JD Squared 3 - Page 15

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Ifwenowrepeatedthesecondbend,usingthesame125/8"fromtheendofthetubing+2"fortheextratubingweallowed,
wewouldendupwithahoop1/2"toowide.Thisisbecausethe1/4"stretchdevelopedintherstbendwillalsobedevelopedin
thesecondbend,givingus1/2"totalincreaseinwidth.Notagooddealifyouonlywanta40"widehoop.Sowhat'sthesolution.
Actually there is two ways to do it.
FIRSTMETHOD:
Lookatgure27andnoticethesecondbendstartsatthetopofthehoopandnotatthetopoftheuprightastherstbenddid.
Also the start of the second bend is drawn as 13 1/2" from the center mark. If you take the 13 1/2" measurement and subtract
the1/4"ofgrowththatwasdevelopedintherstbendandanother1/4"tocompensateforthesecondbend'sgrowthyouendup
with13".Subtractanother3/4"toaccountforthe3/4"BendStartlocationontheBendingDiesetandwehaveanalsettingof12
1/4".Noticewedidnotsubtractan1/8"forspringback.Thisisaccountedforalreadyinthe1/4"weaddedforthesecondbend's
growth.SetthetubesothattheBendingDiesedgeisexactly121/4"fromthecentermark.Makesuretheuniversalprotractor
reads'0'andthecarpenter'sleveliscentered.Asonenalcheckyoucanalsomeasurefromthefarsideofthecompletedbend
totheedgeofthebendingdie.Seegure28.Thismeasurementshouldread:
40" (width of hoop) - 3/4" (radius of tube not in bending die) - 1/8" (springback allowance) = 39 1/8"
Makethesecondbend.Measuretheheightoftheseconduprightandcutofftheextratubingweallowedforearlier.
SECONDMETHOD:
Thesecondmethodisbasicallytheoppositeoftherstmethod.ThesecondbendwillstartatthebottomoftheuprightandNOT
atthetopofthehoopasintherstmethodandasshowningure28.Weusethesamemethodasusedtobendtherstbend
withafewexceptions.Firstcalculatethestartingpointforthesecondbendasshownbelow:
20" (total height of hoop) - 6 1/2" (CLR of bending die) - 3/4" (Bend Start) = 12 3/4"
Add2"toaccountfortheextratubingweallowedearlier.Alsoaddthe1/4"growthdevelopedintherstbendandanother1/4"for
thesecondbend.DONOTADD1/8"SPRINGBACK.Onceagainthisisalreadyaccountedforinthe1/4"growthofthesecond
bend.Weendupwith:
12 3/4" + 2" (extra tubing) + 1/2" (growth for both bends) = 15 1/4"
Setthetube'sendat151/4"fromtheBendingDie'sedge.Makesuretheuniversalprotractorreads'0'andthecarpenter'slevelis
centered.Makethesecondbend.Measuretheheightoftheseconduprightandcutofftheextratubingweallowedforearlier.
Thank you for purchasing a JD Squared bender. Any further questions please contact us.
21"
39 1/8"
Start of 2nd bend
Center mark on tube
Start of 1st bend
C
L
Figure 28