1.5 inch hole in mild steel-how?

CrustyRedExpress

CrustyRedExpress

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Hi all. First post, hope this is in the right part of the forum.

I'm a car guy and need to fabricate 4 exhaust flanges for a turbo application. The exact material isn't a big deal to me as long as I can weld it with my mig welder and it can withstand being in the exhaust stream. Existing products on the market are usually 3/8ths 1018 mild steel or stainless. The flange needs to have two non-threaded holes on either side of a 1.5" hole. See below-Doesn't need to have the extra machining on the inside edge of the 1.5" hole.
flange.png
What is the best way to go about this for somebody who has no machining tools? My first thought was to buy my brother's vintage Craftsman 150 drill press-with a low speed third pulley it should go down to 175RPM (For a 1.5" twist bit I think that's about 69SFM). Unfortunately a lathe is out of the question because of storage and price concerns, as is a mill.

Am I on the right track with the Craftsman 150 running at 175RPM and a 1.5" twist bit?
 
A 1.5" drill is a big ask for a homeowner-grade drill press. It is an expensive bit and would need to be stepped up to slowly, so you'll need an assortment of big expensive bits to go that route.

If you can fix the work to the drill table securely, you can use a boring head and step up to size that way. The outer profile can be shaped by hand on a belt sander or even with an angle grinder and file.

You should be able to make 4 copies of the part without a lathe and mill, just work slowly so you don't throw any work pieces across the shop at the speed of bullets.
 
You'll have a tough time trying to drill the hole with a 1.5" bit. Personally I would drill a series of small holes in a circle to make the basic hole then file the inside of the hole smooth with a rat-tail file- a lot of work though for 4 pieces
-Mark
 
Hi and welcome.


I guess you haven't found an existing part that will meet your needs? That would be the first option but if nothing has the right dimensions it's on to DIY mode.

To duplicate the pictured part on a drill press I would probably use two hole saws and a drill bit. First lay it out carefully with some dykem or just a sharpie and scribe. Then I would pilot drill the center and two outer holes followed by the larger hole saw part way through and a smaller one to finish.

It could be done with a boring head but for your needs good bi-metal hole saws would probably be cheaper and easier to use on a drill press. I would fix the part down to a wooden board secured to the drill press table (could be done with lag screws on the outer holes once drilled) and use plenty of oil with the hole saws.

The outer profile can be done with a hacksaw and grinder/sander.

Or, get yourself a vertical machining center and set up production ;)

There are a bunch of ways to accomplish this, ultimately how precise it needs to be will influence your process but given a general lack of machine tools your brother's drill press sounds like a good start.


John
 
I second the annular cutter comment above! They're a bit pricey but work amazingly well. You could probably finish the outside profile on a belt grinder or even with a file if you are patient enough.

Other option is to post in the "can somebody make this for me" section of the forum. You have a lot of bored hobby guys on here right now.
 
I agree with John, a hole saw is the way to go. An annular cutter would give better finish and accuracy but they are more expensive.
 
A bimetal hole saw will make the hole. I would go undersized and file to fit with a half round file. Like Bob says above, make the large hole first and then the small holes. Do the outside profile last.
 
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