Cutting Vertical

[miniburrell]

Hi

Can any one help,

I am currently making a Stuart 10V and have encountered a problem whilst making the con rod. Before I could drill the hole for the crank, I have to split the con rod into two, to allow it to be clamped onto the crank, whilst I was cutting it in half, the saw wondered off centre at an angle, thus making the con rod useless. Can any one give me any tips on how not to get the blade to wonder off at an angle whilts cutting metal by hand and keeping it vertical

Many Thanks

Mini Burrell

[alanstepney]

I assume you were using a normal hand hacksaw.
In that case, was the blade worn? They often wear teeth on one side or the other, making subsequent cuts curved.

Was the tension correct?
Did you have it lined up square to start with?
All possible reasons for an off-square cut.

BUT, before you scrap the con rod, can it be saved?
Even if the cut is off centre, it might still suffice.
After all, the split is only to enable you to wrap it around the crankpin.

If it isnt possible to use it, file down where needed, and insert a (or 2) small pieces of brass as packing.between the two parts of the con rod.

(Being mean, I never scrap anything unless there is no possible option.!)

[jgb7573]

I must admit I'm always wary of hacksawing expensive castings for the very same reason. As Alan says, they can usually be recovered, but that's more work! One thing I have found is that if you push a hacksaw too hard the cut tends to wander off. It's a case of almost no weight on the hacksaw apart from its own. It then usually cuts vertical for me.
Two possibilities to make things safer. First of all is to use a slitting saw on an arbor in the lathe with the part to be cut clamped to the topslide (or wherever is suitable). The other is to clamp a bit of steel bar along the line to be cut and then use that as a guide for the hacksaw blade.
Good luck!

[lancelot]

Hi M.B.
another trick is to start the cut on both sides of the big end gradually working your way through to the centre...yours can be saved by following Alans advice.
All the best for now,
John.

[paul]

Other things I've found that can improve the accuracy of a cut ...

Having the right blade (tpi for particular metal)
Keeping the cut as close as possible to the vice jaws (reduces vibration and serves as a guide)
Keeping plenty of teeth in contact with the work (the way the work is held might affect this)
Putting a spot of oil on the blade when cutting thicker steel

If all you've done is cut it, it's bound to be recoverable ;D

[baggo]

LBSC used to suggest a way to cut eccentric sheaves etc. in half using the vice. Clamp the sheave in the vice with the bottom edge of the required saw cut flush with the top of the jaws. Then, keeping the saw blade flat against the top of the jaws, saw across the sheave. The vice jaws act as a guide and keep the cut straight and level.

Personally though, I use the slitting saw in the lathe method ;D

John

[ettingtonliam]

Full size engine big ends often had a pack of shims in the joint, so that one or more could be removed to compensate for wear. If you do this, its only replicating full size practice. I agree with the other guys that a slitting saw is best, but another way of sawing square is to start at each corner, at 45 degrees, so that the saw cut is going down 2 faces at once. Do a bit like this at each corner, then proceed as normal. It seems to help (well it helps me!) A good quality HSS sawblade (Eclipse for preference) helps (as ever, cheap blades can give problems), and make sure the blade is well tensioned.

Good luck
Richard

[jgb7573]

I'd forgotten Curly's recommended method with the vice jaws as guide. Mind you, you'd then be cutting horizontal rather than vertical. But the end result is the same. ;-)

[paul]

I've tried that horizontal business before but it didn't work well for me - I think it's difficult to keep the blade truly horizontal and to stop it bending. Each to their own I guess. Now when I get me lathe fixed I might get one of those slitting saws

[Deleted]

I can see that using a hacksaw horizontally in a vice would be akward and somewhat un-natural.

However Machine Mart product V75B which is a 75mm vice fitted with a screw clamp would allow you to clamp the vice to (say) a door and then you could use the hacksaw vertically as God intended.

Regards

Jim

[Tel]

Nah, 'im upstairs meant 'em to be used horizontally - ever tried to lay one on the bench vertical?

[circlip]

OK chaps, don't fall off your chairs laughing, but hasn't anyone ELSE tried putting the blade in UPSIDE DOWN?? Fink abart it.
Regards Ian.

PS. It also works in OZ Tel.

[Deleted]

I have just been in Machine Mart today. Their multi purpose vice rotates so you can cut vertically having set the job in the jaws. Product no. CMV125 cots incl VAT £44.64

Regards

Jim

[circlip]

Upsidedowning the blade costs nowt. And just to explain for the uninitiated, it's the pendulum effect.

[miniburrell]

thanks for all the help, i am currently looking into getting a slitting attachment for my lathe,

thanks again

MB

[Deleted]

I think the problem mentioned is that cutting horizontally is akward. I certainly find it so. How does putting the blade in upside help ? I am mystified.

Regards

Jim

[Tel]

I have several slitting saw arbors that I've made over the years, but in all seriosity it is hardly worth the bother of setting something up for a litte job like that. Put the piece in the vise with the cut lined up with the top of the jaws and USE A JUNIOR HACKSAW. I have a couple that have a wooden, roundish handle so that your hand doesn't really know the difference in orientation. Jus make sure the blade slides along the top of the jaws - ie light downward and in the direction of cut pressure. Most people get into trouble with hacksaws by trying to rush it, so just take your time.

[paul]

Must admit I was surprised how much more control a junior hacksaw gives. The only trouble is finding suitable blades, seems to be a one-size-fits-all approach.

Jim I'm guessing circlip means using the frame in advance of the blade as a support?

[circlip]

Because the frame is hanging underneath the job, there's less tendency for the frame to "Wobble"while cutting. Tel has also put his finger on the main cause for angularity, TEARAR*EING. If you let the blade cut and don't force it you get better results, Oh yes, a SHARP blade also helps.
Regards Ian.

[Tel]

.... and a finger full of Trefolex