TPACtools DRO Bridgeport Mill Install

Technical Ted

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Nov 5, 2016
Received the DRO via FedEx late this afternoon. Great shipping/delivery time since I only ordered it two days ago. Everything seemed to be well packaged. Got the 3 slides (each one came with its' own bag of hardware and cover), display unit (with collet rack and mounting bracket), aluminum angle brackets, aluminum flat bars, installation instructions with text and pictures and an instruction manual for using the display unit.

One thing that will probably end up delaying installation is the fact that it comes with metric hardware. The only metric taps I have is a carbon steel set and if I decide to use the included hardware I will be ordering some HSS taps (I could use some anyways so I'll have them on hand). Or if I go with inch hardware I'll most likely have to order that because I highly doubt I have enough on hand of the correct sizes. I would stick with socket head cap screws although I might temporarily use slotted head which I do have on hand so I can start work and replace them after receipt. I'll see how I feel after reading the paperwork.

Right now I'm just going to start reading the documentation and decide how I'm going to go about things.





I put the same unit on my mill about 3 years ago. It has been working great. I had to make some brackets for mounting the scales.
I started with the X axis, which is done except for installing the cover and securing the cables (I'll do all of that at the end). The X is suppose to be the easiest because the surfaces are the flattest. I decided to go with inch hardware so I'm using some slotted head screws in some places temporarily. I just got back from my local hardware store where I bought the correct length hex socket head cap screws and they cost $.95 each! Oh well, beats ordering a box of 50.

As far as the installation instructions go, if you are looking for step by step, hold your hand type directions, this isn't the kit for you. The information is mostly there, but you have to read the instructions (with tolerance and setup dimensions) that's in the paperwork that comes with the slides/heads in addition to the main instruction packet. All the instructions are written in broken English, but I've seen worse and you can make sense out of them. The only thing so far that wasn't covered at all were the blue plastic clips that come mounted between the slide and the head. I didn't know if these were for installation spacing or just for shipping protection, but after finding the recommended spacing between the slide and head on one of the sheets it was obvious that they couldn't be used for installation and it suggests using a spacer for this purpose. I found a piece of cardboard in the middle of the range and used that. Most of the mounting is intuitive and if you think about how things work, the travel involved and put your machinist hat on, you'll be fine.

There are two ways you can mount the head for the X axis. One (the way I did it) was to face mount it with two screws through the head without using a bracket. The second way was to use an angle bracket. I chose the first way because it seemed the simplest, but if I were to do another one I would go with the bracket mount because I think in the long run it would be easier, even though more operations are involved. Reason being to face mount it like it did the mounting holes are long, all the way through the body of the head and there is not much clearance between the mounting holes and the screws, so you better drill and tap your holes dead on so you can maintain the proper alignment and spacing. I used a transfer punch and did the first hole, then using a screw in that hole punched the second hole. It's a good thing I double checked the punch mark because it was NOT close enough! I had to correct it by walking the center punch mark into the correct location by punching sideways with a center punch. It turned out fine, but extra work and if I hadn't double checked it would have been an issue. If using a bracket, if the holes were a little out of location you could easily open up the holes in the bracket to accommodate, but doing the same in the reader head would be tricky since you'd have to come up with a way of holding it safely and I don't like the thought of doing it! So, I would suggest to anyone doing this to use an angle bracket. The good news is the cast iron drills easily.

So, overall, so far anyways, better instructions would have been nice, but certainly not worth the additional $287 and the lesser warranty for the unit from DROpros. Please don't think I'm bashing DROpros, because I certainly am not... I'm just expressing that I don't mind having to figure a couple of things out on my own to save close to $300. Someone else may feel differently and that's fine.

We'll see how the rest of the project goes. So far, so good.

Using the mag bases to help hold things in position while I work. Also, used a drill guide (rectangular bar with drilled hole in it) and a tap guide to help keep things straight.

The blue clips that come on each head for shipping protection.

