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Hacksaw blade tension

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Derrick Watson11/09/2011 21:22:37
18 forum posts
Hello all,
 
I've read a few times that it's important to ensure that a hacksaw blade (12") is at the correct tension but what exactly is the correct tension and how do you know when you've set it?
 
cheers, d.
russell12/09/2011 05:24:42
142 forum posts
i usually set mine pretty much as tight as i can, by hand, and i try to release the tension when done.
 
haven't broken many...
 
- russell
Bill Pudney12/09/2011 06:19:26
622 forum posts
24 photos
I seem to remember from my apprenticeship that it was....take the slack off then three turns of the wing nut.
Its worked for me for the last 45 years.
cheers
Bill Pudney
Gordon W12/09/2011 09:36:44
2011 forum posts
My old hacksaw has instructions on it :- take up slack, then 3 turns, it's an Eclipse from my apprenticeship days, so a bit bent now. My newer one has a sort of cam action tensioner which seems to be about the same amount of movement. I usually tighten a bit extra when attempting to saw straight lines.
The Merry Miller12/09/2011 09:41:39
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484 forum posts
97 photos

Same routine as Bill and Gordon, take up the slack then three turns of the wing nut or whatever.
Don't forget to slacken off afterwards.
 
 
 
 
 
 
 
 

NJH12/09/2011 10:04:17
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2314 forum posts
139 photos
Posted by Gordon W on 12/09/2011 09:36:44:
 
." I usually tighten a bit extra when attempting to saw straight lines."

Gordon - that's very encouraging. Sadly I didn't have the benefit of an apprenticeship and, although I have been spoiling metal for many years, I've yet to tame the hacksaw into sawing straight. I thought it was just me!
 
Regards
 
Norman
Derrick Watson12/09/2011 10:04:39
18 forum posts
Sounds good, thanks - although I didn't realise you should slacken the tension off after use.
Gordon W12/09/2011 14:39:20
2011 forum posts
Hi again, I don't bother slackening off after use, and my old one is over 50 yrs old, the thread will wear out first, might be because it's made of decent steel. To saw a straight line :- get a good saw blade, not the flexible things, let the saw do the cutting, don't force it, get a good saw, the blade holders must be in line, ie no twist in the blade. I had a cheap saw frame which would not cut straight until I wrapped shim round the back where it fitted into the handle, the back was no longer removable but it was a better saw. PS I still can't cut straight.
Mike12/09/2011 18:25:42
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713 forum posts
6 photos
Agree with Gordon W. When I did evening class engineering training in the early 1970s the instructor always insisted I use stiff hacksaw blades. He said flexible blades were for amateurs. As I remember, they cut brilliantly well, but if you tried to steer them you shattered the blade. Taught you to start a cut accurately, as I can still do it most times. But where on earth do you get stiff hacksaw blades these days?
wotsit12/09/2011 20:59:27
188 forum posts
1 photos
I was always told to tighten them up till they broke, then back off the tension nut by half a turn........

What is the thinking behind slacking off after use?

Mike - I can buy stiff hacksaw blades in Romania, but they are totally useless (or my technique is suspect!) - the metal seems to be so hard, that 'any' misalignment results in a small chunk of the blade breaking out, rendering it useless. It seems very difficult these days to find good blades which will last - there seem to be many useless things offered for sale which simply will not cut anything. The best I have found in recent years are the bi-metal type, (usually sold singly at exorbitant prices), so I tend to stick to my bandsaw - I can (oddly) still get good blades for that.
 
 
John Stevenson12/09/2011 21:35:03
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5068 forum posts
3 photos
For a start get a decent hacksaw frame, if you have a tubular Eclipse one then chuck it at next doors cat.
 
The tension on a hacksaw blade is far more than you think, that much the wimpy frames were grew up with won't cut it.
 
Believe it or not you need the blade under a tension of 28,000 psi to 50,000 psi, no not a typo this also applies to band saw blades and you can but a special clamp on indicator that gives pressure and can be worked out to how much stretch in thous or 0.xx mm
 
See if you can get a cast alloy Lennox frame, with these you fit the blade, take slack up and tighten 9 turns, once tight you can play tunes on it. The tubular ones will not tighten up this tight, they just keep bending.
 
This is the cheaper one, about £20
 
and this is the higher strength one, about £30
 

They are well worth the expense as there is nothing worse than a frame that bends all over the place.

John S.
Balljoint12/09/2011 21:52:38
39 forum posts
12 photos
Where can i buy one of these lenox hacksaws please
 
Thanks
Terryd12/09/2011 21:55:24
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1946 forum posts
179 photos
Hi Derrick,
 
I find that the old fashioned straight grip hacksaws, (which are still sold in France), are much easier to use and have greater accuracy than the later 'pistol grip' type such as the Eclipse. I also find them much less tiring to use. Yesterday using my dad's old straight handled saw I cut a length off a 50mm diameter bar in just over 10 minutes and it was accurate to within 0.5 of a mm. That is less of a statement about my accuracy rather a superior type of saw.
 
