# Mini Tube bender.



## terryd (Jun 23, 2020)

Hi,

I'm building some live steam models and will need to bend quite a few tubes in the near future.  One pressing need was to make a pressure tester for the boilers I build and this also involved some mini tube bending - 3 mm diameter in this case.  So I decided to make a manual bending device to ensure consistent bends - well actually I could have used many methods such as filling the tube with an incompressible material and just bending around suitable diameter bar but I like to have a method of reliable reproduction of results so I decided to make a device.  Besides I'm a masochist and have the time to indulge myself now I'm retired and shielding from Covid-19.

 I looked up quite a few types of bender on the internet and eventually came up with a nice design by one C. Horace Clarke from Model Engineer published in March 1956.  It was a bit complicated but I quite like the challenge using techniques I've not used before, or not recently at least.  I had also seen another design on a forum, not sure which one now, could even have been here and that looked as if it was derived from the one by Horace Clarke.







*This is the one that I found on the forum* which if you examine carefully is very similar to H Clarkes but a bit simpler.  Here is Mr Clarkes from Model Engineer





*Design By C. Horace Clarke*

The main difference besides a few minor details is that the upper Device shown by Mechman48 does not seem to have the clamping mechanism of the Clarke design.

Anyway here is my version of the Clarke bender, actually an exact copy except that I converted to metric from the original Imperial measurements as most of my equipment is metric apart from some Imperial stuff (BA taps, rules etc):





* My version of Mr Clarkes Bender.*

The clamp jaws at the bottom are operated by a cam which is in turn operated by the short flat lever, this clamp prevents the tube from being pulled through the device while bending.  It uses split collets of suitable diameters for different size tubing up to 8 mm, I have made a 3mm and 2 mm ones at the moment for my immediate needs. The brass collet is seen running through the clamp jaws in the picture.   The clamp overall is adjustable in relation to the fixed roller to enable different roller diameters to be accommodated (for different radius bends and diameter tubing) which explains the slots just visible in the base.  The shiny screws shown at the top right are homemade taper screws which lock the arms to the fixed roller spindle.   The long screws enable the lever arm to be adjusted to roll tube around larger diameter fixed rollers.

The bending roller is in an adjustable lever handle which locks in place while bending but releases when retracting the lever and swings out of the way so that the tube can be manipulated.  You can just see the head of the loose pin which holds the bending roller in the lever arm this head locks into a cutout milled in the upper arm which causes it to lock when bending but allows the arm to swing clear at other times, a rather elegant solution, to me at least.





*Another View of the Bender *- the cross head screws are temporary while awaiting delivery of suitable rivets.

This view shows the split collet clearly, the device can make bends up to 180° hence the cutout in the RH clamp jaw (the one fixed with screws).  You can also make out that the clamp is mounted on its own baseplate which is adjustable on the main base.  You will note that the material is not highly finished, it's deliberate, it's not just laziness - I suffered a devastating garage fire in 2010 and much was lost but most of my materials survived but had to withstand not only very high temperatures for several hours but also drenching by the fire crews who attended and several days in the rain before they could be rescued and stored in a new shed erected specially for the purpose.  I still use these materials and de-rust and clean as necessary.  By not bringing then up to a high level of 'bling'  I am reminded regularly of the fire and to take precautions to prevent a second happening.

*Initial Test *

To test the device I made up a connecting pipe for my boiler tester rather than just making random bends.  I first made up a copper wire pattern,






Then I made the bends using the wire as a pattern:






Which was trimmed and fitted using o rings to seal:






Overall a rather satisfying project only spoiled by my making some stupid errors resulting in reworking or remaking some parts which others of course never do or so I suppose.

I have more pictures of the making as well as copies of the drawing which I could turn into an extension of this thread explaining the stages of manufacture if anyone is interested. - let me know.

TerryD


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## minh-thanh (Jun 23, 2020)

*terryd !*



terryd said:


> Overall a rather satisfying project only spoiled by my making some stupid errors resulting in reworking or remaking some parts which others of course never do or so I suppose.
> 
> I have more pictures of the making as well as copies of the drawing which I could turn into an extension of this thread explaining the stages of manufacture if anyone is interested. - let me know.
> 
> TerryD



Please extend  of this thread .. 
Thanks!