All done and aligned! I'll install on the covers and secure all the cables when everything is mounted and ready to be calibrated. You don't have to remove the power feed unit, but I wanted to get it out of the way, especially for the Y axis install.
Got a little more done today. Started on the Y axis. First thing I had to do was remove the zert oiler and bracket I made for oiling the X & Y screws. Not a big deal, I'll relocate it when I'm done with the Y axis.


I saw these three, nice spot faced holes and thought "Oh boy! I bet they are all in line and faced to the same plane." WRONG!!! I checked them with an indicator before starting. I had to indicate each end one to the center one because I didn't have enough travel to go from end to end. It appeared the two end ones (the ones I'm using; I didn't see a need for using the center one too) were 0.030" different in the face plane! I don't understand that one, but it is what it is. I decided to use them anyways since at least they were machined and the casting had humps in it. I made a couple of spacer washers on the lathe that fit in the recess and ground them on my surface grinder to .125". I mounted the aluminum bar that came with the kit and it was .027" off where the DRO head would travel (my initial .030" estimate was pretty close), so I made another .027" spacer and ground it to add the additional length I needed. Remounted the bar and it was dead on. Mounted the slide and it was off by a few thousands so must be the end caps were just a a couple thousands off. Shimmed it and aligned it right on in the two planes. When mounting the aluminum bar keep in mind that you have to mount things leaving enough room so you can add the aluminum cover. If you mount the slide too high you won't have room to clear the saddle with the cover.


Made up a plate out of a piece of scrap aluminum I had (the piece with red Dykem on it; that's why there's a few extra holes). The hole that is in the top center I drilled to act as an oil weep hole since the saddle accumulates oil in the bottom from the ways and X screw/nut. I didn't want a pool of oil building up in there so I gave it a way out. I cut one of the angle brackets supplied with the kit and cut a flat mounting piece that also came with the kit. The flat piece is just laying in there in this picture and is waiting for me to finish up. Tomorrow is another day. Just a little more to do and this axis will be done.

When I first position the slides (just by placing them on top of my two mag bases) and start laying things out I run the axis to both ends and mark the actual center of travel. I use this mark for the center of the slide. Note: So far, both the the arrow stickers that is suppose to show the center of the slide have been off. I mark my own center mark and go by that. You need to leave 0.390" travel with the head on each end and I mark the center using this as a reference. There's plenty of travel and you probably don't really have to worry about it, but I like knowing it is in the actual center.

On a side note, I've never ground anything on my surface grinder that was as thin as the .027" spacer I made today. My magnet doesn't do a good job of holding really thin material. I had to take very light passes because I didn't want it shooting out! I put a piece of shim stock behind it for a backer, but the magnet hardly even held the thin stock. I learned something new... You need a little mass for the magnet to hold tight.

Finished up the Y axis. I’m really happy with the way it turned out. Using those two spot faced areas made things a lot easier. I wish I had the same to use for the Z axis.

As I had thought, the Z axis proved to be a PITA and you have to exercise a lot of patience... Lot's of fitting, trial and error and making modifications based on your measurements.

Originally, I planned on mounting the Z scale/head on the right side, the same side as I mounted the Y axis. But, I didn’t like the way the installation instructions suggested mounting the scale and that’s the way the scale/head/cable was set up. They wanted the business end (open end) facing towards the table where it would be exposed to all the crap! So, wanting the cover to protect it, with the business end facing the back and the cable to exit on the bottom (less stress) and also wanting the scale’s mounting faces to be the closest side to the machine meant that it was getting mounted on the left side. No big deal, just not what I had planned, but it might even be better out of the way on that side. Even if it interferes with the storage door, I don't use it anyways so no biggie. I didn’t want to try to reverse the head in the scale because the end caps were sealed with some type of semi hard rubbery sealant and I didn’t want to mess with it. Don’t know for sure that it can even be done, but mounting on the left side is fine with me. I looked through the operator’s manual and it looks like the +/- readout direction can be reversed in setup mode so it really makes no difference which way the scales face like in some units I’ve read about.

The main casting is not flat at all and curves both out towards the back and out a lot more towards the bottom towards the base, so I had to come up with a way of designing stand offs to hold the scale square and parallel in two planes with the Z axis motion ( within specified 0.003").


