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  1. #1
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    Default Building a cold saw

    I scored a couple of free gear boxes from work. One is not so good. Run when low on oil so although gears look ok, it will need new bearings at least. The other is perfect. Oil in it was like new. All clean inside. These were used on an old barrel plating line to operate the barrels and other stuff. The are SEW brand and are around 30.5 reduction. Now, if I can attach a 2850 RPM motor this will give me around 90 RPM output. Is this speed ok? Also what would the best blade be for general use? How many teeth? With a 400mm blade I will be able to get a 75mm depth of cut. Like to get a two speed motor if possible so I can run it at around 45 RPM as well. Are these available?
    Nev.

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    90rpm might be a bit on the fast side especially with a 400 mm blade.
    Most of the cold saws Ive seen running 350mm blade max out between 20 and about 80 although some of the variable speed ones do go to 100 rpm but maybe not with a 400 mm blade.

    I wouldn't bother to get a two speed motor. Instead get a single speed 2HP (maybe 3HP of you intend using a 400mm blade) 3P 1440 rpm motor and a vector drive VFD. That will give you 45 RPM @ 50Hz (ie full power) and you can easily take that to 90 rpm at full power and down to 25rpm at about 2/3rd power.

    The VFD will also be handy to skip over/under any chatter or vibe that might arise.

    Good blades are pretty exxy. Expect to pay around $300 for a plain 400mm HSS and $400+ for a cobalt.
    # of teeth depends what you plan to cut

  3. #3
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    Hi Guys,

    I have access to the use of a cold cut off saw at a local Blacksmiths, It is made by Makita, 12 inch HSS blade about 60 rpm. The noise it makes when cutting 50 X 12 mm black iron, is horrendous, but its quick. I can't imagine how much noise a 16" blade would cause.
    Best Regards:
    Baron J.

  4. #4
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    Quote Originally Posted by BobL View Post
    I wouldn't bother to get a two speed motor. Instead get a single speed 2HP (maybe 3HP of you intend using a 400mm blade) 3P 1440 rpm motor and a vector drive VFD. That will give you 45 RPM @ 50Hz (ie full power) and you can easily take that to 90 rpm at full power and down to 25rpm at about 2/3rd power.
    Can you recommend a VFD? I know very little about these.
    Nev.

  5. #5
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by SurfinNev View Post
    Can you recommend a VFD? I know very little about these.
    If you are not familiar with VFDs then a cold saw build project is maybe not the time to introduce yourself to them.

    To familiarise yourself with VFDs +/- I would start by adding a VFD to an already functioning machine as there are more than enough headaches to deal with just doing that.

    If you still want to pursue VFDs then perhaps start by reading this thread in the Woodies forum
    VFD install summaries

  6. #6
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    I don't follow your reasoning Bob. Why would incorporating a VFD into a new project be any more difficult than adding one to an existing machine? In fact, I reckon it would be easier, as you don't have to work with the existing switching or machine cabinet.
    Chris

  7. #7
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by jack620 View Post
    I don't follow your reasoning Bob. Why would incorporating a VFD into a new project be any more difficult than adding one to an existing machine? In fact, I reckon it would be easier, as you don't have to work with the existing switching or machine cabinet.
    I was thinking more about the total number of problems to deal with given the OP is building a medium complexity machine and has no experience in dealing with VFDs. Adding a VFD for a first time to the machine just increases the number of problems. Someone with experience with VFDs would certainly find it easier to incorporate them in during the machine construction.

    I have only built one machine from scratch which included a VFD, and the VFD side of things was the easiest part. However, when I built that machine it was after adding more than a dozen VFDs to existing machine.

    Switching
    It depends on the approach taken in dealing with existing switching. I know some folks are determined to fit the VFD to existing switching but my approach is for 3P machines it all gets stripped out, and on a SP machine the mains switch may be retained and if the VFD is going to be attached to or inside the machine the switch output goes straight to the VFD.

