Do what I want, not what I say!

[RandyWilson]

I drilled my first DRO driven circle pattern today. A Chinese DRO with fun instructions. totally useless instructions, but fun to read in a public setting none the less. So like every other function on this thing, I winged it. Target is 127 holes on a 7.75" circle.

Select holes-on-circle button

It asks for DIA. I want 7.75", so input 7.75

It asks for Org and suggests 0. I accept 0

It asks for End and suggests 360. I accept 360

It asks Num, and I input 127.

I then dry run checking every ten points or so. First uh-oh is the first co-ord is 7.75, 0. Run through it to hole 64 and it's a -7.75, xxx. Ohhh kay. It asked for Dia, but really wanted Radius. So I exit and re-enter everything using 3.875 as the "Dia". The dry run looks okay. I didn't look close enough.

The second rut-roh Shaggy can as I passed 90 degrees. The Y coord didn't change betwen the two holes either side of 90. I should stopped and thought it through. But I drilled on to the end..... figured out my massive blunder, then redrilled the entire thing at a radius of 4.05".

Anyone see my mistake? No it's not finished, but the mistake is not in the picture. I had to reclamp it to bore the center out and drill a small pattern or two that I'll need.

 

[JimDawson]

I think the end point should have been at (360/127)*126 or 357.1653° since you started at 0

 

[RandyWilson]

Yep, but that's the hard way. Set the number of holes to N+1. Since 360 is the instant start point of the second rotation , we want the 128 th hole at 360 to be the same as the first hole at 0.

 

[RJSakowski]

On my Grizzly DRO, I enter the center, the diameter of the bolt circle, the no. of holes, the start angle 0, and the end angle 360. The first hole comes up at 4.000,0.0000 and the last hole comes up as 3.9972,-0988. 127 holes on a 360º circle.

 

[RandyWilson]

Interesting. We're dealing with what we called a "fence post error" back in my programming days. Say you want to build 100 feet of fence with posts every ten feet. How many posts do you need?The answer can be 9, 10, or 11. It depends on if you are connecting two existing fences, extending an existing fence, or building a new free standing one.

So, let me pose a hypothetical question. You dial in the DRO to do 10 holes, start point at 0, end point at 90. Do you get holes at 10, 20, 30, ....,90, or do you get 9, 18, 27.... 81 (approx), with it ready to put the 11th hole at 90? In this case I would expect the first behavior which is what I got when drilling the 127 full circle, I wanted the second, but got the first.


This is a three year old GCS-9000, which is what was common on Alibaba at the time.