Thread: Re-birth of the Heska 260 HA horizontal Bandsaw

Hi all,

Several months ago (may 2013) I decided to look further into the options of cutting steel stock with either a power hasksaw or a horizontal bandsaw. I knew little about either but new there had to be a better way than using my noisy/expensive cutoff saw (for certain jobs). I started the thread "Power Hacksaws V's Bandsaws" and that started the ball rolling. It was then that Shedhappens (Thanks Shed) drew my attention to a bandsaw on gumtree which I ended up buying for $200.

It's a Heska 260 HA. I knew little about and in fact had never heard of them before, but it was made in Germany so I figured for the money it was worth a crack. It was in a very poor state and I think that if I didn't buy it then it probably would have ended up as scrap. First and foremost a new worm gear was made by Michael (Thankyou Michael) out of Nylon GSM self lubricating plastic. I mat still make one out of Bronze but bronze prices make it more expensive than the machine cost! I have 2 more blanks, one of CI and another nylon which I am yet to finish.

The original motor that drives the saw was a 2 speed, 3 phase motor and while it worked with the VFD, it was much under powered and early tests showed that it would stall with moderate cutting forces. I decided to swap it with another 3 phase motor I had already. It's a 2 HP variable speed 3 phase motor I got from a treadmill. It's good to 3900 rpm. It has proven to be a good selection, with good power and torque from 30Hz all the way to 130Hz. This produces a blade speed of between 20 M/min to about 90M/min.

There is also a 3 phase hydraulic pump. The "HA" designation in the model 260 HA means it's semi automatic. This means that at the end of the cut, the saw stops and the blade is lifted until the upper limit switch is reached. This was all disconnected and it took a fair amount of searching to find out exactly what it was all meant to do. According to Jaespa (formerly Heska) the serial number on the saw suggested it was made in 1969.

The original hydraulic motor and pump has been retained and seems in good condition, it was even a straight forward job to convert the motor to delta as all the connections were inside the cover. The VFD drives both the saw motor AND the hydraulic pump motor, BUT not at the same time. There are several contactors that switch the supply from one motor to the other once the cut has been finished. This goes against the VFD manufacturer recommendations but all seems to work fine. While the POT is used to select the speed of the saw blade, the hydraulic pump is always run at 50Hz so as not to lift the saw at a violent speed. This is done by using the JOG function of the VFD to run the hydraulic pump and this is latched with the contactor until the upper limit switch is reached. There is also a "Auto/Manual switch which disengages this function in the manual selection and so the blade stops but does not raise at the end of the cut.

In order to keep the blade from falling down at the end of the cut, a hydraulic solenoid valve is used and is activated with either the saw motor OR if "Manual Down" button is pressed.

I have also fitted a blade speed display. It works with a induction sensor fitted just inside the idler wheel and picks up the spokes of the wheel. There are 6 holes or "spokes" and so 6 pulses are produced per revolution. The wheel is approximately 388mm in diameter and so by setting the display to 5 pulses/rev, an approximate (within 2%) speed in Metres/min is read. Funny thing is, now that I have done a few test cuts on the machine, I mostly just leave it at about 60 M/min and so a speed display is perhaps not really necessary but when I was designing the console I included a cut out for it as I was under the impression that cutting speeds were critical! Anyway at $20 for both the display and the sensor I figured it's not a huge issue. One thing I have noticed, even with fairly heavy cutting, the speed does not change by all that much, maybe slows down by 0.5M/min.

I had never owned a bandsaw before, so to get some perspective and to compare with a newer and more modern machine, I took a look at the bandsaws from Hairy Forbes. While my machine was obviously built to last when it was made, design techniques in bandsaws have come a long way. The Heska is big, bulky and somewhat noisy. It's castings are huge by comparison and the Asian machines seem somewhat "nicer" in appearance and have more finesse. One of the biggest design difference is the direction of the blade. I have noticed that most band saws have the blade cutting from left to right. The Heska is opposite. The blade cuts away from the pivot and so the cutting pressure is placed on the clamping jaw and not the fixed jaw. It does not seem to be an issue with the machine but it's just an observation. Out of interest, I changed the blade over and rewired the direction to cut towards the pivot point and found that the blade was rather jerky and tended to bight into the steel so it was changed back. I have since looked for other Heska's of this vintage but the earliest I have found is a 1978 model for sale in Europe. Judging by the blade, It also cuts right to left. Later bandsaws of the same company have changed and cut left to right which seems to be the more favoured convention.

The down feed on this saw is slightly different to most others I have seen. It has a needle valve to control the down feed but in line with this is another valve which varies the flow based on the cutting pressure of the saw blade. The heavier the pressure, the more it pushes a plunger (which is preloaded with a spring) and reduces the flow. The spring preload is adjustable.

The console has the usual functions. Emergency stop, Manual Up, Manual Down, Start, Stop, Coolant on/off/auto, down feed, saw speed, speed display and Auto/Manual

I'm pretty happy with the saw but it has taken a fair amount of dicking around to iron out some blade tracking issues that seem to be a result of a fair amount of runout on the driven wheel. This seems to be a result of the shaft which the wheel is keyed to, it not quite running true. The driven wheel has a lip or an edge which the blade runs against. I have read on several forums that it is not good to run the blade up against the edge as it will wear it out quickly. The driven wheel has no adjustment and so I don't see how to adjust the blade positioning. The idle wheel has adjustment, and this adjusts where the blade sits on this wheel but does not change where it sits in relation to the lip in the driven wheel.

Also, my paint job has been a source of frustration to me. I don't think I will ever paint a machine in winter again.

******** Much thanks goes to Michael G and Stuart for their endless help and putting up with all my emails and PM's of questions!*********

Pic 1: The Bandsaw
Pic 2: Console
Pic 3: Idler wheel with (red) induction speed sensor
Pic 4: VFD housed in aluminium checker plate cover
Pic 5: Electrics including the 4 contactors housed in the hinge out cover
Pic 6: another view of the contactors and 24VAC supply (pond pump)

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Cheers,

Simon