By the way, make sure that you use the correct tpi saw blade for the material you are cutting. Many folk make the mistake of sticking a blade in the frame and using it for all materials.. Terribly wrong that, makes the work hard and tedious. Type doesn't really matter. all hss, carbon steel, bi-metallic. They all do the same job when used correctly the hss and bi-metallic just last a bit longer.
 
I would endorse the 'finger tight plus three turns' recommendation. It is important that the blade is taut. Also the angle of the saw when cutting is important, always use it by sloping the front end downwards, away from you, never upwards. The latter method puts too much force on the blade on the push stroke causing inaccuracy, bending and possibly breaking of the blade. Don't rush your strokes, about 1 per second and use the full length of the blade. The hand, wrist, elbow and shoulder should all be in line making an efficient and accurate stroke.
 
Best regards
 
Terry
The Merry Miller12/09/2011 21:55:46
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484 forum posts
97 photos
 
Wotsit,
 
It was just something that was drummed into us when we were apprentices and it's still a habit today.
All of the hacksaws in those early days, I'm talking about mid 1950's, were metal frames and most were Eclipse so you would not expect any creep in the frame but in the fitters shop you never knew who was going to use the hacksaw when you weren't around so you did not know if the tension had been changed. So slacken off and start again just in case the missus has been having a go behind your back!!
 
A British made hacksaw I had many years ago, I've forgotten the name, had the handle moulded in a plastic compound.
Even with the slackening off ritual the creep was such that I had to keep putting spacer washers under the tensioning wingnut because it kept running out of thread which was at the handle end, until eventually the blade tensioning pin was so close to the handle that you could not fit a blade.
So beware if you purchase one like that.
 
Carry on slackening.
 
 
Terryd12/09/2011 22:14:16
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1946 forum posts
179 photos
Hi John S,
 
Just my experience after 50 years but I would never use a pistol grip hacksaw, they are too tiring on the wrist and hand. I have reverted to the traditional straight grip which are much more comfortable and very accurate to use. Difficult to source in the UK but are available:


accurate and easy to use. Much better than the later so called improved pistol grips. Not all things are improved by so called 'progress'
 
Best regards
 
Terry
Steambuff12/09/2011 22:18:24
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544 forum posts
8 photos

Buck & Hickman Sell the Lenox High Tension Hacksaw in the UK
 
 
Dave
John Stevenson12/09/2011 22:21:36
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5068 forum posts
3 photos
Terry,
Just personal preference.
 
I still have some of these from years ago, I much prefer them over the Eclipse tubular ones but since doing a lot of work on a dedicated band saw with Lennox, 2" wide blade, 1 tpi and could cut thru case hardened steel, I learnt a lot about blade design and mounting.
 
Since using these saws they gave us, blade life has tripled.
 
John S.
DMB12/09/2011 23:18:36
1585 forum posts
1 photos
I had a tubular hacksaw frame years ago and really liked the comfortable pistol grip. However, I just left it tensioned (and one blade for all jobs!) Over time, the whole eggshell thin alli handle gradually bent, so that I kept tightening it up just a bit more till no more washers could fit under the wing nut. I will personally throttle any neighbour who chucks their hacksaw at my cat, John Stephenson.
I now have a collection of hacksaw and junior hacksaw frames, each holding blades of different TPI. I use the little car touch-up paint tubes to mark all sorts of things, in this case, one end of every blade has a dab of colour indicating its TPI. The painted end of all blades is at the back of the teeth, nearest the pistol grip handle, when correctly fitted.
Frames are marked Yellow for use on Brass and other non-ferrous jobs and unmarked ofr ferrous work.
I dont use the bent wire type junior hacksaw frame, only the type with a knurled tensioning screw next to the handle. Again, a yellow frame one for non-ferrous.
Terryd13/09/2011 06:27:39
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1946 forum posts
179 photos
Hi John S,
 
I'm no expert on Blade design or even use but my hacksaw blades seem to last forever, I haven't broken or buckled a blade for many, many years. I just chuck them when the teeth no longer cut properly. Perhaps it comes from years of practice, teaching and demonstrating correct techniques in the use of hand tools to 11 and 12 year olds on an almost daily basis.
 
Over the years I tried many types and makes of frames but it was only when my mum died a few years ago that I found my Grandfathers straight handled hacksaw and can honestly say that it was the best move I made when I tried it out. It was a revelation and made my cutting so much easier and accurate. I wouldn't have believed the difference before I tried it. I can only pass on my experiences, it is up to others to reject them.
 
Best regards
 
Terry
DMB13/09/2011 10:09:32
1585 forum posts
1 photos
Terryd,
Re my prev. post about colouring sawblades and frames. Not original, just a follow-on from school metalwork days where all the handle ends of files were coloured according to type, e.g., I believe all smooth cut files were painted white. Think Mr Stevens used blue green and red for other cuts. I break up sets of allen keys and spanners and keep on/near the mill only those spanners and allen keys which fit said mill, colouring them all blue same as mill. Saves an awful lot of frustration trying to find misplaced tools on one or other maches/benches.
John.
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