Fabrication technique tips (1 Viewer)

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Mar 23, 2007
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Upstate NY
 
 
It seems like it would be good to have a thread for general fabrication techniques. I mean little things that make the difference between a professional-looking finished piece, and something hacked together by a guy with a welder and a chop saw (one such guy being me).

I'd like to start off with a question about getting holes to line up. In my example, I was making skid plates and wanted holes in the plates to line up with the existing threaded holes in the frame for mounting. What is the best way to do this? Since the shape is irregular, it is difficult to measure from a reference and reproduce on the workpiece. Seems like I f'd it up several times and only got it right by luck. Tips?

Also, any links for these types of techniques would be useful.

broc
 
Joined
May 8, 2008
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New Jersey
 
 
It seems like it would be good to have a thread for general fabrication techniques. I mean little things that make the difference between a professional-looking finished piece, and something hacked together by a guy with a welder and a chop saw (one such guy being me).

I'd like to start off with a question about getting holes to line up. In my example, I was making skid plates and wanted holes in the plates to line up with the existing threaded holes in the frame for mounting. What is the best way to do this? Since the shape is irregular, it is difficult to measure from a reference and reproduce on the workpiece. Seems like I f'd it up several times and only got it right by luck. Tips?

Also, any links for these types of techniques would be useful.

broc
McMaster-Carr

These work nice. If you dont want to burn a hole 4x bigger than you need with a torch. Like I do.
 
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McMaster-Carr

These work nice. If you dont want to burn a hole 4x bigger than you need with a torch. Like I do.
A threaded hole transfer punch... Looks like exactly what I'm looking for. Once you thread it into the hole and put your workpiece up, you just give the workpiece a good whack?
 
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A threaded hole transfer punch... Looks like exactly what I'm looking for. Once you thread it into the hole and put your workpiece up, you just give the workpiece a good whack?
yup. I had a whole set at work. they were great! I wish I had them at home more than once. You can get them for blind holes as well as tapped ones. No-brainer locating at its best :cheers:
 
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Spokane Wa.
Here's my contribution

To find bolt hole centers accurately
Measure to the outside Dimension (B)
Subtract Dimension (A) from (B) = Bolt hole centers
Seems to simple to post.. but there was a time when I used to
slide the calipers over the holes to what looked like centers to me
and use that number..
This is far more accurate.
Bon Appetite
tip.JPG
 

e9999

Gotta get outta here...
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Joined
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To find bolt hole centers accurately
Measure to the outside Dimension (B)
Subtract Dimension (A) from (B) = Bolt hole centers
Seems to simple to post.. but there was a time when I used to
slide the calipers over the holes to what looked like centers to me
and use that number..
This is far more accurate.
Bon Appetite

assuming you meant to find out the distance between the centers of the 2 holes, you could also go from one side to same side of the other hole in one measurement, no...?
 
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yep

Thing is calipers are designed to run inside or outside..
not inside to outside.

It depends on how accurate you shooting for.

If you are using a tape your method will
work well enough.
 

e9999

Gotta get outta here...
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Thing is calipers are designed to run inside or outside..
not inside to outside.

It depends on how accurate you shooting for.

If you are using a tape your method will
work well enough.


one can use that technique with calipers and pretty accurately too. Way more accurately than the center technique in fact, and half the work of yours (which is indeed potentially a tad more accurate, depending on your eyes :) )
 
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denver
 
 
 
when you can, I use spray paint to get bolt patterns and shapes transfered onto my work piece. Put piece in place, then shoot paint, now you have a perfect outline
 
Joined
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Cary NC
 
 
 
You can also make some of those center punches by just grinding down an old bolt, not as nice but gets the jobs done.

Here are a few of my favorites:

Never measure when you can mark. Learn to use a story pole.

Mark with a scribe not a sharpie

Mark just once, a few lines scribed one another and how do you tell which one is the cut line?

Learn that the saw has a kerf and that most saws don't cut straight. Practice on scrap and compensate. Most chop saws cut at a slight angle so you can mark and cut all 4 sides to compensate if you don't have a band saw. If you don't cut all 4 sides, you'll get a slightly angled cut. Lay down flat stock for a straight cut even though it's harder to cut that way. Again, get a bandsaw!

Learn how to use a tape measure, the end moves for a reason. It's for inside and outside measurements. Not all measure accurately. If you use one tape to measure don't use another to mark the cut. You may have a 1/16 difference.

Never use a tape to measure anything unless what you need to measure is longer than your shortest ruler. I keep a 48 inch rule handy along with a dozen others. The fact is a ruler is more accurate.

Cardboard templates save time.

Anything you bend will spring back a bit, if you need to bend to 90, you have to bend to 92 or so to get the right angle after it springs back. The amount of bend past your target depends on what your material is.
 

Gumby

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Knee deep in hookers and gin
 
 
 
 
Use a manilla folder template. Hold it up to the holes and tap it with a small ball peen hammer. The outline of the holes will transfer to the template. You can also use the hammer method to make a outside template. Tapping around the edge will cause the paper to cut in exactly the shape you want to transfer.
 
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Gumby, that is a great trick - the old fashioned gasket making method. A friend once got a vintage motorcycle back on the road using that method and a breakfast cereal box! Sometimes you've got to use what you've got!
 

Awl_TEQ

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Calgary Alberta
 
 
To find bolt hole centers accurately
Measure to the outside Dimension (B)
Subtract Dimension (A) from (B) = Bolt hole centers
Seems to simple to post.. but there was a time when I used to
slide the calipers over the holes to what looked like centers to me
and use that number..
This is far more accurate.
Bon Appetite
assuming you meant to find out the distance between the centers of the 2 holes, you could also go from one side to same side of the other hole in one measurement, no...?
Thing is calipers are designed to run inside or outside..
not inside to outside.

It depends on how accurate you shooting for.

If you are using a tape your method will
work well enough.
one can use that technique with calipers and pretty accurately too. Way more accurately than the center technique in fact, and half the work of yours (which is indeed potentially a tad more accurate, depending on your eyes :) )



Use digital calipers - most have a button to "zero" the display. To measure c-to-c of two holes you measure the diameter of one hole and zero the display (without moving the caliper) - then measure outside to outside of the holes (using the inside points of the caliper). The display now reads the c-to-c. The holes have to be the same diameter for this to work.

This is the same thing a Dirtsquirt's method except the calipers "do the math".
 
Joined
Jan 6, 2003
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Another method I use is to measure from the inside edges of the holes, then the outside edges (the "A" measurement above) and just take the average. This works even if the holes are slightly different diameters.

Also for tape measures, I've always learned to "burn and inch", meaning start your measurement at the 1" mark instead of the end. Most tape measure clips are either bent, sloppy, or too messed up to give accurate readings. Just remember to take that inch into account when you're cutting and measuring, because I've heard of some people ;) forgetting and ending up an inch short

Learn how to use a tape measure, the end moves for a reason. It's for inside and outside measurements.

.
It's funny how many people don't know that slight slop is there for a reason. I've seen a lot of people trying to hammer down the rivets thinking that the tape measure end is broken.
 
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