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  1. #61
    Join Date
    Oct 2011
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    Norwood-ish, Adelaide
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    59
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    6,540

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    Simon, get a masonary bit of the right size, sharpen the carbide tip so that you have edges and use that.

    Michael

  2. #62
    Join Date
    Aug 2011
    Location
    Melbourne
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    4,779

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    Ahhh. That's an idea!

    Cheers, Michael. Aust post tracking tells me I'm getting my S/H makita tomorrow.

    I love getting stuff delivered!Biax/Bunax making group project

    Simon

    Sent from a galaxy far far away
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  3. #63
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

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    Quote Originally Posted by Michael G View Post
    Simon, get a masonary bit of the right size, sharpen the carbide tip so that you have edges and use that.

    Michael
    Thanks Michael - reminds me of the Artu drills that were flogged at various events years ago. The demo involved drilling through files.
    Often the same bloke was selling the low temperature aluminium solder

    I looked them up from a nostalgic perspective, and found there's some useful info for DIY versions.
    Multi-Purpose Drill Bits

    The geometry is pretty clear in that image, and note that you don't need (or really want) a sharp positive rake cutting edge like a normal drill bit. You just want an edge.
    Bit like a negative rake lathe insert I guess - it pretty much bulldozes the metal off rather than peeling it.

    Here's the Artu drilling tips - Multi-Purpose Drilling Tips
    Note that hardened steel is a "drill press only" for them. I'm guessing thats because you need the leverage to force the bit to cut.
    The sharpening instructions show the geometry again.

    Steve

  4. #64
    Join Date
    Apr 2019
    Location
    Adelaide
    Posts
    589

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    Quote Originally Posted by jhovel View Post
    @Mk1_oz: have you put some photos of your Ozito'ax on this forum? If so, link please. If not, please do.
    My Ozito multitool driven real Biax head lasted maybe 2 hours. I've got an old Metabo jig saw motor which is what Biax used in their previous model (before Metabo made it obsolete). I'll be making an adapter to drive it with that next.
    Still very much a work in progress so only have the Ozito and gearbox modelled. The gearbox provides a 21:1 reduction and at this time has 10mm wide spur gears. I am thinking to save space and weight these could be reduced to 5mm as I don't expect the loads to be huge. They will also most likely be made in aluminium.


    Ozitax.jpg

  5. #65
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,779

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    Makita arrived today.

    I'll have more of a play tomorrow.

    Simon

    Sent from a galaxy far far away
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  6. #66
    Join Date
    Aug 2011
    Location
    Melbourne
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    Completely disassembled the makita this morning. Not as trivial as I would have hoped. The two saddle clamps that hold the two guide blocks front and rear were screwed in with some sort of retaining compound. Further, the screws seemed to be more mild steel than high tensile and I sheared the heads off two of them.

    I then employed a screw extractor. It snapped in the hole I drilled in the screw.... Things aren't going too well.

    I managed to drill out the remaining screws (luckily not a blind hole so did it from outside) and extracted the screw extractor.

    Those saddles will now need to be through bolted. Not an issue, as I plan on attaching a leather hand strap or hand grip anyway.

    Anyway, the counterweight on the crown wheel is about 6.5mm high.

    I could just lay a T slot and sliding piece on top. Or, I could machine down the counterweight the same amount as the base thickness of the T slot or dovetail. Boring a hole in the base of the dovetail would serve to locate it over the needle bearing outer race of the crown wheel.

    Question is, how important is the retention of that counterweight for scraping purposes?

    A couple of m5 set screws on either side of the dovetail that screw into the crown wheel would be enough to hold it in place.

    So how hard is the crown wheel? Well, it's hard but it's not tool steel hard. A file can mark a scratch on it.... but only just!

    Still thinking about ideas but I can't see any of NOT having to make a spacer to fit between the casing to allow for the height of the stroke adjustment mechanism.

    Certainly a T slot and slide would take up the least amount of room. But a dovetail would be superior and allow radial adjustment and a single hole for an Allen key....

    Simon

    Sent from a galaxy far far away
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  7. #67
    Join Date
    Aug 2009
    Location
    Lara, Vic, Oz
    Posts
    46

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    I wonder if an easier adjustment mechanism than dovetail or t-slot may be to simply have an offset pin locating in the original hole that can be swung closer or farther from the centre to vary the stroke. Perhaps have a grub screw in the green pin (locating in the original hole in the crown gear) that expands the pin (like a collet) to clamp it in position, but allows relatively easy adjustment (though not externally). Be interesting to see if the clamping force would be sufficient to resist the torque seen during use.

    Main advantage is that it would not require any machining of the crown gear, so might work with sintered/v hard gears, and could reduce the stroke to effectively zero. Would just need a thin spacer to account for the thickness of the yellow section to account for added height. Apologies for the terrible diagram, my CAD package is refusing to play ball today, hopefully large enough to get the drift. I already have the Ozito saw, which would require a slightly larger spacer as the centre shaft protrudes through the bearing above the top of the crown gear with circlip retention, so would need to clear that, but the Makita looks flush so could be pretty compact.
    offset drive pin.jpg
    Edit, I was thinking of the jigsaw I was looking at using which has the crown gear retained by circlip and hence protruding shaft, will have to check back to photos of the Ozito or open to check to see if this is similar to the Makita.

