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Power Hacksaw run off

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Peter Simpson 208/02/2012 12:07:18
28 forum posts
1 photos
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
JasonB08/02/2012 12:09:27
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25215 forum posts
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1 articles
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 208/02/2012 12:39:00
28 forum posts
1 photos
Hi Jason,
 
Just ordered new blades, hope this sorts it out.
 
Peter
SteveW08/02/2012 12:41:54
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140 forum posts
11 photos
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_08/02/2012 14:35:06
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543 forum posts
31 photos
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 Builder08/02/2012 17:06:52
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267 forum posts
This one cuts without any run off and can handle large sections.

Les Jones 108/02/2012 18:30:32
2292 forum posts
159 photos
Hi,
Does anyone know how much the plans cost for the myfordboy saw ? I am impressed by its accuracy.
 
Les.
Russell Eberhardt08/02/2012 19:48:54
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2785 forum posts
87 photos
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 Scollay08/02/2012 20:37:21
19 forum posts
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 108/02/2012 20:53:46
2292 forum posts
159 photos
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 Wan09/02/2012 02:30:27
131 forum posts
3 photos
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 C09/02/2012 09:43:35
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7468 forum posts
230 photos
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 209/02/2012 17:43:25
329 forum posts
193 photos
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 Scollay09/02/2012 20:28:59
19 forum posts
You can contact Myfordboy at [email protected] the saw plans are very good
 
Steve Wan10/02/2012 02:08:18
131 forum posts
3 photos
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 C10/02/2012 10:53:00
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7468 forum posts
230 photos
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
DMB10/02/2012 15:00:06
1585 forum posts
1 photos
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 Wan10/02/2012 16:08:05
131 forum posts
3 photos
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

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