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  1. #31
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Thumbs up Ideas !

    Hi Steve,

    Now I've had a chance to get my head around the idea that you sparked in me, I've had a chance to put it down on paper ! Actually a Qcad drawing. Please tell me what you think.

    You may recall that I had/have been building a modified Brooks TCG, and that I had spent a great deal of time and energy filing a base plate for the tool holder. I had been struggling with a method of reproducing the precise angles needed for regrinding cutters and slot drills.

    The idea that you sparked was that I could use a fine toothed gear and a worm to rotate the tool holder and get an accurately calibrated angle that could be precisely repeated. The pictures below illustrate what I'm considering.

    Tool Holder support 1.png
    The black outline is the tool holder mounting plate. The red line is the toothed disc upon which the tool holder sits. The green lines are the tool holder block and the tooth depth needed, which works out at 3 mm. The drawing shows two views of the threaded rod and its mounting blocks, and how it would be placed. Since there is very little depth in the screw mounting blocks, I've shown M4 threaded studs that can have a nut used on the underside to secure them.

    If I can cut teeth into the disc using an M8 X 1.25 mm tap as the hob, I can then use a short length of threaded rod to mate with the disc. The blue lines describe the threaded rod held in a pair of bronze bushes at each end with the rod shaft extended so that a calibrated dial can be used to turn it.


    Tool Holder 1b.png Tool Holder support 1a.png

    The last coloured picture is just the construction lines that I used. The blue lines showing where the threaded rod needs to be machined.
    Best Regards:
    Baron J.

  2. #32
    Join Date
    Nov 2017
    Location
    Geelong, Australia
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    57
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    2,651

    Default Thiel model 17 metal bandsaw

    Looks interesting. Essentially a mini rotary table - so I'd think you would want to incorporate some form of worm disengage feature or it would drive you bonkers every time you had to move more than a couple of degrees.

    Coincidentally I've been looking at various models/designs for T&C grinders recently (sparked partly by your Brooks build).
    I can't say I've noticed anything similar on commercial ones. Most seem to just have a rotating base with graduations so I'm wondering whether its actually a useful feature - ie in practice how accurately do you actually need to set it. I've no TC grinder experience, but I'd think that within half a degree should be plenty accurate enough for most things.
    I guess it also depends whether you need a precise angle (in which case you'd need to work from a known datum), or more just a fine adjustment capability. I'm thinking it would be the latter, but again I've no actual TC grinding experience to base that on.

    I don't think I've posted it already in this thread, but you might be interested in the mechanism Thiel used on this bandsaw for the table tilt adjustment/clamping.
    Essentially there's a toothed sector on the moving part of the table, and the clamp bolt also has a small pinion gear that can rotate. Loosen the clamp nut, rotate the pinion to move the sector/table and then re-tighten the clamp nut.
    I'll see if I can get a half decent photo to show you.





    Steve

  3. #33
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    Default

    Hi Steve,

    Yes you are right it would be a fine adjustment. Reading up some data on end mills, it seems that the angle on the cutting edge is half a degree to three degrees and seven to fifteen degrees back rake. I could make the screw so that it could be disengaged ! I'll have to think about that.

    Thankyou for the pictures of the Thiel table adjustment. My cheap vertical bandsaw has a similar but nasty plastic gear on the underside of the table. Certainly nothing you could rely on for repeatability. The one on your Thiel looks to be very robust and accurate.

    By the way, I notice that Ribbonsoft have put the price of Qcad up. How are you getting on with yours ?

    If you do decide to have a go at the Brooks TCG I would be interested to know how you get on.

    My next job is to make a jig to go on the lathe in order to cut/hob the teeth on the gear. I don't propose to cut teeth all the way round. I only need to obtain about a 30 degree angle of movement based on +- 15 degrees.
    One thing that has just occurred to me is grinding a single point threading bit. I might have to consider that possibility.
    Best Regards:
    Baron J.

  4. #34
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    Nov 2017
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    Geelong, Australia
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    Default

    Haven't done much with Qcad lately to be honest.

    Assuming you're thinking about free-hobbing that worm wheel - I don't think you can practically just do a sector of it.
    The wheel blank usually keeps rotating as you advance it into the cutter - ie the hob pulls it around.

    I've just had a look at the completed Brooks on Gagetbuilder's site. Looks like his one just has graduations on the tool holder base, and a clamp.
    My gut feeling is a worm adjustment is probably going to be unnecessary.

    Steve

  5. #35
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    Default

    Hi Steve,

    Quote Originally Posted by OxxAndBert View Post
    Haven't done much with Qcad lately to be honest.
    I must confess that it is my go to program for all sorts of things ! I've used many 2D cad programs over the years. I've even got a C&G level one and two certificates for learning CAD way back in the late 80's, when it was quite rare to see it outside of technical schools and large corporations. Then much later I became involved with Turbocad as a development tester during its early days. That was before it got sold to Imsi, and turned into expensive rubbish. Qcad is streets ahead.

    Assuming you're thinking about free-hobbing that worm wheel - I don't think you can practically just do a sector of it. The wheel blank usually keeps rotating as you advance it into the cutter - ie the hob pulls it around.
    Yes that is exactly what I'm thinking about doing ! I think that I can persuade the tap to restart at the beginning of a cut in much the same way as single pointing a thread. Anyway I've nothing to loose but an aluminium disc.

    If you will forgive me I'm going to post the details of cutting this disc in the original Brooks thread, then all the information stays together. Anyway it been quite a while since I've done any work on it.

    I've just had a look at the completed Brooks on Gadget builder's site. Looks like his one just has graduations on the tool holder base, and a clamp.

    My gut feeling is a worm adjustment is probably going to be unnecessary.

