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  1. #1
    Join Date
    Aug 2019
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    Revesby - Sydney Australia
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    56
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    Default Cold-cut saw blade adapter flange

    So, a neighbour asked me to turn up an adapter, so he can fit larger blades in his metal cutting saw.
    It is a Tomet T315, and was fitted with 10.5" blades. He got some 12.5" blades cheap from somewhere.
    Of course, in addition to the the larger centre hole (31.5mm -> 39.5mm), the drive pin holes are in different places:

    IMG_0264.jpg

    (only the smaller holes - horizontal in this photo - are used in this machine.)


    So, first hack was turning down a large washer. Bore out the inside to about 32mm,
    grip that from the inside in my 4.5" Pratt chuck (jaws winding out to grip),
    and turn the outside down to interference fit the 40ish mm hole.
    Then angle grind slots in blade, and Dremel the drive holes into position.
    No photos, but worked OK.



    Second, better, version is a new flange with pins...

    1. Find a steel disk in the yard. It has a 2mm raised step on one side which helps centre it in a chuck IMG_0265.jpg
    2. Threaded rod through spindle to actually hold job in place IMG_0266.jpg
    3. Face off, and tidy outside IMG_0267.jpgIMG_0268.jpg
    4. Turn down to roughly 4" to match existing flanges, decide to make it thinner.

    Then remove threaded rod, and carefully bore centre out.

    Re-ground tool and tidied step
    IMG_0270.jpgIMG_0271.jpg
    5. Turn job around, start turning down to 40mm step IMG_0272.jpg
    6. Start to bore out an internal step at 33mm, but the tool was juddering too much, so packed up and went home
















    Next day, turn a tiny nick for locating pin holes, and face down to saw blade thickness. Thinking I had finished turning it, removed job from lathe.
    IMG_0273.jpgIMG_0274.jpg
    7. About a week later, look for something to turn pins out of.
    I choose a rusty old MT2 centre, gripped fat end in chuck,
    used other end's tiny indent in live centre.

    Rip down to 8.5mm, add small groove in middle before parting off.

    These little round "profiling" tools are my new favourite thing!
    IMG_0336.jpg
    8. New $10USD parting tool!

    I try to set perpendicular to job by using the body of my chuck
    IMG_0338.jpg
    9. Slowly start cutting.


    A few mm in, it isn't sounding good. I re-align with a ruler across the jaws.
    IMG_0339.jpgIMG_0340.jpg
    10. As it's getting closer, I have horror flashbacks to all the times this has gone badly (as a teenager when I was playing with Dad's lathe).

    Decide to use my live centre in a safer way, and get it down to 1.5mm ...
    IMG_0341.jpg
    11. before chickening out and sawing the rest IMG_0342.jpg
    12. Drill holes in flange, hammer first pin in, turn second pin, fit it IMG_0343.jpg
    13. Scribe lines in blade (carbide tile scoring tool) IMG_0344.jpg
    14. Angle grind some horrible slots in the middle of the blade IMG_0346.jpg



    and voila: IMG_0347.jpg





    except that, when I try to fit it, the pins are too long, and the internal step (6. above) needs to be deeper to fit over the drive mandrel.

    Sigh. More turning required. Will have to wait for a dial indicator to arrive, because this chuck isn't very centred. Maybe in today's post?
    Last edited by nigelpearson; 20th Nov 2019 at 11:27 AM. Reason: refined a sentence, tidied flow

  2. #2
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
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    654

    Default

    I hope your friend is only lightly loading the blade as they have a bad tendency to develop micro cracks around discontinuities like broken teeth or those slots that you cut for the drive pins. Once the cracks become established they travel reasonably quickly and the blade literally explodes and flies around the workshop with sharp edges and points. Basically they are hard and brittle, about metal's equivalent to tempered glass in terms of letting go without warning, and in sharpness and pointedness of the fragments. Also I suspect that if the blade size difference is significant, they would be running the blades without the saw guard, which means that when a blade that lets go the pieces can go anywhere, rather than being mostly contained within the guard. For my money, if I was making such a drive flange, I would have drilled the drive pin holes to utilise the manufacturers drive holes in the blades, rather than slot the blades.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  3. #3
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
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    Default

    Hi Mal. Thanks for your feedback. I will inspect regularly for cracks.


    Its a water-lubricated saw. User mainly cuts stainless box section on it. The 10.5" blades just wear on the outside edges of the tooth. The blade steel does seem quite hard, but I don't think he has ever chipped/broken a tooth.


    The larger blades just inside the guard. I had to relieve its casting about 2mm near the exit.


    Sadly, the pins go through the blade and into the drive flange, which is attached to the gearbox. Stripping the gearbox, to remove that flange, to mill new holes in it, wasn't an option. He is using it every few hours each day!

  4. #4
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
    Posts
    654

    Default

    Wear with HSS blades cutting SS is always fairly rapid, cobalt HSS blades handle the SS much better but still need regular sharpening. Your friend needs more than water for the coolant/lubricant, a reasonably concentrated soluble oil or synthethic lube mix.

    I used to cut about an average 2 tonne of SS and MS, plus much smaller quantities ali each week for 5 years, rotating about 4 fine tooth blades for tube and another 4 coarser toothed ones for bar, with 2-3 out for sharpening or retoothing at any time.

    You can examine the blades for micro cracking if you wish, but you generally won't see the cracks unless the blade starts grabbing at a certain identifiable spot and you can examine it there. That certainly won't be the case if the cracks originate from the centre of the blade, the blade will break up before it starts to grab in the cut. Magnetic NDT might find micro cracks before they travel far, but even then the blade is effectively junk as the only effective solution is grind the teeth off and reduce diameter by grinding down the diameter until all traces of the crack are removed, then grind a new set of teeth into the blade. In 2005, a new cobalt wheel was around $140 plus grinding in teeth to whatever pattern we needed, a touch up sharpen was about $16, and a grind back and retooth for an undamaged blade was about $35. We used a travelling saw doc who called twice a week to collect blades and return doctored ones.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

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