Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Hi

    So i have my first lathe. Its a hobbymat mini lathe.

    Is there anyway i can change the measurements on the cross slide and tail stock to metric values?

    pic of my current dial.

    Click image for larger version. 

Name:	20171215_233015.jpg 
Views:	30 
Size:	118.2 KB 
ID:	23407
    Last edited by dfox1787; 16-12-2017 at 12:50 AM.

  2. #2
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 4-5 years. Has a total post count of 163. Received thanks 10 times, giving thanks to others 5 times.
    Can you fit DROs? - easier solution.

    Without changing the lead screw to metric, the nut (and half nut assuming it has one) as well as the dial, you're not going to get a very satisfactory solution.

  3. #3
    Quote Originally Posted by Doddy View Post
    Can you fit DROs? - easier solution.

    Without changing the lead screw to metric, the nut (and half nut assuming it has one) as well as the dial, you're not going to get a very satisfactory solution.
    Hi this is my first lathe so I don't know anything about them at the moment so I'm not sure what dros are lol.

    I can work things out. Would it be better for me to buy a new cross slide with a metric dial.

    Sent from my SM-N910F using Tapatalk

  4. #4
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 4-5 years. Has a total post count of 163. Received thanks 10 times, giving thanks to others 5 times.
    DRO = Digital Read Out. Attach a scale/sensor onto each axis, and you get a digital display of position. Zero that, and you have a digital display of displacement. Apply a *2 factor via button-press and you can directly read the influence of a cross-slide movement into the diameter of the workpiece, remove the scale factor and you read the influence on the radius of the workpiece. Store positions into memory for quick indexing around the workpiece. Displays in either imperial or metric.

    Worth a consideration - you can get lash-ups with cheap digital callipers and similar if money is a consideration.

  5. #5
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 4-5 years. Has a total post count of 1,059. Received thanks 186 times, giving thanks to others 5 times.
    There have been (and still are, for all I know) plenty of lathes around with "dual-system" dials - the dial has two sets of graduations and sometimes a sliding cover so that only one shows at a time. However, given that you are not changing the feedscrew pitch, one of these is always going to be an approximation. I don't know what the feedscrew pitch of your machine is, but let's say that it is 0.1", and there are 100 dial graduations corresponding to 1 thou each. You could make up a new dial with 125 graduations, think of the feedscrew pitch as 2.5mm, and then each graduation corresponds to 0.02mm. Obviously, there is going to be a slight error. After one full turn, you will be out by 0.04mm (about 1.6thou). However, you will have just made a cut of 2.5mm depth, which is actually fairly large for a machine of this size and you wouldn't expect a cut of that depth to be a finishing-to-size cut.

    In practice, then, this kind of thing can work. What you are often doing with a machine of this size is measuring, working out how much you need to take off, and machining. Then you re-measure and repeat the process. It is rare that you would, for example, measure your workpiece as 1" and take it down to 0.5" (in a series of passes) without a few intermediate measurements anyway to check progress, so the ability to wind the cross-slide by exactly 0.25" isn't too important when the last few cuts are going to be just a few thou and the error too small to matter. Actually, I realise that those measurement should have been metric equivalents but you get the point. The dial error when you are just doing the final few light cuts almost certainly isn't going to be big enough to make any real difference.

    I'll probably bring down the wrath of all the professional machinists of the forum (I am, after all, only an amateur so what do I know?) and suggest that you try this idea, using a strip of heavy paper wrapped around the existing dial, mark the overlap, take it off and divide into whatever number of graduations makes sense on your machine, and "install" the new dial with a bit of sellotape around it for temporary protection. Use that for a little while and see if the concept works for you. If so, then making a proper dial would be an interesting little project and probably not too difficult and much, much easier than making a new leadscrew and nut (even if that is, undoubtedly, the better long-term solution).

    Or you could do what I did for years on my imperial machine which was to take a copy of the drawing with metric measurements and just write on the imperial equivalents. It isn't actually that much more difficult to work to 0.197" instead of 5mm!

    Actually, from what I have seen the Hobbymat lathes generally came with metric feedscrews, so if yours really is imperial, maybe there are replacement metric spares around that would fit?

  6. #6
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 4-5 years. Has a total post count of 163. Received thanks 10 times, giving thanks to others 5 times.
    A very convincingly argued point from Neale... perhaps I'm being blinkered.

  7. #7
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 4-5 years. Has a total post count of 1,059. Received thanks 186 times, giving thanks to others 5 times.
    I used to use an imperial-only machine. About a year ago I bought an ex-toolroom lathe which is just a little better built - the bed looks like the deck of an aircraft carrier and the whole thing weighs about a ton and a quarter. The "imperial" version of this lathe actually came with dual-system dials but for inexplicable reasons my metric version is metric only. Little bit of a shame as I do a fair bit with old designs with imperial measurements. The saving grace, though, is that the machine came with a DRO already fitted, and I have barely looked at a dial since I started using it. I can take an initial cut, measure with imperial micrometer, punch in the diameter on the DRO in imperial, switch to metric at the push of a button, and start cutting to a final metric dimension. After 40 years without, I hadn't realised just how useful a DRO could be on a lathe until I started using one. However, I doubt that any of the usual commercial DRO kits would comfortably fit in the space available on the Hobbymat machines. A bit of a shame, perhaps, but it shouldn't change the quality or accuracy of the work - it just takes a bit more cut-and-measure and mental arithmetic to get there. Never be wihout a scrap of paper and pencil by the machine to do the odd sum or make notes of dimensions as you go!

