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Thread: Tuning and modifying a scissors style knurling tool

  1. #1
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    Default Tuning and modifying a scissors style knurling tool

    So this is some tuning up and modifying to my scissors style knurling tool that I bought a couple of years ago but which I found had so many issues that it sat in the drawer up until today.

    This little project was inspired by the thread Knurling- How To?
    . A lot of good ideas came up in that thread including the using of one of these inexpensive import scissors style knurling tools.

    I recalled that when I got mine that it had more than it's share of issues. Not really even a good kit of parts. But thanks to an afternoon worth of tinkering I think I'm well on the way to making this work and FIT my lathe... more on this "fit" thing below...

    To follow along here's a picture showing the broken down modified and new parts so far....



    Let's go through the parts starting from the scissor parts. The parts were coated with a pebbly textured finish that seems like it's likely powder coat. Really nice actually. But it was causing a lot of friction and "cogging" in the swing of the arms. Plus the finish, being so thick, was holding the arms slightly outwards so they arms were not in line. The scissor unit being wider than just one arm. So both arms were set into the four jaw and given a skim cut on the mating surfaces as shown on the one with the inside facing out. At the same time I figured why have the other parts of the finish riding on the mounting leg's washer all rough and the same for the washer on the other side of the scissors unit. So both arms were also skimmed very lightly to clean up smooth surfaces for the washers to ride against.

    At the same time the center holes were bored out to 0.502 in preparation for a new thicker wall bushing to replace the one which was too short and really thin.

    Next to the pivot bolt and other parts that hold the whole thing together. The new bolt is shown. The original bolt was found to have a bend in it. And the head was a bit wonky to the upper smooth portion. It's neatly machined but neatly machined badly... .it looks real neat in the scrap bucket now.old original So the new one started as a regular allen cap head screw and I cut down the threads so only the part that the nut needs is there and the bushing and mount leg only get the smooth shank portion.

    I also found that the two supplied black washers were badly burred and held the scissors pack at some angle due to those burrs. The burrs were filed smooth so the washers now lay flat. They didn't before. Check yours and fix or replace.

    Because the head is so small I made a nice heavy washer for under the head. Then there's the new thicker wall bushing that should resist deforming when tightened. It's made from a scrap of 1/2" drill rod and parted off at about .01" longer than the scissor arm stack so there's some slight play and no binding.

    So it was all back together and I set up to try it. Now I ran into a FIT problem. Normally I leave my compound sitting at the usual 29 for threading. It angles the tool post position slightly towards the chuck so I can get the tools in close to the jaws without the outer part of the jaws running into the cross slide. But it's also neatly out of the way of the tail stock riding in close which isn't the case if I set the compound to 90. BUT..... I find I can't back off the cross slide enough to get the knurl axles positioned right over the center line of the head stock. So I fudged the angle to give it a try. And I've got a 12" swing lathe! ! ! ! Those of you with smaller swing machines would not have a snowball's chance in Hades of using this tool as it comes out of the box due to this reach issue.

    First time around the size of my scrap was just right to result in double cutting from both kurls. Made for a neat looking super fine knurl though ! ! ! I skimmed off the double and tried again and this time I got a really nice looking knurl. I used lots of cutting oil on the pass in and then a healthy spray of WD40 on the way out to flush things. I'll show the results later of this first good knurl but it's super clean and sharp. And it was done on a bit of 1/2" scrap with 3" of it sticking out. No way I could do that with the old push type ! ! ! !

    So next up which I'll post in a few hours is to drill and tap the BXA post's big blocky boring bar holder to also let me directly screw the scissors to the tool block. That'll get rid of the mounting leg and also let me get the whole scissors pack about 2" further back with ease.


    More in a bit and some more pictures.

  2. #2
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    Nice work.
    I have been able to get good knurls without worrying about stock diameter. If the knurls do not track right, just increase the pressure. I have not had much luck with the AXA and BXA knurling tools. It is difficult to get both knurls engaged equally. I go back to my lantern toolposts and use the old fashioned swivel head knurling tool.
    Last edited by Illinoyance; 03-13-2019 at 10:44 PM.

