1.5 inch hole in mild steel-how?

The flanges are so cheap to buy, making them yourself with no machine tools is just not worth it.

If making a large hole in thin mild steel, an industrial quality hole saw would be your best shot.

jack vines
 
Hole saw, drill, then band saw, don't waste your money on an annular cutter unless you're going into production. These are bearing retainers for an 8" Ford rear end, you can see the pattern lying on the floor.
 

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As mentioned before. For only a few holes, a bi-metal hole saw will work. SLOW RPM. Mount work securely. Lots of oil. I did this same type of operation when I was just a kid in High school and needed a big hole. Another tip is to start drilling until the 1.5 dia hole starts to cut in, then back out the cutter and drill a couple of small holes all the way through where the 1.5 dia. is located. This gives the chips a place to get out of the cut.

I drilled a large hole through some 1" plate by doing it this way.

D
 
or cnc plasma to cut the profile and large hole. don't do the small ones with plasma as they will not be exact and if you try to drill afterwards you will need carbide - i learned that from experience.

other than that an annular cutter as proposed.
 
Take it to a machine shop they can bore it out in lathe in 20 minutes. Probably cheaper than fighting holes saws, drills, and you don't have to supply the labour
 
machPete99 said:
Google "exhaust header flange 1.5", here is the first hit:

M & T Manufacturing - Selling volkswagen parts for more than 30 years

www.mtmfg.com www.mtmfg.com
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This is the route I would take. For under $6/pair, that buys you a lot of effort with a file. If each piece takes you an hour to make, would you like to spend 4+ hours with a file, or spend $12 for pre-fabs? My time, especially with a file, is worth more than $3/hr. I don't make my own standard grade nuts or bolts for the same reason, my time is worth more than it costs to buy small hardware that may even be better than I can make in my shop. So just because you can, doesn't mean you should in this case. That's my two cents, which means you're less than $2.98 from buying a flange off the shelf.
 
pontiac428 said:
This is the route I would take. For under $6/pair, that buys you a lot of effort with a file. If each piece takes you an hour to make, would you like to spend 4+ hours with a file, or spend $12 for pre-fabs? My time, especially with a file, is worth more than $3/hr. I don't make my own standard grade nuts or bolts for the same reason, my time is worth more than it costs to buy small hardware that may even be better than I can make in my shop. So just because you can, doesn't mean you should in this case. That's my two cents, which means you're less than $2.98 from buying a flange off the shelf.
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This brought to mind an incident I was involved in some 30 years ago. We had just completed a production facility in Missouri and were putting the final touches on some machinery. I asked one of the mechanics to go to the store room and bring back half a dozen 3/8-16 X 2" bolts. Half an hour passed and I finally I went looking for him. I found him in the machine shop parting off some 6" long bolts.

When I asked what took so long he told me the plant manager was so cheap he would only buy 1 length of each size bolts. If the job called for a shorter length bolt they had to cut them to size. For the price of a bolt the manager was turning a half hour job into a two hour job. Not only that he had a dozen production employees standing around with their hands in their pockets waiting for us to complete the job. Gives new meaning to the old phrase penny wise, but pound foolish.
 
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