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Discussion Starter #1
Alright. This will be someone of a long post so please try to bare with me. I need some help/advise on my jig that I'm slowly building. Id like to have my car moved to my house late this year/early next.

I have a question about the firewall pin/bolt locations. Which one is more critical?

after drawing the tow plans over each other in MasterCam, the Fisher Body dimensions seem to be off the body alignment hole while the 1stGenJig plans are off the actual body bolt. I would think the Fisher Body alignment hole would be better then the body bolt as the body mount nut has play inside the nut cage.

I'm also thinking, if I adjust the jig to use the fisher body alignment hole, I can utilize the body mount to bolt the firewall/body to the cart.

Any thoughts or insight from others that have done this already?? Do/did you need the extra play in the body bolt to get panels to align properly on the car?

I hope I'm describing this properly for everyone to understand.
 

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Yours was not a long post. The one that you are now reading is going to be a long one because I like to ramble on and on…. and then some more. :boring:

First Generation Jigs designed my jig. Two ½” studs stick up through the 5/8” captive nuts on the firewall. The captive nuts do move around so there is some built in tolerance when you place the body on the jig. Therefore, what you are worrying about is a valid concern.

A jig needs more than two alignment points to make sure the body is in the correct position. If only two points were used, then a possibility exists that one of the points could be too far forward and too close to the other one. The measurement would still be correct in this instance. You need a minimum of three points to form a triangle. The more points the better. The FG jig has six alignment pins plus two clamps that holds the rear frame rails. All six points has some tolerance because the jig’s ½” studs are inserted into 5/8” body holes or captive nuts.

Think about this. Your unibody car is almost 50 years old. The firewall alignment holes and the frame rails guide holes could have shifted a little during the life of the car. You will need a little slop the jig’s small alignment pins and the movement of the cage nuts provides to be able to drop the body on the jig.

You could use the firewall alignment pins after the body is dropped on the jig. Fabricate a little “L” bracket that has a 5/8” pin welded to it. Drill two holes in the jig’s firewall support pillar and the fabricated bracket. Bolt the bracket to the pillar. Make sure the firewall pins are the correct distance from each other. Measure the diagonals from the frame rail guide hole pins on the jig to the new firewall alignment pins. The two diagonals should be the same. Do you remember the triangle comment I mentioned earlier? Unbolt the “L” bracket. Drop the body on the jig. Now make small movements to the body until you can insert the firewall pins in the firewall holes and bolt the bracket back onto the jigs pillar.

You will find that the F body car was not built with much precision like how you are thinking. You will find the reproduction panels are built with even less precision.

I made some modifications to my jig and added extra bracing to help keep everything from shifting while I cut the car apart. The modifications are documented in this link:
http://www.camaros.net/forums/74-tools-shops/332553-extra-jig-bracing-rusty-1st-generation-f-bodies.html

Most of all have fun. It is impossible to mess up. Sometimes I make very small, teeny tiny, missteps and I have to cut out my work and start over. It is no big deal. It is all part of the fun.
 

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Discussion Starter #3
Thanks for the reply. I guess I fail at this concept because I am coming from a CNC programming background. I expect to hold tight tolerances as I would at work on new CNC machines. I find I do this with most projects around the house, garage, working on engines, doesn't really matter what it is. Its almost a illness. I have a couple buddies that are also in the CNC machining/programming career field as well and they are the same way as I am. Maybe it just comes with the territory?

I already machined the plate to align to the fisher body with threw holes to bolt the 5/8 bolt to. I will at the very least see how well they bolt up to the car tomorrow as I will be over my parents house anyway. Worst case, I find the flaw in them and made/modify new ones.
 

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Al - Waterloo, Iowa
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Erik, Keep in mind precision is relative to the task at hand. I also come from a cnc programming and machining background having been in the industry since the days of punch tape. I've owned and operated my own machine/cnc shop since 2004. If you're boring an engine or grinding a crank, you bet precision is required. Remember when these cars were built cmm machines weren't available and cnc machines were rare. In many areas the dies and these cars were built by hand with function in mind. Not so much form. Good luck.
 

