1. #1
    Due to a bent Y axis leadscrew I want to replace with a ballscrew as I mainly do PCBs so need accurate work. I also found that the Y axis was much slower than the X axis, so if ballscrews are less draggy I should be able to speed up a little here? But I don't want to at the expense of accuracy.

    So, how do I work out what I need? If I measure my X axis leadscrew teeth per inch is that a valid measurement and can base my ballscrew pitch on that? As that speed is fine.

    I take it that I get them to do the ends to suit my bearings and motor coupler? i.e. the whole thing is a custom length. And what's the most suitable ballnut for me?

    I think linearmotionbearings2008 on ebay is a good seller - best to get from him?

  2. #2
    John S's Avatar
    Lives in Nottingham, England, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,950. Received thanks 127 times, giving thanks to others 44 times. Referred 1 members to the community.
    No Tpi and pitch of a ball screw won't match unless you have a really course screw.
    The ebay seller you quoted is good and the most cost effective screws are 16 x 5 which means 16mm diameter by 5 mm pitch.

    Whether or not it will fit in the space needed for the ballscrew is another matter but possibly will as some 3020'sdohave ball screws.

    They will machine to suit the ends. However Chai now uses Fedex and you always now get hit for VAT plus a Fedex handling charge, usually 310.
    Chai usually lies on cost so it drops the vat a touch but often the extra Fedex costs are equal to the goods, bear this in mind and possibly look to see replacing both X and Y at the same time or at least buy them both ?
    John S -

  3. #3
    Chances are your screws are TR14x3 14mm dia 3mm pitch so like John says you could go with RM1605 and increase speeds slightly and loose some resolution. . . . OR go the other way and use RM1204 12mm Dia 4mm pitch which if your doing mainly PCB work could suit better.?
    The thinner screws won't matter here because the length isn't great and the screw speeds won't be high causing whipping. The finer pitch will give slightly more speed than TR14/3 but not much.

    I think your main weak area here will be the end fixing.? Chances are they just used standard deep grove bearings which will allow a certain amount of end float there reducing accuracy ballscrews give. So suggest you don't go rushing into ordering without checking out how your going to adapt or get round such an issue.
    Could be has simple as change of bearings to pair of angular contact if they fit in same space but could also mean completely different approach and need some bearing blocks making or buying.?

  4. #4
    Thanks guys, this is the sort of info I was after. The current leadscrews are 16mm and mount into what I would say is a normal ballrace.

  5. #5
    Quote Originally Posted by richie00boy View Post
    Thanks guys, this is the sort of info I was after. The current leadscrews are 16mm and mount into what I would say is a normal ballrace.
    Rich, Are you sure they are leadscrew and not ballscrews.? Asked before in other thread but if you can post better pictures of both the screw and nut it's easy to tell.
    One clue if it's a ballscrew is to look on the top of each thread and you will see C shaped grove.

  6. #6
    I've put a video on the other thread, maybe you can tell from that. I can't see any kind of C shape in the thread and the advert didn't say anything about ballscrews. Just said 1204 trapezoidal screws, and I've just measured them and they are 12mm not 16mm. It is the slide rails that are 16mm.
    Last edited by richie00boy; 02-08-2013 at 01:55 PM.

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