Thread: Power Hacksaws V's Bandsaws

I should have known better than to doubt my super powers!

Now, how do I make one?

Stuart

Originally Posted by shedhappens

I reckon the speedo would/might be handy, it would look cool anyway Given that he has to run the saw with a VFD he will get his speed control anyway, hopefully whoever modified the belt drive got the speed somewhere near to close ?

I keep forgetting about the VFD. The perils of having 3 phase in the shed. My thoughts with the VFD are that if it was set at say 60 to 70Hz (so that it could drop to half that for say CI) then the hydraulics may keep up (and the odd excursion upwards for things like brass. The speedo could be calibrated with a digital tacho and a white mark on the blade. As the length of the blade is known, the speed is easy to work out - maybe the speedo needs a little card in it, like cars did when all the road signs were changed over to km/h

Originally Posted by simonl

So far, I think I have worked out everything except what the valve does on the blade guide....

Based on the manuals Dave popped up, I'm wondering whether that is a coolant tap. It would make some sense as when starting the cut you would be close to it (looking) and so the tap would be at hand...

Michael

Originally Posted by simonl

Hi Shed,


Maybe it's two systems we are looking at. There must be a valve to regulate the downfeed which I assume does not require the pump to be running, it just allow fluid to be gravity feed and pushed out through the weight of the saw. Once the saw cuts through the material and triggers the preset limit switch, it must stop the saw motor and starts the hydraulic pump to lift the saw?

Cheers,

Simon

That theory looks good, when you look at the switch you will know.

But I think you will still need a couple of check valves

I'm in the same situation, I bought a hare and Forbes bandsaw secondhand recently and I must say,it is brilliant! I can only kick myself for not buying one years ago,what was I thinking? It was $600 and a new blade was $50, it paid for itself on the first day. Buy one, best thing ever. It's a bls7 model I think.

I have been thinking for a while how nice it would be to own something to cut large pieces of metal stock (other than my rough & ready cut off saw)

I'm thinking of a secondhand old thing that will suite my purposes such as Parkanson Power Hack SAW 6 Inch CUT | eBay or
Classic Antique Power Hack SAW | eBay or

Power Hacksaw "Little Giant" | eBay or

POWER HACKSAW | Miscellaneous Goods | Gumtree Australia Mitchell Area - Wallan

What are the advantages of a bandsaw over a power hacksaw? I assume the band will last a bit longer since each tooth is not cutting as often with a bandsaw?

If both can cut say 6" then what is the main difference? Perhaps the time taken for each cut? If so then it's not a big deal since I'm not in production. What about accuracy or straightness of cut?

Who has a metal bandsaw?
Who has a power hacksaw?

Info and feedback on these machines would be much appreciated.

Cheers,

Simon[/QUOTE]

Thanks River! I can't wait to get this up and running!

OK I think I have most of it sorted now. You need to bare with me here.

Now, the owners manual that Dave found (thanks Dave) does capture a number of models, some of the features are not present on mine, other features I think were but are not now (refurbished? ) and other feature are. It makes mention of a hydraulic saw band tensioner. I think this is what one of the valves does.

I also now know for a fact that the valve shown in my hand is in fact the down feed adjustment. Looking at the pic of the hydraulic pump, I have now worked out that the top left hose is the high pressure (output) side of the pump. It goes to the bottom of the ram. The hose (steel braided and smaller) is the return. It comes from the ram but higher up, it also passes through both the flow control(down feed adjust) and saw band tensioner before coming back to the tank. It had me confused because initially I thought the smaller hose was the output (high pressure side) of the pump and the larger hose was the return but this is not the case. It also is in agreement with what Shed says in terms of the brass hydraulic connectors are not rated to very high pressure, there are on the drain side of the pump. The valve and handwheel on the pump goes from the ouput (high pressure side) and back into the tank and I think it may be an adjustable pressure relief valve or further flow control to adjust how fast the ram is lifted. The ram cannot be lowered with the pump, only lifted and the pump does not operate on the downfeed.

At the end of a cutting sequence, the micro switch is struck, this turns off the motor (one of the control boxes has a latching relay) off and turns the hydraulic pump on. It lifts the saw up to the limit set by another limit switch. This limit switch is adjusted so that the saw blade just clears the stock being cut. It should then stay there until the operator hits the start button and the saw begins again.


The only thing I am yet to work out is if at the end of the cutting sequence, the saw stops and the hydraulic starts, what stops the hydraulic oil leaking back though the other line in the downfeed? It would require someone to shut off that flow control valve to stop that, which kind of defeats the purpose of the semi automatic sequence.