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Discussion Starter #5
Erik, Keep in mind precision is relative to the task at hand. I also come from a cnc programming and machining background having been in the industry since the days of punch tape. I've owned and operated my own machine/cnc shop since 2004. If you're boring an engine or grinding a crank, you bet precision is required. Remember when these cars were built cmm machines weren't available and cnc machines were rare. In many areas the dies and these cars were built by hand with function in mind. Not so much form. Good luck.
Im really tring to get in that mindset, it's just hard. I keep telling myself, the closer I get it to tolerance now with the jig, the better off I'll be when lining the car up.

I'm going to test for the brackets I machined up tomorrow. If it fits nice, I'll start welding on the jig soon. Big step for me will be getting the car on the jig.





 

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Wow, nice work on those. I think you might be in for a bit of a surprise when you start fitting up repop sheet metal....

Don
 

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Wow, nice work on those. I think you might be in for a bit of a surprise when you start fitting up repop sheet metal....

Don
That is the problem. After market does not fit like original. The major work on the jig is fantastic. It with be worth the hassle because at least you will have the placement as close as you can get. you will likely have to mod the new parts to get it where you want it. I am very impressed with the detail of your jig. Good luck.
 

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Your profession explains a lot. You are one of those fellows that thinks out to the fourth decimal place. I always wondered why Fisher body dimensions never mentioned any tolerance values.

It is good to have your jig built to the highest precision that you can accomplish. You will find that when something does not fit correctly, the jig will always be your corner stone. If you build the jig all wonky, then you will wonder which is incorrect, the reproduction piece or the jig.

Below are a couple of photos of a brand new, state of the art sub-frame for a 1st generation F body. Notice how much adjustment the machined aluminum bushings have that go between the body and sub-frame. Maybe 0.25" tolerance?



 

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Discussion Starter #10
Your profession explains a lot. You are one of those fellows that thinks out to the fourth decimal place. I always wondered why Fisher body dimensions never mentioned any tolerance values.

It is good to have your jig built to the highest precision that you can accomplish. You will find that when something does not fit correctly, the jig will always be your corner stone. If you build the jig all wonky, then you will wonder which is incorrect, the reproduction piece or the jig.

Below are a couple of photos of a brand new, state of the art sub-frame for a 1st generation F body. Notice how much adjustment the machined aluminum bushings have that go between the body and sub-frame. Maybe 0.25" tolerance?



I thought I remember seeing tolerances either in a book or on here before. Think it was around +/- .125? I could be wrong, it was years ago I seen it.

Kinda surprised how much room those bushings have. And I'm guessing that a 5/8 bolt in a the .610 alignment pin hole.

I ended up taking the front mount plates over to my parents house to check them on the car. Although all the holes lined up great, I have to remove the back outer corner. The bracket interferes with the firewall. I didn't think to bring a grinder so Ill have to grind it off and check fit again. Ill take the grinder with me this time in case I need a little more clearance.
 

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Discussion Starter #11
I just got the jig under the car and have a question for you guys that have just the first gen jigs.

When using these jigs, is the bottom of the rocker level(parallel) the to top of the jig?

We leveled out the car (off bottom of rockers). Slid the jig under the car. Jacked the jig up to the front body mount and bolted it on. Leveled the jig by jacking the back up. When I do this, the back of the jig isn't contacting the back frame rails.

The underside of my car is very rough so it's not to say it's right or wrong. I just want to be sure the car is in the correct spot. It rather the car be correct location so I can weld the new panels in the correct location.

Please get me your two cents. Really starting to get the itch to get this thing goes to full force. Ones I get this figured out, I can't get the car moved to my house and spend a little more time on it.
 

