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  1. #1
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    Default Layout & bending Jig Tables -Optical Centre Punch

    I’m in the process of making two tables for my workshop for jigging and bending.

    One is a two inch thick surface ground plate so it was just a case of blueing it up.

    The other is only an inch thick and had quite a thick,coating of paint in a few colours.



    After wirewheeling for what seemed like a decade it got a light going over with a nylon abrasive disc.


    Now the hard part marking it out.
    The 2 inch plate will just be a straight grid of holes with 50mm spacing. The inch thick plate will look more like a map of the constellations. It’s designed for making scrolls and setting angles and setting leg splays for tripods etc.


    I have found the edges of the plate are slightly concave over the length due to water/laser or whatever cutting was used and I have no facilities to improved them. To compensate I have clamped a straight edge in position to be my datum.

    I’m using a percussion automatic centre punch but I’m not as happy with the accuracy to what I’d like so I started looking for an optical centre punch. The veritas one being the cheapest at $83 and I have read reviews saying the punch is too soft for steel. The rest seem to be around the $100 mark. The household is a bit in the red at the moment so can’t really spend that. I thought about trying to make one but don’t have the equipment to do so with the needed accuracy.

    Are there any other ideas? I have a lot of points to mark out!
    …..Live a Quiet Life & Work with your Hands

  2. #2
    Join Date
    Jan 2004
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    Mackay North Qld
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    I thought you had lathe.

    Its easy enough to make.

    If you don't have a lathe, one of the lathe blokes might make you one in exchange for some of your excellent blacksmith work.

    A piece of silver steel could be made hard enough,surely?

    Theres some links I can see( Similar threads ) on previous Optical Centre Punch discussions are at the bottom LH side of this page.

    Grahame

  3. #3
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    Yes I do have a lathe but it’s a clapped out one. Ok for turning up non critical things and things for a blacksmith no good for any level of accuracy. For the plans and videos I have looked at the body needs to be reamed, so I’d have to buy a reamer also.

    Happy to discuss a trade for some Forge work.


    Sent from my iPad using Tapatalk
    …..Live a Quiet Life & Work with your Hands

  4. #4
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    Aug 2008
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    Adelaide
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    I've had the Veritas one for years and it's still fine. The thing is, you only need to use it to lightly mark the intended position and then follow up with a conventional centre punch. Perhaps the bad reviews are by people belting the living daylights out of the Veritas punch.

  5. #5
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    Jan 2004
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    Quote Originally Posted by Gavin Newman View Post
    Perhaps the bad reviews are by people belting the living daylights out of the Veritas punch.
    I totally agree Gavin,
    I too have a Veritas Optical center punch . All it ever needs is a tap.
    Grahame

  6. #6
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    Oct 2008
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    N.W.Tasmania
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    I have an optical punch that you can borrow if you like, if your turns out ok, I might get you to make me one.
    It looks like the old Black and Decker is about to get a bit of a flogging though.
    Shoot me a PM with your postal details if you want to borrow it.
    Rob.

  7. #7
    Join Date
    May 2011
    Location
    Castlemaine
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    When I did my first welding table (45mm thick) with drilled and tapped holes I avoided the marking out by using a jig.

    The jig was a piece of 50 x 20 aluminium extrusion. I then used the mill to drill holes at 100mm centres.

    I then turned up some drill bushes in the lathe for a pilot drill and final tap drill.

    the drill bushings also helped with keeping the holes square as I did all the drilling with a hand drill.

    I have a new bigger table. I am about to do but I will use a mag base drill this time.

    Cheers

    Piers
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  8. #8
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    Oct 2007
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    Sydney
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    Even the most clapped out lathe would almost certainly still be good enough to turn an accurate centre. If you're happy enough to spend the money on a commercial optical punch, but want to give it a bit more welly when marking out, simply turn up a new punch to replace the existing one. A regular centre punch is one of the first projects an apprentice will make at trade school so there's lots of information out there on the making, hardening and tempering this type of tool. In your case it's even easier as the body is just cylindrical. However I'm surprised the Veritas one is said not to mark steel well, as the punch is advertised as A2 steel.

