Purchased - Mill DRO

Proposal Type:

Kevin Welton - WeldyGrindy

The WeldyGrindy team have discussed purchasing a 3-axis DRO for the metal mill, and I volunteered to research options and write this proposal. A DRO will significantly expand the capabilities of the mill, without the need for any extra training beyond the already compulsory induction process.

Proposed Purchase:
Having researched a range of sources, I plan to buy the equipment from AliExpress, specifically the machine listed HERE. This kit contains 3 linear scales with a 5 micron accuracy, a digital display, and all cabling/mounting hardware.

There are many, many DRO variants available on AliExpress, which had the lowest prices (even when factoring for VAT). My choice is not the cheapest overall, but it is the cheapest option I could find with a couple of KA-500 scales. In the lengths required to fit the mill, there are two common scale options: the KA-300 and KA-500. Some of the axes on the mill have a limited amount of space for fitting the scales, and I’m concerned that we may have trouble finding enough clearance for a KA-300, which is why I’ve opted to go for the less common KA-500, a slimline scale.

Proposed Installation:
This DRO is to be fitted to the existing metal mill, and will require no additional space. I will perform the installation, with help from other members of the metalwork team.

The listed price is £286.11; while not stated explicitly, my assumption is that this price is exclusive of the VAT which will be due on import, giving an estimated total of £343.32.

There will be no ongoing consumables cost for this device.

Funding type:
Fully funded by Hackspace.

Health & Safety

This will not require any change to the existing risk assessment for the metal mill.

Medium Proposal < £500 - Majority of Board Members and 10 general members

Board Majority Agreed?:
3/5 - yes

Supporting Members:

  1. Kevin Welton
  2. Marcus
  3. Samuel M.
  4. Thinkl33t
  5. garlicbread
  6. MikeH
  7. FoodNoTear
  8. Nathan
  9. RJ
  10. BlueTin


Count me in


+1 from me

I support this!

I support this




Hi Kevin,

Thanks for putting this together, sorry i’m not familiar with what a dro is. It looks like a measuring device from a quick google?

I’m always weary of AliExpress, just as you never know whether what you’re actually going to get will live up to the published specs. Is there a chance of this becoming an expensive brick that doesn’t do anything with no chance of repair? How much are we looking at for a UK based seller? I had a quick google as a sense check, and i presume units like this are no good.

I’m generally in favour but just want to check this before i give my support.

Basically a dro stands for digital read out
it’s a set of 3 slidy bits that fasten to the milling machine that measure exactly where it is in all 3 dimentions (forward / back, left / right, up / down), in this case of around a 0.005mm accuracy.
and a single box that shows a readout of it’s position in number form (300mm across to the right, 50mm to the front, 2mm down etc)

The reason why these tend to be very useful on milling machines is that you get a certain amount of backlash or slop / wiggle in the gears so when you move 200mm left then 200mm right you might loose a tiny bit of travel without realising it which throws off the tiny measurements, so instead of ending back where you started you might be off by 0.5mm for example which can be an issue with metalwork.

In the case of DRO’s aliexpress is ok, there’s quite a lot of examples online of people fitting them. The main unit is fairly simple as a digital read out, and the sensors are optical along a glass side with tiny engraved grooves.

Trying to get one outside of aliexpress would be too expensive typically.
I think when we asked the guy we bought the mill from he said he just bought them from china in the same way so I can’t see it being an issue.

Thanks for clarifying Richard. I’m guessing the one I linked is the screen only and to use it we’d need to buy 3 scales in addition?

Here’s my board +1

@DominiqueTink and @AlanPatrickGood might hopefully be able to add their support.

You have my support! :grin:

[Apologies for the delayed reply - work was utterly frantic, then I got sick. =8( ]

@Josephxtian: you are correct in that your link was just for the display, you’d have to add the cost of 3 sets of scales on top of that. My searches had suggested that prices were significantly higher, like-for-like buying in the UK rather than from China, but now I’m not quite so sure of that.

I found an equivalent offering of my proposed system on eBay for £348.00, which is inclusive of VAT, therefore comparable to the AliExpress listing. Buying the parts separately, the total would come to £530.88, very close to the £539.00 it would cost to buy a full set of the discrete Warco components in the configuration we would need. I know that’s not comparing like-for-like, but I will have another quick check for UK-sourced complete systems, in case I’m missing something.


Looks like we have a Go on this - thanks everyone.

I now intend to buy the system from THIS eBay page, rather than AliExpress - £348.00 for the 2x KA-500, 1x KA-300 option.

Hiya Kevin,

Is there an update with this?

We’re getting the parts fabricated ready for installation. I’ll chase people up.


Hey Kevin,

Just so we can close up this thread, this is all installed and working now i believe?