    Cabinet
    I've not usually seen the cabinet as a problem as I normally mount the VFD on a bracket attached to the machine or on the nearest wall and attach remote wired control of the VFD. If there are issues, it's usually when a SP motor has to be replaced with a 3P motor eg motor size, mounting, shaft/pulley sizes etc but the same but these would be similar when building a machine from scratch.

  8. #8
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    This sounds like an interesting project. I think getting a good gearbox is a key component. Can you cut stainless steel with this sort of machine or is it too hard for the blade?

  9. #9
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by paul33 View Post
    This sounds like an interesting project. I think getting a good gearbox is a key component. Can you cut stainless steel with this sort of machine or is it too hard for the blade?
    The cobalt blades will cut SS - they need to be run slowly and with high pressure as with any tool cutting SS it works better as long as it keeps cutting. As soon as it starts to rub then it work hardens.

  10. #10
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    Quote Originally Posted by BobL View Post
    Adding a VFD for a first time to the machine just increases the number of problems.
    That's true. If I was Nev I'd build it in two stages- initially without the VFD, then add the VFD later. That's assuming Nev has 3 phase power. If not, I'd bite the bullet and do it all at once. I reckon the advantages a VFD brings are worth any initial heartache.
    Chris

  11. #11
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by jack620 View Post
    That's true. If I was Nev I'd build it in two stages- initially without the VFD, then add the VFD later. That's assuming Nev has 3 phase power. If not, I'd bite the bullet and do it all at once. I reckon the advantages a VFD brings are worth any initial heartache.
    There certainly are benefits. The ability to slow the saw right down to ~20rpm to cut SS and high carbon steel alone is worth having. The motor might not have as much power at these speeds, but power is only essential when cutting larger stock

    If Nev wanted to incorporate a VFD that runs from single phase it's worth looking out for a 3P motor that can be converted from 425V "Y" to 240v "∆" .

    One advantage of cold saws over Bandsaws is the cutting speed but that assumes you have the right toothed blades and the blades are very expensive so unless you are a commercial operation or have plenty of $$ its unlikely you will buy that many. Forcing the wrong toothed blade though the work just leads to greater wear and shorter blade life. Bandsaw blades are cheap so having a few sizes is no big deal. OTOH if you are a high turnover operation a good cold saw blade should last a long time especially if coolant is provided.

    Something else to consider is a good quality sturdy vice since the forces involved are quite high. A deadman switch on the handle is also a good idea for instant stopping without having to reach across any parts of the work pieces.

  12. #12
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    Thanks for all the tips. These did come with motors that could be wired either way but they are in poor condition. Very corrosive environment in a plating shop. Will start by cleaning and painting the gearbox first then think about the other challenges. One motor has a plate still attached but not able to decipher what is on it yet. I will probably have to make a new output shaft to suit the blade so will get in the good books with the boss, as he has just purchased a new AL336D to replace the other lathe lost in the recent fire at work. I do not have three phase power.
    Nev.

  13. #13
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    Last time I spoke to a bod about his cold saw, was told they are a 3 blade commitment. 1on saw, 1 getting sharpened, 1 spare.
    Mind u of course he is a commercial operator.
    Frisky wife, happy life. ​Then I woke up. Oh well it was fun while it lasted.
    From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".

  14. #14
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    Hi Jatt,

    Quote Originally Posted by jatt View Post
    Last time I spoke to a bod about his cold saw, was told they are a 3 blade commitment. 1on saw, 1 getting sharpened, 1 spare.
    Mind u of course he is a commercial operator.
    Yes I agree, that is what I used to do with mine. Having three blades is a must in a commercial environment, an expensive investment that you don't realise at first. Those three blades were about half the cost of the saw originally !
    Best Regards:
    Baron J.

  15. #15
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    Thinking about this motor - https://www.colliermiller.com.au/pro...400rpm-approx) - and get a Powtran VFD. Good choice? Now which VFD to buy is the next question. How about the PI160 2R2G1Z. The above motors are the same size and flange on the Hercus Mill so would like to use it there as well (when I get it back together) if possible.
    Nev.

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