Square cut?

[CTB]

Hi, I'm making an adjustable post to shore up my roof rafters so I can replace the rotten beams underneath. I've found an 8 cm round post onto which I will weld a 4 ton hydraulic jack to raise and lower the rafters. The problem is that I need to cut the ends square to weld on a plate so I can mount the jack on it. Both ends of the post have jagged ends.

How do I make a cut on the post so that its perpendicular to the end? I don't have a fancy cut-off saw or band saw, only my trusty old green bosch angle grinder. I've thought of putting a can or piece of plastic sewage pipe over the postand tracing around it, but I dont have one the right size. How would you do it?

 

[Debs.]

To mark it circumferentially for cutting?

Large sheet of paper/art-card: with 4 x 90 degree corners......wrap around the old pipe and carefully line up the paper`s/card`s edges (at each end), tape in place and that`ll give you an annular/square edge to mark/scribe around for cutting.

 

[CTB]

Sounds like a winner. Thanks Debs, I'll try it in the morning.

 

[Hitch]

As Deb's solution, a bit of card/paper wrapper round. When you tack the plate on you will square it up anyway before welding...

 

[CTB]

Ah, yes. Finally a use for those damn magnets that I bought on sale!

 

[oilcooled :)]

or put ur belt on it off ur jeans, get it as thight as possibe, mark it, and you have it

 

[bigbadbugga]

Use a large jubilee type clip,

 

[MrFluffy]

Just a note, have you checked out how much a cheap acro style prop is? that'll be more than sufficient to lift a large beam and support it. In fact Ive got a outbuilding waiting for me to get round to demolishing safely which currently has its entire roofing truss supported by a couple of them. Ive used a pry bar to tension them in the past when using them to raise heavy objects too...

When I first got to france I made my own longer acro's from short ones and pipes with welded bits etc and unless you get it all dead square, some of the forces trys to skid or bend the acro and error is amplified by the lengths involved. Then one day I walked into a local builders merchant and found out I could have just got a complete real one for under 15e...

 

[MrFluffy]

If you need to move more than the thread allows, you can use two and stagger their use walking up between them.
Wind one full up, then fit the second, wind up freeing first, wind first down and change pin position etc.
That gives you the ability to lift any height supported by the props throughout their range of adjustment.

Also if you need to line up your card as above, you can lay a length of angle iron along the tube to establish the line to square off against.

 

[busa]

A pipe wrap round is one of the most common marking out tools any pipefitter will ever use. It consists of nothing more than a parallel strip of reasonably stiff yet flexible material. The strip is wrapped tightly around the pipe and over itself again, taking care to align the edges of the first wrap and the overlap. There is absolutely no reason to mark a centreline to square off, a wrap round long enough to give a reasonable amount of overlap will always produce a line square to the longitudinal axis of the pipe.