Best way to get a precise sliding fit in a home shop with just a decent lathe - Page 2
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  1. #21
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    Quote Originally Posted by avturphil View Post
    Automotive "cylinder bore" hones are generally junk. Phil
    not true. you must be confusing a hone with a de-glaze tool.

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  3. #22
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    Usual to finish the bore first.
    Get it round and get it straight.
    Round and straight and size on bore is generally more work than round and straight and size on a plug.
    Grind or lap the plug to size.
    As noted above, easier to futz with the OD than the ID.

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  5. #23
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    You can make a lap for finishing outside diameters, I think there are some vids on youtube showing how,

  6. #24
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    Always make the OD to match the ID bore, if you have a choice. A lot easier to nail an OD than an ID, especially a long one. Learn to tilt your compound and feed in with it for fine depth of cut control. You don't want to try to take super light cuts, you want consistent. Three .005 depth of cut passes, last one can be varied by a few thou either way to land you right on target. Get within .001 oversize of your target and polish to within tenths using emory cloth. Divide the length up into several segments and mic each one, using narrow strips of 120# emory to cut to size, then use a wide strip of 220# to blend it all in and polish. The trick is to run the emory while counting. Hold the emory to say, 1-2-3 and then mic it. You'll figure out how much it takes off at a given grit in that time. Now you can vary your time, depending on if you have a high spot of low spot. You can land within .0001 pretty easy once you get the hang.

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  8. #25
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    Hi Tony, i'm sure between centres is the only way, both for the male (quill) and housing / bush, leaving in the machine as much as possible of course. Thanks for your reply, Phil

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    Hi Conrad and thanks, I'm getting fairly sure that lapping is the way to go - but I still haven't decided which to finish first ..... I'm tempted to finish the Quill 1st and bore to suit it, but I'm still wondering ........ Phil

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    Dimensions are approx 2" diameter and 5" if possible stroke, absolute minimum play,(positional accuracy is vital), nominal loads only except when they're not (I know, I know - so must be capable of taking massive overloads without breaking but deflection then less important) Not very helpful, sorry, Phil

  11. #28
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    I don´t see this as difficult .. but it is not easy either.

    S:
    Use a line-bore type of lapping operation for the inside.
    Make the rigid lap adjustable in some way.

    Make some inside gage plugs with 1 micron size differences.
    About 1-2D in length.
    This is not hard to do.
    Incremental cuts on a lathe will produce good plugs where the differential in size from one to another is 1 micron.

    Smoothing the surfaces with abrasives is easy and can hold a 1 micron accuracy fairly easily.
    Use some form of rigid abrasive or soft metal laps embedded with grits of choice.


    Fwiw..
    My interest for some time has been making similar things commercially.

    Imho:
    It is easy to make a 0.01 mm difference for a short bore, where both parts have == 0.01 mm TIR, give or take.

    It is not necessarily *hard* to make a long bore to 10x the accuracy and cylindricity and roundness and surface finish.
    But you need to make tools and tools and tools and jigs to do so.

  12. #29
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    It certainly sounds like some here are confusing spring loaded junk deglazing hones with legitimate honing equipment. Otherwise they're using the equipment all wrong. It's important that the gap between the "centering" blades and the bore is correct. It's important not to let the hone fall too far out of the hole, and it's important to get the ratio of rotation to longitudinal movement correct. It's also important to use the correct grit stones for the job. When used correctly it's quite easy to get straight and round bores with a good hone like a Sunnen AN or similar.

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  14. #30
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    "Incremental cuts on a lathe will produce good plugs where the differential in size from one to another is 1 micron."

    please teach me how to do this. also interested in how to measure it.

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    Quote Originally Posted by adh2000 View Post
    I don't believe professionals would be using files and emery cloth etc. The process would be to turn the quill to size. If adequate surface finish could not be obtained on a lathe then have it cylindrically ground. The bore would be made second. It would be bored on a lathe or boring mill to a few thou over size and then honed to final size by hand fitting the ground spindle if necessary.
    I was using a file just yesterday. Small, fairly precise parts. Not really practical to put between centers or grind. I was getting about a thou taper due to spring, and a quick lick with a file made it spot on. Not everyone has access to all sorts of equipment, even working in a professional shop. You use what you have on hand.

  16. #32
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    12x industrial cnc lathe refit.
    1500 kgf push force, on 32 mm ballscrews, via 10.000 count ac brushless servos.
    220V servos, 750W each, x and z.
    Step resolution 0.2 microns theoretical.

    An external digital dti proves quite easily, programmed moves and moves via mpg can easily position to 1 micron, incrementally.

    Quote Originally Posted by dian View Post
    "Incremental cuts on a lathe will produce good plugs where the differential in size from one to another is 1 micron."

    please teach me how to do this. also interested in how to measure it.

  17. #33
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    Also, keep in mind, the OP is starting with a EE clone, not a usual worn out South Bend or forbidden import model with a flimsy bed. Get the taper dialed in when starting between centers and it should come out very well. I wouldn't be afraid to go at this quill on such a machine. My main go-to at work for things of this size is a 12" LeBlond Regal. It'll do .0002"/ft taper all day on something that substantial (2" diam).


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