Second pic shows what I did today. It's in a million bits now! It's quite well made. Lucky because it's had lots of use and even more abuse. If it was a cheaper brand I think it would be a throw away. I still trying to work out an operational sequence for a VFD to work. Now the running of the main motor and the hydraulic motor are mutually exclusive. That is, they never run at the same time, if one is running the other it not. This may allow me to use the same VFD to operate both? Maybe all in the switching sequence. I'll have a little bit more of a think.

Cheers,

Simon

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Are you going to replace the hydraulic pump motor with a single phase one ?

Hello Simonl,
I have a big old Heska, a simple beast without the hydraulic lift feature. Has a cylinder with the feed rate valve across it, and you manually raise the blade after the motor cuts off at the end of cutting. Can you dispense with the rest of the hydraulic raise feature for simplicity? I don't find it too inconvenient for one off jobs to use manual lift.
Just a thought . Combustor.

Hi Simon,
First thing you need to work out for your VSD is if and how you are going to run the motors on 240V? A two speed motor isnt a good start.
Whats the inside of the box on the pump motor look like?

Stuart

Hi Andre,
I'm not sure yet. I would prefer not to. In fact if it really comes down to it, I may just ditch the hydraulic pump and run it like Combuster does.

Hi Stuart,

So you don't think I can run a 2 speed 3 phase motor of a VFD? I must admitt to not knowing anything about 2 speed motors but at this stage I am just assuming it contains 2 independent windings such a 2 pole and 4 pole windings giving the 1375 and 2770 rpm speeds. There are 6 wires going in, 3 wires for each. Seem reasonable? It's star wired so I was hoping to perform the ol' star to delta switcheroo on both!

I could be totally barking up the wrong tree but that's basically my plan at this stage. Failing that idea, I have a 3 phase motor waiting to go into my lathe for yet another VFD conversion, once I do this it will free up a single phase motor. I could thgrow that in and run it off single phase, ditch the hydraulic pump, sell the coolant pump and buy a cheapie single phase coolant pump. Just some ideas.....

Inside of the box? You mean the coolant tank? It's filthy and yuck. Not looking forward to cleaning that!

Oops I think you meant the hydraulic pump? I have yet to open that too. I will do that tomorrow.

Cheers,

Simon

Edit: mis-read Stu's question

Simon could you make a drawing of the hydraulic system ?

It would be a shame not to get that working, you could use separate switches and the power
from the mains side of the VFD to run the hydraulic pump.

Originally Posted by simonl

So you don't think I can run a 2 speed 3 phase motor of a VFD? I must admitt to not knowing anything about 2 speed motors but at this stage I am just assuming it contains 2 independent windings such a 2 pole and 4 pole windings giving the 1375 and 2770 rpm speeds. There are 6 wires going in, 3 wires for each. Seem reasonable? It's star wired so I was hoping to perform the ol' star to delta switcheroo on both!

Oops I think you meant the hydraulic pump? I have yet to open that too. I will do that tomorrow.

Sure you can run it, its just a question of how. If you'd be happy with 60% power you can run it as is on 240V.

Its to late in the evening to think about 2 speed motors. I'll have to have a look tomorrow.

I've been told but never tired that its ok to switch small loads independent of the main motor, so MAYBE you could leave the blade running while the pump starts and returns the to top of stroke? Though switching from one motor to the other should also be doable.

Yes the wiring of the pump

Originally Posted by shedhappens

It would be a shame not to get that working, you could use separate switches and the power from the mains side of the VFD to run the hydraulic pump.

I thought the pump was 3 phase also?

Still no rush you have a gear to make.

Stuart

Just been looking at the wiring of 2 speed 3 phase motors. I'm not even sure you can wire them to delta, and even if you can, it's going to get very messy in there!

I forgot, I still have a spare 3 phase variable speed 1.5HP motor that I could use. It's already configured for VFD use. I've been waiting for a project/use for that...... This may be it.

More pics:

Pic 1: The hydraulic pump assembly removed.
Pic 2: The hydraulic pump
Pic 3: The hydraulic oil reservoir (after cleaning!) Has some corrosion/pitting in the bottom but still plenty of life left in it
Pic 4: The saw clamp assembly after much scrubbing and cleaning
Pic 5: Same as 4
Pic 6: The coolant tray after some cleaning and a bit of panel beating for aesthetics.

That's about it for me today.

Cheers,

Simon

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Originally Posted by Stustoys

Still no rush you have a gear to make.

Stuart

Yea OK i know!

Originally Posted by Stustoys

Still no rush you have a gear to make.

Stuart

Originally Posted by simonl

Yea OK i know!

Waiting on CTC for a cutter - probably another week or so , so the gear team are doing fine. How's the electrical section going?

Michael