  3. #3
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    Quote Originally Posted by Illinoyance View Post
    Nice work.
    I have been able to get good knurls without worrying about stock diameter. If the knurls do not track right, just increase the pressure. I have not had much luck with the AXA and BXA knurling tools. It is difficult to get both knurls engaged equally. I go back to my lantern toolposts and use the old fashioned swivel head knurling tool.
    The holder needs some "float" to do it right. Perhaps try again but don't lock the piston or wedge. Just let the tool holder float on the dovetail.

  4. #4
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    Quote Originally Posted by BCRider View Post
    The holder needs some "float" to do it right. Perhaps try again but don't lock the piston or wedge. Just let the tool holder float on the dovetail.
    I am pretty sure it's a little bit of endwise float on the actual knurls that accomplishes the trick to do that .
    ...lew...

  5. #5
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    Quote Originally Posted by Lew Hartswick View Post
    I am pretty sure it's a little bit of endwise float on the actual knurls that accomplishes the trick to do that .
    ...lew...
    You mean like along the pins? That's not the issue. In THIS LISTING FOR AN ALORIS STYLE TOOL SET if you look at the knurling tool there's no up and down or in and out float. The knurls are simply pinned to the block. And if the block is not free to self adjust vertically there will be uneven pressure on the two wheels. And I'm thinking that the way around that is to just not lock the wedge so the holder can float vertically.

  6. #6
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    Quote Originally Posted by Illinoyance View Post
    Nice work.
    I have been able to get good knurls without worrying about stock diameter. If the knurls do not track right, just increase the pressure. I have not had much luck with the AXA and BXA knurling tools. It is difficult to get both knurls engaged equally. I go back to my lantern toolposts and use the old fashioned swivel head knurling tool.
    Is it like mine below? I have pretty good luck with it. And I do indeed lock it down. They work well but are too expensive. Prolly because of the name on them. Dont pay for names, pay for quality. It is a quality piece though.. JR

    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  7. #7
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    Quote Originally Posted by Illinoyance View Post
    Nice work.
    I have been able to get good knurls without worrying about stock diameter. If the knurls do not track right, just increase the pressure.
    This. Work diameter does not matter if you take a deep bite right at the start. Trying to sneak up on the knurl with gentle bites and multiple passes is how you get double tracking.

    In most materials I go for a full depth knurl in one pass; that tracks correctly every time regardless of stock diameter.

  8. #8
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    Quote Originally Posted by Yondering View Post
    This. Work diameter does not matter if you take a deep bite right at the start. Trying to sneak up on the knurl with gentle bites and multiple passes is how you get double tracking.

    In most materials I go for a full depth knurl in one pass; that tracks correctly every time regardless of stock diameter.
    I've also found with the old push type that it often worked well to start with only half or even less of the width of the wheels engaged so the teeth could obtain a good deep bite. The very odd time I'd still get a double start on one or both wheels but it was FAR less common. And even then a bit more dig often fixed even that.

  9. #9
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    Quote Originally Posted by BCRider View Post
    You mean like along the pins? That's not the issue. In THIS LISTING FOR AN ALORIS STYLE TOOL SET if you look at the knurling tool there's no up and down or in and out float. The knurls are simply pinned to the block. And if the block is not free to self adjust vertically there will be uneven pressure on the two wheels. And I'm thinking that the way around that is to just not lock the wedge so the holder can float vertically.
    I don't know about that tool but the ones I have do have the ability to swing up and down. The whole tool pivots on the same pin and the scissors move on and it's adjusted to have the knurls axles on a diameter of the work so the pressure WILL be equal on the work. So the quickly applied "squeeze" and the bit of "sliding" on the axles does away with any non-tracking problem .
    ...lew...

  10. #10
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    Quote Originally Posted by BCRider View Post
    I've also found with the old push type that it often worked well to start with only half or even less of the width of the wheels engaged so the teeth could obtain a good deep bite. The very odd time I'd still get a double start on one or both wheels but it was FAR less common. And even then a bit more dig often fixed even that.
    Yes, starting with the knurl wheels only halfway on the work is my standard practice for good knurling and getting a deep bite.

    You really can't reliably get a deep enough bite in most steels with a bump knurl tool, which is why I don't use them any more. Most of the small clamp style tools aren't much better IMO. A strong scissors tool can do it easily though, and takes load off the carriage and the spindle bearings as well.

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