Measuring tricks - finding precise dimensions over a long distance?

[astro_al]

Hi guys, seems like a simple question, but...

Does anyone have any tricks for taking exact measurements for a railing to fit between two brick pillars (for example). I need to make something to bolt precisely against the inside faces of two pillars, the railing is about 4.5 metres long as a single span (with feet too).

A tape measure is too floppy/imprecise to be exact to the nearest mm (on my own). I don't want to end up with a significant gap between railing and brick, so how to measure exactly so it just slots in and bolts up?

What do the railing makers out there do if something is a few mm short for a fixed length space?

Cheers, Al.

 

[Tigman]

I make cleats for the wall fixing from angle iron, bolt the cleat to the wall and rest the railing on top of the angle, slot the hole in the cleat to take the bolt for the railing, then make the railings 10mm or so shorter than your measurement ! no accuracy required !

 

[rtbcomp]

Could you use one tube that slides inside another to make a slip gauge? Fit a screw to clamp them together once in place between the pillars.

Fit a spirit level and take measurements at ground level, mid way and top.

Rest the pole on the ground to take measurements with a tape.

 

[eil]

I remember seeing piano wire pulled tight between spans and measurements taken off that.

 

[BillJ]

Just a question (and I've never made railings so I don't know) but what would happen if a 4.5m span with no gap between it and the pillars expanded on a sunny day? Now I come to think of it, what do any railings do about expansion?

 

[Justme]

Bow?

 

[BillJ]

Bow?

That's all I can think of. Would it be noticeable?

 

[Blackjack]

Probably not.

What I will say is that you need to be careful about being dead accurate, because builders aren't.

I used to make securtiy grilles, and the people who I was making them for would assume that because the left side of a grille was a given length, then the right side was going to be the same, that window apertures were square, and that the front of the aperture wasn't going to be smaller than the back of it (makes the grille difficult to fit if it's bigger than the hole it has to go through...)

 

[Tigman]

like I said make it smaller, slotted holes in fixings +/- cant lose!

 

[Arsonista]

Like Tigman said, obround slots are your friend, being too accurate can work against you.

 

[Drains]

Er, I think you'll find that string is your friend. Non stretchy stuff. Failing that, use a piece of timber slightly under size, measure gap, add to length of timber. Voilà.
Oh aye, re accuracy and fitting and slots- don't forget how much 4.5m of railing will expand on a hot summers day.

 

[BillJ]

don't forget how much 4.5m of railing will expand on a hot summers day.

Just what I said. Or how much it will contract at -10C on a really brass-monkeys-unfriendly winter's night.

 

[Tigman]

could always make a middle post with slotted holes , make the panels smaller , save the piers on the wall from cracking !

 

[silversurfer]

you could always try a laser measure,like surveyors use....!!

 

[Luke]

I've had success with the not-quite-long-enough-stick method.

If it's only just too short, it's easy to get levelled up and measure the difference with a steel rule, rather than a bendy tape.

In this application though, I think the slotting route could be a better way forward?

 

[brightspark]

clock the pillars with spirit level make sure there level then make your railings 1/4 inch short fit railings and pack either end with spacers if necessary and fasten them in

 

[Hitch]

Cleats fixed to the pillars, and a slot in the top face of it is the way to go. I like to leave about 6mm at each end of a panel. If the stone/brickwork is a bit uneven, 10mm wont hurt. You will barely notice the cleat.

I trust the panel will have a few support posts also?

I fitted a job yesterday that was measured with one of them gadgets, spot on. Couldnt have done it better with a tape. A quality one though, not sure id trust the cheapy ones that much.

Measuring tapes, a good 8/10m one with a wide blade makes long runs easy to measure.

 

[Welderpaul]

Same here really, measure the gap as accurately as you can using a normal tape, two of you taking the measurement, tape pulled tight and held square. Measure at the tightest point. Cleats cut from 50x50 angle, or bent out of 30/40 x 8mm bar then a slot in the top and a fixing hole in the side. Anywhere between 5 - 10mm gap either end when its fitted gives quite a bit of tolerance.

 

[pidgeon chit welder]

I used the stretcher tubes from the roof of my caravan awning and marked the distance off at the join with a pencil .( it is a 4 .5 mtr total stretch 0

Took it away and made each panel ( OK mine were wood ones but that dont matter ) just check that your measurement is still on the marking points and that you remove them if making individual unrelated measurements .

 

[pidgeon chit welder]

Same here really, measure the gap as accurately as you can using a normal tape, two of you taking the measurement, tape pulled tight and held square. Measure at the tightest point. Cleats cut from 50x50 angle, or bent out of 30/40 x 8mm bar then a slot in the top and a fixing hole in the side. Anywhere between 5 - 0mm gap either end when its fitted gives quite a bit of tolerance.

If you then put a penny washer under the bolt head and one under the nut ( Nylock type ) you can grease the area and get the sliding grip needed .

If you worrry about someone undoing things and legging it with the gate , rails etc use a longer bolt and tack weld on a standard nut below the lock nut.