Need a lesson in steel

I have a project to build using some 2.5 x 1.0" steel, which will require several 2" holes drilled/bored thru it. My local steel supplier has hot rolled and cold rolled steel. I am wondering if I could get a lesson on which would have the tendency to machine nicer. Thanks, Ryan

Reply to
Ryan
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Cold-rolled. Hot-rolled has nasty and sometimes hard mill scale on its surface, and the grain structure makes it harder to get a good finish.

That's a big hole. I hope you have the machine horsepower to do it, or that you're farming it out.

Ed Huntress

Reply to
Ed Huntress

Cold rolled mild steel machines nicer than hot rolled mild steel, but costs quite a bit more. If you center the 2" holes on the 2.5" flat you'll have only 1/4" material nominal left over on each side. Several holes you said, can't you use chicken screen: It comes with lots of holes which are held together with thin galvanized wire and is much lighter?

Reply to
John

Yes, that was going to be my next question... I have a 5HP bridgeport copy mill with 10x50 table, so I think if I go in steps, it should be OK, but the biggest drill bit I have is 1.5 inches. My plan was either to drill in steps up to 1.5 inches, then bore out the rest. I was not too eager to go about it this way, so I was looking at my starrett hole saws wondering if that was feasible? Never used a hole saw in that thick of material steel before.

To be more specific, I require one 2 inch hole near the end in each 20" length of 2.5 x 1.0 material, and need 6 lengths in total, so that is six holes to do.

Cold rolled it is, thanks for that info. Ryan

Reply to
Ryan

Ok, can I butt in with a question? On a job like this, would it work to rough out the hole with an endmill then finish it by boring? Or does boring require an non-interrupted cut that would be hard to rough out by hand?

Reply to
Jim Stewart

Oh, you have plenty of horsepower, then. What you need now is some advice from someone who actually drills holes like that. It's a pretty rare event for most of us.

Ed Huntress

Reply to
Ed Huntress

Hole saws wouldn't last long in this thick a material.

I have a similar machine. This is how I'd do it with the tooling you have.

Set up vice with stops so you can quickly go from part to part without moving table. Do all parts at each step to minimize tool changes.

Drill all holes 1/2"

Drill all holes 1 1/2", use your slowest speed here and lots of coolant.

Ruff bore to say 1.85".

Finish bore to size.

Karl

Reply to
Karl Townsend

Assuming you need a precise hole. Either the 1.5 inch drill or a hole saw will work, depending on how big a hurry you are in. (Hurry is bad). If using the drill method, I would start out with a pilot hole and work up to about 3/4 or so by hand, in back gear past about 5/8" diameter, then switch to power down feed for the rest of the sizes. Table locked in place. Get down to around 80 RPM for the larger drills. Be careful, lot of power going on here. Controversial, but I do a lot of my drilling dry. No problems for me, speeds and feeds and bits must be right though. When the 1.5 hole is complete, I would go with the boring head or bar, whichever you have. If you opt to use a hole saw, my method is to attach an air line with a regulator blowing a stream of air into the cut to cool the saw and keep the chips clear. Once had to holesaw through 1 1/4 cast iron at 4 1/4" diameter, following a team that was unsuccessful. They used several hole saws for one hole. I attached an air blow and drilled 128 holes horizontally through the castings with just a very few saws, using a fairly slow mag drill. In your case, after using the hole saw, go to the boring head/bar as above. Take a pee break before you begin.

RJ

"Ryan" wrote in message news:1hARb.25120$A7.18937@edtnps84...

Reply to
Backlash

You don't say what kind of tolerance you need to hold the hold id to, but a hole saw should do the job provided that you can go slow enough. Plan on running about 60 rpm, with mist/flood coolant or plenty of cutting oil.