    Having said that, I believe an optical centre punch is really a misnomer and they should really be considered an optical prick punch or something similar and used in the same way. If I were making one, and it's something I've been meaning to make for years, I wouldn't have a 90 degree centre on the punch, which is what the Veritas appears to have.

    When marking out accurately you first use a prick punch, transfer punch, or in this case an optical punch to mark the position of the hole, they are struck only just hard enough to mark the feature and won't normally centre a drill reliably. A prick punch has a smaller angle and it's reasonably easy to feel them drop into a scribe line. Because of the angle, if you really whack a prick punch there's a good chance you'll damage it. The indent it leaves is pretty small and reasonably easy to shift if you screw it up, something I do with monotonous regularity so trust me on that one! Even though it won't centre a drill, that's typically all I use before drilling as I'm not building Space Shuttles down here. However it you want to get more serious about an accurate hole, you'll then follow the prick punch with a centre punch, as the prick indent is sufficient to locate the centre punch, and the centre punch is then sufficient to locate a drill (hence the name). You can strike a centre punch pretty hard, and if it's any good it should withstand the strikes without damage. Cheap ones are rubbish, as it's brutal on the steel. The centre punches also come in different sizes. It's worth buying decent punches as they're not expensive in the grand scheme of things. I use Elora punches (made in Germany), I find their prick punch especially good. I also use Stanley, yes believe it or not, and honestly can't fault them. I have some home made ones that are pretty crap if I have to be honest with myself, and some cheap Chinese ones that are a complete waste of time. You'll find the centre of a cheap punch will damage easily as is then next to useless.

    As an aside, I've had a few automatic punches and have never really liked them. I find they're not accurate enough and tend to shift slightly when they fire. In fairness I haven't ever bought a really good one, and maybe my life is miserable and pointless as a result, however I've never seen the point in them ... if you excuse what I thought was rather a good pun :P

    As much as I have been meaning to make an optical punch, the reason I haven't is because I find if the layout lines are reasonable the prick punch falls in to them pretty well, and results every bit as good as optical punches.

  9. #9
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    Dec 2007
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    Default Layout & bending Jig Tables -Optical Centre Punch

    Pete what is the angle on a prick punch?


    My issue is getting a good fit between all the optical punch parts, facing them square and centred. I’m no good with a 4 jaw chuck and an indicator, there is definitely some black magic involved that I’m not privy too. My lathe have a lot of slop & back lash in all parts.
    …..Live a Quiet Life & Work with your Hands

  10. #10
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    Quote Originally Posted by Ropetangler View Post
    I have an optical punch that you can borrow if you like, if your turns out ok, I might get you to make me one:
    I think I have something in the works, but thanks for the offer.
    …..Live a Quiet Life & Work with your Hands

  11. #11
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    Quote Originally Posted by Piers037 View Post

    The jig was a piece of 50 x 20 aluminium extrusion. I then used the mill to drill holes at 100mm centres.

    I then turned up some drill bushes in the lathe for a pilot drill and final tap drill.

    the drill bushings also helped with keeping the holes square as I did all the drilling with a hand drill.
    I like that idea but don’t have the mill to make the jig accurate. If I made the jig by hand I’d worry about compounding errors.

    I bought a 16mm annular Cutter and plan to use a borrowed mag drill.
    …..Live a Quiet Life & Work with your Hands

  12. #12
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    Oct 2011
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    Quote Originally Posted by DSEL74 View Post
    What is the angle on a prick punch?
    I've always worked on 60 degrees included; a centre punch is 90.

    Michael

  13. #13
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    …..Live a Quiet Life & Work with your Hands

  14. #14
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    Default Layout & bending Jig Tables -Optical Centre Punch

    Quote Originally Posted by Michael G View Post
    I've always worked on 60 degrees included; a centre punch is 90.

    Michael
    I based the drawings above on what is commercially available. Is it the consensus that the shallow punch (120deg) should be scrapped and a 60deg substituted?
    …..Live a Quiet Life & Work with your Hands

  15. #15
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    Quote Originally Posted by DSEL74 View Post
    I bought a 16mm annular Cutter and plan to use a borrowed mag drill.
    Have you seen this video?

    https://m.youtube.com/watch?v=Prik-_GVHss

    when are you planning on drilling the holes? I am just about to make a 16mm annular cutter jig to drill my new table

    Cheers

    Piers
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