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## Ken I (Jun 23, 2020)

Excellent bender Terry.

Not to steal your thunder, I posted my own bender some time back




You mount it in a vice and the stops permit "production runs" of bends.
For whatever reason, it appears to have disappeared off the Downloads section so I have added the files here for anyone who's interested.




I have bent 7mm diameter mild steel with this rig - but I have to admit that comes close to breaking it.
Regards,  Ken


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## terryd (Jun 23, 2020)

Ken I said:


> Excellent bender Terry.
> 
> Not to steal your thunder, I posted my own bender some time back
> View attachment 117359
> ...



Hi, 

that's a lovely piece of work, not quite as adjustable as the one from Mr Clarke but would have been sufficient for my purposes but as I said, I'm a bit of a masochist and enjoyed some of the challenges and at the moment I have no need to bend solid rods.  I also like the ability of Mr Clarke's design to firmly clamp the free end of the tube as I found on an earlier type I tried without such clamping that the tube tended to creep while bending and this affected the accuracy where multiple bends were involved and I don't have the skill needed to make allowances for such movement.

But again, a lovely piece of work demonstrating good skill levels

TerryD


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## terryd (Jun 23, 2020)

minh-thanh said:


> *terryd !*
> 
> 
> 
> ...




Hi Minh-Thahn,

I will do that if there is more demand,  in the meantime I will sort out the pictures and put them into some sort of order.

TerryD


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## ICEpeter (Jun 23, 2020)

Hello,
If anyone is interested to take a look at another pipe bender please search for a post titled "Bending brass tube" that I contributed to in 2015.


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## Ken I (Jun 23, 2020)

Terry, thanks for the comments - once again sorry for butting into your post but since Minn-Thahn was asking I thought I would just add in the link to my plans - but could no longer locate or find it - I did find the PDF file but not the rest - curiously missing - probably during the platform change a couple of years back ?
You are correct about "creep" - I never provided for clamping to stop it - I was aware it would happen but didn't concern me at the time as I intended to dress to size after bending. As you say you can allow for it but in retrospect the omission of clamping was an oversight.

I just dropped the plans I had to hand in here for Minn-Thahn's perusal more than anything else.
Look forward to any further elaboration you might provide on yours.
Regards, Ken


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## stanstocker (Jun 24, 2020)

A nicely done tool indeed.  Thanks for posting your pics and descriptions, look forward to additional pics you choose to share.

For those interested, the ME issue with these plans is 2861, 22 march 1956.  Pages 470 to 473.  Looks like a nice little bender to be sure, and here I was thinking the project list was getting down to only three lifetimes of things to enjoy making!

Best to all,
Stan


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## minh-thanh (Jun 24, 2020)

*Ken I !*


Ken I said:


> Excellent bender Terry.
> 
> Not to steal your thunder, I posted my own bender some time back
> View attachment 117359
> ...



Great tool !
Thank you for sharing the plan  .

*ICEpeter !*
I will find
Thank you.


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## HennieL (Jun 24, 2020)

terryd said:


> I will do that if there is more demand...



Terry, consider this as more demand 

Actually, I would never dream to demand - but please, do post your plans and/or construction details if you can - I too would like to try my hand at making a mini tube bender, and your model looks really nice.

Thanks in anticipation


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## terryd (Jun 24, 2020)

HennieL said:


> Terry, consider this as more demand
> 
> Actually, I would never dream to demand - but please, do post your plans and/or construction details if you can - I too would like to try my hand at making a mini tube bender, and your model looks really nice.
> 
> Thanks in anticipation



HI Henniel,

How can I resist?  I know that in French at least to demand or command is not as strong as in English so I'll forgive you.  Please be patient I have other projects on the go but will post within a few days and take it step by step.

I hope that is ok.  Here's another view just to help in the meantime






Best regards

TerryD


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## HennieL (Jun 25, 2020)

Thanks Terry,



> Please be patient I have other projects on the go but will post within a few days and take it step by step.



