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  1. #11
    Quote Originally Posted by birchy View Post
    Hmmmm, they're expensive. Maybe I should buy a dividing head (was gonna get one anyway) and make them myself? Where can I find specifications for such things?
    They certainly are. I used a vertex 6" rotary table and put a stepper motor on it.

    Can cut the pulleys quite quickly if you grind a form tool and hold it in boring head, or just make a quick holder as it's not exactly complicated. I've posted a thread with more about it somewhere, including a program I wrote to mill the pulleys. My pulleys are XL so in the end I just ground a trapezium of the right dimensions on the end of a piece of 5/16" HSS from the lathe.

    5mm Pitch

  2. #12
    Isn't it ironic how I could do with a cnc mill to make the parts for my cnc mill? I know there's a load of timing pulleys dumped in a box at work. Will have a mooch through it when I get time. I certainly need to buy a rotary table or dividing head. Not really sure whether to get the Vertex HV6 rotary table or go the full hog and get the dividing head or just make my own rotary table with a standard industrial gearbox and indexing via a plate with suitably positioned holes.

    I guess timing pulleys could also be made with a home ground broaching tool. First of all, I need to find me a pulley so I can decide the easiest way to copy the profile...

    EDIT: B'jaysus, look what I found in me scrap bag. It's a 30 tooth with OD of 93.5mm and 30mm wide. Bit big though. Bummer. We have lots of them at work. Tooth to tooth is 10mm so I assume it's a 10mm pitch?
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    Last edited by birchy; 23-03-2011 at 01:17 AM.

  3. #13
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,840. Received thanks 192 times, giving thanks to others 5 times.
    Personally I'd go for the rotary table, as it's a bit cheaper.
    Remember, you'll still need some method of holding the pulley blanks onto whatever you buy.

  4. #14
    Birchy, I use thease timeing pullys on my mill conversion http://uk.rs-online.com/web/search/s...duct&R=182-694 RS generaly arent the cheepest but there service is second to none and delivery is free (normaly next day). i used a 1:4 ratio but im only useing 205 oz-in steppers so your 425 oz-in steppers should work well on the 1:2 ratio you were thinking of useing. i also used the original leadscrews (5mm pitch i think mine are). the max speed i get with my 1:4 ratio is 1800mm/min so its pritty slow but does get the job done. this was only a temporary conversion to help me cut parts for the router/plasma table im makeing. i will buy a new mill with a vertical dove tail colum to do a proper permanant conversion on after i finished my currant project. btw my mill is a Champion mill from chester uk.


    Hope this helps

    regards
    Simon

  5. #15
    Agree on the rotary table as the savings could be spent on a decent chuck and other tooling.

    These don't seem too bad on price: http://www.bearingstation.co.uk/prod...ing_Pulley_5mm
    I'm guessing the 16mm wide belt is about right? 10mm seems a bit narrow. Only thing they don't show is the maximum bore size. Any idea what size pulley I can go down to on a stepper with an 8mm shaft? I'm guessing about a 12 or 14 tooth to have some meat for the grub screws?

  6. #16
    Birchy, I use thease pullys on my mill conversion http://uk.rs-online.com/web/search/s...273+4294955369 RS usualy arent the cheepest but there service is second to none and delivery is free (usualy next day). I used a 10 tooth on the motor and a 44 tooth on the leade screw (used original leade screws as this was a tempray conversion just to help cut parts for my router build). Im only useing 205 oz in motors and get a max feed raite of 800mm/min so its pritty slow but gets the job done (can get 1200mm/min but sometimes loses steps at that speed). So i think useing your 425oz-in motors runing a 2:1 ratio you should get decent speed and still have enough power. Oh and as for concern about haveing enough "meat" on the hub of the small pulley for your motor i just put a grub screw in the center of the pulley bettween two of the teeth and aslong as you debur the hole propley you wont have any problems with it chewing up the belt. think i taped the motor pully for a M4 grub screw and the leadescrew pully M6. Btw my mill is a Champion mill from chester uk. If your motor shafts are 8mm Dia i would recomend atleast a 12 tooth pully.

    I posted on this thread lastnight but it didnt show up, not sure what happend.

    Hope this helps

    regards
    Simon

  7. #17
    Just ordered T5 pulleys and belts in sizes 14 tooth for the motors, 28 tooth for the X and Y, and 42 tooth for the Z. So I have 2:1 on XY and 3:1 on Z. Went with www.bearingstation.co.uk as they have a "price match guarantee" and were cheaper than the trade prices Brammer and RS give the company I work for.

    Out of interest, how did you find the accuracy using the standard lead screws?

  8. #18
    Might be too late but this site is very cheap for timing belts, lots of pulleys too:

    http://www.fish4parts.co.uk/Mechanic...-Belts.109413/

    I've got most of my belts from them.

    My Vertex HV6 rotary table works well as a 4th axis. I just made a mount for a 1nm motor on to it from a piece of 3" aluminum bar - not difficult to do at all. Wear on the worm drive might be a problem though.

  9. #19
    Quote Originally Posted by Jonathan View Post
    Might be too late but this site is very cheap for timing belts, lots of pulleys too:

    http://www.fish4parts.co.uk/Mechanic...-Belts.109413/
    Hmmmm, they be very expensive I'm afraid! I paid 3.01 each for T5 x 15 x 14 teeth pulleys and they're 7.76 each on fish4parts. The 42 tooth was 6.94 on bearing station and a whopping 16.69 on fish4parts. Need I say more?

    Quote Originally Posted by Jonathan View Post
    My Vertex HV6 rotary table works well as a 4th axis. I just made a mount for a 1nm motor on to it from a piece of 3" aluminum bar - not difficult to do at all. Wear on the worm drive might be a problem though.
    I've only got a 3 axis kit at the mo, but the facility is there to add a 4th. I was also a bit concerned about gear wear...that is why I mentioned using an industrial gearbox in a previous post. Rotary table and 4th axis is going on the back burner for now as I have to do!

    You didn't mention the performance of your standard lead screws. What was accuracy like and how much backlash compensation did you have to set in EMC?

  10. #20
    The lead screws on my chester mill have a 5mm pitch i think. As for precision it depends what kinda work im doing, if im just drilling holes in flat plate (basicaly just useing the table to eaqualy space out a row of say 5 holes) i get accurate results but if im milling and puting side force on the cutter accuracy is not so good. im useing mach3 and the backlash comp is set to about 0.13 mm (cant remember exactly), backlash comp is only a last resort and doesnt substitute for a good solid mechanical set up. also the lead screws have 2 ball thrust bearings near the handles and thease dont cope well with the radial force put on them by the belt tension. as i said this was a tempary conversion and just wanted to CNC it as fast and cheeply as poss. you will probly find yourself switching to ballscrews soon after you have done the cnc conversion but no harm in giveing it a go with the standard screws and see how it goes. cool thing with ballscrews is not only the minimal backlash but you only lose about 5% of your motors torque in the nut where as with norm screws you use around half your motors torque just in the friction of the nut/screw.


    Oh and the max feed rait i get on my set up is 800mm/min not 1800 as i said in a previous post, musta had my mini lathe in mind when i said 1800


    regards
    Simon

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