• TouchDRO TDA-420 wireless DRO adapter for milling machines, shown with an Android tablet displaying the 4-axis position readout
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DRO for Milling Machines
4-Axis with RPM and Touch Probe Inputs

A 4-axis DRO interface box for manual mills, with RPM and touch probe inputs plus quill/knee readout summing. Reads modern and legacy optical, magnetic, and capacitive scales, and sends position data to the TouchDRO Android app.
$299.00 USD
$299.00 USD
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  • Ships in 3-5 business days
  • Free shipping on orders over $200
  • 5-year warranty
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The TouchDRO TDA-420 is a wireless scale interface box for manual milling machines. It connects most modern and many legacy DRO scales (glass, magnetic, and capacitive) to the TouchDRO app on an Android tablet. The app provides a graphical layout view, touch probe routines, quill/knee summing, and RPM display. The adapter handles scale reading, touch probe input, and position tracking internally — it will accurately keep track of the scale positions even when the tablet is asleep, disconnected, or switched to another machine.

Key Features

  • Graphical layout view — the app shows a top-down 2D view of your workpiece alongside the numeric readouts. Overlay an imported CAD drawing or photo and machine complex profiles by tracking the cutter position on screen.
  • Hands-free DRO automation — as you move the table, the app can automatically select the nearest sub-datum, switch tool offset direction at fence lines, trigger near-zero warnings, and create sub-datum coordinates on spindle down.
  • Bolt circles, hole patterns, and saved coordinates — create pitch circles, arbitrary angle circles, arc milling paths, hole grids, and other coordinate layouts directly in the app, or import them from a spreadsheet.
  • Touch probe support — indicate a workpiece edge or corner, or quickly find centerlines and hole centers. Pick up feature dimensions and coordinates from an existing part and store them as sub-datums for reproducing the part or setting up new operations on it.
  • Quill and knee summing — combine two scale inputs into a single Z-axis readout so the display always shows true tool-to-table distance, whether you move the quill, the knee, or both.
  • Works with the scales you already have — supports most modern and many legacy glass, magnetic, and capacitive scales, either directly or with adapter cables and converters we offer. Check the compatibility table below.

See the complete TouchDRO feature list →

What's Included

In the box

  • TouchDRO TDA-420 adapter
  • USB-A to USB-C power cable
  • Two Mini-DIN 4 mating connectors for the tachometer and probe inputs
  • Stylus
  • Quick start card

You'll also need

  • A set of compatible DRO scales — see the compatibility table below, or our recommended scales
  • An Android tablet — see our recommended tablets
  • A tablet mount
  • A 5V USB power supply (powers both the adapter and the tablet through a USB hub or splitter)

Compatible Scales

If you already have DRO scales on your mill, the table below shows which ones plug in directly, which need an adapter, and what TouchDRO pinout to choose. Otherwise, see our recommended scales to choose a set for your machine.

DRO Scales

Scale TouchDRO Pinout Additional Adapter
Sino, Ditron, Aikron, Easson, Vevor, M-DRO Default (Ditron, Sino, Aikron) Not needed
ToAuto, Jing Generic (ToAuto) Not needed
Electronica/EMS, PM MagXact Electronica/EMS Not needed
Acu-Rite
SENC 50, SENC 150, SENC 250, ENC 150 (9-pin D-sub) Acu-Rite Not needed
100/200-series Mini-Scale (6-pin Bendix twist-lock) Default (Ditron, Sino, Aikron) 6-pin Bendix → DB-9 cable
NewAll
Spherosyn & Microsyn TTL models (MHG-TT, DSG-TT, DMG-TT, MAG-TS, etc.) Acu-Rite Not needed
Anilam
6-pin twist-lock (Wizard, Mini Wizard, Super Wizard, Spirit) Default (Ditron, Sino, Aikron) 6-pin Bendix → DB-9 cable
9-pin D-sub (post-Heidenhain rebrand) Default (Ditron, Sino, Aikron) Not needed
Sargon Default (Ditron, Sino, Aikron) DB-25 → DB-9

Capacitive Scales and Digital Tools

Scale TouchDRO Pinout Additional Adapter
Mitutoyo DigiMatic Default (Ditron, Sino, Aikron) Mitutoyo SPC converter (SIC-5V-MIT-A)
iGaging Absolute DRO Plus, EZ-View DRO Plus Default (Ditron, Sino, Aikron) iGaging converter (SIC-3V3-IG-A)

If your scales aren't on the list, or you don't know the brand or pinout, see how to identify an unknown scale for help figuring out what you have. For tested brands and full compatibility detail, see the full compatibility list. Or send a photo of the connector and label to info@touchdro.com, and we will do our best to help you identify them.

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:

Pinout 1 2 3 4 5 6 7 8 9
Default (Ditron, Sino, Aikron)A'0VB'ShieldR'/Z'A+5VBR/Z
Electronica/EMS+ZZ'Vcc/5VShield0V/GndAA'B'B
Acu-Rite AA'BB'0V/GndVcc/5VRR'
Generic (ToAuto)5V0VAB     

If you intend to use a mix of the above pinouts, you can purchase additional pin mapping boards and change the pinout yourself.

Specifications

  • 4 Quadrature A/B scale inputs with a reference signal (5V TTL, RS-422, NPN, PNP, or Push-Pull quadrature)
  • Supports Mitutoyo SPC, iGaging EZ-View, and BIN6 serial scales (input converter required, sold separately)
  • 2 touch probe/tool height setter inputs
  • 1 spindle RPM input
  • Bluetooth 4.2 (Classic) or USB
  • 5V USB-C power, 1A supply recommended
  • Field-changeable scale pinout via plug-in board (sold separately)

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 machine. 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?

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.

What's the difference between the DIY kit and a pre-assembled TDA adapter?

The kit and the TDA-4xx share the same 32-bit architecture, scale protocol support, tachometer input, and TouchDRO Plus features. The pre-assembled adapters add touch probe input (TDA-420), reference mark support, power-loss position backup, 5-year warranty, and full technical support. If you enjoy hands-on electronics work, the kit gets you there for less. If you'd rather skip the soldering, see DRO for Milling Machines or DRO for Metal Lathes.

Can I use this with a Windows PC, iPad, or iPhone?

No. TouchDRO runs exclusively on Android tablets. The TDK-40 communicates via Bluetooth to the TouchDRO Android app. It is not compatible with Windows, Linux, or iOS devices.