How do I accurately drill evenly spaced holes?

[mmcmdl]

The old fashioned way . On a handheld calculator , store .417 . Press 0 + reclaim . Repeat for however many holes needed . Personally , I would not do this incrementally on your DRO . You could be stacking tolerances on each move so stay in absolute .

 

[tq60]

Use the spreadsheet or just a piece of paper and calculator.

If more than 3 do not do the reset to zero and move as errors compound.

By having a set of "targets" then any errors are singles.

Good short and rigid starting drill helps as bit may wander on entry.

What size hole?

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[RJSakowski]

When making drawings, I always dimension my arrays using ordinate dimensions rather than the incremental distances. This is largely to eliminate stacking errors in machining. For example, if the spacing between holes is .500", there will be an allowable tolerance for that spacing, say +/- .001". If there are ten holes in the array, the final hole could be off it's desired position by as much as .010". By using ordinate dimensions, the actual position will be the desired position by the specified tolerance, in this example, +/-.001"

 

[Shootymacshootface]

Use DRO, if no DRO, then use the dials. If you have to match holes on something you can access use a transfer punch.

 

[yukon_rose]

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.

This one works for me. I wanted a "self-contained" method. That is, No Computer. No Calculator. No hand written list.

I bought a DRO so I could avoid all the "peripherals".

Thanks.

Gary

 

[LKeithR1946]

A DRO is a tool, not a crutch. A good, high quality DRO will do this in incremental mode just fine
without producing stacking errors. With a cheap one you may see some small errors. A lot depends
on how accurate everything needs to be.

Having said that, if you've got to create a table of coordinates and use absolute mode to locate your
holes that's what you've got to do. Make the best use of your tools but also understand their limitations...

 

[Latinrascalrg1]

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.

If you slightly modify your design so that there are 3 holes properly spaced and in line with one another along with 2 locating pins you will have a jig that both properly spaces the holes while Also keeping them straight in line without needing a 2nd jig. If you add even more holes and pins to the jig you will gain a more precise placement for the next hole.