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Old 12-14-2012, 10:02 PM   #241
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A decent bridgport is in the teens of thousands. It's not a logical way to cut an opening for a flange.

A cut off wheel however, is. Ask Abe or someone how he does it. A pneumatic cut off wheel like listed above would work, however an electrical angle grinder would be better, since you don't need a compressor powerful enough to keep an angle grinder running. Most home garages won't have a compressor good enough for much more than a minute or so of cutting. Very annoying.

The issue with larger cut off wheels like that however (3"+) is that you run the risk of cutting larger than you need to, or reaching your desired cut before cutting all the way through.

What I'd suggest is measuring 5 or 6 times, marking where you need to cut, center punch, drill holes at each corner (accounting for the diameter of the drill bit), cutting what you can with a angle grinder and a small cutting disk, then finishing the cuts with something smaller, like a dremel. Dremels suck though. I hate using them for much more than thing sheet metal, and even a small cut seems to eat 20 disks.

Metal work in general kind of sucks. Always makes a huge mess, there's always lots of deburring you have to do, and even when you think one cut off wheel is all you'll need, you end up using 5 or 6 tools to finish the job. This is in a typical home garage of course. A decent machine shop should do it all with one tool, but we don't all have that luxury available.
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Old 12-15-2012, 12:06 AM   #242
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I use a 4.5" angle grinder for just about everything. All I've got is that angle grinder, a drill, and a die grinder. Those sparse power tools, my TIG and a decent set of hand files have gotten me along just fine.
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Old 12-15-2012, 12:52 AM   #243
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I find those 4.5" discs are very sensitive to how straight you hold them, and shatter very easily.
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Old 12-15-2012, 01:05 AM   #244
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The fiber discs hold up really well...have not had one come apart on me yet.
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Old 12-15-2012, 01:44 AM   #245
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Quote:
Originally Posted by curly View Post
I find those 4.5" discs are very sensitive to how straight you hold them, and shatter very easily.
Gotta have a steady hand, that's for sure. Back when i first got my cutoff saw i had one snap on me. Simple reason, i wasn't holding it straight, it cough and started bouncing and it shattered.
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Old 12-15-2012, 06:36 AM   #246
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Quote:
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Gotta have a steady hand, that's for sure. Back when i first got my cutoff saw i had one snap on me. Simple reason, i wasn't holding it straight, it cough and started bouncing and it shattered.
Kinda my issue. I have a fairly steady hand and would consider myself skilled with an angle grinder, but if you try to justify buying 4.5" discs instead of 3" discs because they're roughly the same price and you'll get more life out of the 4.5", I wouldn't suggest it.

Sorry for the thread jack, back to the manifold building.
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Old 12-15-2012, 05:20 PM   #247
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+1 for 3" discs. I've got a 33 gallon compressor w/ 6hp motor. The 3" electric angle grinder is much easier to cut with than pneumatic cut-off wheel, as long as I don't need a precision cut. The compressor just can't keep up with continuous cutting.

I saw this in the image galleries from Turbo94. Not sure if it's DIY or not.

https://www.miataturbo.net/members/t...0&ref=gnr-prev
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Old 12-19-2012, 08:16 PM   #248
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Quote:
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You use an endmill on a bridgeport.
You mean a milling machine lol. Bridgeport is a brand.
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Old 12-20-2012, 05:45 PM   #249
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So I've run into a new problem that I'm hoping some of you have some advice on. My manifold is complete, ported etc. etc. The car runs and drives, but still waiting on parts to finish the intake so I can drive more than around the block. However, the flanges warped enough when I welded them to cause small exhaust leaks, which drive me crazy. I've tried the hand file method, and it's helped considerably, but still leaks. A number of machine shops around here have said they can't do it. For the life of me I can't figure out why using a big belt sander (like the kind used for resurfacing heads) can't be used. Is there something I'm missing, or are these machinists just too dumb to know what I'm talking about? I'm thinking about just breaking down and buying my own damn belt sander.
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Old 12-20-2012, 05:47 PM   #250
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Belt sanders are pretty cheap from harbor freight. Some people love using them for grinding tungsten though I've never done it.
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Old 12-20-2012, 06:03 PM   #251
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That's where I'm looking. I've got a dedicated bench grinding stone for tungsten, and I won't do it any other way. In general I'm a lazy welder when it comes to cleaning and contaminated metal, but one sure way I've found to get crappy welds is to have contaminated tungsten. I just want my f-ing manifold to not have exhaust leaks.
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Old 12-20-2012, 06:05 PM   #252
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Yes, belt sander. Not the best, but they'll work. I know my Artech manifold and downpipe flange came belt sanded.
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Old 12-20-2012, 06:26 PM   #253
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Well, damn, if it's good enough for Artech, it's good enough for me. Thanks curly.
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Old 12-20-2012, 06:41 PM   #254
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Just be careful, go slowly, and pay close attention to where/how you are applying pressure. I've sanded plenty of flanges flat, but once in a while **** up and create a high spot that's a pain to resolve.
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Old 12-20-2012, 09:21 PM   #255
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This advise is to late for you but may help someone else, when I build this manifold I only raked the fittings to the flange, once I had everything g welded up I cut the tacks and sanded the tubes on a Grizlly belt sander (see lower left of photo) to get then all linger up, then welded the tubes to the flange, no warp or leaks that way.
The trouble with a long belt sander is that when sanding a flange is easy to take more from the ends than the middle.
The flange can be milled but it would require some custom 90 de brackets and no one will want to make them for one job, they may be willing to do it if you tack one good size piece of angle to each end of the manifold so they can clamp it on a mill table. Good luck
http://i1084.photobucket.com/albums/...E45F0C24E9.jpg
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Old 12-20-2012, 10:29 PM   #256
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I'm not a noob with a belt sander, and using a finer grit, I'm fairly confident I can get it flat enough to seal with a gasket. I was doubting my belt sander approach after having 5 machine shops talk to me like I was crazy when asking about it. I was just hoping to pay a machine shop 20 bucks to do it quickly rather than 80 for a new belt sander.
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Old 12-22-2012, 02:18 AM   #257
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So from my research the reason that most machine shops think you are crazy is because they are usually used to sanding aluminum heads, and our stainless flanges would not be good for their belts. I got a huge belt sander from enco for this exact purpose, and it works wonders. If anyone doesn't think a belt sander is the "right" way to do it, tell them to look up toxic fabrication online, I haven't seen a nicer manifold from anyone in my life, and yes that includes tim/Abe . Toxic uses the exact belt sander that I got.
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Old 12-22-2012, 07:30 AM   #258
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Agree with you, if it is the right belt sander that you can put the entire flange on the sanding surface and has the HP to pull the sanding belt without stalling, your sander is not an $80 tools either.
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Old 01-02-2013, 09:33 PM   #259
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This thread has inspired me to build my own turbo manifold. This is my first real intricate fabrication project, so I hope it goes well!
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Old 01-03-2013, 07:55 AM   #260
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Most of the time I don't sand anything but sometimes I do kiss the head flange on my small craftsman 4" wide sander. it's just long enough to fit the entire flange on it length wise. I do weld the entire thing while it's attached to an old cylinder head however, this helps tremendously in keeping things flat.

I did this for someone who was concerned with sealing. Added a small amount of filler around each port and then sanded them all flat. Welding the 'o ring' material made the flange not flat haha. But after it was done I'm sure it sealed great.

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