Cutting Truck Frame

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I am taking 10" out of my '89 pick-up frame, just in front of the rear cab mounts. Does anyone have any advice on the cut and bracing used to make this as tough (tougher) than new. I was told cutting with a Plasma in a z-pattern (stairs) is best...any thoughts? Should I tack a cross brace in front of the cuts to keep it square??I have access to an old tig welder...will this do the job? What thickness of plate should I use to reinforce? Should I reinforce the inside of the frame with a piece? Thanks!
Reply:Are you taking it out of the cab section or the rear section?Disclaimer; "I am just an a$$hole welder, don't take it personally ."
Reply:cab section in front of the rear cab mounts. The old cab was 10" longer than the new (older) one.
Reply:I've shortened and lengthened many truck frames over the years.  In fact, I have a stand made that is adjustable height, will span the width of the frame channels, and has 4 heavy duty casters.  I position the truck on a level floor, position jack stands under the part that will be stationary and my moveable stand under the other section. I make the cut (I use torch and prepare a butt joint), prepare the weld joint by beveling, roll the sections together, clamp and do comparative measurements to insure I have frame rails as straight and parallel as posible. Weld with MIG, grind the outside weld smooth to accept a plate, attach and weld plate.  On a P/U, you'd probably only need a 1/4" plate on the outside. Shape of the plate is your choice.  Some like the diamond, some rectangular, some square.  I lean toward the rectangular as I like to have the plate extend at least 6-8" on each side of the frame weld joint. On heavier duty trucks I'll add flat stock on top and bottom rails and perhaps another plate on the inside of the frame channel.  Sometimes I have to install another frame rail that will fit between the flanges (real heavy duty stuff).  Some frame jobs require bolting the things together and no welding (heat treated frames, although I have welded these also). One frame job I did:  A guy brought me a 2 Roll Back trucks.  One had a car caught fire on the bed, the cab was good.  The other the front part was destroyed by fire.  I cut the frame behind the cab on the good front, cut the frame on the other at the same location, rolled the pieces together.  Different frame designs, One was a wider frame Channel. Both Fords, 1 year apart.  At least the widths were the same.  Got the job done and it's still in operation.Never heard of the "Z" cut.  Doesn't mean it's not used, or a common practice somewhere.  Just not here in Central PA.Good luck with your job.
Reply:Pics might help.   Its always cool if your able to sleeve a frame sometimes w/ 2x4 or slightly smaller or bigger stock.     There are plenty of ways of doing it.  Post up some pics if your able.  Im sure your get some good answers. weld it like you own it
Reply:Thanks for the tips...a guy on my Toyota Forum suggested this site. This was very good advice as this seems to be where the experts are who have done these jobs with success.
Reply:I like to cut the frame on a 45* angle, but its not necessary.  Sometimes they are just broke straight.  I make a plate that is twice as long as the frame is tall.  If I use a rectangular plate, I don't weld the ends and plate the flanges the same way.  Sometimes the way the truck is built only one flange plate makes it on the truck or the length is shorter due to a cross member or what ever.  Its no big deal. 7018, or MIG are MY choices.  You sure can tig it if you are good at out of position. I did  a cheby pick up with an SP100 using flux core.  (flame away!)I never heard of the Z thing.  As long as you do a good job, fitup is good, and a plate is added, you will be fine.David Last edited by David R; 10-07-2008 at 08:50 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Guys whats your opinion on doing a rosett weld on the rectanglar plate along with the other welds?Drill a hole say 1/2" and weld up the hole instead of welding the ends.  R U confused yet?I've done it once ...just never heard anyone else do it.  weld it like you own it
Reply:I watched a episode of "TRUCKS" on Spike not long ago.  They cover this on one of their shows.  A '65 chev long box was converted to a short box.  If you check their web site, you may be able to view the shows.   In addition, they also covered shortening the box it self.  It was interesting to watch.
