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Thread: Knurling - how to?

  1. #1
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    Default Knurling - how to?

    Hi all,

    I have a possible repeat batch-job coming up but need to knurl around 75mm of an 8mm shaft.

    I had a try this morning as not really done any before, i have a clamp type tool and tried the fitted wheels first, these were the medium of the three provide but although it did cut, one of the wheels was bored off-centre and the little lathe was not happy, it started off bad but cut in the end, this is the right-hand of the two in the picture.



    Then i changed to the coarse wheels and they ran better but now i get a double-cut on one angle?? (left image)

    Is there a secret to knurling i need to learn? Does feed-rate matter, can i expect to knurl 3" / 75mm in one hit with no tail support?

    Any tips ?

    Thanks

  2. #2
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    Default

    Some pointers: https://www.youtube.com/watch?v=9Zwi0ZAUCUc

    Cheap knurling tools can be tricky to beat to submission. Paul had a match with one recently:
    http://bbs.homeshopmachinist.net/thr...light=knurling

  3. #3
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    I don't think you'll ever do 3" of that thin a stock without tailstock support. We do lots of knurling a school and I have no trouble getting the kids to knurl 4 1/2 inches of aluminum bar on the first try. Ive done steel pipe up to 1 1/4 (what will fit in the spindle) down to 1/4" rod (admittedly very short lengths) with the same knurling tool (one of the scissor type BUT with a new set of knurls, the tapered edge ones) . Another good thing is to knurl towards the tailstock to avoid any sliping in the chuck. It does take a bit of axial force. Slow RPM and fairly fast travel. keep it wet with any oil. Been at this for 20 years.
    ...lew...

  4. #4
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    a coarse knurl on small diameter work with a less than an ideal tool makes it a challenge.....but you did get good results for part of it. With a clamp style, I'd do it in one pass, with maybe a 5-10 thou feed rate. The clamp style with two wheels holds the work in the up and down direction, but without the tailstock, movement in the "in and out" direction may be an issue. There is a clamp style with three wheels so its entirely self supporting so you can do long very small dia work with no tailstock.

    A cut knurling tool would make quick work of that....although when I've done so it wasn't with so coarse a knurl. One pass, at speed.

    Last edited by Mcgyver; 03-09-2019 at 09:41 AM.
    .

  5. #5
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    Thanks all, seems i have some learning to do

    I always thought knurling was forming, never heard of cut knurling, have now.

    A three-wheel clamp style sounds ideal hear but i cant find one, not yet anyway.

    I can modify the part for tailstock support and cut that off later.

  6. #6
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    Most of the tools are forming tools. Cut knurls are a special case. Not uncommon at all but you buy one or the other.

    There's a lot of cheap and badly made tools around that make getting a good start a chore. It may well be that you simply need a better tool than what you have with better knurls.

    There very much is a pitch to all this too. The knurls will try to pull themselves to a true cut like you show in one portion where it's a nice clean diamond. But if the diameter is just right it can "stabilize" on a double cut easily. Then the trick is to change to a different pitch knurl if you MUST cut that size.

    If it's a simple push tool, as many are, then you most certainly want to use a tail stock with a piece that long and small. It's not really an option in fact with something that long and small. And you might well find that you need to move into the work through the middle then ease off as you get closer to the chuck. In effect riding along with a consistent amount of pressure through the portion where the work tries to flex away from the tool.

    For long and skinny like this a clamp style tool would be aces. Far easier and more consistent as all the pressure needed is kept within the tool so the part can't flex away from the knurls easily.

    But the cheap clamp style tools are not always the best either. Some of them are going to work a lot better if you take some time to improve them with things like less wobbly pins and the like. It has to hold the knurls so they sit at proper right angles to the work surfaces to get a nice formation.

  7. #7
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    thanks, I do think this tool is junk, has slop everywhere and probably not worth trying to patch up.

    I'll look for a better tool.

  8. #8
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    Quote Originally Posted by Davek0974 View Post
    A three-wheel clamp style sounds ideal hear but i cant find one, not yet anyway.
    .
    I first encounted them in watch/clock stuff where you might be making very small diameter tools so it needs that self supporting function. Horia makes a beautiful one, and they are very proud of it (as they are all their stuff, but its as good as it gets). There's also Knurlmaster which are more reasonable

    http://www.penntoolco.com/eagle-rock...-hand-knurler/
    .

  9. #9
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    Knurling seams pretty easy. Just scrub the ice really hard if your puck is moving to slow, and maybe create smooth paths to change its course. I never understood why it was an Olympic sport.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  10. #10
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    If the job's likely to repeat and is worth it, you might look for a turret knurling tool. I have a job I do occasionally where I knurl the full length of 1/4" drill rod. So I got a Hardinge turret tool off eBay, made a special tool holder for it, and set it up for just what I needed:



    I don't dismount the tool from the holder or ever adjust it at all - I just take it out for that one job and stick it back in the drawer.

    It does a great job:



    A decade after I set it up, I can take it out, run it over a drill size "B" 0-1 rod and end up with a 0.249" (+ - .001") knurled rod anytime I need it.


    Here's the full deal: http://www.frets.com/HomeShopTech/Projects/LongKnurl/longknurl.html
    Cheers,

    Frank Ford
    HomeShopTech

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