Recommended Touch Probes and Edge Finders
The TouchDRO Adapter for Milling Machines (TDA-420) supports standard triggering digital touch probes and tool setters with NPN or Push/Pull output. This covers the vast majority of hobby-grade and commercial touch probes on the market, ranging in price from $50 to many thousands of dollars.
In the app, a probe works through the Edge Finder function to pick up edges, centerlines, and hole centers, and each instrument's tip diameter and offsets are stored in its probe profile.
Do You Need a Touch Probe?
In order to machine accurate parts, you generally need to start by accurately indicating the stock or the casting, and you spend a surprising amount of machine time doing it. Each pickup is also a chance to add the tip radius when you should have subtracted, one of the most common ways to scrap a good part.
A touch probe fixes both problems at once. It triggers the moment it touches, in any direction, without spinning, so you can pick up an edge in seconds; and because the tip diameter and offsets live in a saved probe profile, TouchDRO does the compensation math for you. The app sets the origin exactly on the edge, every time, with nothing to remember.
A probe also picks up features an edge finder can't reach. You can find a centerline or a bore center by touching opposed walls, and the three-point circle measurement finds the center of a bore even when only a partial arc of it has been milled, which no wiggler can do.
Our Recommendations
For most people running a TouchDRO-equipped mill, we recommend the Drewtronics s5000LED wired for the TDA-420. When set up correctly, it repeats to within one encoder count and has generous overtravel protection, which puts it in the same territory as probes that cost several times more. This version ships with the probe cable already made up, so there is nothing to wire. Drewtronics is a small US shop that stands behind what it builds.
For EU customers, we recommend the Slavtec probe. It's a bit more expensive than Drewtronics, but once you factor in shipping and tariffs, the prices are very similar.
Note on Chinese Touch Probes
The most important touch probe parameter is repeatability. Even though a kinematic triggering touch probe is a very simple device, to achieve good repeatability it must have very precisely spaced contact points and spring rate matched to the stylus length and rigidity.
There are many touch probes on eBay and AliExpress in the $50-$100 price range. This is a very appealing price, but based on our testing and feedback from our customers, these low-cost probes are very inconsistent from unit-to-unit, and overall quality control appears to be non-existent. Some had excellent repeatability, and others (sometimes from the same batch) were completely unusable.
Recommended Touch Probes
| Models | Rating | Price Range | Notes | |
|---|---|---|---|---|
| Renishaw | Wired mechanical probes | $$$$ | Renishaw probes are the gold standard. New, they are prohibitively expensive, but mechanical CMM-class probes (TP2, TP6, TP20) can be found on the secondary market for $400-$900. Recommended for CMM and digitizing setups; overkill for machine shop use. |
|
| Acu-Rite Heidenhain |
Edge Finder - KT3D | $$$$ | KT3D is a high-end conductive edge finder. New, it's very expensive, but can be found on the used market for $300-$500. |
|
| Drewtronics | s5000LED | $269 | Drewtronics is a small shop located in Texas; probes are made in the USA. This version ships with a cable already wired for the TDA-420, so it plugs straight into the adapter's probe input. Repeats to within one encoder count when set up correctly, with generous overtravel protection. Build quality and after-sales support have held up well in our experience. Our top pick for USA and North American customers. |
|
| Slavtec | Waterproof 3D Probe | $309 | Slavtec is based in Poland (EU); the probes are made in Poland. Slavtec touch probes offer excellent repeatability of ± one encoder count. The probes use standard 2mm threaded styli. The company has very good support via email. Our top pick for EU customers. |
Setting It Up
Once the probe arrives, the setup is three short steps. Wire it to the probe input on the adapter, as described in the TDA-4xx manual. Create a probe profile for it, so the tip diameter, offsets, and trigger port are stored once. Then run tip diameter calibration, which measures the tip's effective size against a reference gauge; this is what makes probed edges land where the contact actually happened.