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Mini Tube bender.

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terryd

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Terry, I'm one of many such like-minded people 👍

Thank you so much for the detailed description and photos - this will make building this pipe bender much easier than trying to figure it out from scratch - MUCH APPRECIATED :)
Hi Henniel,

Thanks for that I'm very glad that there are some who appreciate the efforts it takes to provide such information, it can take a long time to take and edit photographs,so that they are asunderstandable as best I can.

If no one is interested it is a pointless exercise and not worth the time and effort which I can put into other things. I'm just trying to help others especially the inexperienced who may not have the range of skills and experience that I have.

Best regards

TerryD
 

Stefan-K

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Terry
I´m also interested in building a pipe bender with multi capabilities. This one looks like it can do the job. I do have some homemade benders for small pipes and they all work more or less good, but none of them has the range to bend pipes from 2 to 8 mm. At the moment i`m working on a Benz Motorwagen engine and i need a thinwalled (0,25 mm) 5mm Brasspipe to be bend. I want to bend it with 10 to 15 mm radius. I know this is very tight and i couldn`t get it bend. No matter what i do, it keeps collapsing. I´m not expecting any "wonders", just another well thought pipebender with different diameter and radius capabilities. Looking forward to the metric Plans you`re just working on.
Thanks for the excellent explanation...

Stefan
 

terryd

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Glad you appreciate it Stefan,

I'm working on the drawings but it's a bit of a slow process. If you notice the original drawings (in the earlier pdf I added) the dimensions are all fractional but there are one or two errors that I found. The norm in English engineering drawings used to be that decimal dimensioning was only used when dimensions need high levels of accuracy and the range of the decimal, i.e. one two or three decimal places would determine the accuracy needed usually accompanied with a + or- tolerance.

However, I noticed when working with drawings from the US, when I was once contracted to convert US engineering drawings from imperial to metric as the US company had a factory in Sweden and of course the Swedes had metric tooling and were not able to work with the imperial system and the Americans were so ignorant of the decimal system that as I was confident with both I was given the job, and the Americans used wholly decimal dimensioning and even when dimensions were not critical they were often to 4 places of decimal if that was the fractional equivalent and had little to do with accuracy needed. - very strange. I also often see that when Americans publish drawings on forums such as this. For example, a dimension of 3/16" would be translated a 0.1875" no matter what the level of accuracy needed. I find this most confusing as that implies a high level of accuracy and much time spent trying to achieve that can be wasted.

Regards
TerryD
 

Ken I

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Terry, I know you know this but having worked for a US company for many years, I refer to the process of simply multipyling by 25.4 as "metricizing" as opposed to "metrication" - in your example of 3/16" I would metricate it to 4mm.
If you look at my metric version of Gerrys Beam engine this is how I "redesigned" it, the 1/2" bore became 12mm, threads made metric etc. etc.
Of course this is more complicated than simple multiplication as all sorts of things change slightly and it effectively becomes a redesign effort.

Whenever I find a strange dimension (in metric) like 22.82mm - I divide it by 25.4 and multiply it by 128 = 115 (thus turning the metric value into 128th's of an inch - typically the smallest subdivision used by US engineers) - if you come up with a rational number like 112 then it can be further resolved 56/64 = 28/32 = 14/16 = 7/8" FYI - my personal "trick".
Regards, Ken
 

terryd

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Terry, I know you know this but having worked for a US company for many years, I refer to the process of simply multipyling by 25.4 as "metricizing" as opposed to "metrication" - in your example of 3/16" I would metricate it to 4mm.
If you look at my metric version of Gerrys Beam engine this is how I "redesigned" it, the 1/2" bore became 12mm, threads made metric etc. etc.
Of course this is more complicated than simple multiplication as all sorts of things change slightly and it effectively becomes a redesign effort.

Whenever I find a strange dimension (in metric) like 22.82mm - I divide it by 25.4 and multiply it by 128 = 115 (thus turning the metric value into 128th's of an inch - typically the smallest subdivision used by US engineers) - if you come up with a rational number like 112 then it can be further resolved 56/64 = 28/32 = 14/16 = 7/8" FYI - my personal "trick".
Regards, Ken
Hi Ken,

Thanks for that interesting account of your methods, in the UK the smallest fraction we would have used would usually be 1/64", the raison d'etre being that it is just about the smallest measure that a technician would read off a rule with any accuracy, which is generally how fractional measurements are made, drawings for machined components would invariably be dimensioned using the decimal system whether imperial or metric for obvious reasons.