T> > That's a big hole. I hope you have the machine horsepower to do it, or > that

Reply to
Tony

Ryan,

Consider purchasing and annular cutter. They are expensive, but your application is what they were made to do. The following is a link to a manufacturer:

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Regards,

Ron Leap

Reply to
Ron Leap

That's the right idea. Heck, you're only doing 6 holes, not a production run. If you have a flycutter, use that to bore out from 1.5 to 2.0. Do it in increments, naturally. The flycutter will be more rigid than a boring head womping around with a bar hanging down. With the flycutter the cutting edge is a lot closer to the body of the tool and the spindle nose, way less opportunity for chatter to develope, and you can push it harder. Grind your bit with a chipbreaker in it so as to not get string.

michael

Reply to
michael

I made some parts a few years ago that had a slightly larger than 2" hole in 3/4" steel plate. I used a hole saw and it worked "ok" for my purposes. The finish turned out better than I expected. The holes came out a bit larger than the saw diameter, which I expected and didn't matter because the tolerance for the holes were pretty generous. On the negative side, it was kind of a hassle to do - took a long time and it was easy to jam the saw. I used a lot of cutting oil and sort of pecked at it to clear the chips and keep it from jamming. Of course I was using a cheesy little drill press so it was way too fast on the lowest speed and also way underpowered. It might work better with your machine. Also I've heard of or seen in a catalog something called, if my memory serves, a core drill? that might work better. Sort of a much higher quality hole saw (probably also much more expensive).

Hope this helps you, good luck! Eric

Reply to
curly

Those are the things to go for. They only cut an annulus so use a lot less power than a drill. Sizes are limited though. They are used a lot by construction workers with mag based drills. I have used one once and it was very impressive.

John

Reply to
John Manders

When using a hole saw..drill a hole though the material so the hole intersects the edge of the saw line. This gives the fines a place to escape and fall through. I try to make sure its at least 3/8" if possible

Gunner

"This device is provided without warranty of any kind as to reliability, accuracy, existence or otherwise or fitness for any particular purpose and Bioalchemic Products specifically does not warrant, guarantee, imply or make any representations as to its merchantability for any particular purpose and furthermore shall have no liability for or responsibility to you or any other person, entity or deity with respect to any loss or damage whatsoever caused by this device or object or by any attempts to destroy it by hammering it against a wall or dropping it into a deep well or any other means whatsoever and moreover asserts that you indicate your acceptance of this agreement or any other agreement that may he substituted at any time by coming within five miles of the product or observing it through large telescopes or by any other means because you are such an easily cowed moron who will happily accept arrogant and unilateral conditions on a piece of highly priced garbage that you would not dream of accepting on a bag of dog biscuits and is used solely at your own risk.'

Reply to
Gunner

Cold-rolled and hot-rolled are just finishes, the names are commonly applied, though, to mild steel, although you can get those finishes in a wide variety of steel alloys. I commonly will use hot-rolled for most of my mild steel needs. The reason is that cold-rolled has a lot of stresses locked up in it from those finishing passes that make it nice and shiny. You can get hot-rolled mild steel with the mill scale removed, so if you have other features to machine into the surface of your workpieces, they're not so apt to warp on you than if you use cold-rolled mild steel. A lot of hot-rolled scrap is from construction and architectural work and those grades won't machine as easily or get as good a finish as cold-rolled mild steel, I think that's where a lot of the bad press about it comes from.

Stan

Reply to
Stan Schaefer

Great tip, one of those "now why didn't I think of that" ideas... I'll certainly give that one a try as I hate pecking away using a hole saw...

Reply to
Dave Keith

Interesting that this company tells you everything about their products except what they cost. Mike

Reply to
MikeM

CRS is not the best machining material. Frequently the finish when turning on the lathe is rough. I got some HRS once and after I removed the scale, it machined very nicely. chuck

Reply to
Charles A. Sherwood

Another materials hint for the un-initiated. Whenever machining a part that is to be electric welded to another part, don't waste your time using 12L14 (A.K.A. Ledloy). Hot rolled works much better for this. Ledloy doesn't weld worth a sh*t. Outgasses as it welds, produces bubbles in the weld. It's a machinist dream in a lathe though, for spacers and other such.

RJ

Reply to
Backlash

Hi, Michael.

This is exactly what I would do.

Probly shoot for ~ 1.95 dia. or so with a flycutter or old stubby regrind

2in endmill, then bore with a criterion head to finish size.
Reply to
PrecisionMachinisT

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