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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

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I've owned this machine from new and used it intermittently and never brought it to its full potential as a CNC machine, or done much proper maintenance. I still need/want a machining platform and I still don't have room for proper separate mill and lathe, but I have 22 years of accumulated thoughts for improvement.

Individual improvements that I actually execute on can go in other sub-projects. I'm using this one to list all the ideas and to-dos.

The 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 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 . 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 
  • 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. 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. Already purchased. Awaiting install.
  • 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
  • Coolant feed/cycle
  • chuck key holders.
  • Bolt up the cross-slide dead-square and never rotate it again.
  • Tool box under the table
  • retractable wheels
  • floor bolts.

Things to do - Lathe

  • deferred maintenance. 
    • Gearbox oil change - overdue. 
    • 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. 
  • Install Chinesium "BXA" quick change tool post
  • Come up with a solid reliable way to manually thread under power without a compound.
  • 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)
  • Generally improve my skills
    • metrology - maybe figure out if my ways are...
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  • New Vice

    Alastair Young2 days ago 0 comments

    Under $100 and free shipping. 4" Kurt knock-off. No obvious manufacturing flaws other than the hex hole in the handle needs some relief. I haven't checked squareness or flatness yet, but the rigidity improvement is vast. Small cuts done to relieve some clearance at the bottom of the DRO end brackets.

  • DRO Y axis complete

    Alastair Young6 days ago 0 comments

    Rough mounting showed the scale should be spaced out 3mm from the table to match the head below, so I made end brackets that act as spacers, end caps and cover supports. 

    Parts are mounted with 5mm screws that came with the scales. The cover is attached with 3mm screws from my electronics stuff. The top ones stand slightly proud but are so near the end of the table that I doubt they will hit anything. If they do, I can find some countersink ones.

    The scales come with only one set of yellow dust covers but with slots for two so I bought 3m of the stuff on aliexpress and doubled them up. I think it is pretty well protected from flying debris. Some tape along the line between the table and the cover would be a good idea to keep out any fluids, but without a drip tray I'm not going to flood coolant any time soon.

  • Y axis scale rough mounted

    Alastair Young03/17/2020 at 06:35 0 comments

    taps and drill arrived from drillsandcutters.com and transfer punches from harbor freight. The y scale ia almost fitted. I need to make end brackets that will do:

    • Space out the scale to line up with the head
    • Close the ends of the cover
    • Provide something to screw the cover to

    The cover is 16mm longer than the scale and comes with a vertical lip to allow you to screw it to a flat surface. I bent/hammered that lip flat as the top of the cover will be flush with the table. This also makes it wide enough to reach out over the head bracket.

  • DRO Y axis head bracket done

    Alastair Young03/08/2020 at 02:08 0 comments

    One of the scales arrived broken, so it is useful to use for checking fit without worrying too much about cleaning.

    Mounting the scale should be straightforward now. I need a 2mm spacer between the table and the scale, and a cover. This could all be the same thing. I'll also need transfer punches and the appropriate tap drills and taps.

  • DRO Y axis progress and tool shopping

    Alastair Young03/04/2020 at 05:12 0 comments

    I've started work on the Y axis DRO mounts, using Fortal alloy (7075 T-651 from ebay seller scottkrez). This is a material I have used before and I know it machines well and can be made very shiny.

    I'm on a learning curve with Fusion 360 and I'm on a relearning curve with the milling machine. The last time I used it in anger there were a lot less youtube channels on machining and I was doing a lot of things wrong. There are also some tricks for the Shoptask which I had forgotten. For instance my biggest mill is a 5/8" for which I purchased a 5/8" MT3 collet so it could mount up close to the head or in the 4" MT3 extension. What I forgot was that I really need a stop in the collet or the mill creep up in the collet vertically under heavier cuts. Properly tightening the mill column and the drawbar are also Good Things.

    After some trial and error I have the piece down to 35mm in one dimension. The other dimension as to come down to 25mm from the current ~35mm. Lengthways was cut on the 4x6 bandsaw so that dimension does not need much taken off. I may try taking the 9mm of the face of the block with the bandsaw in vertical mode, though that thing is a bit scary.

    The part I am making will mount to the base of the cross-slide and wrap around the DRO sensor head to use the side mounting screws. I would rather have made it slimmer and support from underneath, but that would block access to one of the nuts that tightens the table rotation. The scale and head will be 2mm out from the base though I may skim that down a bit depending on what material I use to run behind the scale. As the scale overlaps the base somewhat some clearance is needed.

    I have ordered some parallels for the vice, as for cutting the channels into the part it will have to sit up high. The first time round with this machine I didn't even know what parallels were and I managed with random stuff. The best I have at the moment is to use dies. As these are ground I was able to find a couple of matching thickness to do the job for now. The vice I have is a tilting angle vise that I bought with the machine that looks very like this: https://www.hhip.com/4-deluxe-tilting-angle-vise-3900-2684.html

    This has to be set up on two 1-2-3 blocks on the "2" side to raise it high enough, and setting the tilt to properly horizontal is a pain., and I'm pretty sure it lacks some rigidity.

    So the next thing on the shopping list is a 4" mill vise of the Chinesium-Kurt-Knockoff variety, along with the swivel base. I think this will be nice and high and by mounting the swivel base at an angle I should be able to my two (narrowly spaced) T-slots and get it centered on the table the "normal" way round. 

    Also purchased is a used Starrett S828H wiggler set for $25.

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