Power Hacksaw

My Blackgates Power Hacksaw cuts on the back (inward) stroke, from memory the crank centre line is on the centreline of the pivot point on the hacksaw frame.

Viewed from the side with the crank on the left of the frame, the crank turns clockwise.

As it passes 90° past TDC it pulls down and "in". As it passes 90° after BDC it lifts the blade slightly and back "out" ready for another stroke.

It's a nifty little bit of kit but I'd swap it for a Kennedy in a heart beat

"Circlip, not all bandsaws cut with the blade going in the backward direction, the company I used to work for had one where the blade went forward, but technically speaking, bandsaw blades can only work by being pulled, whichever direction they are going."

If it goes in the backward direction that means the teef are pointing the wrong way.

Pulling is pulling wiv the teef pointing towards the PULLING direction.

  I'll try that one again, All bandsaws cut in the PULLING direction.

Regards Ian.

Edited By Circlip on 25/09/2015 10:50:46

Thanks Clive. I started making the 'Duplex' hacksaw, as a starter project, when I first acquired my lathe. It took a long time to finish it (other projects intervening) . In the mean time, I came across a garage-sale bandsaw for a good price and bought it.

I find I use the small Duplex quite a lot for small items that are difficult to easily support in the bandsaw. There is also the additional satisfaction of using a self-built tool (or am I weird?). The bandsaw, of course, handles the larger cross sections much quicker.

If I had the bandsaw at the beginning, I probably would not have started building the Duplex. But now having both, I'll keep both of them!

Rod.

Hi Ciclip, I think we may both be misunderstanding each other. What I was meaning is that some machines are designed for the blades teeth to run backwards (that is, the teeth are pointing backwards) and some are designed for the blades to run forwards (teeth pointing forwards) and the drive to the blade is always at the back end. I've used both types and they both seem to work as good as each other.

Regards Nick.

Hello Gentlemen,

Thank you all for your replies concerning the cutting stroke of power hacksaws. It has been quite interesting.

Firstly, may I give my apologies for stuffing-up the sending of the original email. It just took off before I had finished the contents. Still don't know what happened.

I am not a formally trained engineering person, so have had to find things out along the way. Hence a question,

the answer of which, may seem so obvious to others. Thank you all for your various points of view.

An observation was made that a power hacksaw may be outdated and a metal-cutting bandsaw would be a better proposition. I agree, if I was initially equipping my workshop. However I already have a power hacksaw which does a fine job and when the blades are beyond useful life, they are recycled into all manner of cutting tools.

My best wishes,

Jim Crawford

Perth, Western Australia.

An if you really want to get carried away with power hacksaws, the hot air engine is a Ross Yoke ALPHA type that will produce 5 Watts, maybe + a little. 20 minutes through a bit of 12.5 mm rebar. It uses a Junior hacksaw blade.

Ian S C

Ian,

That's sweet !!

MichaelG.

I have an Axminster branded (Now Sieg) hacksaw and there are no clear instructions as to which way it cuts so I enquired and was told it is designed to cut on the pull stroke.

I have a rapidor and it cuts on the forward stroke. At the end of the forward cutting stroke the saw frame will have risen to the top of an incline, and the dashpot oil/piston will hold the saw frame in a slightly elevated position during the return stroke (provided the oil bleed is set correctly on the dashpot. By the time the saw frame has returned to the start of the cutting stroke, the frame should have lowered itself ready for the next cutting stroke. The axis of the slide bars is at a slightly different angle than the axis of the blade from memory in order to give the correct geometry for the incline during cutting and holding the blade off the cut surface during the return stroke.

I hope this makes sense.

Neil.

MichaelG, if you / I have a hot air, or any engine, it should be put to work, try and flog the life out of it. Five years ago that motor with a generator attached ran a radio for a couple of days when we had a bit of an earth quake that sort of upset such thing as the power supply, I had a fresh bottle of LPG, and it was handy to keep up with news, "Yes I did have batteries for a radio, but why not do it differently.

Ian S C

.

Great attitude, Ian

MichaelG.

That looks like a good machine, if a bit pricey. I have looked at this for a replacement for my Kennedy - longer cut. Has it worked out OK for you?