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I just got the jig under the car and have a question for you guys that have just the first gen jigs.

When using these jigs, is the bottom of the rocker level(parallel) the to top of the jig?

We leveled out the car (off bottom of rockers). Slid the jig under the car. Jacked the jig up to the front body mount and bolted it on. Leveled the jig by jacking the back up. When I do this, the back of the jig isn't contacting the back frame rails.

The underside of my car is very rough so it's not to say it's right or wrong. I just want to be sure the car is in the correct spot. It rather the car be correct location so I can weld the new panels in the correct location.

Please get me your two cents. Really starting to get the itch to get this thing goes to full force. Ones I get this figured out, I can't get the car moved to my house and spend a little more time on it.
Hooray for progress! :hurray:

I can't answer your question too well because I didn't check it like that. Plus you know how rough mine was. That said, I knew the jig was where it was supposed to be, so the car is built to the jig. I can't think of a reason not to trust the jig, especially with the precision you built yours with.
 

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When I use my jig I make sure the four subframe mounts are resting on the jig and let the frame rails sit where they land. I use the bolts in the side of the frame rail supports to lock it in position.

How far from the jig are your rear frame rails? Where are your subframe mounts under the seats sitting?

Don
 

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Discussion Starter #14
When I use my jig I make sure the four subframe mounts are resting on the jig and let the frame rails sit where they land. I use the bolts in the side of the frame rail supports to lock it in position.

How far from the jig are your rear frame rails? Where are your subframe mounts under the seats sitting?

Don
I don't think I can trust the rear subframe mounts either. The floors have been patched previously and I'm not sure they are in the correct location.

With the jig against front subframe and the far rear frame rail, I'm still 1/2" from the jig to the rear subframe mount. With this set up, the jig is not level with the rocker. So this is why I was questioning if these two need to be level to each other.

With just the bare replacement panels on the jig, the all fell right into place.

Just to be on the safe side, thinking I will have to make adjustable mounts for the rear of the car and adjust as needed once the new panels are in place.

Trying to do all this the correct way and not rust it too much, that's when I know mistakes will happen. I really wanted to get the car under its own support today but want to figure this part out first.
 

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I don't think I can trust the rear subframe mounts either. The floors have been patched previously and I'm not sure they are in the correct location.

With the jig against front subframe and the far rear frame rail, I'm still 1/2" from the jig to the rear subframe mount. With this set up, the jig is not level with the rocker. So this is why I was questioning if these two need to be level to each other.

With just the bare replacement panels on the jig, the all fell right into place.

Just to be on the safe side, thinking I will have to make adjustable mounts for the rear of the car and adjust as needed once the new panels are in place.

Trying to do all this the correct way and not rust it too much, that's when I know mistakes will happen. I really wanted to get the car under its own support today but want to figure this part out first.
Post 2 in this thread should let you figure if you are right.

http://www.camaros.net/forums/12-body-shop/201765-rear-frame-rail-replacement.html

Don
 

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Discussion Starter #16
Post 2 in this thread should let you figure if you are right.

http://www.camaros.net/forums/12-body-shop/201765-rear-frame-rail-replacement.html

Don
Thanks for the help, Don. I think I will have to take Matts advise and trust the jig is in the correct spot.

Its all nerve-racking and excitement...I'm finally making progress on it. I think it will be much easier to work on the car once I move the car to my house. Have a whole team of friends that are willing to help me out, which is always a nice thing to have.
 

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Hmm. Do you know what they have over an inch difference between the vertical on b and c? Is on to the top of frame and other is top of bushing/bottom of car?
No idea. The drawing is not clear. Sorry.

Don
 

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If the bottom horizontal beam of my jig was level, the rocker was level. The rocker should run parallel with a level surface. A bubble level is all you need for this measurement.

I measured point “c”. It was exactly right because the solid aluminum bushings are exactly the correct thickness. The difference between point “c” and point “b” is the bushing thickness.
 
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