Hacksaw blade tension

[alan frostParticipant @alanfrost17805]

Tension. Good article here http://homemetalshopclub.org/news/11/newsletter1108.pdf#Page=7

 

If you have n’t come across this site b4 have a feast and read the article titles. I’d be surprised if you don’t find something worth tasting.

 

The tensions quoted endorse JS’s comments and I would certainly endorse his opinion on the tubular types although I suspect you’d have trouble hitting the cat judging by the way they saw-I do have one I keep with an abrafile blade in it. I use this for sawing curves which the tubular type are particularly adept at.

 

For most of us with 4X 6’s the tension translates into as hard as you can tighten it unless you’ve got exceptionally strong wrists , which I would n’t admit to if I were you. Makes people wonder how you spent your youth.

 

By the way among several mods to my 4X6 ,I added an old valve spring to the tensioner so the blade rides on spring tension (an easy 60 minute modification ) and my blades last a long while even when sawing up dubiously procured railway track -embryo anvils-(a severe test of man and machine I can assure you. . Rail track is much bigger than it looks from 10 feet up in a train compartment and bloody heavy. I actually got mine legally ,which I hate to admit , when they rebuilt the Alloa -Stirling line ., “Go down the yard and pick a few bits and I send a couple of my men to help you load it. Don’t want you nicking bits when the trains are running, do we ”  

Edited By alan frost on 16/09/2011 01:28:17

Edited By alan frost on 16/09/2011 01:35:24

Edited By alan frost on 16/09/2011 01:39:33

[MikeParticipant @mike89748]

Starrett are still very much in business, and you can buy direct from their website at

http://www.starrett.co.uk/shop/

No sign of the yellow and green blades Stub Mandrel mentions, but their bi-metal blades look good, and there is also very rigid looking hacksaw frame at a reasonable price.

[Ian S CParticipant @iansc]

When mums father came to NZ for a holiday in 1952 he bought some of his tools (he woukl have bought more but they exceded some weight limit), amoung bthem was a hacksaw bkade, “Elephant ” brand I think, it is 1″ wide with teeth on both sides, its had a fair bit of work over those years, and I don’t think it was new when it came here. Its in our local museum now. They don’t make them like that any more. Ian S C

[John Stevenson 1Participant @johnstevenson1]

My experience with bandsaw blades took a leap up when i got involved in building a saw that was designed to cut the runner and riser pipes that come from the sea bed up to a drilling rig.

 

When a well is finished the big valve on the sea bed is closed and the pipes were blown off about 70 feet below the surface as the rigs can only lift 70 foot of string at a time.

 

However new regs introduced say all pipe has to be removed so then send an expanding tool down like a 3 fingered hone which grinds away as it opens up and severs the pipe just above the valve, quicker that submersibles trying to undo the flange. They then lift this pipe up to max hight and clamp it there.

 

two machines go into action, a big bandsaw that cut the top 70 foot off to go into a supply boat and below this a double ended core drill that belts a 4″ hole thru from both sides for a pin to go in for the next lift.

This drill pile can be different sizes but usually the outer is 32″ diameter and about 1″thick, inside this is a 24″ pipe about 1 1/4″ thick and inside this is an 18″ pipe same thickness.

Between the two outer tubes they are filed with cement, not concrete and also in the pipe are butterfly clamps that are spring loaded to keep the pipes concentric whist the cement is poured.

For some reason these are hardened ?? and no one knows where they are when you are cutting.

 

The saw in question was fabricated out of 6″ square stainless tube with a 1/2″ wall thickness, plenty of gussets etc and carried a 2″ wide blade 1 tpi, tipped and was powered by a 10 HP hydraulic motor [ no electric motors allowed on deck ]

 

We had a section of pipe specially made for us 8 feet long with 30 butterfly clamps fitted and marked, every test cut had to be thru a clamp. When we started off blade life was in minutes and we got Lennox out to assist.

 

first question they asked was how tight were we tightening the blade and the answer was we didn’t know but we thought we were not over tightening it. They put their gauges on the blade and got us to tighten it up, gauges never moved.

We kept tightening and it still never moved and we ran out of adjustment.

 

All we were doing was bending the frame.! !

 

Back to the drawing board and the frame was stiffened up with side plates of stainless 6″ x 1 1/2″ this time we got a reading but it was far, far more than I would have tightened up, thing 3/4″ drive socket with 5 foot of bar on it !!

 

Lennox were magnificent on this and first cuts were 1 hour 20 minutes and with a bit of tuning we got it down to just over the hour.

They came back with a 1 1/2″ wide blade, vari tooth with tips on it the size of match heads. I laughed when I saw it and told the guy no was, on the blade we had we were loosing 10 or so tips per cut and one blade did 4 cuts and was scrap.

