- Joined
- Feb 17, 2013
- Messages
- 4,418
I just installed a 2 axis TAPC Tools DRO on my Grizzly 12x24 lathe.
https://www.tpactools.com/2-AXIS-LATHE-DRO-DIGITAL-READOUT-_p_22.html
It included a "slim" scale for the slide and a "normal" scale for the Z axis. If you plan to order one, it's best to email ahead of time, and let them know the X and Z travels of your lathe. They can then help you pick the correct scales.
The DRO display unit I got was a "general purpose" unit, so it has a bunch of mill-type functions I don't use. It does have a radius/diameter function for the cross slide, a very handy feature for lathe work. The manual does show a lathe-specific version of the display unit. I guess TAPC just buys the lathe/mill version from their wholesaler (Sino?), to simplify inventory. The manual is in Chinglish, but not too difficult to understand.
Installation instructions are mainly a black-and-white copy of an HM post by @BGHansen
www.hobby-machinist.com
Here are some photos of my installation. The vertical 2x4s are where the back board usually mounts.
The short aluminum angle screwed to the cross slide holds a bit of weatherstrip against the scale guard, to help keep chips from getting underneath, where they'd be hard to remove.
Cable exit from cross slide and reader head installed on the Z axis.
Both cables exit through a piece of polypropylene (relatively low friction), to drape down into a loop at the end of the lathe. The weight of the armored cables is just enough to keep the cables from gragging through the swarf, oil and debris that normally inhabit the chip pan.
Completed installation.
Close=up (somewhat fuzzy) of the display unit
So far, I've not seen any need for digital scales on either the tailstock or the compound.
PS - The instructions make a big deal about installing the scales precisely parallel, etc. I got a bit worried about this, and asked @BGHansen for advice. His insights (paraphrased below) were extremely valuable:
(1) There's a compliant coupling between the read head housing and the actual scale reader, so a small amount of misalignment is not likely to be a problem. When delivered, there are plastic keepers between the read head and the scale. These hold the parts in "perfect" alignment, and prevent damage during shipment. But if you remove the keepers, you'll find that the read head can (gently) be moved around a bit. This is your mechanical "alignment tolerance." My procedure was to first mount either the scale or read head, and then with the keeper in place, work on the (relative) mounting of the other part. Once both parts are mounted, remove the keepers.
(2) If the scale bar is not parallel to the axis of motion, you'll introduce an error in the reading. OK ... let's see how bad this error might be. We'll start by assuming you misaligned the Z axis scale bar as badly as mechanically possible, given the (internal) compliance of the read head - say 1/10" over a 24" length (the Z travel of my lathe). So we have a triangle whose base is 24", height is 0.100". The length measured by the DRO will be the length of the hypotenuse of this triangle. Displayed length = SQRT( 24^2 + 0.100^2) = 24.00021"
As far as I'm concerned, an error of 0.00021" across the full travel of my lathe is absolutely trivial!
https://www.tpactools.com/2-AXIS-LATHE-DRO-DIGITAL-READOUT-_p_22.html
It included a "slim" scale for the slide and a "normal" scale for the Z axis. If you plan to order one, it's best to email ahead of time, and let them know the X and Z travels of your lathe. They can then help you pick the correct scales.
The DRO display unit I got was a "general purpose" unit, so it has a bunch of mill-type functions I don't use. It does have a radius/diameter function for the cross slide, a very handy feature for lathe work. The manual does show a lathe-specific version of the display unit. I guess TAPC just buys the lathe/mill version from their wholesaler (Sino?), to simplify inventory. The manual is in Chinglish, but not too difficult to understand.
Installation instructions are mainly a black-and-white copy of an HM post by @BGHansen
Grizzly G0709 Lathe Dro Install
Absolutely LOVE the 4-axis DRO on my Mill, figured it was time to put one on my Grizzly G0709 14” x 40” lathe. Many options out there for DRO’s, I chose TPACTools.com. I paid a little more than I could have from some of the eBay overseas vendors ($375 delivered), but went with Tom for a few...
www.hobby-machinist.com
Here are some photos of my installation. The vertical 2x4s are where the back board usually mounts.
The short aluminum angle screwed to the cross slide holds a bit of weatherstrip against the scale guard, to help keep chips from getting underneath, where they'd be hard to remove.
Cable exit from cross slide and reader head installed on the Z axis.
Both cables exit through a piece of polypropylene (relatively low friction), to drape down into a loop at the end of the lathe. The weight of the armored cables is just enough to keep the cables from gragging through the swarf, oil and debris that normally inhabit the chip pan.
Completed installation.
Close=up (somewhat fuzzy) of the display unit
So far, I've not seen any need for digital scales on either the tailstock or the compound.
PS - The instructions make a big deal about installing the scales precisely parallel, etc. I got a bit worried about this, and asked @BGHansen for advice. His insights (paraphrased below) were extremely valuable:
(1) There's a compliant coupling between the read head housing and the actual scale reader, so a small amount of misalignment is not likely to be a problem. When delivered, there are plastic keepers between the read head and the scale. These hold the parts in "perfect" alignment, and prevent damage during shipment. But if you remove the keepers, you'll find that the read head can (gently) be moved around a bit. This is your mechanical "alignment tolerance." My procedure was to first mount either the scale or read head, and then with the keeper in place, work on the (relative) mounting of the other part. Once both parts are mounted, remove the keepers.
(2) If the scale bar is not parallel to the axis of motion, you'll introduce an error in the reading. OK ... let's see how bad this error might be. We'll start by assuming you misaligned the Z axis scale bar as badly as mechanically possible, given the (internal) compliance of the read head - say 1/10" over a 24" length (the Z travel of my lathe). So we have a triangle whose base is 24", height is 0.100". The length measured by the DRO will be the length of the hypotenuse of this triangle. Displayed length = SQRT( 24^2 + 0.100^2) = 24.00021"
As far as I'm concerned, an error of 0.00021" across the full travel of my lathe is absolutely trivial!
