Using a CNC Touch Probe

Using a CNC Touch Probe

Category : Useful Stuff


CNC touch probe, everyone should have an electronic probe on their machine but I’m sure there are lots of reasons why you don’t have one.

CNC touch probe

The purpose of this article is to show some of the alternatives to buying an expensive touch probe systems. Please note if you can afford to one of these systems I’ll guarantee you’ll soon get your money back with increased productivity.

Probe Shaming

Now I know there is a lot of this about but if you’re guilty then I’m sorry but you deserve all you get.

What the fuck is he on about?

Yes you know who you are. Yes you, you with that gorgeous once shiny Renishaw CNC touch probe left to get covered in grease, shit and swarf in the back of your machining centre.

Sorry just remembered I must change my pants.

Yes I regularly come across this when training people onsite on their CNC Machines. The machine originally came with a touch probe and maybe got used a few times but then no one bothered to properly learn how to use it.

Most likely the bloke who knew how to use it left to buy a chip shop in Bradford.

As a result it was ignored for three years and left in the tool carousel to generally decay and rot.

Please sort it there’s a lot of cash sat there in the tool carousel oh and don’t leave your dirty pants lying around either.

Avoid People Who Own Wobblers

Maybe you call them wibblers never mind the fuckin semantics they are basically a piece of shit on a stick. Bin them.

Now I’m an old school engineer I remember the old halcyon days of engineering. I have the missing limbs, teeth and scars to prove it.

  • Pissing in the coolant tank on nights.
  • Using your finger as a work steady on a long component.
  • Dividing heads.
  • Clocking in cards.
  • Smearing engineers blue onto machine handles in the tea break.
  • Shaping machines
  • Vernier Scales.
  • Slide Rules.
  • Donny Osmond
  • Opportunity Knocks
  • Making star shapes in sheet steel to throw up and stick in the ceiling of the sheet metal training department at Rolls Royce.
  • Cleaning my Norton motorbike parts in the degreasing tanks.

Listen to David “it’s time to let this shit go”

You might be stuck in a 1950’s time warp but it’s costing you money.

Wibbler Wobbler

When you use a Wibbler there are so many things to go wrong. Get the speed wrong and it will kick off at the wrong point. If you don’t engage it far enough down the part it will probably snap off.

Maybe if you practice for long enough you can set a datum in less than an hour.

Why am I telling you this?

Just bin it and spend just a small amount of cash on some of the more up to date solutions.

  1. Buy a full blown probing system such as Renishaw, Blum, M & H.
  2. Buy a 3d taster type tool, loads to chose from.
  3. Electronic edge finder
  4. DTI clock
  5. Cutting tool
  6. Rip off a bit of paper

In that order the costs are thousands, hundreds, tens and units.

Advantages of a CNC touch probe

There are many, you can quickly set your part datum must be the most obvious one.

If the probe software is already on your machine then your machine will most likely have all the routines built in. These will quickly set your datums on corners, centre of bosses and bores and in slots. All at the press of a soft key.

Also you can quickly set your indexer or fourth axis to zero. Not least of all you get to measure shit. That means anything you make on the machine you can check all it’s sizes without taking it out of the machine.

CNC touch probe

If you can be arsed to learn Macro programming then the possibilities are endless. This will allow you to write your own routines and cycles.

For example within a program you can measure a part and update it’s offsets ready for the next run. Most probes will have simple cycles with this built in.

Don’t forget to download the apps for your probing system, the Renishaw one is amazing it just guides you through what you want to set or measure and then gives you the cycle. It even tells you where the results are stored (Variables)

You can even use your touch probe to recognise fixtures or parts. It’s quite common to drill holes in strategic places on fixtures so that the probe can detect the presence of the hole and thus identify the fixture.


It is a good idea to justify the cost of your probing system, do this by timing setups and things without the probe.

Soooooo, when you bust it which inevitably you will. Look back at this justification and you’ll see that the cheapest option is to buy a new one I guarantee.

3D Taster or similar

I love these, I mean I really do. I actually sleep with one by my side I love it so much, oh and it doesn’t fart all night like the fuckin dog did.

When these devises are on the edge of your part you don’t have to allow for the diameter of the ball, it’s all done for you. Magic how do they do that?

It is worth spending time setting these up getting them calibrated to length and running really true.

Once you clocked it all up, take some time here to get it spot on. Oh yea and keep it in the same holder so it’s always calibrated true and to length.

Don’t leave it in the machine although the new ones are waterproof.

This means that by simply zeroing your display in X Y or Z you can use it to accurately inspect your parts.

Make sure to get the long stilus this means you are always well away from the body when your using it. Worst scenario is you break a stylus. It’s like cleaning up dog shit, best done at arms length.

CNC touch probe

Easy to Break

Handle with care because these devices are easy to break. Don’t don’t don’t leave it lying on the bench. It will roll off and fuckin break so put it on a proper stand.

These are not too expensive to buy. You can even make your own from an old porridge box and the cardboard centre of a toilet roll.

Here’s one I made earlier not quite fully developed but you can see where I’m going with this one.

CNC touch probe

Learn Macro Programming

By the sounds of this you’d think I ran a training school. Really how cynical of you.

But really if you can write macros you can do loads of clever stuff with 3D tasters by getting them to write into system parameters n stuff. Once you are in position you can automatically write into your work offsets.

Electronic Edge Finder

Still way better than a wobbler these devices pick up the edge of your part and sound a buzzer as well as lighting up. They don’t work on all machines as a circuit needs to be completed.

Again there are loads of macros you can write to make life easier.

Not good on Z as the ball does not compress.

DTI Gauge (Old School)

This method was traditionally used on jig borers and is very accurate if a tenth clock is used.

Very time consuming and fiddly but it is accurate.

Use your dti gauge to find the edge of the part. Simply rotate the clock on the edge of your part and zero the dial. Now zero your position display on your machine.

Hold a slip gauge on the edge you just zeroed. Now clock the slip on the opposite side.

Half this final figure on you REL display to get to the edge of your part.

dti gauge

Cutting Tool (Endmill)

Touch your endmill on the edge of your part, best to have it rotating.

Move over the radius of the tool. Some controls even have a screen with icons to do this.

Make sure you know the exact diameter of your endmill and make sure it is running true.

Safety First CNC touch probe

If you use an electronic probe there are no safety issues unless your boss thumps you for breaking it.

Some of the methods decribed above are quite tricky to do with the machine doors closed so be very careful.

Never try to override any doorlocks or safety mechanisms on your CNC Machine






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