The conversion work I was carrying out was on large precision machinery where, as you say, once you start making changes to dimensions you are making changes to the relationship of parts and the process is basically a redesign which is what I was doing not just a simple translation. Like you, I would make basic changes to simple dimensions such as substituting 1/2" with 12mm but of course, you also have to keep in mind 'preferred sizes' of the metric system as defined by the ISO (International Standards Organisation), which is a similar system to that used by the old 'British Standards' here in the UK, to reduce the amount of tooling needed, I'm not really familiar with the ASA standards in the USA.

We don't usually need to turn metric dimensions into fractions as we now are fully metric using decimal dimensioning, except for some older model engineers who have a lot of imperial tooling and experience or for the specialised repair of archaic machinery. I'm now 73 and was converting the drawings mentioned in the late 1960s and when I was equipping my workshop the advantages of using the metric system was a no brainer. I am familiar with both Imperial and Metric systems and am quite happy working and calculating in both, I would also resolve fractions to the lowest possible denominator as you suggest and although I haven't needed to for a long time I can still apply all of the arithmetic functions to fractions, I was always able to conceptualise the process from the off, much to the annoyance of my school classmates and surprise of my teachers.

Best regards

TerryD
 

Bentwings

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Terry
I´m also interested in building a pipe bender with multi capabilities. This one looks like it can do the job. I do have some homemade benders for small pipes and they all work more or less good, but none of them has the range to bend pipes from 2 to 8 mm. At the moment i`m working on a Benz Motorwagen engine and i need a thinwalled (0,25 mm) 5mm Brasspipe to be bend. I want to bend it with 10 to 15 mm radius. I know this is very tight and i couldn`t get it bend. No matter what i do, it keeps collapsing. I´m not expecting any "wonders", just another well thought pipebender with different diameter and radius capabilities. Looking forward to the metric Plans you`re just working on.
Thanks for the excellent explanation...

Stefan
You can look on McMaster Carr for certo bend. It’s a very low melting point metal that you can fill the tube with then proceed with the bend. An melt it out. It has about a 200 deg F. Melting point. Ive used this on brass and aluminum model fuel lines for a long time. I’m about out of it however. Do remember that the wall on the OD can simply get stretched too thin and it will either leak or crack if the bend is too tight. I found bending with ceros ben increases the bending force required rather dramatically so be sure your bender can handle this. I just used hot water to melt it.
 

Ken I

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Terry - I was two years into my four year engineering diploma when we metricated.
This permanently left me conflicted - I still conceptualize pressure, stresses etc. in psi as Pascals have never "taken" in my psyche - other than that my brain is wired to metric.
Regards, Ken
 

Bentwings

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Terry - I was two years into my four year engineering diploma when we metricated.
This permanently left me conflicted - I still conceptualize pressure, stresses etc. in psi as Pascals have never "taken" in my psyche - other than that my brain is wired to metric.
Regards, Ken
I had to laugh at this one. I too was hit with metrics in college engineering. To this day I simply can’t relate without mental recalculation or conversion To English herein the States. Certainly most calculations are easier in metric. When i5 comes to mass force and gravitational constant I have to look up the conversion to slugs. I keep thinking slugs are something used in football or hockey. I took and gave plenty in those sports. But saying I “neutoned” someone or got “neutoned” just doesn’t present the picture. Something gets lost in the scheme of things. Even measuring gas or oil or motor size in liters just isn’t right. My boat has two 454 cu in big block Chev engines that represents a lot of motor converting to metric just doesn’t seem right. But putting 100 gallons of gas in the tank at just under $4 a gallon means something . A good dent in the pay check for sure. Then using it at 30+ gallons per hour per motor means you can almost see the gas gage dropping. That’s real numbers. LOL
 

rpf

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Having been brought up an metric, used imperial when starting work I have found that both systems have their uses and do in fact compliment each other!

