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  1. #161
    Quote Originally Posted by Jonathan View Post
    I know, but proper double nuts aren't as good as two nuts and springs / belville washers are they.
    When I referred to 'double nuts and a spring' earlier I was thinking of doing something like this as it's a simple way of implementing it:
    Ok as my final comment on this.!! . . Yes and no. Yes Belville washers will apply far more preload but at the potential cost of shortend life.! There is such a thing as too much preload.
    So then for that very reason NO it doesn't make them better.!! . . . .They will only be better for shortened period of time, obviously how long depends on Belville force, but they will wear sooner with the ultimate result of a wornout knackerd screw.
    If good quality screws with high preload doublenuts are used they will give zero backlash with trouble free service for years, if installed correctly and maintained properly.
    Yes they come at an high cost but theres a reason for that, precision costs.! . . . . If it was just a simple case of sandwhich a few Belville washers between 2 std nuts without any consiqences or performance costs then thats what they would do dont you think.?

    Anyway all of this is Ballcocks for 99.9% of DIY level machines and certainly cheap C7 chinese screws.

    James I appologise for filling your thread with unrelated post's so know I will say no more unless related to your specific build, which this originally kind of did.!

  2. #162
    Dear Jazz thank you for the y-axis jigs they have arrived they came on Saturday.
    I would like to thank you for your time and for rushing a second set out The first set are no where to be seen
    I can only now confirm this as Luke has only opened the parcel.

    I did email Jonathan saying they had arrived but I was not a 100% sure Sorry for the delay

    James & Luke

  3. #163
    I've been looking at my gantry all day and some think is not right and after about 3 hours I decided to get my set square out.


    and this is what I found

    Click image for larger version. 

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    The above image shows that the gantry is out of square by 1.5mm
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    the above image shows the joint is fitting nice and tight (this is the left side)
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    the above image shows the gantry is out by .5mm

    am I being to picky does it really matter that much that the Gantry is not square

    Well I think so

    there is no stress to force the gantry out of square as all bolts have been taken out and the rails are not bolted down the only fixings is the three button bolts in the side of the gantry.

    Now I have tried to force the gantry square but it is solid and will not move.

    I am at a lost and getting frustrated
    what is my options Please Please advise what I need to do :question::question:


    James

  4. #164
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    if you take one side off and measure the depth of the machined groove on each edge to see if the groove is machined level to the face. It may be a good idea to machine the edge of the plate the side is clamping too, to make sure the mating faces are square and flat.

  5. #165
    Quote Originally Posted by JAZZCNC View Post
    So then for that very reason NO it doesn't make them better.!! . . . .They will only be better for shortened period of time, obviously how long depends on Belville force, but they will wear sooner with the ultimate result of a wornout knackerd screw.
    I think the spring method will be better for longer as wear with the double nut will lead to more backlash, whereas wear with the sprung nuts will not have much effect. It will reduce the preload a bit, but you can adjust it so it guarantees that backlash is eliminated. Which is pretty pointless on a router anyway...but I know which method I'll be using when I convert my lathe/mill.
    Either way for hobby machines they are used so little (relative to in industry) than wear on the ballscrews/nuts is negligible. If you've used it for long enough to wear out the ballscrews then you've probably made enough money to replace them.

    James: That not being quite square is one reason that I suggested you used triangular plates from the X-bearing mount to gantry side. They will stop the deflection.

    I cut the slots in the gantry sides on my router as they wouldn't fit on the mill. The bad had been surfaced recently, so they shouldn't be far off ... if you want me to skim the bearing mount plates to get them square that's not problem. I meant to do it anyway but forgot.
    Bear in mind SBR/TBR type bearings will tolerate some rotational misalignment, so will it make a difference when the machine is running? I don't think so, but I'd still add reinforcement triangles to make sure.
    Last edited by Jonathan; 10-10-2011 at 08:31 PM.