 

So we ran it, not our blade anyway and lost 2-3 teeth per cut, 7 to 8 cuts before it was scrap and cutting time down to 45 minutes.

They gave all the lad on the job a hacksaw and a load of blades, one lad didn’t want his so I got two.

 

I asked about releasing tension and the Lennox guy just smiled and said if you have to release tension something isn’t right.

 

Modern version of the original but not for runner and risers pipes.

 

http://www.youtube.com/watch?v=wHvJNHFqldQ

 

John S.

[EtheAv8rParticipant @etheav8r]

Thanks John S for the pointer to the Lennox in your post above; as a result of which mine arrived today with 3 packs of blades.

 

However I must be wary as your posts keep costing me… time, effort and dosh and a huge (but fun in an odd sort of way) learning curve on several fronts, after all I was planning on just getting a smallish manual mill and ended up getting a KX3, and now I am fighting with DraftSight and Cut-2D in the hope of one day being able to pass a file to Mach3 and make something!

 

Edmund

 

PS I am not allowed to throw my Eclipse hack saw at the neighbours cats – even though they come in a poop all over my garden, so not quite sure what to do with it, seems a waste to just bin it!

Edited By EtheAv8r on 16/09/2011 23:42:22

[alan frostParticipant @alanfrost17805]

Put an abrafile in it and use it for curved cuts. The name Eclipse comes from the fact that they eclipse all others at sawing curves.

[blowlampParticipant @blowlamp]

Posted by EtheAv8r on 16/09/2011 23:42:07:

… and now I am fighting with DraftSight and Cut-2D in the hope of one day being able to pass a file to Mach3 and make something!

 

Edmund

 

Edmund.

If you want a test file to cut on your mill, just let me know what you’re after and I’ll draw something up and generate some Mach3 compatible g-code for you to play with.

 

 

Martin.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, well I’ve always tightend hacksaw blades up as tight as I can get them, and I’ve never slacked them off when not in use, I have never found a problem. IMO they should be at least tight enough, so there is minimal twist in the blade. In my experience I have found that the Eclipse all hard blades to be the best.

 

Eclipse blades can be obtained from Buck and Hickman and various other suppliers.

 

http://www.buckandhickman.com/find/Manufacturer-is-ECLIPSE/psi-is-21

 

Regards Nick

 

P.S. no connection with Eclipse or Buck and Hickman

[EtheAv8rParticipant @etheav8r]

Posted by blowlamp on 17/09/2011 00:56:51:

Posted by EtheAv8r on 16/09/2011 23:42:07:

… and now I am fighting with DraftSight and Cut-2D in the hope of one day being able to pass a file to Mach3 and make something!

 

Edmund

 

Edmund.

If you want a test file to cut on your mill, just let me know what you’re after and I’ll draw something up and generate some Mach3 compatible g-code for you to play with.

 

 

Martin.

Martin

 

That is very kind og you thank you. It is not that I have something specific I want or need to make – yet; it is a question of getting to grips with the various tools (hardware and software) and the work and process flows. I am making slow progress, but I am at out of the house on work days from 06:40 to 21:15 so only really have week-ends, which are filled with a lot of other stuff!

 

From December I will be switching to part time (3 days a week) working and will have a bit more time.

 

Edmund

[Derrick WatsonParticipant @derrickwatson66926]

Been away from the forum for a couple of days.

 

Just wanted to say thanks for all the useful info. Alan – very nice website you listed – hadn’t seen that before, lots of useful information and ideas for stuff to make.

 

Oddly enough, I do have a straight handled hacksaw (somewhere) but have always used my pistol grip one assuming it would be better – sounds like I should give it a go.

 

cheers, .d

[TerrydParticipant @terryd72465]

Hi Derrick,

 

I would certainly give the straight handled saw a go. With care and correct technique accuracy depends on the user not on the frame. To quote the old adage, “A bad workman blames his tools”.  The straight handle allows a more delicate approach and more control of the blade.

 

I have used all sorts of frames, good, bad and mediocre, solid and tubular, and have managed to cut quickly and accurately with them all. The straight grip is just easier. 

 

Use the full length of blade, keep your strokes steady (about 1 per second), don’t force the blade and envision where you want it to cut. The rest is just practice. Success is 30% skill, 30% technique. 30% observation, 9% perspiration and 1% equipment.  Without skill the most esoteric and expensive equipment is naught.

 

The blade should always slope downwards away from you i.e. the front of the blade lower than the handle.  The alternative is a recipe for disaster.  Inaccurate cuts and broken blades are the result.  The secret of the success with the hacksaw is patience.  As I taught my students “make haste slowly”

 

Regards

 

Terry

Edited By Terryd on 20/09/2011 22:17:22

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