Retrofiting a Table Lock on an 1100

[DLawrence]

Have been doing runs of several hundred phenolic gear blanks, and stacking them 5 high to drill, ressulting in stack heighth of about 1.250

The top one or two have a hole dia at least 2 or3 tenths larger than the ones on down in the stack, this I attribute to compressability of both ballnut springs and so on, allowing viberation or wiggle which stopps as the drill enters more deeply into the stack. And this does matter . A very experienced machinist seemed to be sure this would happen without table locks, I am thinking how to implement such....on x and y axis

The both axis table backlash is well within Tormach specs, using their specified measuring method.

Any thoughts on this ....other reasons for the dia descrepancy or way to approach the locking ?

Thanks
Dave

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[smokediver576]

What about some sort of bushing on top? Just throwing a sticky ball at the wall.

[mountaindew]

Mount drill in collet not a Jacobs chuck. High quality drill bit would be my next step and supporting the stack in a column style holder Andrew mentions. Mostly when I want nice holes I use end mills or mill/drills and or drill bits sized smaller and then ream to size.

[ShortTrack]

DL;
Just a quick thought here, and you are likely on top of this already...

I would first lock the table in place manually, then execute the snippet of code that does the holes and see if there is a difference. No need to pursue locks if the problem is elsewhere - such as the areas Mountaindew suggests above.

-ST

[Davez64]

Have been doing runs of several hundred phenolic gear blanks, and stacking them 5 high to drill, ressulting in stack heighth of about 1.250

The top one or two have a hole dia at least 2 or3 tenths larger than the ones on down in the stack, this I attribute to compressability of both ballnut springs and so on, allowing viberation or wiggle which stopps as the drill enters more deeply into the stack. And this does matter . A very experienced machinist seemed to be sure this would happen without table locks, I am thinking how to implement such....on x and y axis

The both axis table backlash is well within Tormach specs, using their specified measuring method.

Any thoughts on this ....other reasons for the dia descrepancy or way to approach the locking ?

Thanks
Dave

I would drill a smaller hole first, followed by final drill or reamer.


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[nitewatchman]

[QUOTE=DLawrence;2209566]
The top one or two have a hole dia at least 2 or3 tenths larger than the ones on down in the stack, this I attribute to compressability of both ballnut springs and so on, allowing viberation or wiggle which stopps as the drill enters more deeply into the stack.
/QUOTE]

To me "2 or 3 tenths" assuming that we are in fact talking about 0.0002" to 0.0003" variation in a drilled hole is quite remarkable.

Typically, I see this caused by run out in a chuck or most likely caused by one flute lip being ever so slightly longer than it partner pushing the drill dead center out of center. There is slight wobble when the drill starts that tends to be stabilized as the drill flutes enter the drilled hole. I would suggest a drill, bore (could also be a plunge with an end mill) and ream operation.

gary

[Eldon_Joh]

[QUOTE=nitewatchman;2209914]

The top one or two have a hole dia at least 2 or3 tenths larger than the ones on down in the stack, this I attribute to compressability of both ballnut springs and so on, allowing viberation or wiggle which stopps as the drill enters more deeply into the stack.
/QUOTE]

To me "2 or 3 tenths" assuming that we are in fact talking about 0.0002" to 0.0003" variation in a drilled hole is quite remarkable.

Typically, I see this caused by run out in a chuck or most likely caused by one flute lip being ever so slightly longer than it partner pushing the drill dead center out of center. There is slight wobble when the drill starts that tends to be stabilized as the drill flutes enter the drilled hole. I would suggest a drill, bore (could also be a plunge with an end mill) and ream operation.

gary

if the drill bit is only a few inches long then the hole at the bottom will be on diameter while the hole at the top will be larger by about half the diameter of the run out, regardless how bad the drill is ground.. (presuming the hole is already drilled)