    It's not a quesion of being blinkered - a Bentley Continental might get you there more quickly, more quietly, and more comfortably but the Ford Escort will get you to the same destination in the end! Although it's difficult to go back to a Ford Escort after driving a Bentley (I would imagine...)

  8. #8
    Quote Originally Posted by Neale View Post
    There have been (and still are, for all I know) plenty of lathes around with "dual-system" dials - the dial has two sets of graduations and sometimes a sliding cover so that only one shows at a time. However, given that you are not changing the feedscrew pitch, one of these is always going to be an approximation. I don't know what the feedscrew pitch of your machine is, but let's say that it is 0.1", and there are 100 dial graduations corresponding to 1 thou each. You could make up a new dial with 125 graduations, think of the feedscrew pitch as 2.5mm, and then each graduation corresponds to 0.02mm. Obviously, there is going to be a slight error. After one full turn, you will be out by 0.04mm (about 1.6thou). However, you will have just made a cut of 2.5mm depth, which is actually fairly large for a machine of this size and you wouldn't expect a cut of that depth to be a finishing-to-size cut.

    In practice, then, this kind of thing can work. What you are often doing with a machine of this size is measuring, working out how much you need to take off, and machining. Then you re-measure and repeat the process. It is rare that you would, for example, measure your workpiece as 1" and take it down to 0.5" (in a series of passes) without a few intermediate measurements anyway to check progress, so the ability to wind the cross-slide by exactly 0.25" isn't too important when the last few cuts are going to be just a few thou and the error too small to matter. Actually, I realise that those measurement should have been metric equivalents but you get the point. The dial error when you are just doing the final few light cuts almost certainly isn't going to be big enough to make any real difference.

    I'll probably bring down the wrath of all the professional machinists of the forum (I am, after all, only an amateur so what do I know?) and suggest that you try this idea, using a strip of heavy paper wrapped around the existing dial, mark the overlap, take it off and divide into whatever number of graduations makes sense on your machine, and "install" the new dial with a bit of sellotape around it for temporary protection. Use that for a little while and see if the concept works for you. If so, then making a proper dial would be an interesting little project and probably not too difficult and much, much easier than making a new leadscrew and nut (even if that is, undoubtedly, the better long-term solution).

    Or you could do what I did for years on my imperial machine which was to take a copy of the drawing with metric measurements and just write on the imperial equivalents. It isn't actually that much more difficult to work to 0.197" instead of 5mm!

    Actually, from what I have seen the Hobbymat lathes generally came with metric feedscrews, so if yours really is imperial, maybe there are replacement metric spares around that would fit?
    Thank you for the information. I have only recently got the lathe and it came with plenty of spares so maybe there are some spare indicators.

    I do like the idea of using digital read outs and I'm not looking for precision accuracy at this stage. Some of the parts I intend to make don't need to be spot on.

    I did consider converting the measurements but at the moment I don't even know how to read the current dial indicators.

    If I knew what metric dials would fit the machine I could look on ebay. I could make one I do have a cnc with a 4th axis to engrave the metric readouts but that's something else I'm still trying to get right.



    Sent from my SM-N910F using Tapatalk

  9. #9
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 4-5 years. Has a total post count of 163. Received thanks 10 times, giving thanks to others 5 times.
    Quote Originally Posted by dfox1787 View Post
    I could make one I do have a cnc with a 4th axis to engrave the metric readouts but that's something else I'm still trying to get right.
    That's what all the time-off around Christmas is for :-)

  10. #10
    mekanik's Avatar
    Lives in Barrow in Furness, United Kingdom. Last Activity: 11 Hours Ago Has been a member for 7-8 years. Has a total post count of 559. Received thanks 64 times, giving thanks to others 73 times.
    If the cross slide dial has 10 divisions and you have the capacity to screwcut you could make a metric feedscrew(for cross slide) 6mm left hand taps sometimes come up on ebay. make a new nut and use that as a gauge to screwcut your new feedscrew. as for saddle travel i tend to work to a saddle stop and various gauges if doing anything fussy.
    Regards
    Mike

Similar Threads

  1. Mini lathe as a 4th Axis
    By Leadhead in forum Gantry/Router Machines & Building
    Replies: 15
    Last Post: 24-08-2017, 08:53 AM
  2. Mini Lathe Part
    By fragger6662000 in forum Milling Machines, Builds & Conversions
    Replies: 2
    Last Post: 15-11-2011, 07:13 PM
  3. Mini CNC lathe builders
    By GeorgeD in forum Lathes, Lathe Rebuilding & Conversions
    Replies: 7
    Last Post: 28-07-2010, 10:00 AM
  4. A Mini Lathe
    By irving2008 in forum Milling Machines, Builds & Conversions
    Replies: 19
    Last Post: 03-05-2010, 04:11 PM
  5. WANTED: SIEG C3 Mini Lathe
    By derekm in forum Items Wanted
    Replies: 5
    Last Post: 07-04-2010, 08:35 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •