Do-it-yourself pipe bending without a pipe bender


The home mas­ter is well aware of the advan­tages of pipe met­al. From the basics of strength of mate­ri­als, we know that the moment of resis­tance of a tubu­lar sec­tion is much greater than that of a sol­id one with the same area. There­fore, pipes have increased val­ues ​​of allow­able bend­ing stress­es. But this also presents cer­tain dif­fi­cul­ties when try­ing to bend a prod­uct at home: with­out the appro­pri­ate tool, you will most like­ly receive a part with a deformed sec­tion and with unaes­thet­ic folds. Rent­ing (and, even more so, pur­chas­ing) the nec­es­sary equip­ment is in most cas­es unprof­itable. How­ev­er, you can bend the pipe with­out a pipe ben­der, and in sev­er­al ways.

Why do metal pipes bend badly

They bend well, the prob­lem lies in the unsat­is­fac­to­ry appear­ance of the prod­uct, which is accom­pa­nied by a dis­tor­tion of the perime­ter. The lat­ter cir­cum­stance is espe­cial­ly crit­i­cal for pro­file pipes of rec­tan­gu­lar, square or oval sec­tions.

In the process of plas­tic bend­ing, dif­fer­ent sec­tions of the pipe are under the influ­ence of stress­es of the oppo­site sign. The out­er sec­tions at the fold are stretched, and the inner ones are com­pressed. If com­pres­sive stress­es are safe for most met­als, then ten­sile stress­es con­tribute to the for­ma­tion of cracks and tears. This is espe­cial­ly true for pro­files that are made from mate­ri­als of medi­um plas­tic­i­ty, for exam­ple, medi­um and high car­bon steels, nick­el-free stain­less steels, some brands of bronze, etc. It is very dif­fi­cult to deter­mine the exact grade of the met­al from which the prod­uct is made with­out the appro­pri­ate tools and devices dif­fi­cult.

met­al pipes

Bend­ing, as a process of plas­tic defor­ma­tion, is gen­er­al­ly quite capri­cious to the con­di­tions of its imple­men­ta­tion. To achieve a pos­i­tive result, you will need:

  • Take into account the phe­nom­e­non of spring­back of the bent pro­file, in which the final val­ue of the bend­ing angle is always less than the cal­cu­lat­ed one.
  • Ensure accu­rate fix­a­tion of the bend area to pre­vent dis­place­ment of the work­piece.
  • Deter­mine the min­i­mum required val­ue of the radius of cur­va­ture of the deform­ing tool.

There­fore, before start­ing work, they are deter­mined with the min­i­mum pos­si­ble bend­ing shoul­der, bend­ing method (open or closed), as well as the sequence of oper­a­tions. In par­tic­u­lar, suc­cess­ful bend­ing is guar­an­teed if the ratio r/s > 5 (here r is the assigned bend­ing radius, s is the wall thick­ness).

In the future, options for self-bend­ing pipes are con­sid­ered, which can be imple­ment­ed at home.

Option one — bend the pipe with heating


In this case, no spe­cial devices are required at all, it is enough for the mas­ter to have an oxy­gen-acety­lene torch or a con­ven­tion­al blow­torch. In the first case, the mouth­piece should be locat­ed at some dis­tance from the place of the intend­ed bend. The torch should not be made con­cen­trat­ed, since in this case the tem­per­a­ture dif­fer­ence between the zones will be too large, and the plas­tic char­ac­ter­is­tics of the mate­r­i­al will be uneven (this is espe­cial­ly true for car­bon steels con­tain­ing an increased per­cent­age of man­ganese and sil­i­con). ).

Pipe bend­ing by heat­ing

After heat­ing to the required tem­per­a­ture (it is eas­i­ly cal­cu­lat­ed from the tint col­ors), the part to be bent must be clamped in a bench vise, and the desired sec­tion must be free-bent.

Heat­ing with a burn­er is more uni­form, but is asso­ci­at­ed with the risk of reduc­ing the strength of the work­piece mate­r­i­al, espe­cial­ly if it is intend­ed for use in pres­sure pipelines. It is bet­ter to use a blow­torch in order to avoid unnec­es­sary vaca­tion. The fol­low­ing sequence of oper­a­tions is rec­om­mend­ed:

  1. The sec­tion to be deformed is clamped in a bench vise, for which spe­cial rub­ber pads are used that do not dam­age the met­al.
    Clamp­ing in a vise of a bent part of a tubu­lar bil­let


  2. Light a blow­torch, bring it to the required area, and, even­ly turn­ing the flame source around the out­er diam­e­ter of the pro­file, warm it up. Note that it is impos­si­ble to over­heat the pipe with the heat ema­nat­ing from the blow­torch torch, but you can smoke it.
  3. Turn off the blow­torch, move the heat­ed area to a dis­tance equal to the allow­able bend­ing arm. Fur­ther, using a tubu­lar wrench (some­times even man­u­al­ly), bend the prod­uct, some­times using a tem­plate.
Heat­ing a tubu­lar blank with a blow­torch

Bend­ing with heat­ing, for all its sim­plic­i­ty, is char­ac­ter­ized by the fol­low­ing lim­i­ta­tions:

  • Degrades the appear­ance of the mate­r­i­al.
  • If the heat­ing tem­per­a­ture is insuf­fi­cient, the for­ma­tion of folds along the inner radius of the bend is like­ly (it is impos­si­ble to cor­rect such a dis­ad­van­tage).
  • The process requires as quick bend­ing as pos­si­ble, because thin-walled pipes cool quick­ly.
  • The tech­nol­o­gy is not rec­om­mend­ed for small bend­ing radii.
  • Increased safe­ty require­ments must be met because open flames are involved.

