Restoring an old powered hacksaw


H-M Supporter - Silver Member
H-M Supporter - Silver Member
Nov 7, 2019
Figured I'd share my restoration project!
I've always found these old machines quite cool and when a neighbour offered me a defective one for free, I couldn't say no! :D

This is the machine as I got it, it runs but won't lower the sawblade so you have to manually push it against the work piece, which becomes quite the challenge and dangerous as heck when it's moving back and forth.

The thick bars protruding on the side are from an automatic feed system that's been cut off.
By pure chance I came across a previous owner of this saw and he gave me these two pictures of how it used to look.

At first I was just going to get the downfeed to work again and leave it at that, not spend too much time on it because I have quite a lot of other stuff that also needs doing.
But just trying to understand how the machine is built and what could be the problem, I was already in waaay too deep to not do something more serious.
Just trying to get the downfeed mechanism out I somehow ended up with this after like 14 hours of work ... Many of those were just shoveling out old sludge and nasty cutting oil.

Every little mechanism is completely packed with old grease that is long overdue for a cleanup, this picture was after I scooped handfuls of it out.

Eventually after a lot of beating I managed to get the entire hinge mechanism off and the parts are starting to pile up.

One really interesting thing is this motor. It's 2 motors in one, double shafts and everything.
There's a smaller shaft, inside the bigger shaft, powering the smaller pulley.

With everything stripped it was time for it to travel outside for some major cleaning.. Quite a big of degreaser, scrubbing and high pressure washer.
By now you can even see that it has some color underneath all the crud. :D
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Continuing on.
Using a mix of sanders and wire brushes, I got most of the old crud off.

Both sprayed and brushed on a layer of epoxy primer.

And ontop of that a layer of grey polyurethane.
It looks quite light in the pictures, as it hardened it became a bit darker.
I did so many mistakes here that really ****** me off. Stupid mistakes like how I somehow forgot to mask the top and floor, sprayed way too much paint on and so on.
I will have to get back to this and sand down the runs and do a final top coat again.

I did a quick brushjob on the legs, I think the black should constrast nicely.

To get away off from the frustration of the bad paintjob(I don't like painting but I like a good end result..), I started working on the pump which was the initial problem.
To the left you have the "lid" of the main piston and to the right is the main unit I guess.
The big rod on the lid has a smaller rod inside it, and the big piston has a smaller piston inside it that gets act upon from this smaller rod.
Basically as the saw runs, it acts upon the smaller rod, transfering the motion to the smaller piston down inside the bigger piston.

A closer look on the main piston and the smaller rod.

With the bottom taken off the main piston, you can see this smaller piston. I have taken the seals off it for the photo.

Eventually all that was left to take apart was this part on the lid.
Aaand here we find a completely busted seal.
Hopefully this is all that was keeping it from working as intended.
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You have a great saw there! Nice job.
Not sure I understand what the dual pistons do, but it looks interesting. Great work.
This is very interesting, I have never seen a unit like that.
Thanks for sharing this.

I bet all your photos will come in real handy as it all goes back together!

wow, that's a serious power hacksaw. You'll have a very useful machine on your hands when you finish working on it.
Thanks all!

Not sure I understand what the dual pistons do, but it looks interesting. Great work.
I find it hard to explain! :D

At the top of the hydraulic piston unit, there's an axle with an oval part on it. This oval part keeps pushing and releasing the smaller rod inside the bigger rod.
The smaller rod transfers this pushing motion down inside the bigger piston, thus making the smaller piston move back and forth(it's spring loaded in one direction).
Somehow this pumping creates pressure to push the big piston down, bringing the entire saw down onto the workpiece.

There's a seperate adjustment where you can adjust how much to bottleneck this system, thus controlling how fast or hard it pushes against the work piece.

Hopefully that makes more sense.
Hmmm... So the little piston creates the hydraulic pressure to move the large piston as well as acting to regulate the pressure?
That seems similar to the Kasto power hack saw. I suspect the dual piston provides for a blade lift on the return stroke. The small change in volume from the smaller (inner) piston, which is controlled by the oval mechanism on top, allows the main cylinder to apply the blade down pressure on only the forward stroke.

I'm not sure if the Kasto is the same (I've never pulled mine apart), but it also uses a rear cylinder to force the blade down. I know on the Kasto, if it has been sitting for a long time, you have to bleed the hydraulics before the feed system will function. That had me stumped for a while - as always, it is an easy task - once you know how.
It's indeed a Kasto, a VBS 202A according to Kasto themself.
Definitely sounds like that function would make sense!
The pressure regulation is done seperately elsewhere on a big rotating plate, there seems to be like a bleed function.
There more you tighten it, the more it constricts the flow. Since I haven't gotten it running yet I'm not sure if tighter means faster or slower downfeed.

On this version there's only this main piston that controls feed.
On the back there's a spring which I assume is to help pull it back up and there's also a big damper/spring combo on the front, next to the piston unit.
The one in this picture:

Hopefully I can get back to working on the saw this weekend.