machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most. n.b. There is a list of my first 800 posts in my post of 17 June 2021, titled "800 Posts"

Tag: DRO

Digital Read Out (DRO) for Colchester lathe, and problems with Apple Mac

WTF is going on with Apple?

Since Steve Jobs died, I have had nothing but difficulties with My Mac.

I upgraded to the latest operating system for my Mac, and since then I am unable to insert photographs into my Word for Mac.  And it is a real hassle trying to insert photos into this blog.   That is one reason why my posts have been less frequent lately.

There has been a couple of patches for the latest Mac OS, but still problems.  Are they competing with Microsoft to be the most user unfriendly OS?

Anyway, I have not done much on my Triple expansion steam engine.  Any spare time in the past few weeks has been spent on the Colchester lathe.  The quick change tool post from the USA has been a big success.  I have been installing a digital read out for the past few days.  Finally hooked it up today, and it works.


It is not CNC, but is the next best thing.  The imperial lead screw and imperial dials are much less relevant, when you have a DRO, which is set to metric.  And I really like setting the cross slide to diameter mode, being able to set the micrometer readings on the workpiece to match the readings on the X axis on the DRO.  Of course the Z axis readings remain set for actual movement, mm=mm.

The DRO came from China via Singapore, from thedrostore.  I have bought several DRO systems from thedrostore and they have always been relatively cheap, well packaged, fast, and with comprehensive instructions.   Thanks Scott!

The installation of cross slide scale on the Colchester was problematic, due to limited space, despite buying the “mini” scale, and I eventually positioned the scale on its side.  Said to be OK by thedrostore instructions.

I do not have space to install the Colchester in my workshop, so it is still sitting in a storage shed, on a pallet.  I am supposed to sell some other lathes, to make space for the Colchester, and to appease SWMBO.  But I have a real problem.  I just cannot part with any of my other lathes.  I obviously have a disease.  What to do?

TAPPING HOLES. BOLTON 9. (Triple Expansion Marine Steam Engine)

Today I drilled and tapped the holes for the bolts which secure the crankshaft main bearings.  I had accurately marked the bearing mounts  in the previous session (see previous photos), and calculated and recorded the DRO (digital read out) position for each hole.  So going back to that position for each step in the process was easy and quick.  The steps today were centre drilling, drilling the 3.3mm holes, and tapping the 4mm threads to a depth of 20mm.

Centre drilling is done with a centre drill bit in an accurate chuck in the milling machine.  Centre drill bits are inflexible and will not wander over the work like an ordinary twist drill bit,  The centre drilled hole is deep enough to create a chamfered edge to the hole.  All 12 holes are drilled with the centre bit, then all 12 drilled with the 3.3 mm bit, then all 12 are threaded.  The DRO positions the work within 0.005mm each time, and the repositioning is very fast, much faster than going to a position doing all 3 processes, changing the bit for each one, then moving to the next position.

The threading was done with a Tapmatic 30 tapping head in my milling machine.  See photo.  This takes about 10 minutes to set up, but the tapping process for the 12 holes then took about 5 minutes.  I use Rapid Tap lubricant for tapping, even in brass.  I guess that manually tapping the holes would have taken about the same time, but it was so satisfying to see the Tapmatic do its stuff.  I use the Tapmatic for any tapping job involving more than about 8-10 holes.  Fewer than that it is quicker to do them manually.  The Tapmatic has a adjustable clutch.  I have never broken a tap in the job using this machine.

Incidentally, I have decided to use nuts and bolts and screws and studs in preference to metric cap screws for this model.  The appearance wins out over practical expediency.  So why the metric threads for this job today?  The specified thread was 5/32″ which is 3.96mm, so I decided to go with the 4mm metric, for which I have the tools already.


Tapping the main bearing blocks using the Tapmatic and Tap Magic.

Tapping the main bearing blocks using the Tapmatic and Rapid Tap.