Alastair YoungThe 3-in-1 lathe/mill/drill form factor is necessarily a compromise. You can't just set up a job on the mill, switch to the lathe and back again like you can on separate machines. Depending on how it is implemented you also run into space issues and rigidity problems. Also these machines are aimed primarily at the hobbyist on a budget and made in China, so quality is variable.
The Shoptask 1720 XMTC Gold (1998) differed from its competitors at the time in that is was aimed towards CNC while retaining the major features of manual use. Shoptask are still around at shopmasterusa.com (now seems to be chicagolathe.com) and they are still making the descendant of my machine - the Mill Turn 2019. This is now a dedicated CNC system without the manual controls. My machine came with the mountings for CNC components, the first design iteration, with the CNC components themselves as optional add-ons - which at the time were beyond my budget. So what I ended up with was a manual machine with a design compromised to aid CNC use - without the CNC. Also with some other quirks related to Shoptask's forward thinking.
Rolling forward to 2020 - at least two of the competitors to Shoptask are still selling roughly equivalent machines - without the CNC options or compromises. These are the Smithy Midas and the Grizzly G9729 . (note that the current Grizzly G4015Z appears from the pictures to be exactly the same as the earlier Shoptask 17-20 BB 1985 – 1988.) There are some minor design differences between these machines, but the overall layout is the same:
- Separate 3/4 HP s-phase motors for lathe and mill
- Mill quill suspended over lathe bed via long unsupported beam
- Lathe spindle high over ways
- no gearbox - swap gears to change lead screw feed for threading
- pulley belt changes to change spindle speeds
- no mill knee - mill quill only. Shoptask only has 3-1/8" travel (Smithy has 3-5/8" and the head raises "40%", Grizzly has 4-5/16")
- fine and gross feeds for mill (gross = drill)
- mill table acts as cross-slide
Smithy also have a beefier machine - the Granite - with 2HP variable DC motor and a quick change gearbox and a 4-7/8" quill travel (and the whole head can be raised another "30%"). If I were not fixated on having CNC and manual use on my machine, I'd probably upgrade to one of those, rather than fixing up my Shoptask.
The Shoptask differs in two major ways from these other 3-in-1 designs
- The traditional half-nut and threading dial are not there. The lead screw nut is solid bronze. This makes manual threading a challenge but is a logical step for CNC.
- This also means there is no fast feed handle on the apron, as those need a disengaged half-nut.
- There is no compound and top slide. Because that would be handled by CNC? Instead the whole table/cross-slide rotates. A bit. Not a lot - its too big. Which means every time you rotate it you have to indicate it square again.
Things to do - General
- Install 3-axis DRO. Its 2020 for chrissakes. MOSTLY DONE. X-Y-Z done! See logs.
- Make a splash guard and drip tray. I have been using a modified plastic storage bin for a tray that was almost the right size but it has seen better days - and it's a pain to access to fish out dropped things. I have no splash guard - the motor ends up buried in chips and a lot of chips end up on the floor. DONE - https://hackaday.io/project/173386-shoptask-1720-xmtc-stand-upgrades
- Coolant feed/cycle - DONE Kool Mist I bought in 1998 installed
- chuck key holders.
- Bolt up the cross-slide dead-square and never rotate it again. DONE - but it still moves. Re-check when I mount the vise.
- Tool box under the table - DONE https://hackaday.io/project/173386-shoptask-1720-xmtc-stand-upgrades
- retractable wheels - DONE no wheels, use dollies as needed
- floor bolts.
Things to do - Lathe
- deferred maintenance.
- Gearbox oil change - overdue. DONE
- Spindle bearings - open and inspect and grease. If not both OK and Name Brand, replace with new Timken. These are car wheel bearings so not outrageously priced. I've never had these out -regreasing is supposed to be annual maintenance. DONE - regreased
- Install Chinesium "BXA" quick change tool post - or multifix A? - DONE Multifix A
- Come up with a solid reliable way to manually thread under power without a compound. - NOPE -> CNC
- Variable speed drive.
- Backlash reduction/elimination (XY axis on this machine - traditionally ZX on lathe)
- Tailstock storage - it would be nice to be able to effortlessly take it off while milling. Its heavy and awkward to install.
- Modify the forward-reverse to auto-stop the power feed (this was a later upgrade from Shoptask) - NOPE -> CNC
- Generally improve my skills
- metrology - maybe figure out if my ways are straight and parallel to the spindle etc. Get a surface plate and stuff.
- HSS tool carving
Things to to - Mill/Drill
- deferred maintenance - overdue
- spindle bearings - see lathe (DONE - cleaned, greased and adjusted)
- Get a decent vise. And parallels and stuff. (DONE - 4" Kurt knock-off and a set of parallels)
- Get more clamping hardware. And riser blocks and stuff.
- Backlash reduction/elimination - z-axis
- The quill has less than 3-1/8" travel and my taper extensions are more than 4" long. So with any given tool there is a "blind spot" it can't reach. Swap tools with different lengths in one job - maybe now you can't reach the part or get the tool in the quill. Figure that out. Later Shoptasks could raise the while mill head a few inches - Smithys have this feature. I want to figure it out with tool holders. DONE - more MT3 collets and ER32 collets
- Right-hand support for the quill. That has to help with stiffness.
- Variable speed drive.
Things to do - CNC