DRO error

Hello all i am a newbie at milling so my question might be simple for you to answer but it is driving me mad,i recently bought a Chinese 3 axis dro and was testing it out once i fitted it so i started on the Bolt hole patterns and inputted all my info 20 mm diameter, 4 holes ,first hole starting at 90 degrees and when i went through the process of moving to the given coordinates and tapping the work piece with a centre drill when all 4 inputs where done the drill holes weren’t spaced out equally as i expected so i went on to a web site and inputted all my info into the online Bolt hole calculator and checked it against my info on the dro and it was different now i can get to my question have i missed out something whilst using my dro to get the wrong coordinates i haveposted a small video on youtube which shows what i mean any help would be very grateful

youtube link is https://youtu.be/WX0OlsN_QnY

Thankyou in advance

kevin

Hi Kevin,

I think it's because you have put the end angle in as 0°. It should be 360°

The DRO is thinking that you want the four holes to cover an angle of 90° instead of the full 360°.

John

Edited By John Baguley on 23/05/2020 01:01:26

Wow John many thanks for the speedy reply i cant believe im that stupid i will give it a go straight away and let you know

thanks again

kev

I would tend to enter 4No holes start at 0, end at 270 for ones at right angle to the axis, if diagonally placed then 4No, start at 45 and end at 315.

There is an alternative which is to enter 5No holes start at 0 and end at 360

That's a useful feature to have that would be very handy. My DRO, s are just the simple basic type so it's Zeus and a calculator for me but it works well enough.

Maybe one day though.

Many thanks for all your advise its a lot for me to take in but ill have ago at every suggestion

thanks again

kevin

No need to think you're stupid Kev, you got a quick answer because so many DRO owners ask the same question!

Dave

It's rarely explained well in the manuals being one of those obvious when you twig it things that can be totally impenetrable if you don't get it straight away. My usual approach to explaining such things has been to wave a ruler or, better, seamstresses cloth measuring tape at folk. Usually takes a time or three before they agree you need 5 positions to define 4 spaces or whatever. Then roll it round a circle and, usually, the penny drops.

Imperial inches work better than metric centimeteres!

As Jason says you don't actually have to step round the last space as it "should" be right if nothing has moved. Being an untrusting soul I always do the last step. Its never been wrong yet but I just know that the one time I don't and just trust things the gremlins will swoop ...

Another point to be wary of is that with many of the affordable DRO systems the more advanced functions either don't work at all or don't behave properly in imperial measurements. Best to check that everything behaves and works as you expect whilst all is new and shiny.

Do as I Say not Do as I Do advice. I'm invariably up to my ears in something complicated when forced into using the clever stuff on anything for the first time. Nowt like a bit of pressure to ensure you get it right first time I say.

Clive

Don't worry about it Kevin. I did something similar the other night. I also wanted four holes, put the start angle as 90° but put the end angle as 270°. Took me a while to realise what I was doing wrong.

Only just learnt the difference between Absolute and Incremental measuring after watching a YouTube video by Joe Pie!

John

I fell into the trap in the early days of my dro but have now got into the habit of adding an extra hole and using an end angle of 360 as Jason suggests which suits most of the work and only requires a little extra thought if starting at a different angle.

Different DRO's handle it differently too you'll have to experiment (or read the manual)

For instance, mine will give an error if you set the end angle to 0. If you specify end angle as 360 it'll put a full-circle pattern in starting from the start angle (regardless of the value) but if you specify anything below 360 it'll put a part-circle pattern in between the start angle and the end angle. It might seem strange at first but it makes a lot of sense.

This is an interesting discussion. On my commercial (Newall) DRO on the vertical mill I have a bolt hole function, but it assumes the holes are spaced around a full circle. You enter the centre point, circle diameter, number of holes and the starting angle (zero being at 3 o'clock). Then you zero the display at each press of the > key to move to the next hole. Dead simple and no confusion between holes and spaces. In nearly 20 years of operation I've never had the need to space holes around part of a circle. If I did I'd simply enter data for a complete circle and stop part way, or use the CNC mill.

Is this a case of more not necessarily being better?

Andrew

I dunno Andrew, it sounds like mine is just like yours except you have to specify 360 for a full-circle. It remembers the setting though so I never change it and like you I've never had to drill an arc of holes.

I suppose it's no harm having that function even if you never use it, when it doesn't complicate 'normal' useage.

Andrew.

How would you do an arc with, say, 7 holes from 0 to 200 degrees on the Newall, if you had to? Seems like it might be a bit tricky if it only works with a complete circle.

Martin.

Use 108 holes, drill the first hole at zero and then drill every 10th hole with the last at 60.

Andrew