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Lessons Learned and Tooling Updates

A project log for Reviving a Shoptask 1720 XMTC Gold 3-in-1

This thought project is notes on reviving my 1998 Shoptask 1720 XMTC Gold late-mill-drill

Alastair YoungAlastair Young 12/03/2020 at 05:030 Comments

In order to build the steam engine I acquired a bunch of tooling.

To build this project I had to machine at all heights in my Z-space, with a bunch of different tooling lengths. This has always been a bugbear on this machine as the MT3 extension is extends the spindle more than the spindle has travel, so there are places I just couldn't get to in the past. With the tooling I have now this is less of a problem, though it results in a mixed bag of solutions.

While the randomness of this is a bit annoying it is no longer blocking. I don't have to dismount the work and space it up just because I'm changing from a mill cutter to drill like I used to some of the time.

One major annoyance was the lathe toolpost and tooling. I essentially have only one lathe tool that works - a 12mm 60 degree threading bit. It's the only one that gets to the correct spindle height on the standard turret toolpost. The Shoptask "quick change" toolpost is a bad design. While it is adjustable, it's hard to do, and quick change it is not. Worst: the tool holders are narrower than the tool post, so the toolpost gets in the way. Don't get me started on the "compound". Which is why I've ordered a Multifix 'A' toolpost from PeweTools in Deutschland. With a bit of luck it will be here by Weihnachten. That's the topic for the next sub-project.

While using the DRO on a real project for the first time with many hours of use I find that I almost never look at the handwheels anymore - or worry about backlash much. I'm habitually locking the unmoving axes. This is removing my concern about retaining inch leadscrews which opens up the option of cheap metric ballscrews when I get to the CNC stage. Prices for these are now under $100 per axis. While CNC with DRO position for feedback should care less about backlash than a "blind" setup, backlash should still be minimized. At his point it is up to 75 thou on the Y axis as apparently the set-screw on the acme nut has loosened again.

Another concern for the lathe is the distance from the center of the toolpost to the edge of the table. If the swing of the work (and chuck jaws) hits 200mm, something would always hit the table if I got in too close. Now that the DRO scale is on the chuck side, this issue issue is even worse. I ran into this cleaning up the steam engine flywheel (over 6") in the 6" 4-jaw chuck. I ended up using the 200mm tool blanks extended way out to get it done. Not very rigid. A partial solution would be a smaller 4-jaw chuck. Like a 5" or 130mm like the 3-jaw. Another solution would be to make a toolpost support block that extends forward - somewhat like a traditional compound extends the toolpost out on a normal lathe. When I do the ballscrew conversion I think I'll spin the table round so the gibs are towards the lathe chuck and the DRO is safely on the other side. In the meantime if I do need to do big things I can use a beefy boring bar tool on the Multifix to reach out over the divide. 

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