How do I accurately drill evenly spaced holes?

[yukon_rose]

I need to accurately drill a bunch of evenly spaced holes. I have a drill/mill with a DRO attached. The holes need to be spaced 0.417" apart making it difficult to position the mill table and make sure I don't calculate each position incorrectly.

What do you suggest?

Gary

 

[Cadillac]

Write down all your coordinates before you start the job and have on the mill table to help you remember.

 

[extropic]

I need to accurately drill a bunch of evenly spaced holes. I have a drill/mill with a DRO attached. The holes need to be spaced 0.417" apart making it difficult to position the mill table and make sure I don't calculate each position incorrectly.

What do you suggest?

Gary

Your problem isn't clear to me. How many holes is "a bunch"?
Is the problem that the number (N) of holes (and the length of your work-piece) is a pattern exceeding the table travel?

 

[brino]

Is it keeping track of the math of repeatedly adding 0.417 that's the problem?
You could zero that DRO axis after every hole and just keep cranking to 0.417".

I do NOT have a DRO, but I have previously made up excel spreadsheets to help me keep track of "stepping over" for cutting a rack, etc.

A few more things......

What exactly do you mean by "accurately"?
0.4170" or
0.417 +/- 0.001

Is that 0.417 the centre-to-centre distance, or the material left between holes?
If the latter, then you need to figure the hole size in too.

Knowing the application would help us to help you.

-brino

 

[Technical Ted]

When I need to do something like this I use an Excel spreadsheet and print out the calculations. Easy peezy...

Ted

 

[Technical Ted]

Did this in about 3 seconds...

Ted

 

[ttabbal]

With a DRO, I would do this..

Find the first hole.
Lock the table.
Spot drill, drill and ream/bore as needed.
Switch DRO to incremental mode and zero.
Unlock and reposition.

Now just repeat for however many holes you need. Keep the other axis locked if possible. Switch back to absolute mode and your zero from the beginning is preserved.

 

[BGHansen]

Depending on your DRO, you might have a linear spacing function. Pretty sure mine from TPACTools.com (5 years old) has it.

Couple of methods; punch in the starting coordinate and ending coordinate and tell it how many holes. The down arrow key steps through the coordinates to each hole. The DRO targets each subsequent hole at 0,0; so do a hole, hit the down arrow to move to the next hole and move the hand wheels to 0,0.

The other method is incremental: Go to the start coordinate and tell the DRO the offset for each subsequent hole. Do the first hole, hit the down arrow and the DRO updates 0,0 to the next hole. Hitting the down arrow steps further down the string, up arrow works upstream.

Lots of good ideas above this post that'll work well also.

Bruce

 

[ttabbal]

I always forget my DRO has a linear pattern function!

 

[RJSakowski]

Another way for those without an accurate way of moving work is to make a jig consisting of two holes with the proper spacing. The frirst hole is drilled and a pin which fits the hole is inserted in the first hole on the jig. The second hole now indicates the position of the next hole. That hole is drilled and the jig is moved to the next position.

A secondary fixture like a fence is needed to keep the holes in a straight line and one needs to realized that errors stack up so the jig spacing needs to be accurate. Drilling a large number of holes will cause wear on the jig. Hardened drill bushing are available to prevent that. Another way is to cut a drill down so only a short length of the flute is left. Regrind the drill tip and you're in business. A center drill will also work for drilling a pilot hole, then follow with the finish drill.