Author Topic: Suitable replacement for a Jig Borer?  (Read 1980 times)

Offline DeanDK

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Suitable replacement for a Jig Borer?
« on: November 24, 2016, 12:40:23 AM »

I'm from Australia, where quality used machines aren't easy to come by, and jig borer's that can fit in my man-cave are even harder to come by.

I need to drill small holes 0.5mm - 2.0mm in brass in very precise locations.

I had a thought (I have my flame suit on).

Would say using a Cameron Micro Drill Press (high speed, low runout spindle) with a high precision xy linear slide (Zaber brand) produce good results? The travel distance I would need would be 60mm in either direction.

Anyone care to provide insight why this would be a half decent/bad idea?   :scratch: :scratch:

Offline Jo

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Re: Suitable replacement for a Jig Borer?
« Reply #1 on: November 24, 2016, 04:04:59 AM »
Precisely how precise is precise?  :scratch:

Your average DRO scale is 0.01mm, the cheapy linear scales I wouldn't trust to better than 0.1mm. I would trust my Sexy to 0.001mm except that the library where he lives is suffering with a 5 degree change temperature at this time of the year  :(

With drills that small you could mark it out and centre punch for the drills to a better accuracy than the cheap scales.

Then we need to think about the drill speed/type  :thumbup:.

So many engines to build and yet so little time.

Offline Lew_Merrick_PE

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Re: Suitable replacement for a Jig Borer?
« Reply #2 on: November 24, 2016, 11:55:28 AM »
Dean -- Back in the Dark Ages (when I was an apprentice) we used a system whereby (1) we made a plate with a (standing "proud") X and Y (square) index edges to which were located three very precise "disks" with an accurately bored centerhole to position the center of the to be bored hole.  The location of said "disks" were such that the bored centerhole was at the precise location when the (three) "disks" were mounted (over the "working material") to the X and Y index edges and tangent to each other.  Thus, we could dial in the centerhole and be "on" within the tolerance of the indicator (usually .00005 inch).  The bored centerhole was large enough that we could "spot," drill, and ream/bore through it without disturbing the set-up.

I was burned out by an arsonist/thief in December of 1974, but I used to have a "roll away" chest that was filled with several hundred pounds of such "disks."  Back then, having such a "collection" was one of the hallmarks of a machinist who could work to great precision.  It is a labor and time intensive approach, but it was the way truly precise hole locations were laid out in the days before accurate way indicators were available.  ???

Online awemawson

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Re: Suitable replacement for a Jig Borer?
« Reply #3 on: November 24, 2016, 12:03:13 PM »
I used to have a commercially made 'setting out frame' - can't remember the makers name - that essentially was a pair of accurately marked axis with vernier scales that allowed you to move a frame that held what was effectively a drill bush to a precise location. Thus you could mark out a piece of work using the co-ordinates of points from your drawing.

The whole thing was compact and you clamped it to your work - it's entirely possible that I've still got it in a cupboard or drawer - if it surfaces I'll post up a picture.
Andrew Mawson
East Sussex

Offline hanermo

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Re: Suitable replacement for a Jig Borer?
« Reply #4 on: November 25, 2016, 05:01:11 PM »
Add cheap chinese 1 micron DRO glass scales.
You can easily do better than 0.01 mm, and I think better than that by a lot.

A high speed spindle, pre-drill, ream to finish.
I would expect to do == 2 microns in true position.

Are reamed holes that round ??
Most manufacturers say no, to 0.01 mm or so.