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Greta

Going Round The Bend

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Advice Please

I want to make a small box section with Magnetic feet on which to mount my analogue Stopwatches so the unit is fixable and removable to/from my rally dash.

On paper - its fairly simple to measure the sequence of rectangular sections that I'll progressively fold - however in making a thick cardboard mock-up it seems that I need to account for a "x"  measurement that will disappear into the radius of each fold! Does anyone have experience on how much should be allowed for each fold. I'll be using 1-2mm sheet steel to make my box. ( I'm not bothering to close the ends as this will allow spanner access to tighten nuts etc.

Thanks

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You're quite right, Greta, but does it matter?     If the rectangular tube you make is symmetrical, then it will just be a fraction smaller than you planned.  If that doesn't matter, then it doesn't matter!

There is a way to estimate an allowance for bends.   I'll look it up if you wish.

John

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Didn't take long to find:

Add the Bend Allowance to your original dimensions:  

Bend Allowance = Bend Angle in degrees x ( Pi/180) x Internal radius + (K x Material thickness)  (note the plus sign)

You'll also note the fudge factor, K, that can vary from 0.3 t0 0.5 (soft to hard, if you're using steel, go for 0.4)

John

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If you have a black and yellow Dzus engineering booklet then it is in there.

 

Roger

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Great thanks John - seems like I should allow 3mm for every 90 degree bend.

As I'm mounting the clock bracket in front of the navigator on a new full width dash but also trying to keep the taller front facia of the box proud of the dash top - yet keep the whole unit slim enough not to intrude the cabin ( map boards etc etc ) ... and I don't currently have enough scrap sheet to make a MKII - I'd like to try to get it right from the off.

And btw - isn't it great that all such things have already been worked out by some one.

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Got one of those...… don't remember bend details being in there, but I bought the book for thread info...… will look later.

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The book does change with each edition. 

Once upon a time it was really good for BA threads without a trace of Millimeter.

 

Roger

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Had one 30yrs ago, no idea where it is now, saying that has anyone seen my mobile i had it a few minutes ago  and no, i've no idea what the number is as i never ring it :-)

RR

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On 5/14/2019 at 6:49 PM, RogerH said:

If you have a black and yellow Dzus engineering booklet then it is in there.

 

Roger

So I looked and there it is...... among many other treasures. Never got beyond the threads before.

The sheet metal bending info is all imperial units though...... 

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2 hours ago, Nick Jones said:

So I looked and there it is...... among many other treasures. Never got beyond the threads before.

The sheet metal bending info is all imperial units though...... 

Hello Nick

                 All the things in life you never Knew you needed (its been my bible for 40+years maybe 50?)

I do have big charts on the well as well(old eyes) and being a sad get one at one end of the workshop and one at the other end!!! (its only 20 feet long!!!!!)

still saves the old legs and one next to the bench and one next to the lathes

Roger

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Hi Nick,

 0.004" = 0.1mm  (almost)   it is too easy.

 

Roger

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