Here is a very interesting quote I came across a few years ago from Napoleon Bonaparte when he was imprisoned on St Helena around 1824;

"The scientists adopted the decimal system on the basis of the metre as a unit. Nothing is more contrary to the organisation of the mind, memory and imagination. The new system will be a stumbling block and source of difficulties for generations to come. It is just tormenting the people with trivia"
 

terryd

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Hi rpf,

He was obviously not a scientist or mathematician, just a warmonger after all. I should add that is not so dissimilar to at least one of todays Leaders

TerryD
 
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terryd

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I had to laugh at this one. I too was hit with metrics in college engineering. To this day I simply can’t relate without mental recalculation or conversion To English herein the States. Certainly most calculations are easier in metric. When i5 comes to mass force and gravitational constant I have to look up the conversion to slugs. I keep thinking slugs are something used in football or hockey. I took and gave plenty in those sports. But saying I “neutoned” someone or got “neutoned” just doesn’t present the picture. Something gets lost in the scheme of things. Even measuring gas or oil or motor size in liters just isn’t right. My boat has two 454 cu in big block Chev engines that represents a lot of motor converting to metric just doesn’t seem right. But putting 100 gallons of gas in the tank at just under $4 a gallon means something . A good dent in the pay check for sure. Then using it at 30+ gallons per hour per motor means you can almost see the gas gage dropping. That’s real numbers. LOL
And of course, your gallon is quite a bit smaller than here in the UK. Many folk discussing the difference in the price of petrol (gas) between the US and UK seem to think that there a huge difference and say "petrol here is around $6.25 a gallon but in the US it is just under $4" what they forget is that the US gallon is approximately 0.83 smaller than a US gallon so our equivalent price is now between $4.75 and $5.1 depending on where you are living. so not such a huge difference really plus our engines tend to be smaller and more efficient (driven by high fuel costs in the past) and fewer kilometres to travel.

TerryD
 

HennieL

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"The scientists adopted the decimal system on the basis of the metre as a unit. Nothing is more contrary to the organisation of the mind, memory and imagination. The new system will be a stumbling block and source of difficulties for generations to come. It is just tormenting the people with trivia"
So, who is this Napoleon guy - sounds like an American... 😇

Hey, come on - just joking everyone - and I did not mention the word president 😀😁

Seriously though, I became metricated back in 1970 (if I remember correctly...), and I'm forever thankful to the people who made this wise choice when I was still a teenager, especially when I occasionally have to "fight" my way through the archaic imperial fractions, not to even mention the numbered drills... 🤪
 

terryd

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So, who is this Napoleon guy - sounds like an American... 😇

Hey, come on - just joking everyone - and I did not mention the word president 😀😁

Seriously though, I became metricated back in 1970 (if I remember correctly...), and I'm forever thankful to the people who made this wise choice when I was still a teenager, especially when I occasionally have to "fight" my way through the archaic imperial fractions, not to even mention the numbered drills... 🤪
A few years ago there was a movement against the metric system in the UK, mostly by market traders who refused to use the metric weights system calling themselves "the Metric Martyrs". One of the leading members was a greengrocer who ran a market stall selling vegetables and moaned that he could pick up a handful of potatoes which would weigh just about one imperial pound. Why he never realised that the same handful was just about half a kilo or two handfuls were just about a kilo I shall never know.

On another occasion a rightwing politician, when debating metrication in parliament, declared that the Kilogram was "too heavy" for British Housewives. I'm not sure what he was implying, was he saying that British housewives were wimps (despite the fact that everyday granulated sugar was being sold in 2lb bags, near enough to 1kilo as can be), or was he saying that other housewives around the world were all 'Amazons', or that it would not be possible to buy, say, 1/2 or 1/4 kilo of anything, only he knew what he meant, and they say politicians today are a bit thick in the head?

TerryD
 

rpf

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A few years ago there was a movement against the metric system in the UK, mostly by market traders who refused to use the metric weights system calling themselves "the Metric Martyrs". One of the leading members was a greengrocer who ran a market stall selling vegetables and moaned that he could pick up a handful of potatoes which would weigh just about one imperial pound. Why he never realised that the same handful was just about half a kilo or two handfuls were just about a kilo I shall never know.

On another occasion a rightwing politician, when debating metrication in parliament, declared that the Kilogram was "too heavy" for British Housewives. I'm not sure what he was implying, was he saying that British housewives were wimps (despite the fact that everyday granulated sugar was being sold in 2lb bags, near enough to 1kilo as can be), or was he saying that other housewives around the world were all 'Amazons', or that it would not be possible to buy, say, 1/2 or 1/4 kilo of anything, only he knew what he meant, and they say politicians today are a bit thick in the head?