No rush - projects come first


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## terryd (Jun 28, 2020)

*Baseplate and vice:*

Hi'
the baseplate and vice are made from standard flat stock.  They are relatively simple to make mostly using hand tools, bench drill and milling machine.  I missed some pictures but the processes are quite straight forward to understand and parts made.






*Vice and baseplate sub-assemblies*

The marking out from the drawings was done with standard tools, I use a cheap digital vernier to draw lines parallel to.edges, an engineers square and scriber to layout hole centres, a spring divider for stepping out multiple hole centres and arcs, and a centre punch for spotting hole centres.
I marked out the four major components: the main baseplate, the vice plate and the two jaws. and spot drilled using a small spot drill, not a Slocomb pattern, and drilled the main holes on the drill press, the two baseplates were then assembled using superglue (cyanoacrylate adhesive)






*Vice and main baseplates secured with superglue and drilled*

The holes in the upper vice baseplate were spotted through to the main baseplate on the drilling machine,  This was to ensure accurate alignment of the slots in the baseplate (see picture above) which will eventually enable the whole vice to adjust to larger diameter rollers and different diameter tubes in the range 2 to 8 mm diameter.

The baseplate was completed by sawing out the top right-hand section leaving a filing allowance which was quickly filed to size and draw filed to a reasonable finish.  It was not worth setting up the milling machine as accuracy is not crucial, the cut out is merely for clearance of the moveable arm.  The round bar with holes to the left is my small tapping guide. it is drilled for taps from 2mm to 8 mm plus there are holes drilled to accommodate other sizes (e.g. BA, small Whitworth) which I drill as needed.  I used the guide to tap the holes in the vice baseplate.  These holes are used for studs which pass through the slots in the baseplate.  The studs can be seen in the picture of the underside of the vice.  I prefer that solid plain rod slides in the slots rather than a threaded part.







*Underside view of the vice showing the studs secured with Loctite*

The studs were made by threading a  6mm length of a 5mm rod in the lathe using my home made tailstick dieholder.  The correct length was cut off, the end of the rod faced off and process repeated.  The studs were threaded by reversing in the lathe collet and threaded by the same process as before.  Using the collets meant that the already threaded end is not damaged.

The manufacture of the vice jaws themselves and the clamping pivot was a little more complicated and will be described in the next posting.

I am preparing a new set of drawings translated to metric dimensions and I will publish these as well as the original imperial drawings.

TerryD


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## Roskrow (Jul 2, 2020)

I have been following the item on Mini Pipe Bending, and have a simple solution to offer.

I have a Mini bender made by Record Tools ... This is now known as Irwin Record the model is No. 210 Mini Bender

It is available on line at Amazon (UK) and covers Capacity 3, 4, and 6mm. O.D. 1/8, 3/16, and 1/4in O.D. 

Cost about £29.00. I find it excellent.
Hope that is a help
Malcolm Farrant


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## terryd (Jul 2, 2020)

Hi Malcolm,

I know about those benders.  They are good, I have a couple of similar ones which cover 3mm to 12mm tubing, after that, I tend to use bending springs but they do not have the wide range of applications, bend radii and tube diameters than many of the workshop designs available, the design I have chosen works from 1 mm to 8 mm tubing simply by making the correct size guides and rollers and the bend radius can be from 3 to over 25mm according to tube diameter and forming roller size. 

 Furthermore, personally I really enjoy making working high-quality tools as part of my workshop activities and by making from available stock in my workshop they cost zero.  Of course, I can't speak for everyone but I'm just publishing this for like minded folk.  My latest tools include this versatile bender, an equally versatile ball turning device, and a tailstock die holder which accommodates thread diameter from 2mm to 8mm threads up to 300mm long.  I regularly use the latter to make 5/32" BSW threaded rod, 11 1/2" long for my Meccano builder friends.  Such versatility is often not available on commercially produced products for the home workshop.