Above, you can see what I'm talking about (first two mounting holes drilled). It got worse the farther down the column you go. The top mount placement was the easiest, only off by about 1/16". But at the bottom of where the scale was going was really bad. I settled on a location a few inches up from the bottom of the scale where I thought I had a fighting chance. After giving this some thought I felt that using single point of contact stand offs (as in a round post or whatever) would be a real struggle to get true and be repeatable with multiple removals and re-installs (after making modifications to line things up) so I decided on a two point contact design. This worked out very well. I fitted the contact spots with the base first, then ran an indicator on the scale mounting side, using that indicator reading to line them up in the vise on my other mill so I could mill it to the correct angle. It took some back and forth, but came out within the specified 0.003" all the way around. Worked great!


Above you can see the two stand offs ready to mount the supplied aluminum bar to mount the scale to. The mount for the read head will go between the zert and the plug for the Z axis lock eccentric.


Ready for the scale mount. I had to add some shims to get the scale within the specified 0.003", but that was the easy part! The secret is to have something "true" to work off from... the shimming and aligning is the easy part. All it takes is a lot of cranking to get the indicator readings!!! Especially the Z!


I might even be able to get enough room so I can open the door without moving the read head out of the way (by lowering the knee). So, I'm on the downhill side now. Still have to mount the Z axis head, but that will be a lot easier than mounting the scale. I wanted to leave enough room in front of the scale to mount the protective cover and maintain the specified clearance between the cover and the scale.

Hi Ted,

Your installation looks great. I put a Z-axis single scale on my Bridgeport and did the up/down thing more than I care to remember. Something about cranking 50 turns and only getting 5 inches of travel gets old really fast. I ended up putting on a Z power feed which I obviously would of loved to have had prior to getting the Z scale.

Here's the thread to my Z-axis power feed if you get tired of cranking. Another Chinese "kit" tool, but pretty easy to install. I've done a couple of mods since. Cut some coils off the crank disengage spring as it was stiffer than I'd like for engaging the crank. Also had to adjust the micrometer dial some as I didn't shim it enough to not drag when the clamp nut is engaged. Discovered that the hard way when I cut too deeply into the part because the dial dragged and slipped on me.

Great work!


Finished up the Z axis before moving on to install the display. The storage door just hits the hex socket head cap screws that mount the reader head. I've come up with 3 ways of fixing this (1- replace screws using pan head - the winner, 2- mount reader head using side screw holes instead of rear screw holes, 3- mill a little off the door), but I'm leaving it as is right now so I can play! :) The reader head install was a piece of cake... went smooth using provided mounting angles.


I mounted the arm low, because I wear bifocals and I'm trying to save my neck! You younger guys will know what I'm talking about in a few years and you older guys already know.


The first thing I did after firing up the display was some configuration. I switched to inch display, removed the 5th decimal digit display (no sense going beyond tenths) and changed the +/- direction on the X and Y axis so they displayed the way I wanted (using Cartesian coordinate system ). Next was axis calibration (setting linear compensation). I used a setup block with my edge finder for X and Y and my tenths indicator for Z. Y and Z were dead on after double checking, but Y was a whole 0.0002" off... Probably my error with one of the four times picking up the edge with the edge finder. I think I can live with that for now;). I'm going to go through this process again after adding the covers, securing the cables, and letting things settle in a little to see if anything has changed in a couple of weeks. It doesn't take long and it's easy. Just a little math and enter the correct offset parameter.


So, there it is in all its' glory! All I have to do is learn how to use it, but that's the most fun part. I still have to install the covers and secure the cables. For the Y and Z axis I need to install a spacer to hold the guard out because those two axes scales got mounted using an supplied aluminum bar. I plan on just using strips of wood cut to thickness on my table saw for those. Should work fine since they are only there to keep the chips and crap out. I'll put a light layer of silicon chaulk to help seal things up tighter.

