adapter is identical to the lathe-centric TDA-410 adapter.

My scales are not listed. Are they supported?

Please check the "Supported DRO Scales" page for detailed information on how to verify if your scales are compatible.

The pinout of my scales is not listed. Can I still use this TouchDRO adapter?

Yes, you can, but you will need to rewire the scales to match the adapter's requirements.

Can I change the pinout if I get different scales later?

Yes, the adapter's pinout can be changed using a small plug-in board, which can be purchased separately. Switching the pinout is quick and easy—it involves removing 6 screws, swapping the board, and installing a new one.

Will a wireless DRO be reliable in my shop?

Yes. TouchDRO uses Bluetooth 4.2, a highly reliable protocol with excellent range and robust error correction. Additionally, TouchDRO incorporates extra data integrity checks and anomaly detection to ensure smooth and accurate operation in your shop.

Isn't an Android tablet too brittle for a shop environment?

Not at all. Tablets are built to withstand years of daily use in various environments. High-quality tablets feature tempered glass and are well-protected against moisture and dirt. For extra peace of mind, you can add a rugged case and a screen protector.

Will leaving my tablet plugged in damage the battery?

No, it will not. Tablets have smart battery management systems that prevent unnecessary discharge cycles, and most models bypass the battery when plugged in, protecting it from damage.

Still have questions? Contact us