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Ok folks, I've been threatening to post this for a while now but finally have the time to do it. I've had all the parts in hand for months, but travel and RealLife™ got in the way there for a bit.
This thread is a demonstration of one method for mounting scales and a DRO (Digital Read Out) on a mill. The mill in question is the Sieg X2 mini-mill clone sold by Harbor Freight (HF 44991), and also by Grizzly (G8689), ToolsNow/Cummins (7877), etc. See this comparison page for more info. It is an entry-level benchtop mill, costs about $350-500, and is about the smallest mill that is useful for most gunsmithing projects such as finishing 80% lowers, making custom parts, and such.
Pretty much all the lower-end (< $1500) mills available are Chinese-made and as such leave a bit to be desired in the fit & finish and precision categories. They are typical of ChiCom products: cheap and serviceable, but a bit crude and rough. One of the biggest shortcomings of these mills out of the box concerns the control of the X & Y movement of the table and Z movement of the spindle head: the mechanisms involved are not of the highest quality, and high-precision movement is difficult. Backlash is pretty much a given when changing directions, and can be hard to account for. On top of this, lead screws that move the table sometimes have odd threads, so that one revolution of the turn crank may move the table 0.0625" or something, which can make it a pain to count turns in order to move the desired amount. These are all issues that can be dealt with/worked around to varying degrees, but the best way is to install a DRO. A DRO keeps track of where the cutter is in real XYZ space at all times. It allows one to move an exact amount in any or all dimensions, return back to the same spot again, etc. No more counting turns if the handle, and if there is backlash, it is accounted for. So if you have a mill, you want a DRO.
OK, enough explanation and justification. Let's get on with the demo. Having made the decision to add a DRO to one's mill, one must choose a DRO. The available options range from complete packages including all scales, they display, mounting brackets, etc., to very DIY setups that require much more assembly and in some cases even electronics fabrication. As one would expect, prices vary accordingly, with some of the higher-end DROs costing in the thousands, and the very cheapest options a couple hundred. The DRO displays themselves range from simple 2- or 3-axis models that just show the current coordinates and can be zeroed, to actual small computers that can calculate the coordinates for round bolt patterns, take into account cutter diameter, and the like.
In the spirit of not putting Recaro seats in a Hyundai, it seems silly to spend more on a DRO that the mill cost to begin with, so I opted to buy the parts individually. I purchased electronic scales from Shars & a simple DRO display from CDCO.
Parts list:
Shars
12" Horizontal Digital Machine Scale 303-9307 1 $49.00
8" Horizontal Digital Machine Scale 303-9305 1 $39.00
12" Vertical Digital Machine Scale 303-9308 1 $56.00
Shipping cost $43.72
Total $187.72
CDCO
Item Number: 30011
Item Name: 3 - Axis DRO Display Unit ( Scales not included)
Price Each: $189.00
Quantity: 1
Order Sub-Total: $189.00
Shipping Cost: $15.00
Total Cost: $204.00
Here are the scales and display (the cables that connect the scales to the display are not shown):
From bottom to top, the scales will be used for the X, Y, and Z axes, respectively.
This thread is a demonstration of one method for mounting scales and a DRO (Digital Read Out) on a mill. The mill in question is the Sieg X2 mini-mill clone sold by Harbor Freight (HF 44991), and also by Grizzly (G8689), ToolsNow/Cummins (7877), etc. See this comparison page for more info. It is an entry-level benchtop mill, costs about $350-500, and is about the smallest mill that is useful for most gunsmithing projects such as finishing 80% lowers, making custom parts, and such.
Pretty much all the lower-end (< $1500) mills available are Chinese-made and as such leave a bit to be desired in the fit & finish and precision categories. They are typical of ChiCom products: cheap and serviceable, but a bit crude and rough. One of the biggest shortcomings of these mills out of the box concerns the control of the X & Y movement of the table and Z movement of the spindle head: the mechanisms involved are not of the highest quality, and high-precision movement is difficult. Backlash is pretty much a given when changing directions, and can be hard to account for. On top of this, lead screws that move the table sometimes have odd threads, so that one revolution of the turn crank may move the table 0.0625" or something, which can make it a pain to count turns in order to move the desired amount. These are all issues that can be dealt with/worked around to varying degrees, but the best way is to install a DRO. A DRO keeps track of where the cutter is in real XYZ space at all times. It allows one to move an exact amount in any or all dimensions, return back to the same spot again, etc. No more counting turns if the handle, and if there is backlash, it is accounted for. So if you have a mill, you want a DRO.
OK, enough explanation and justification. Let's get on with the demo. Having made the decision to add a DRO to one's mill, one must choose a DRO. The available options range from complete packages including all scales, they display, mounting brackets, etc., to very DIY setups that require much more assembly and in some cases even electronics fabrication. As one would expect, prices vary accordingly, with some of the higher-end DROs costing in the thousands, and the very cheapest options a couple hundred. The DRO displays themselves range from simple 2- or 3-axis models that just show the current coordinates and can be zeroed, to actual small computers that can calculate the coordinates for round bolt patterns, take into account cutter diameter, and the like.
In the spirit of not putting Recaro seats in a Hyundai, it seems silly to spend more on a DRO that the mill cost to begin with, so I opted to buy the parts individually. I purchased electronic scales from Shars & a simple DRO display from CDCO.
Parts list:
Shars
12" Horizontal Digital Machine Scale 303-9307 1 $49.00
8" Horizontal Digital Machine Scale 303-9305 1 $39.00
12" Vertical Digital Machine Scale 303-9308 1 $56.00
Shipping cost $43.72
Total $187.72
CDCO
Item Number: 30011
Item Name: 3 - Axis DRO Display Unit ( Scales not included)
Price Each: $189.00
Quantity: 1
Order Sub-Total: $189.00
Shipping Cost: $15.00
Total Cost: $204.00
Here are the scales and display (the cables that connect the scales to the display are not shown):
From bottom to top, the scales will be used for the X, Y, and Z axes, respectively.
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), and with that we're talking very light cuts.
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