TerryD
Just to get it clear... I presume you mean 0.5 & 0.25 kilo?!!!
 

terryd

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A few more pictures

here is another picture of the vice mounted on the main baseplate:

DSCN3577.JPG


The 'L' shaped cutout on the upper right of the main baseplate is for clearance of the main pivot arm when beginning a bend. The half-round component at bottom right is a packing plate to raise the centre line of the form roller to the height of the vice centre line so that tubing of any size can be accommodated. The hole in the centre of that part is for the pivot of the bending arm. The actual size of these features is not actually critical. The milled out area on the moveable vice jaw is there to clear the forming roller of the main bending arm.

Cam, Cam Swivel Pin and Vice Handle

DSCN3578.JPG



The cam is made from a length of 12 mm bar which was turned down in the 3 jaw chuck to 10 mm diameter for a length of 10mm this was then parted off to a total length 0f 14mm. The 3 jaw chuck was replaced with a 4 jaw and the 10 mm diameter section of the cam blank was mounted in the 4 jaw chuck and offset by 0.4mm using a dial gauge on a magnetic stand to ensure accuracy. The centre hole around which the cam revolves was centre drilled and drilled 8mm.

To form the square on the head of the cam for the lever I used a rotary table fitted with a 3 jaw chuck. The cam blank was mounted on a homemade split mandrel to mount it on the offset pivot hole so that the handle would be centred on the pivot hole rather than the cam itself.

DSCN3564.JPG


In the above picture, you can see the mandrel which is a simple turning job. the section for mounting the cam is turned to be a good fit in its pivot hole. the centre was drilled and tapped M4 in the lathe. The head of an M4 cap head screw was turned down to an angle to match the large taper left by the centre drill in the end of the mandrel.

DSCN3563.JPG


The above picture shows the cam mounted on the mandrel after machining the square. If I need to face off any part accurately using a mandrel I ensure that the mandrel is short enough that the head of the screw expander sits inside the part being machined to allow clearance to the facing tool. Note the 1mm wide section left of the 12 mm diameter bar, that prevents the jaw lifting.

The mandrel was mounted in the 3 jaw chuck on the rotary table of the milling machine and split down the centre with an 0.5mm slitting saw. The cam blank was then mounted on the mandrel and the screw shown in the picture tightened into the mandrel. The screw does not need to be overtight as the clamping force of the split mandrel is considerable - I make these for all sorts of purposes, for example, I use one to mount loco wheel blanks on so that concentricity is assured when turning the rim and central boss.

Once the cam blank was mounted on the mandrel I set its axis at 45° so that the corners of the square would be at the thinnest and thickest part of the cam, I think that is shown in the picture above.

I set the milling cutter, and end mill, to just touch the 12 mm section of the blank using the 'cigarette paper' method and set to leave a 1mm wide section of the 12mm diameter. There is a picture of the set up below. I had calculated the amount to be removed and I did it one side at a time rotating 90° between each so that I had a good accurate square section.

DSCN3567.JPG


To ensure that I can remove and replace the mandrel accurately on centre every time I mark the position of each mandrel in relation to the number 1 jaw of the chuck in which it is used. If the mandrel is to be used on both lathe and milling machine I will mount the same chuck on each machine as necessary but normally I have one on each machine permanently - unless I am using other mounting methods such as faceplate in the lathe or table clamps on the milling machine, that is.

DSCN3570.JPG


You can see the two registration punch marks adjacent to jaw number 1 of the chuck. This mandrel will always be registered this way in what I call chuck number 2, if it had been made in number 1 chuck it would have only 1 registration punch mark, this ensures accuracy.

The cam operating handle is straightforward to make from a section of 15mm flat bar, I marked and drilled a 10 mm hole in one end and marked the square by marking the tangents of the hole using a 45° engineers square and scriber with layout blue, I then hand filed it to a good fit on the cam. The handle was then shaped by filing to what I think is a simple but pleasing shape but that is left to the maker as 'beauty is in the eye of the beholder' or so it is said.

The cam pivot pin as is shown in several of the pictures above is made from a standard M10 hex head machine screw with the tread turned off and the lower section turned and threaded M6 to match the hole in the vice baseplate. It is accurately sized to length to ensure that the cam can just rotate and the moveable jaw cannot lift more than 0.1mm or so.

Hope that is reasonably clear and anyone finds it helpful, best regards,

TerryD
 
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terryd

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Just to get it clear... I presume you mean 0.5 & 0.25 kilo?!!!