    Edit 2, post #28 from Pippin88 suggestes the Ozito has flush shaft so like the Makita could be a neat installation. Reckon that's the way I will try.
    Last edited by SiJ; 2nd Feb 2022 at 04:14 PM. Reason: May as well attach the drawing...

  8. #68
    Join Date
    Nov 2017
    Location
    Geelong, Australia
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    57
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    2,651

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    Clever idea SiJ.
    I need to think about it more when I’m not so tired, but I think for the stroke range required for scraping there will be an ideal length link that will result in almost all the force being in line with the link and minimal torque on the pin.

    The other idea that comes to mind is to use a wider link and have it slotted for a clamp screw like old style ignition points.

    Steve

  9. #69
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
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    Just a thought with the saws that have a bearing in the crownwheel and a fixed shaft in the case (as compared to a shaft in the crownwheel and bearings in the case like the Ozito and my Bosch).
    It might be practical to replace that needle roller bearing with a shaft, and run standard bearings in the case.

    It should then be possible to run the adjuster mechanism in the space where the bearing was.

    Extending the idea slightly, if the new shaft was made larger diameter in the crownwheel (even to the point of the crownwheel becoming just a ring that attached to a flange on the shaft), the adjuster could be fully contained in the shaft stub.
    I expect it would be possible to bore the crownwheel out on a lathe with carbide (but I could be wrong).
    The pros of going down this track would be that the case wouldn't need spacing for the extra adjuster bits, potentially better crownwheel bearing support and since the shaft wouldn't need to be hardened the adjuster dovetail slot would be easy to machine with HSS tooling. Bearing replacement (if ever required) would be easy
    Cons - more work, and potentially the case isn't suitable to take a couple of bearings without more work.

    Steve

  10. #70
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,779

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    I just tried drilling the crownwheel with standard HSS, as Joe reported, too hard!

    Joe drilled his with TC so I suspect it can be face milled or milled with a TC type endmill.

    Placing a bearing in the case and replacing crownwheel bearing with a shaft may not be that easy. I'll have to look at the case and see if I can bore a bearing housing in there.

    Simon

    Sent from a galaxy far far away
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  11. #71
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,439

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    Hi Guys,

    There used to be a German company that made carbide tipped drills ! They looked identical to a normal HSS drill, indeed they were HSS but they had a carbide tip ground like a normal HSS drill. Very similar to a masonry drill but the carbide was sharp and didn't overlap the flutes like masonry ones. I bought several of different sizes, mainly for drilling SS and cast iron. I'm sure that everyone has seen the drilling holes in a file, well these go through files like the file was made of butter !
    Best Regards:
    Baron J.

  12. #72
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

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    Solid carbide drill bits are available on eBay at reasonable prices: https://www.ebay.com.au/itm/37376790...kAAOSwkCNhdlJ1
    Chris

  13. #73
    Join Date
    Aug 2010
    Location
    Near Bendigo, Victoria, AUS
    Age
    72
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    3,102

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    @simonl: the problem with embedding the slide in the crownwheel is the height of the bearing. My case looks identical to yours in photos, and there isn't enough 'meat' there to put a bearing in the case.

    I've now made a start with the spacer disk, complete with eccentric tight fitting pin and screwed it to the crownwheel. I ended up drilling and tapping an M4 thread into the eccentric pin, countersinking the crownwheel's 7mm hole and screwing the spacer disk on there as well.
    I'll have a shot at milling a dovetail slot in there tomorrow night. I'll take photos of the progress. This is my current thinking:
    Saw conversion1.jpg
    Saw conversion2.jpg
    Saw conversion3.jpg
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  14. #74
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    Aug 2011
    Location
    Melbourne
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    Hi Joe,

    I like the look of your design. Couple of questions if I may;

    As mentioned, there is little existing room between the two case halves. I see your dovetail adjustment assembly is 8mm total height, are you planning on making the case spacer 8mm as well?

    How are you planning on making this spacer?

    Just tracing it out and cutting by hand?

    Also, I agree that machining down the crown wheel is not really an option since it would interfere with the bearing mount.

    Edit: what materials are you planning to make the dovetail assembly out of?

    Cheers,

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  15. #75
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    Aug 2011
    Location
    Melbourne
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    Hi SiJ.

    That's probably the simplest method to achieve the desired result. As suggested, I think you would need to add a clamp screw and include a curved slot in the adjustment plate for the screw to clamp onto.

    While it is the simplest and easiest method, the downside is the ability for fine adjustment of the stroke without a large hole in the case, or complete disassembly of the case.

    A dovetail slide lends itself to a single adjustment screw and a single hole placed strategically in the side of the case lining up with the screw.

    Sure, you would need to buzz the motor to line up the crown wheel and screw to the hole, but you have to do this with a Biax as well.

    Cheers,

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

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