Most often, a pipe made of stain­less steel or non-fer­rous met­als is bent in this way, which, when heat­ed, are not prone to oxi­da­tion.

Option Two — Using Back Pressure

Fail­ures in con­ven­tion­al pipe bend­ing are often asso­ci­at­ed with the pres­ence of an unbal­anced stress-strain state of the work­piece, when the exter­nal pres­sure from the work­ing tool is not bal­anced by inter­nal coun­ter­pres­sure (the resis­tance of the met­al itself is not enough in this case, since it is obvi­ous­ly below the plas­tic lim­it).

Such back­pres­sure can be achieved by inject­ing a gas, liq­uid, or oth­er incom­press­ible work­ing medi­um, which is char­ac­ter­ized by high com­plex­i­ty. Gas and liq­uid are exclud­ed, because at home it is very dif­fi­cult to per­form a sta­ble seal­ing of the open ends of the tubu­lar blank. But sand or fine slag is always avail­able — they are homo­ge­neous, non-tox­ic and easy to han­dle.

Con­sid­er the sequence of bend­ing a round tubu­lar pro­file with the appli­ca­tion of coun­ter­pres­sure:

Sub­se­quent bend­ing of the heat­ed sec­tion


  1. First you need to install a plug on one of the ends of the work­piece, for which you can use a reg­u­lar bolt (see Fig. 5). The bolt shaft must fit snug­ly into the inner hole.
  2. We pre­pare the aggre­gate, it must be uni­form and small so as not to cre­ate inter­nal voids. For peri­od­ic sand/slag com­paction, any pin of suit­able diam­e­ter is used as a pis­ton (see Fig. 6). The entire tubu­lar blank must be com­plete­ly filled with filler (see Fig. 7).
  3. The work­piece is placed in a vise and bent. Since the ten­sile strength of sand or slag is always low­er than that of the mate­r­i­al of the part, rup­ture or crack­ing will not occur. After bend­ing, it is nec­es­sary to care­ful­ly clean the inner lumen of the pipe from the rem­nants of the filler.

Option three — the use of tension springs

To imple­ment the method, a spe­cial spring is required, the out­er diam­e­ter of which should be as close as pos­si­ble to the inner diam­e­ter of the work­piece. The range of ten­sion springs is giv­en in GOST 18794–80; their char­ac­ter­is­tic fea­ture is the pres­ence of an annu­lar grip on one of the ends. This cap­ture can be closed, as shown in Fig. 8, or in the form of a curly hook. The lat­ter is con­sid­ered to be prefer­able, since it pro­vides a more con­ve­nient extrac­tion of the spring from the work­piece after the bend­ing process is com­plet­ed.

Installing a plug in one of the ends of the pipe
Com­paction of the back­filled mate­r­i­al
Pipe filled with filler
Exten­sion spring appear­ance
Ver­sion of the exten­sion spring with a shaped grip


The select­ed spring is insert­ed inside and secure­ly fixed at the oppo­site end of the pipe. Since the out­er sur­face of the spring fits tight­ly against the wall, it pro­vides the same back pres­sure as the inter­me­di­ate medi­um in the pre­vi­ous embod­i­ment. The advan­tage of the method is that such bend­ing springs can be used repeat­ed­ly.

The last option — why even come up with some kind of bending technology

In some cas­es — for exam­ple, when the r / s ratio is much high­er than the min­i­mum rec­om­mend­ed val­ue — suc­cess­ful bend­ing of the pipe in a cold state with your own hands is pos­si­ble, pro­vid­ed that one of the ends is firm­ly fixed, fol­lowed by bend­ing accord­ing to a pre-pre­pared tem­plate.

The tem­plate is made of mul­ti­lay­er ply­wood, you can even use the out­er sur­face of any durable object that is suit­able in diam­e­ter — a bar­rel of water, or a wood­en flow­er­pot. One of the ends is fixed in a clamp / vice, and the oppo­site one is bent along the required radius (see Fig. 10). In this way, it is quite pos­si­ble to obtain, for exam­ple, blanks for the steel frame of a green­house or green­house. After defor­ma­tion, it is not worth imme­di­ate­ly releas­ing the part from the clamps, since any met­al has iner­tial prop­er­ties.

In all cas­es of bend­ing with­out a pipe ben­der, you should pre­pare:

  • Stock up on levers (the bend­ing moment, depend­ing on the required para­me­ters and pipe mate­r­i­al, can be quite large).
  • Pre­pare a tem­plate that must be accu­rate­ly dimen­sioned for the char­ac­ter­is­tics of the bend­ing area.
  • Thor­ough­ly clean the inside of the bent pipe (par­tic­u­lar­ly if the prod­uct is to be used for pump­ing liq­uid media).

Before start­ing work, it is worth remem­ber­ing the sim­ple safe­ty rules. Before bend­ing by hand, it is advis­able to wrap the work­piece with coarse leather, burlap or oth­er dense fab­ric — this will pro­tect your hands and cre­ate addi­tion­al fric­tion that will pre­vent slip­page dur­ing bend­ing.

Large radius bend­ing of steel pipe


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