What's new
What's new

Sino DRO install on Wells index mill

jlakes85

Aluminum
Joined
Sep 10, 2011
Location
Northern NJ
I just finished a 2 axis install on my model 847 Wells index mill. The scales are off by about .003 in y and .002 in x. This appears to be a fixed error as I'll show 2.002 and 19.002 in x, and 2.003 and 9.003 in y. Since this doesn't appear to be cumulative, where would be the first place to suspect a mistake in the install? Machine is well used so I'm not sure if this might be as good as it gets and trying to hit the .0002 is a pipe dream.
 
Scales are off based on what? What are you using as the length std and what are you mesuring it with?
 
I just finished a 2 axis install on my model 847 Wells index mill. The scales are off by about .003 in y and .002 in x. This appears to be a fixed error as I'll show 2.002 and 19.002 in x, and 2.003 and 9.003 in y. Since this doesn't appear to be cumulative, where would be the first place to suspect a mistake in the install? Machine is well used so I'm not sure if this might be as good as it gets and trying to hit the .0002 is a pipe dream.

There is a reason it was cheap. Spend 3x as much for an Acurite and it will be accurate.
 
Can we see some pics of your mounting? aside of any compensation adjustments a more experienced eye may help you to detect a mounting issue. Also, do remember if there is any wear in the machine you will often see changes in one axis when positioning the other.
 
There is probably your issue, your measuring the slop - error in your screws. Normally scales will only ever read short if they get crud build up and need a clean, do to how they work its incredibly unlikely they would read long. If you have some gauge blocs stack em together then measure those and see what you get.
 
Adama,

Gotcha. I thought I would be ok just going in one direction only from say 2.002 to 16.002 in 'x'. I wasn't expecting uneven wear in the lead screw pitch, which is what I think you're referencing, correct?
 
my “ sino/tpactools/ DRO pros elcheapo” DRO on my mill was showing an error like that when I first installed it. Turns out it was set to metric and the resolution was too high. I did a restore to factory settings and set to inch and .0001 resolution it was then within a tenth over 6”. I then did my linear compensation adjustment and it’s dead nuts.
Btw it’s been a good DRO for the past 2 years, I just bought a 2 axis for my lathe
 
Akajun,

Sounds good. I think I'm already set to inch as the error offset stays consistent rather than accumulate/decrement. I'll read up in the linear error compensation adjustment and hopefully that will do the trick.
 
IME if you want to mess with calibration you need to be comparing it to accurate length standard, not a worn lead screw. Most mill lead screws are a simple cut thread and they will have pitch errors, also any table slop can show as error so make sure you ways are tight, the further the scale is mounted from the lead-screw axis the more this effect is noticeable.
 
Greg,

Now that I'm reading this, I have to laugh too. Thinking back to when I just used dials, and I had to count something out in 'x' to 10.xxx or 14.xxx and I finally got to 50-70 turns and then some, I can't recall running into a miss that required me to scrap a part. Given the type of work I do, I'm thinking I should just leave the setup as is.

Adama, would would be the best gage block setup to check?
 
Does not matter, but a proper calibration of any new mesuring system is always nice - good practice, if you have a stack of gauge blocks or similar high accuracy length stds use a dti and you can prove which is out, but lead screws are not really pitch perfect especially over some distance.

Glass scales do to how there made - work are normally far more accurate, but you have a discrepancy and IMHO you want to get to the bottom of it.

As to dial counting, when ever i was doing it over long distances i learnt a crude layout with a sharpie + tape mesure sure prevented any miss counts,
 
In another life, I installed digital readouts and 99.99% of the time, the error was in the machine tool, either the lead screw, bearing backlash, or pitch and yaw of the table / saddle / knee (on a knee mill). As long as it is installed correctly and nothing is flexing, that scale is going to be accurate. An indicator and jo blocks should be used as a standard and the DRO calibrated to it (if it has that capability). If you need accuracy over a longer distance, shoot it with a laser. But yes, some kind of calibration against a know standard is advisable. Same theory as checking a new micrometer when you get it.
 
Mic standards if you dont have gauge blocks would be one option, you know there good to better than 2 thou!
 
As promised, here are some shots of the setup. I used a 4.000 gauge block to verify distance traveled. It looks like 'Y' is dead on while 'X' is still 0.0045-0.005 inches off. There is a linear compensation procedure listed in the Sino manual and oddly enough it can only be done in metric mode. I'm surprised X is the worst axis, since that is the much easier install.IMG_20180103_201458247.jpg
 








 
Back
Top