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  • power hacksaw issue.

    As I've allready mentioned I had a barn find, a model engineers bandsdaw, well also with the saw there was a power hacksaw, a mini model engineers version that uses standard hacksaw blades, well thats what I have fitted, the originals that came with it are 40 years old and rusted up, they are a little wider, from bottom to top not thickness.
    The problem is the saw will not cut straight, even after taking it all apart and cleaning, lubing all the parts.
    The saw starts the cut perfectly straight, but then starts to wander out to one side as the saw cuts through the job.
    I checked the saw arm to the vice and with a square it looks quite accurate.
    I tried both a new hacksaw blade and a couple of the ones that came with it in better nick and I still get the same issue.
    Any ideas, I'm fairly new to little stuff like this.
    Build it, bodge it, but dont buy it.

  • #2
    Id think its the same issue that occures with a real hacksaw:
    Is the blade tight enough? aka, stupidly tight. Look at the lever mechnism in a normal hacksaw, lots of tension.
    Is the machine using too much downforce? Enough force will start to deflect the blade. often its adjustable, even in a spring loaded unit. (or maybe the springs have worn out or one in a set is broken)

    Does the hacksaw arm 'ways' have much 'play' in it?
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      dr pepper,

      This may not solve the problem but I am curious... What's the tooth count of the blade? On a hand hacksaw the finer the tpi the more the tendency for it to wander off course. Have you tried something like 14 tpi?

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      • #4
        Hi mike, didnt know that, the new blade I put in is a fine one, its all I had at 24tpi, I have some 18tpi ones ordered, I'll try one tomoz.
        Will also tighten the blade silly tight.
        The slide mech of the saw is quite rigid, theres no noticeable slop in the motion, theres a weight that slides to vary the downforce on the blade, I've only used this in its lightest position.
        There are some real course blades with it, like 10 tpi which look like they are for wood, might also try one of those, there is some warp in the blade so they probably will cut steel.
        I spose a neat looking cut isnt all that easy then with these machines, unless you can get a tall blade.
        Last edited by dr pepper; 05-07-2010, 12:49 AM.
        Build it, bodge it, but dont buy it.

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        • #5
          if too much weight is on the blade, it will wander. Slide the weight back. Some go on two ways, with one sliding back farther

          using a narrower blade also allows wander, that is one reason the real blades are wide, as in an inch or so.

          is it a Covel type? those should hold a good cut..... the one I refurbed for my FIL did for sure, although I never tried it with a narrow blade.

          Also, look at the mounting for the blade. The narrower hand hacksaw blades may let the wavy area of the teeth set against a support.... in that case, the blade may be setting at a very slight angle, which will cut at an off-angle almost from the start.

          And, the blade should be quite tight.... too loose tilts and wanders.
          1601

          Keep eye on ball.
          Hashim Khan

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          • #6
            Pics?

            Originally posted by dr pepper
            As I've allready mentioned I had a barn find, a model engineers bandsdaw, well also with the saw there was a power hacksaw, a mini model engineers version that uses standard hacksaw blades, well thats what I have fitted, the originals that came with it are 40 years old and rusted up, they are a little wider, from bottom to top not thickness.
            The problem is the saw will not cut straight, even after taking it all apart and cleaning, lubing all the parts.
            The saw starts the cut perfectly straight, but then starts to wander out to one side as the saw cuts through the job.
            I checked the saw arm to the vice and with a square it looks quite accurate.
            I tried both a new hacksaw blade and a couple of the ones that came with it in better nick and I still get the same issue.
            Any ideas, I'm fairly new to little stuff like this.
            Any chance of a few pics please as it will save a lot of guessing?

            Comment


            • #7
              The Kennedy mini hacksaw used 12" hand hacksaw blades broken into halves, and the recommended tooth count was 24TPI. I had another small hacksaw which used 10" blades, and, at the time, you could still get, with difficulty
              10" machine hacksaw blades which were thicker and wider and did not wander as much as a hand hacksaw blade. It might be worth trying some of the older engineer's merchants to see if they still have some. you certainly won't get them at the likes of B&Q

              Richard

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              • #8
                I believe Starrett still sells power hacksaw blades. See if they have one that will fit. They are much stiffer.

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                • #9
                  The OP doesn't say what length of hand hacksaw blade his machine uses. Starrett in the US still list 12" power hacksaw blades, but not 10", although Starrett in the UK only list hand hacksaw blades. The Starrett on-line shop in the US apparently can only sell to customers within the US.

                  Richard

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                  • #10
                    DP

                    Does your power hacksaw have a cam that lifts the blade so that the blade doesn't drag on the back stroke.
                    If it doesn't try reversing the blade so it cuts on the pull stroke not the push stroke.
                    It's worth a try.

                    Hal

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                    • #11
                      Yep well, er at first I had the blade in backwards, your right it is meant to cut on the back stroke, there is no cam that lifts the blade, however if you hold the saw frame while its running there is a definate lift effect on the non cut stroke, this is effected by the arrangement of the crank and the slide.
                      The machine takes what looks like 8" blades, I have drilled and cut 12" blades to fit, the blades that came with it look like they are made from heavy bandsaw stock.
                      I'll see if I can get a spare proper 1" tall power hacksaw blade and make it fit, in fact I'd make 2 maybe 3 from one blade.
                      I'll post some pics later, Ive been called out to work just now.
                      Build it, bodge it, but dont buy it.

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                      • #12
                        OK back at work again, heres a couple of nasty pics of the saw in mention as requested.
                        The original question was that I'm having trouble getting the machine to cut straight, the blade wanders.

                        Oh yeah, thats a new stand I bashed from ply, I cleaned up the machines, they were scrap before I started, 30 years of pigeon poo and all that.


                        Build it, bodge it, but dont buy it.

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                        • #13
                          OK, I can ID the hacksaw for you. Its a 'Duplex', and was a build it yourself job, described in Model Engineer in the UK around 1953. Until around 6 months ago, I had a set of drawings and a set of ME describing the build, but I sold them when I got the Kennedy. It was a perfectly good little hacksaw, and I think it was intended to use hand hacksaw blades. Check out the bearings where the frame runs on the long flat bar to make sure there is no slack, and check that the frame itself is not twisted.

                          Regards
                          richard

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                          • #14
                            Yes I'm reviving an old thread.

                            I have dug out this machine again after a house move.

                            I didnt know it went all the way back to '53, it does give it away a little when you look at the pictures on the tin that the spare blades are kept in.

                            I'm going to revisit this machine as now I have space to use it, the machine looks ok and doesnt show any major wear or out of straight in the frame, one thing I noticed is that the blade isnt sat perfectly straight as the teeth on the blade are making the blade itself sit squiffy, so I'll try grinding the teeth flat at the very ends where the blade contacts the holder.

                            The bandsaw also pictured maybe destined to the scrap bin, the blade guides look unsubstantial and theres no guides at all below the table, I think its probably only good for making jigsaws, I recently aquired another that more deserves the title bandsaw.
                            Last edited by dr pepper; 03-03-2013, 07:27 AM.
                            Build it, bodge it, but dont buy it.

                            Comment


                            • #15
                              I dont know if this will be any help but I have a 6" Qualters & Smith Donkey saw, unlike yours it takes propriety blades for this type of machine (14" 6TPI).
                              The one thing that is critical for a straight cut is blade tension it has to be correct in my case one and a quarter turns on the tensioner after it goes tight.

                              Paul

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