Hi rpf,

(what a horrible way to have to address you, I prefer to use a name)

Absolutely, I concur, please excuse me from falling into the vernacular.

However, I spend a lot of time in France and when ordering say, cheese, in a supermarket or a street market one asks for perhaps, a demi kilo or a quart (pronounced 'car' - a quarter, not a fluid quart) i.e. a 1/2 or 1/4 kilo, or perhaps alternatively 100 or 200gm if the fractional amounts are too much or too little. The scientific/mathematical decimal terms don't quite fit vernacular situations. So I apologise for the slip.

Yours respectfully,

TerryD
 
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terryd

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Forming arm

The forming arm is free to swivel in the main pivot arm so that it can be swung free from the tubing after forming. The swivelling pivot is around the centre hole of the arm as seen below.


DSCN3575.JPG



As you can see the lager swivel pin is shouldered to ensure that the nuts on either side do not tighten on the arms so that the forming arm can pivot freely. The dimension between the shoulders is quite important.

The lower pivot pin in the picture is a loose pin which holds the forming roller at the end of the forming arm, it is left loose as it is trapped in place in use by the main pivot arm, and is left loose so that it is easier to change the forming roller for different tube diameters (the outer diameter of this roller does not need to change, just the semicircular groove). The head is turned such that it will not jam in the locating section of the upper arm.

The forming arm is laminated from a central 10 x 15mm flat with a 3 x 15 mm flat riveted to both sides. The handle is a length of 8mm bar which has an 8mm thread screwed into the end of the centre part and Loctited into place. It is not essential to Loctite the handle if you are making a box to store the bender, in that case, the handle could be left so that it could be unscrewed for storage.

Making the arm

DSCN3576.JPG


Cut the three blanks for the fabrication and using layout blue and normal techniques mark out one of the 3mm outer arms. This involves the two pivot holes, the rivet positions and the 7.5mm radius of the ends, hole centres are centre punched. Then superglue the two outer arms together very carefully to ensure accurate alignment. Then drill the rivet holes to ensure exact alignment of both parts but leave both pivot holes undrilled. The ends should now be hand filed to their semicircular shape while they are together to ensure a consistent look. Then heat the assembly to break the bond, separated and any adhesive left cleaned off (acetone does a reasonable job of that) adhesive bond.

The hole for the handle is marked on the end of the middle spacer part of the assembly, centre punched and mounted vertically in the Milling machine vice, checking it is upright with an engineer's square. The punch mark is aligned with a 'wobbler' and the tapping hole for M8 is drilled and the hole tapped with the tap in the chuck but turned by hand while still in position in the vice. The handle is simply a length of 8mm diameter rod tapped for 10 mm ready to screw into the end of the assembly when completed.

One of the outer arms was then superglued to the middle spacer arm and the rivet holes drilled through. If you do that accurately you can now rivet all three parts together using countersunk head rivets. I actually used 4mm diameter brass rod which was annealed, I peened the upper part of the rivet into the countersunk part of the rivet hole, to do this I made a sort of rivet 'dolly' by drilling a shallow blind hole about 3mm deep in a flat bar and used that to support the lower end of the 'rivet' while I peened the upper end, The whole fabrication was turned over and supported on a plain part of the so-called 'dolly' so that the lower end of the 'rivet' could be peened into it's countersunk hole while the upper end was supported. The rivet is now filed level to the upper and lower arm and the process repeated for the other rivet.

The pivot holes are now drilled - by doing it at this stage we can ensure that the holes are all aligned perfectly. The assembly is mounted in the milling machine vice on thin parallels, and a 'wobbler' mounted in the drill chuck is used to align the centre punch mark of the forming-roller pivot hole at the end of the arm assembly. The hole is then spot drilled with a 3mm spot drill and the hole drilled. As the centre line of the arm assembly is aligned with the long axis of the milling machine the table is moved along by the dimension specified and the process is repeated for the main pivot hole. As I said, this method ensures that the pivot holes are perfectly aligned top and bottom which cannot be guaranteed if the parts are drilled independently.

I do hope that all of the above is clear. It is difficult to proofread one's own work as one understands the full meaning. If there is any clarity needed please do not be afraid to ask. It may be necessary to read the text several times to grasp its full meaning.

I'll deal with the pivot pins in a later posting when looking at the final assembly.

Here's hoping

TerryD
 

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