Best regards

TerryD


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## Roskrow (Jul 2, 2020)

Terry, You are Correct....But I am just Old and LAZY !!
Best wishes
Lazy Malcolm


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## terryd (Jul 2, 2020)

*Mini Bender Jaws*

Hi,
 I have attached a pdf of the original document by Mr Clarke from the 1956 Model Engineer.  I was reluctant to publish earlier due to copyright considerations but discovered that the present owners of the magazine only have the copyright on articles published since they have owned it, the copyright on an article from before reverted to the original author and if he wishes I will remove it.  I believe that this is the reason that John Tom can publish ME designs from an era before the present owners of the magazine.

Anyways up, on to the making of the jaws for the bender.  These are made from two 3/4" (20mm)x 3/8" (10mm) stock x 1 3/4" (44mm) long flat stock.  In order to make the semicircular longitudinal cutouts for the clamp, he suggests mounting them on the lathe cross slide side by side on suitable packing to raise the height and with 1/16" (I used 0.7mm) packing between the jaws longitudinally, and then and drilling using a chuck mounted 5/16" (8mm) drill.  


I did it rather differently.  I glued the jaw blanks side by side with a strip of thin stainless steel between them,  I then mounted them vertically in the Vice jaws of my milling machine such that they were pressed together and ensured that they were vertical  I also used a toolmakers clam to prevent them coming apart while drilling.  I then set the centre of the jaws to be drilled on the centre of the mill using a 'wiggler', I spot drilled and then finally used an 8mm jobbers drill to drill through to size.  I didn't drill a pilot drill due to teh set up, it had to be all or nothing, and it was 'all' luckily.  I had of course taken extra safety precautions because despite doing such stuff since 1963 I still have two good eyes, eight working fingers and two thumbs.






*Jaws drilled* Note the other holes.

While in the milling machine chuck I also drilled the hole which is the basis for the cut out in the fixed jaw to allow 180° bends to be produced.  I drilled 3 rivet holes in that yaw and 1 x 10 mm hole for the clamping cam in the moving jaw  You can make these out in the pictures above and below






*Another view of the jaws*

This shown more clearly the arrangement of holes in the jaws.  The waste was removed from the fixed jaw where the long hole can be seen to produce a step for clearance of the tube when making a 180° as mentioned above. as can be seen below.  Being a masochist I used a hacksaw and files to remove the waste.  I love doing things manually for several reasons.  First I like the quiet, gentle rhythms involved in hacksawing, filing etc and they are both quite easy to do if you used the correct blades and grades of file for the job in hand.  I am quite happy to hand cut a length from a 50 mm (2") round bar when making loco wheels and through make that cut accurate so that the length can be faced off in one pass usually, occasionally I may veer off a little but that is usually because I can't be bothered to change a slightly worn blade.
Such exercise also helps to prevent muscle wastage which is a part of growing old and sedentary.  The process of hacksawing uses many of the upper body muscles not just the arms and of course I do it standing so my leg muscles are getting a bit of a workout to add to my walking.  SAves a fortune in Gym fees alongside my gardening activities.





*View showing the fixed jaw shaped to allow 180° bends*

My Clarke also suggests not using a reamer as the texture left from a dill will help the gripping action of the jaws.  I have made a couple of sleeves to allow in my case 2 and 3 mm tubing to be accommodated and will make more as needed.  These can be seen in the picture above and ae simply turned brass leaving a collar, then drilling the appropriate size then slitting along both sides.  The slit goes completely along one side but stops about 5 mm short of the end on the other.  This section is then thinned to leave about 2 mm of material.  I used a junior hacksaw to cut the slits as I couldn't be bothered to set up a slitting saw on my milling machine for such a small job.