  6. #166
    James,
    I agree with i2i on this one. It might not be the side plates but the cross axis beam. It might not be perfectly square cut or it might be slightly short. If you have bolted up one side and its a bit short it would give this result when fitting up the other side.

    Ian

  7. #167
    thank you all Jonathan I will bring the gantry sides with me at the weekend :)

    Ian and i2i the cross axis beam is not tight and only has two bolts on each side top and bottom

    James

  8. #168
    Quote Originally Posted by Jonathan View Post
    I think the spring method will be better for longer as wear with the double nut will lead to more backlash, whereas wear with the sprung nuts will not have much effect. It will reduce the preload a bit, but you can adjust it so it guarantees that backlash is eliminated. Which is pretty pointless on a router anyway...but I know which method I'll be using when I convert my lathe/mill.
    Either way for hobby machines they are used so little (relative to in industry) than wear on the ballscrews/nuts is negligible. If you've used it for long enough to wear out the ballscrews then you've probably made enough money to replace them.
    Ok jonathan you seem to know something all the top Ballscrew manufacturers in the world don't so get on with it and good luck.!!

    James first I would double check the square is accurate.? Those type of wood working squares are not the best for accurecy.! Ideally you want a good engineers square, longer the better.

    The gantry is not neccesorally out of square, check the angle between the cross brace and gantry sides.! . . . Are they 90deg.?
    Like as been suggested the cross brace could be short or the rebates in the gantry sides could have been cut fractionly deeper than intended creating the same affect.
    If the difference is only small then you could easily place a shim/s in the rebate effectively widening the gantry back to original width and/or use them to bring back into square if rebate is uneven depth or wedged shape.?

    Because your using round rail you can accomodate this slight angle difference were the bearing plate meets the gantry side. (Easily fixed with with triangle braces like Jonathan suggests)
    Thou it's actually not a big problem if the gantry sides are not exactly 90deg to the cross brace because your using round rail. (If was using profiled rails then yes it would be a big deal.)
    Yes ideally you would like absolute square and true but So long as the error is not so great that it affects the screws then you'll be ok

    Far far more important is the gantry runs square to the X axis.

    I say get your self a good accurate square and some shim steel, It's not un-common to have to use shims to bring things into line or back to square so dont consider it a bodge.!
    Far better to hold something square with shims than force it square.!!!

  9. #169
    Quote Originally Posted by JAZZCNC View Post
    Ok jonathan you seem to know something all the top Ballscrew manufacturers in the world don't so get on with it and good luck.!!
    All the top manufacturers are aimed at industry where the expectancies (life, accuracy etc) are significantly greater. So if we slightly reduce the life by using double nuts or springs with the same preload it's still going to last a very long time. Most DIY builds don't lubricate the ballnut which clearly is reducing the life expectancy similarly to what we're discussing, however they still run for years... I did consider lubricating mine properly, but when you're rotating the nuts it's easier said than done. Even if you could connect the tube for the oil the oil just flys out.
    My comments apply to the C7 screws almost all of us buy where the spring helps compensate for the lead error, not your C1 ballscrew!

    James: You can check how accurate the square is by placing 4 equal diameter cylinders in it arranged in a square and measure the diagonals (i.e. placing the caliper across the tangents). If they are equal you know it's good. That's fine in theory... the problem is finding 4 accurate cylinders, bigger the better-I don't advise using your router's rails!

  10. #170
    If you've used it for long enough to wear out the ballscrews then you've probably made enough money to replace them.
    thats the way iv been looking at it :naughty:

    Ok jonathan you seem to know something all the top Ballscrew manufacturers in the world don't so get on with it and good luck.!!
    thats a tad aggressive jazz .... in this sport there is an element of "art" and "on the cheep" im struggling to knock jonathans logic till i know better..... out of interest has anyone managed to wear out a ball nut in our DIY circle ?
    and did they make enough to replace them lol

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