Reply:The z cut that he is referring to Is a stair step you cut straight downt o the half-way point then cut straight across the frame the same amount as the down cut then cut straight down again. I learned this a long time ago it gives a lot of area to weld so you have to watch how much heat you build up. I like to weld the verticals then let it cool weld the horizontal. On the inside add a a formed channel. This can be welded or bolted. Bolting it seems to work really well especially if you drill the holes with an annular cutter and your inner frame goes well past the heat affected zone as the annular cutters don't destroy the heat treatment. Now I know from reading similar post that there will be some who disagree with this but thats how I do it and it seems to work well so take a lil from mine a lil from the others and come up with something that works for you.
Reply:To make your Z cut , make a template out of a piece of sheetmetal, Mark the area of the cut in the front of the chassis, then slide it back the amount you want to take out of the frame and mark it again. this will give you a very good match on the joint. cut the top of the line on the first cut. Cut the bottom of the line on the second cut, Use a die grinder or saws all with a demoition blade or a fire rescue blade by Lenox. This will give you a very accurate cut unless you have a plasma which is even better. Clamp a flat stock along the top rail to push the template against for even better accuracy. There are sites on the web for truck and body builders that detail factory recomendations for truck frame alterations. They also use the plug weld methods."Si Vis Pacem Para Bellum"Lincoln Idealarc 250 AC/DCMillermatic 251   Syncrowave 300   30A spoolgunLincoln MP210Hypertherm 45(2) LN 25(2) Lincoln Weldanpower 225 CV(4) SA200   1 short hood    SA250    SAM 400
Reply:I've done 1/2 ton pickups up thru 2 1/2 ton gang trucks that are always overloaded and take a hell of a beating on oilfield roads that are never maintained. Shortened them and lengthened them. Plain ol' 90 degree cut vertically, bevel it and do a butt weld on the outside of the frame with 7018 all the way. Clean up the inside and do a pass up it. Grind the outside flat leaving the top and bottom flange alone and weld a diamond shaped plate with all the corners rounded on the outside of the frame with 7018 making a full fillet weld. 1/4" mild plate on the smaller and 3/8" on the larger trucks. Never had a problem. I didn't address line up of the frame but it's critical. It always bothers me when someone wants to do a potentially dangerous job and has to come here and ask how to do it. I feel like they should just go to someone qualified to do the work and have it done.
Reply:I appreciate the advice and also what sounds like concern for safety. I am working with a body guy who does a good deal of welding, but has not shortened a frame before. If I outsourced every potentially dangerous job, I would be broke with no skills.
Reply:He subscribes to the old "Learn by doing" method.You learn nothing but finance management, by outsourcing everything.
Reply:Originally Posted by bcryer35I am taking 10" out of my '89 pick-up frame, just in front of the rear cab mounts. Does anyone have any advice on the cut and bracing used to make this as tough (tougher) than new. I was told cutting with a Plasma in a z-pattern (stairs) is best...any thoughts? Should I tack a cross brace in front of the cuts to keep it square??I have access to an old tig welder...will this do the job? What thickness of plate should I use to reinforce? Should I reinforce the inside of the frame with a piece? Thanks!
Reply:Originally Posted by lewrayGuys whats your opinion on doing a rosett weld on the rectanglar plate along with the other welds?Drill a hole say 1/2" and weld up the hole instead of welding the ends.  R U confused yet?I've done it once ...just never heard anyone else do it.
Reply:Originally Posted by farmersammI'll try to post a link.  I'm not too good at posting links.
Reply:Originally Posted by Craig in DenverSamm: Just copy and paste the address. If it doesn't work as a link, we can copy and paste it into our browser window thingie.
Reply:Originally Posted by farmersammWHAT???  I'm doin' good just gettin' here.  I'll go ahead and look up the article later tonite, and copy the address(?) at the lower left in the screen.The article came up when I did a search for fishplating a frame.
Reply:Originally Posted by duaneb55Was it this one?http://trailer-bodybuilders.com/mag/..._truck_frames/