Lathe DRO from Digital Caliper .. 10 Bucks .. 6" caliper has range of entire 16" bed

[jjr2001]

I was in the process of completing my little steam/air engine and have quite a few
small parts to turn. I had previously added a graduated dial and handle to my
lead screw which works pretty good but it is much faster to use a DRO on the carriage.
Not only faster but easier to set distances to be turned. It does not interfere with
the threading dial or the tailstock. The only limitation is the 6" length of the caliper but
the caliper may be placed wherever the 6" of travel is needed. Most of my parts
are not 6" long.

So off to the shop. I used an older 10 buck HF digital caliper. Cut off the inside and
outside jaws with an abrasive grinder, drilled and counter sunk one hole in the main
body of the slider. Drilled one hole in the remaining part of the jaw for attachment
to the carriage. Drilled and tapped one 6-32 hole in the carriage right rear as shown.
One hole drilled in the carriage was all that was done to the lathe. The last part would be
the large sliding nut that fits a 10-32 allen cap screw which holds the main mount and
allows it to be positioned within the slots.

Made one aluminum angle for the main mount. This angle has two vertical slots
that line up with the holes for the rear chip shield that I previously removed and
mounted on a small frame that sits on the bench. That makes it much easier to
work with my taper attachment and clean up chips. It has two slots that the mounting
block for the caliper can be inserted into. This allows the 6" caliper to read the
entire 16" length of my mini lathe. The main mount may be located where most
convenient for the part being turned. Six inches of continuous travel is so much
better than using the 2" dial indicator that I had rigged up previously.

Here are a few pics of the result of this one evening project:

Cheers, JR

[mklotz]

Nicely done, JR.

I've been told that the stainless in these calipers is harder than the hinges of Hell. The fact that you used a grinder rather than a saw to modify the calipers suggests that there may be some truth to that. How difficult was it to drill that hole in the jaw? Did you use a carbide drill?

[jjr2001]

Thanks Marv, The steel on the jaws is quite hard. I actually put the entire slide minus
about 3/4" of the jaw in the aluminum jaws of the vise and tempered it prior to drilling.
Then I just used a center drill and followed with a twist drill.
The sliding frame at the rear was not that hard and I just center drilled, twist drilled and counter sunk for the 6-32 screw.

I ended up distorting the facing on the slide a bit and would use some new smooth aluminum if I
were to do another one. However I don't see any errors in the readings comparing it to my
old dial indicator method. Time will tell how long it will last. It is very nice to use.

Cheers, JR

[DIYer]

Thanks jjr2001! We've added your Lathe DRO to our Lathe Accessories category,
as well as to your builder page: jjr2001's Homemade Tools. Your receipt:

Lathe DRO by jjr2001

tags: lathe, DRO

[Al8236]

One point I think worth mentioning here for anyone doing this is the caliper choice. The calipers from Harbor Freight have an auto off function that on the decimal/mm caliper turns back on at 0.000" whereas the decimal/fraction/mm model turns back on at its last known setting, this can be a real problem if you stop to look at plans / think about your next step etc. and the caliper auto-offs requiring you to re-start your settings from a known point! I highly recommend using the unit that starts from its last known position.

[mklotz]

One point I think worth mentioning here for anyone doing this is the caliper choice. The calipers from Harbor Freight have an auto off function that on the decimal/mm caliper turns back on at 0.000" whereas the decimal/fraction/mm model turns back on at its last known setting, this can be a real problem if you stop to look at plans / think about your next step etc. and the caliper auto-offs requiring you to re-start your settings from a known point! I highly recommend using the unit that starts from its last known position.

Many of the cheap import calipers, such as those sold by HF, memory or not, have their measurement electronics on all the time; turning them off merely turns the display off. This constant drain on the battery means they eat batteries rather quickly.

In a fixed application like this, an external power supply would be a very good idea. Make an SR44-sized button of non-conductive material, glue on some thin electrodes to which are attached some fine wires and stick it in the battery compartment. Attach a 1.5 volt D-cell to the wires and you won't need to worry about mid-job battery failure.

This high rate of battery consumption seems to be a feature of the cheap calipers coming from China. I have two Mitutoyo calipers (Japanese), one with no memory and the other with memory, and they both go years before needing a new battery.

[rossbotics]

Good job jjr, that will definitely help you with your linear measurements, turning something to a precise length will be allot easier now, might as well go ahead and do this to your cross slide and tail stock now, what the heck it's only money.
Great Job

Doug

[jjr2001]

Good job jjr, that will definitely help you with your linear measurements, turning something to a precise length will be allot easier now, might as well go ahead and do this to your cross slide and tail stock now, what the heck it's only money.
Great Job

Doug

Thanks Doug, I will do the tail stock in the future but I have not found a "good" spot for the cross slide.
Just seems like it is in the way and I can usually keep track of the dial without too much "measuring twice".

Marv, Thanks for the tips on the battery. I think they may have changed their design on the shutdown for the newer calipers.
I have one that is at least 5 years old and it might get a battery once a year. The others are newer and the same applies. I do
not seem to have a battery run time issue with any of them. I have notice that the Pittsburgh type seems to quit shutting down
when the battery gets low and that certainly makes the battery die shortly after that. I never trust them fully and always check
with a micrometer on critical dimensions. Just bought two new igaging 6" digital calipers and they are very nice right out of the box.

AI8236 Could you tell us how to identify the calipers that don't keep their readings. I have several HF and Igaging in the shop and
they all keep their settings after a power restart. Just moving the caliper turns them back on and they all just continue from where
they were set when they powered down. I have both the inch/mm and the inch/mm/fraction type and they all retain their position.


Thanks to all and

Cheers, JR

[Al8236]

I really don't know of a way to tell the ones that don't keep their readings other than to open the box and trying them out.
The ones I have are all 3-5 years old so perhaps they have changed the design or found a new manufacturer but none of the inch/mm ones I have will retain memory.
Sometimes they feel like they have grinding dust in them and are gritty to operate so the last time I bought some I opened about 10 boxes and picked the best 3 out of the lot.
As far as the batteries I have found them to last anywhere from a year to a year and a half unless the shop gets below -10 deg. that seems to kill the batteries where warming them up won't bring them back.

[Toolmaker51]

I'd add some detail.
Measuring this way is a real plus when;
1] Accuracy in the readings versus actual movement relate to machine axis/ instrument axis having the best alignment you can determine.
Some rightly say the difference can be negligible.
2] Careful fabrication and installation hold parallel in two planes, that is a good start. Minimize sine error.
3] Without testing, variance in completed set-up present at least one unknown factor...

Setting a 2" travel indicator squarely by eye has less potential error than 6" of another instrument. Only when two different methods reveal agreement [or acceptable divergence] that's baseline or more correctly a ratio.
Example. Graduations on handwheel and indicator are within .002 in 2 inches, digital scale should have .006 in 6" or less.
Comparing two kinds of readings will also determine backlash.