Power Hacksaw run off

[Peter Simpson 2Participant @petersimpson2]

I have nice Meddings HS4 power hacksaw which does not cut the bar stock quite square. As it cuts it runs off away from clamped bar stock. It appears to cut with the same error every time. Other than the gib strip there does not appear to be any adjustment to correct this error. Has anybody out there had similar issues with power hacksaws.

Is a 14″ power hack saw blade the total length of the blade or is it 14″ between fixing hole centres?

 

Any responces greatfully received

 

Peter

[Peter Simpson 2Participant @petersimpson2]

[JasonBModerator @jasonb]

Does it do it with a new blade, if the old one has lost some set on one side the blade will cut towards the other.

 

J

[Peter Simpson 2Participant @petersimpson2]

Hi Jason,

 

Just ordered new blades, hope this sorts it out.

 

Peter

[SteveWParticipant @stevew54046]

Ii think thiis is a ‘feature’ of most power hacksaws. As Jason indicates I also think caused by an uneven set but often still present in new blades. We underestimate the amount of feedback we provide with a hand saw in order to achieve a (fairly) straight cut.

 

SteveW

[_Paul_Participant @_paul_]

I have both “Rapidor” & “Qualters & Smith” donkey saws, and no matter how carefully I set up the work or the machine/s they will always cut slightly off.

 

I put it down to the set on the teeth, I have tried both 6 & 14tpi blades & reversing them so it cuts on the forward stroke and not much difference either way.

 

The 6″ “Qualters & Smith” is certainly the better of the two and quite bizarrely it seems more accurate when cutting through bigger stock ie. > 2″ I can only attribute that to the better quality feed adjustment this machine has.

 

Regards

 

Paul

[Engine BuilderParticipant @enginebuilder]

This one cuts without any run off and can handle large sections.

[Les Jones 1Participant @lesjones1]

Hi,

Does anyone know how much the plans cost for the myfordboy saw ? I am impressed by its accuracy.

 

Les.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Les Jones 1 on 08/02/2012 18:30:32:

I am impressed by its accuracy.

 

From the video it looks as if his foot was impressed by that large lump he cut!

 

Russell.

[George ScollayParticipant @georgescollay44108]

Hi, Les I think the plans were about 10 pounds, I had a set from Myfordboy last year and they are very good, I have just got the saw made now and seems to work very well but I did not get it as accurate as him, but according to him it depends how well it is made,if you send him an email he will let you know the price

[Les Jones 1Participant @lesjones1]

Hi George,

Thanks for that information. I have been thinking of buying one of the 6 x 4 bandsaws or the Seig power hacksaw but I do not really have room for them. Myfordboy’s design looks much more compact.

 

Les.

[Steve WanParticipant @stevewan33894]

Hi folks

 

I suspect that the saw blade is not aligned properly that causes the run off.

I’m in the process of making a compact power hacksaw with ample info from various designs on the web. The frame itself is a 11″ G-clamp, heavy for the weight to saw and it will be driven by duplex pulleys of bicycle chain drive and step pulley.

 

I shall look into the ‘Run off’ problem soon once I get my main saw frame done.

Making a power hacksaw is challenging than buying one. These days bandsaw blades are expensive for model engineers too.

 

Steve

 

 

[Ian S CParticipant @iansc]

If the amount of run out is consistant, you can pack up the work to compensate, if nothing else works. Ian S C

[RICHARD GREEN 2Participant @richardgreen2]

Hello All,

In my own engineering business over the years I have had three serious power hacksaws, an Ercole 300 mm, a Speedax 9″ and I’ve still got a Qualters and Smith Bulldog 200 ( 8″ ),

About 10 ish years ago I had trouble with the Speedax cutting crooked, even with a new blade fitted,

I had a representative from a Sheffield power hacksaw blade manufacturer call on me to have a look at it, the saw was in reasonable condition with no serious wear or slack in the slides etc,

He told me the most important thing with a power hacksaw is blade tension !

Think about it,……… when the blade warms up during cutting, it will expand length wise reducing any blade tension there is, the blade can then lose it’s vertical alignment due to it being slack, there’s a lot of vertical pressure on the saw blade, so it’s going to try to flop over a little bit if it can ( that’s the only way it can go ), once it has started cutting crooked it’s not going to straighten up, only get worse !

Part of the answer is to always use coolant or some kind of cutting oil to keep the blade cool,

Of course starting with correct blade tension is important, but how we determine that I don’t know, the representative had an all singing all dancing test gauge, I think was made by Starrett, but I’m not sure,

Anyway, different blade sizes would probably mean different tensions ?

The Qualters and Smith saw usually cuts straight, but I always use a good quality cutting oil, whatever material I’m cutting, and really flood the blade and material to keep it cool.

Hope this helps, I would be interested in your ideas of getting the correct blade tension.

 

Richard.

 

 

 

 

 

[George ScollayParticipant @georgescollay44108]

You can contact Myfordboy at Myfordboy@yahoo.co.uk the saw plans are very good

 

[Steve WanParticipant @stevewan33894]

Hi guys/Richard

 

Thanks for the tip! Yup, heat generated by sawing will bow the blade. Has anyone here built his very own compact power hacksaw? I like to know what other measures to take to prevent run off with all the pointers commented here in mind.

 

By far, there’re only 2 types of casting supply for power hacksaw in the UK by Blackgates and Westbury (ceased in 2006). Wonder are there others? Myfordboy is relatively new.

 

Steve

[Ian S CParticipant @iansc]

I read not that long ago about the tension in blades, it was conciderable, hundreds of pounds, I must have a look around. Ian S C

[DMBParticipant @dmb]

hello all,

I want a small portable hacksaw m/c, possibly with a view to getting rid of the space eating bandsaw and I found a design in an old ME – Vol. 82 No. 2042 27/6/1940.

The bandsaw also needs expensive good makes of blades – pay rubbish price, get rubbish. At least with the other type ordinary blades can be used and even good ones last a long time. The old 1940 design probably needs long bearings to guide it to cut straight/square. I have necessary ali angle motor and worm reduction gear so will probably tackle this job soon.

John

[Steve WanParticipant @stevewan33894]

Hi John

 

We’re in the same boat needs space and saw blades are cheaper using power hacksaw. I don’t have an angle motor and saving my worm gear for my small horizontal mill project. The long bearings you were saying caught my attention.

 

I have a drawing with the support bar milled with slots to hold moving saw frame instead of using collars which may have contributed to the run off problem.

 

Do you like to share more design ideas via email?

I have just made the heavy frame out of 11″ G-clamp using half the hacksaw blade. All necessary metal blocks/pulleys are purchased. Soon I shall go into the finer aspects of this challenging project

 

Steve

stewan@gmail.com

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