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Thread: Help With Power Hacksaw
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28th Jan 2017, 10:13 PM #1Novice
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Help With Power Hacksaw
G'day all
Not sure where the best place is to post this thread.
I have recently inherited a power hacksaw. I havent been able to locate a manufactures name or any other identifying marks i can search online. Im hoping to get it fully operational again weather it be a quick tidy up or a full restore im not too sure. there was a bit of slop in the saw arm which i was able to eliminate with the tension bolts. The flywheel has a bit of backlash in it which i think i can resolve fairly easy. The main issue i see with it is the hydraulic lift on it has a bit of a leak from the top and also doesnt successfully lift the arm back up at the end of the cut, which i assume it is supposed to as it has quite a violent thrust when the arm is at its lowest point. There is a tank of sorts under the machine which im assuming is for coolant but nit entirely sure. Any assistance would be greatly arrpeciated
Cheers
Marty
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29th Jan 2017, 08:15 AM #2Philomath in training
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That's nice looking machine. It needs some exploration but there are a couple of things worth having a poke around to find out. Firstly, it could be that the seals on the pump and/ or cylinder have dried out so it would be worth stripping things down in those two bits and replacing them. Power hacksaws are not rocket science so it could be that the hydraulic fluid levels are low so there is not enough fluid to push the ram all the way up. Whether the ram uses oil is an interesting question as it may use the same fluid that is used as coolant. Really you need to trace what goes where before you can say.
Michael
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30th Jan 2017, 06:59 AM #3
Hi Marty,
Studying your pictures of that power hacksaw, put me in mind of a design by Edgar T Westbury. It was published in 15 December 1964 issue of Model Engineer. In his design the motor was inboard and used a worm drive to the main gear shaft.
Westbury Hacksaw.pngBest Regards:
Baron J.
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30th Jan 2017, 12:05 PM #4
Based on what mine does from memory (the one I use regularly is different) the hydraulic piston is only to control the rate of decent (Speed of cut) and the lifting action is controlled by the cam. The Tank underneath is usually a coolant reservoir.
…..Live a Quiet Life & Work with your Hands
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30th Jan 2017, 02:34 PM #5
I'd also suspect that what you are thinking is a hydraulic lift is in fact the dashpot, a cylinder half-filled with oil, and with a vented piston inside, that is there to slow the arm's descent as it cuts the metal - so that the blade is in effect slightly suspended above the work rather than bearing fully on the work as it cuts. The dashpot works by oil at the bottom of the cylinder squeezing up past the piston when weight (the weight of the saw arm) is put on the piston. When the descent is finished and you raise the weighted saw arm, a valve attached as part of the piston pulls open so that the oil can quickly flow back down through the ring of holes in the piston, and so flow out back down under the piston again.
See pics (of a different brand but same idea) here back a couple of years ago - //metalworkforums.com/f65/t1857...w-clean/page-3
- Ian -
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31st Jan 2017, 03:48 PM #6Novice
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Hi all, and thanks for the replies
I couldn't help myself after my first post so i started to have a closer look and started unbolting things. The tank is just a coolant tank, which i would say wasn't used for a very long time. I put a bit of water in it and spun the pulley by hand and it works!!! all be it there is a bit of a leak from around the shaft and i assume there was a gasket in there at some stage that sealed the 2 surfaces where the pump meets the tank. There is a nut that around the shaft that is quite stuck so will have to gently persuade it off.
I had never herd of a dsahpot before, thank you for the link Ian. I hope to get time this weekend to remove and strip the cylinder down and figure out if i need to fix anything or if its just low on oil. I suspect a seal is gone by the air and oil bubbles at the top where the shaft comes out. There is a bolt at the top of the cylinder body that is done up as tight as it will go, i assume this is to control the speed of decent?
Thanks again
Marty
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31st Jan 2017, 04:33 PM #7
If the pump is the same as on mine (and it looks similar) there's a gland packing under that nut which has probably dried out. It may be possible to save it by running fluid through the pump for while (perhaps drive the pump at slowish speed with a drill) so the leak lubricates the gland. You may also get the gland to seal by tightening the nut very slightly.
On the other hand I have seen them where the pump shaft has pitted due to non-use in which case you'll need to fix that before it stops leaking.
If you are not worried about antique authenticity and just want a machine that cuts you could abandon the pump and tank and use a small parts washer slung under the unit instead with some locline tubing to get the coolant where you want it.
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31st Jan 2017, 05:46 PM #8
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4th Feb 2017, 12:00 PM #9Novice
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I have pulled the cylinder out of the saw this morning and dismantled it. The oil was filled to approx 2cm from the top of the cylinder, it had gone really think and has lots of sludge in the bottom of the cylinder. The piston has started to disintegrate and looks like it was installed with a bend in the outer edge. When i touched the piston to wipe the oil off, it started to come apart.
I have uploaded a few photos of the cylinder.
Cheers
Marty
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4th Feb 2017, 02:50 PM #10
So it's like an old-style bike pump, where the leather cup is forced to expand against the bore on the way down, and can slightly narrow on the way up. That way, it takes time for oil to 'leak past' the leather when the blade is descending, but when the blade is raised again, the oil easily can flow past.
You'll need to make or get a replacement leather cup, I guess - can you still get them, I wonder.
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4th Feb 2017, 03:31 PM #11Golden Member
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Yes, they re still available - google leather pump buckets, or make your own:
https://www.youtube.com/watch?v=6xFhThdnYqE
I think nitrile rubber ones are also available.
Frank.
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4th Feb 2017, 03:44 PM #12Novice
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Thanks Ian and Frank
I did a search after i saw Ian's reply and watched that exact video. Looks simple enough to make one. Blackwoods also have 2 on their website but no photos. Ill check the dimensions. Should be able to find something. I also noticed that there is a tiny hole in the 2 washers that clamp on either side of the cup.
Chers
Marty
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6th Feb 2017, 12:29 PM #13Golden Member
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Are the two holes in the washers fitted so they are in line? If so, is there a corresponding hole in the leather bucket? If so, they are probably bleed holes to allow the oil to pass slowly from the under side of the bucket to the top side to control the speed at which the arm carrying the blade carrier drops when the cut finishes.
Frank.
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6th Feb 2017, 07:41 PM #14Novice
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The 2 holes are lined up and there is also a corresponding hole in the cup. I have looked on the Ludowici website and found nertile rubber piston cups. https://www.ludowiciseals.com.au/sea...SizeProduct=24 Will take the old leather cup to them and see if there is a rubber one that will be similar.
Marty
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21st Mar 2017, 11:55 AM #15Novice
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G'day everyone
I have finally got around to putting the dashpot back together. I drilled a matching size hole in the runner cup to the one in the leather cup I removed. I have put some oil in and reassembled it. I used 20W50 grade oil. Not sure if that is the best grade but it was mentioned a few times in Google searches. Previously I said the holes were lined up but is it possible they shouldn't be? I haven't reinstalled the cylinder in the saw yet but just pressing on the shaft there is little to no resistance. How full should the cylinder be? At the moment it's just over half full as measured the amount of oil I removed and replaced the same amoumt.
Thanks for all the assistance
Marty.
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