    Steve
    Thankyou for your notes, often a reality check is needed. Your input is greatly valued.
    Best Regards:
    Baron J.

  6. #36
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
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    59
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    6,540

    Default

    Quote Originally Posted by OxxAndBert View Post
    Assuming you're thinking about free-hobbing that worm wheel - I don't think you can practically just do a sector of it.
    The wheel blank usually keeps rotating as you advance it into the cutter - ie the hob pulls it around.
    No you can't for that very reason. However, one thing you could do is use a straight cut helical gear as for adjustment purposes, a worm will run on them fine provided the teeth are inclined at the helix angle of the worm. For the small amount that is likely to be (say around 3 degrees), you could cut on a vertical mill by moving the dividing head from horizontal. Because it is a sector, there are also no issues with cutting exactly the right number of teeth on the PCD as small errors will not result in a 1/2 tooth at the end.

    Another option with a vertical mill is to incline the head the helix angle and plunge in with a gear cutting cutter (that is, do not travel along). The closer the diameter of the cutter is to the worm diameter the better, but regardless of that, that will also produce a wormgear that although not as 'form fitting' to the worm as a hobbed version will still work nicely as the tooth gap profile will be the same.

    Michael

  7. #37
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    Nov 2017
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    Geelong, Australia
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    Default Thiel model 17 metal bandsaw

    A quick update to say I'm finding the bandsaw to be a very useful bit of gear.
    Its quiet, and just cuts things with no fuss.

    A couple of days ago I cut a small bracket out of some aluminium angle. Nothing I couldn't have done with a hacksaw or thin disc in then angle grinder, but it was done in less time than it would have taken me to change the disc on the grinder.

    Today I made a start on a swing gantry project, and needed to cut a piece of 100mm diameter scrap steel (probably CrMo of some flavour) for a bearing housing. Couldn't get to the power hacksaw as its squashed in the back of the shed due to the current "rearrangement" that's in progress, so I used the bandsaw.

    I didn't time it, but probably took 5 mins at a guess. Being hollow was a bonus, but still not something you'd willingly take on with a hacksaw if you had the choice.
    The small vice clamped on the end is to stop the blade grabbing and rotating it. Simple and works well.



    I haven't bothered to change the blade speed at all for anything I've done. It seems to happily cut whatever I've thrown at it so far so I figure why bother messing with it!!

    Steve

  8. #38
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Default

    Hi Steve,

    That Thiel bandsaw looks as though it could cut through a tank if you could get it on the table ! It certainly is far more robust and capable than most on the market today.

    I wish I had bought my 6X4 years ago ! As you say better than using a hacksaw, way better.
    Best Regards:
    Baron J.

  9. #39
    Join Date
    Aug 2010
    Location
    Toorloo Arm, VIC
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    39
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    Default

    Just caught up on this one - interesting design with the round column.

    You've worked out most of the features, but I think I can possibly help with the bolted on flange on the drive wheel - it's possible that this would be exchanged for a different flange in order to drive a segmented file chain. It seems a lot of vertical bandsaw manufacturers used to offer these sorts of thing, of course it seems they all used their own proprietary variant and one from a Grob wouldn't fit a Doall, etc, etc. They weren't very popular on the whole apart from a few niche applications, so they all kind of died off into obscurity, and are mostly unobtanium. There are a couple of Grob ones on us eBay at the moment, like so:

    s-l1600.jpg

    My latest toy, from the same country as yours (although probably quite a few years younger), has this arrangement to drive it's variant (on both top and bottom wheels):

    Drive for deathchain.jpg

    I'm not sure if you just took the blade guides out, or whether there was supposed to be specific guides for the chain as well. In my case, I highly doubt I will ever find out!

    On the topic of speeds, I would feel reasonably confident in saying that whoever composed that chart you posted earlier stuffed up, and it's meant to be in ft/min, in which case those speeds make perfect sense. Don't remember which manufacturer the following was from, but note that even carbide speeds are nowhere near that table you posted earlier.

    speed chart.jpg

    You can also find a Lenox chart here: https://austechsaw.com.au/documents/...t.pdf?u=1TuZTE which is in the same ballpark, and pretty much every other chart lists about the same speed for bi-metal blades, so there's just no way one manufacturer has managed to figure out how to make their bi-metal blades run 3 times faster - well, unless of course they're a Chinese seller on eBay...

    So you're actually right about the ballpark, if you look at the Lenox chart and make the adjustments for no cutting fluid and thickness....

    And yes, I'll probably do a thread on mine sooner or later, predominantly because although you think of a vertical bandsaw as a very simple device, a number of the older ones have a lot going on! A surprising amount of engineering in it to nerd out on...

  10. #40
    Join Date
    Nov 2017
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    Geelong, Australia
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    Default

    Thanks for that.
    Yes, those chain filers where an interesting animal. There was one came up in Melbourne somewhere a couple of years ago - possibly before I bought this saw as I recall looking at it with a view of using it as a bandsaw. I never knew that there were conversion options.

    Did you happen to get yours on FB marketplace recently? I saw one that looked VERY similar to my Thiel, but was a different brand. A round logo with 3 letters in it from memory….

    Steve

  11. #41
    Join Date
    Aug 2010
    Location
    Toorloo Arm, VIC
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    39
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    Default

    Quote Originally Posted by OxxAndBert View Post
    Did you happen to get yours on FB marketplace recently? I saw one that looked VERY similar to my Thiel, but was a different brand. A round logo with 3 letters in it from memory….

    Steve
    Nope, mine was an auction buy out of a factory in Clayton, and is rather more.... 'conventional' in appearance than yours. Does still have a little style though, given it's from the 50's. Possibly even has surplus V2 rocket parts mixed into the castings...

    I really should find some time to do a thread.

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