*Image showing pivot pin and eccentric (centre left) and clamping jaw (top left)*

To fasten the fixed jaw to the vice baseplate, I glued the jaw on to the baseplate using superglue (cyanoacrylate) spotted the holes through with a suitable size spotting drill then drilled tapping size for M3 screws (for temporary fixing) using my tapping block to ensure vertical tapped holes and then fixed with M3 countersunk screws.  The clamping jaw was a little more difficult as the hole centre is based on the eccentric one in the cam and not the hole in the jaw itself.  I did this by light clamping the loose jaw in position with the cam set in the hole in the jaw set just before full clamping pressure would be applied.  I had to find the centre of this eccentric hole in the baseplate and I wasn't sure how to go about it, which I'm sure most of you all would know a method.  What I did is that while everything was clamped in position I made a length of brass to fit the eccentric hole and drilled a 1.6mm hole on centre to accommodate an old gramophone needle (of which I have a few to make replaceable tip scribers and they work remarkably well).  The brass was put in the eccentric hole, the gramophone needle inserted and hit with a hammer indicating the centre of the hole.  I'm glad to report that no gramophone needles were injured or otherwise harmed in the making of this bending machine.

That's about all there is to say on the making of the jaws.  I'm still awaiting countersunk head soft iron rives, you wouldn1t believe how difficult they are to find. I may have to make do with homemade brass ones which will be strong enough for such light clamping.  If anything needs clarifying please let me know and I will do my best to please!


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## terryd (Jul 2, 2020)

Roskrow said:


> Terry, You are Correct....But I am just Old and LAZY !!
> Best wishes
> Lazy Malcolm




Hi Malcolm, 

 I too am old with not too may left and have always thought of myself as lazy, but as I have been retired for many years than I care to remember I take my time.

Best regards

TerryD


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## HennieL (Jul 3, 2020)

terryd said:


> Furthermore, personally I really enjoy making working high-quality tools as part of my workshop activities and by making from available stock in my workshop they cost zero.  Of course, I can't speak for everyone but I'm just publishing this for like minded folk.


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


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## terryd (Jul 4, 2020)

terryd said:


> *Mini Bender Jaws*
> 
> Hi,
> I have attached a pdf of the original document by Mr Clarke from the 1956 Model Engineer.  I was reluctant to publish earlier due to copyright considerations but discovered that the present owners of the magazine only have the copyright on articles published since they have owned it, the copyright on an article from before reverted to the original author and if he wishes I will remove it.  I believe that this is the reason that John Tom can publish ME designs from an era before the present owners of the magazine.
> ...






HennieL said:


> 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,

I mentioned using a brass insert and old gramophone needle and I forgot to photograph the process so I just made a reconstruction and pictured it as an aid to understanding.  Note that the cam is positioned so that it is in maximum clamping mode whereas you really need to adjust it so that it clamps fully just before that maximum think 10° before TDC (for internal combustion aficionados) then the work can be clamped in the direction such that the clamp tightens if there is any movement of the work being clamped.






*This is a reconstruction of the pivot centre finding*

The brass insert fits the hole in the cam quite closely and the centre hole in it was drilled to a sliding fit for the needle,  Note that  I had to move the clamping jaw to the left as the needle dropped through the existing hole in the clamp plate.  When I did it originally I included the brass adapter and lightly clamped the jaws together with toolmakers clamps take care ot to clamp the jaws too tightly..


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## terryd (Jul 4, 2020)

HennieL said:


> 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


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## Stefan-K (Jul 5, 2020)

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


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## terryd (Jul 5, 2020)

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


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## terryd (Jul 5, 2020)

[


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## Ken I (Jul 6, 2020)

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


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## terryd (Jul 6, 2020)

Ken I said:


> 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.
> 
> ...



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


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## Bentwings (Jul 6, 2020)

Stefan-K said:


> 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.


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## Ken I (Jul 6, 2020)

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


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## Bentwings (Jul 6, 2020)

Ken I said:


> 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


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## rpf (Jul 7, 2020)

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"


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## terryd (Jul 7, 2020)

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 (Jul 7, 2020)

Bentwings said:


> 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


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## HennieL (Jul 7, 2020)

rpf said:


> "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...


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## terryd (Jul 8, 2020)

HennieL said:


> 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


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## rpf (Jul 8, 2020)

terryd said:


> 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?!!!


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## terryd (Jul 8, 2020)

*A few more pictures*

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







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




*


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.






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.






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.






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.






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 (Jul 8, 2020)

rpf said:


> 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 (Jul 8, 2020)

*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.








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




*

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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