I'm very happy with the way everything turned out. The only thing I would have done differently was mounting the X axis read head using an angle bracket instead of mounting directly to the table (I posted this earlier above). Other than that, everything went smoothly. The Z axis scale mount was really the only one that was a PITA. Using the two point of contact mounting blocks was the way to go. I think I'd still be trying to line things up if I just tried to use single posts!

The install is finished! All that's left is the playing! :)

I installed the protective covers first using strips of wood I ripped on my table saw as extensions where needed. I also added a stand off stud to protect the X axis scale from hitting the Z ways (you loose a little bit of travel there). Then, I routed and secured the cables. I used some rare earth magnets to hold the cable clamps in place while I made sure the cables hung the way I wanted as I cranked the axis back and forth... worked great!


Above is a couple of magnets holding a clamp. Boy! Those suckers are strong! And sometimes they stick to stuff you don't want them to and have a hard time getting them off... but they sure can come in handy.

Lastly, I installed wooden end caps for the protective covers since they were not provided in the kit (funny, since they did provide some small screws for them). No big deal; easy enough to make. And then I painted the wood the same color as the mill.


In summary, I would suggest to anyone considering adding a DRO go for it! To me, some of the other kits available weren't worth the addition cost. At first I was considering a H&W Mititoyo on sale for just over $1000. So, for what I saved there I can buy a nice, new Kurt vise! :) But, I was more comfortable buying from a USA based company than to save even more money and buy off shore. So, for me, this was a nice compromise.

I can't comment on support from TPACtools since I did not try to contact them. They did have extremely fast shipping and I received my unit two days after ordering it. I did get additional information from the internet and from watching YouTube videos. All the glass scale units basically work the same way so watching some of the other brand's videos and reading their documentation helped me install this one. And if anyone does need help they can try to contact TPACtools directly or probably better yet post a question here on Hobby Machinist and I'm sure you'll get a lot of good advise from people who have done the install before.

So, go for it!
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Hi Ted,

Congrats on the upgrade! Miss counting turns yet? I haven't used the SDM 200 point sub-datum function yet. I bounce between ABS and INC modes all of the time. Have used the "1/2" function on occasion finding the center of a hole (touch one side, zero, touch the other side and do a 1/2 function in that axis). Never used the built in calculator. Have used the PCD function a dozen times (Points on a circle/arc). One thing I do on that function (just easier math for me) is if I'm doing 5 holes on a circle, I punch in 6. Do a starting angle of 0, ending of 360. Otherwise you have to do the math to calculate the angle of the last hole (360/5 * 4 for 288). Seems easier to just plug in 0 to 360 and realize 0 and 360 are the same point, so add 1 to the number on the circle.

I have two TPACtools DRO's and they both included aluminum end caps. Tom will send them to you but your solution works great.

Hi Ted,

Congrats on the upgrade! Miss counting turns yet? I haven't used the SDM 200 point sub-datum function yet. I bounce between ABS and INC modes all of the time. Have used the "1/2" function on occasion finding the center of a hole (touch one side, zero, touch the other side and do a 1/2 function in that axis). Never used the built in calculator. Have used the PCD function a dozen times (Points on a circle/arc). One thing I do on that function (just easier math for me) is if I'm doing 5 holes on a circle, I punch in 6. Do a starting angle of 0, ending of 360. Otherwise you have to do the math to calculate the angle of the last hole (360/5 * 4 for 288). Seems easier to just plug in 0 to 360 and realize 0 and 360 are the same point, so add 1 to the number on the circle.

I have two TPACtools DRO's and they both included aluminum end caps. Tom will send them to you but your solution works great.


Bruce, thanks for the heads up about the end caps. I emailed Tom and got an immediate reply back that he would ship them out to me. Once I get them I'll decide if I want to swap them out or stay with the wood.

I've got some other stuff I've got to do around the place that I've been putting off until after I got this install finished up, but I'm going to play with some of the functions and try to figure them all out. This is one area where I think the manual could be a little more helpful... But, hopefully, there's enough there that I can play around and figure all the functions out. I doubt I'll use some of them at all, but it's nice to know how just in case. The common functions that I am sure I will be using seem pretty straight forward. It's just the more advanced ones that will require some playing.

Thanks for the help,