Very poor large hole result

[AllenV]

I am making special pads adapted to the frame of my '55 Ford F100 to go on the two-post lift. This involves a short length of 1/4-inch wall 2x2 square tubing steel with 1.125" through-holes in one end. I will then turn a steel post to fit into the holes and weld them together. This does not require tight tolerance. The diameter is not important as I will turn the diameter of the post to match. But, every project is a learning exercise and I'd like to make it right.
I just bunged up the first 1-1/8 inch hole in the square tubing. I used a Lenox hole saw that I had sitting, unused, in a drawer. The saw made short work of cutting at 300 RPM. However, as soon as the cutter bit into the metal it went eccentric, very obviously. The mill was rock-solid. The cutter went sideways. The result is a nasty looking mess (photo). Oversize with a non-uniform diameter top-to-bottom. Clearly this was the wrong tool or technique.
How would I better approach this? I see 3 options.
1) A better hole saw. Which one?
2) An annular cutter. Which one would work with PM833TV? 2HP with VFD?
3) A boring head. I don't own one, yet.
4) ??

FYI, I do own a set of taper shank drills up to 1 inch. Those would fit in the drill press. However such large holes in the drill press usually results in exciting oscillations and oval holes due lacking rigidity. I view those drills as "lathe tail stock only"

I'll go make another 2x2 tubing section now.

 

[D.sebens]

Use the 4 jaw(or faceplate) in your lathe and bore it to size after drilling a smaller hole? If it’s not super critical center punch then use your tailstock with a center point to hold it in place as you fixture it. Then drill and bore.

Outside of that I would imagine an annular cutter would be plenty rigid.

 

[matthewsx]

I am making special pads adapted to the frame of my '55 Ford F100 to go on the two-post lift. This involves a short length of 1/4-inch wall 2x2 square tubing steel with 1.125" through-holes in one end. I will then turn a steel post to fit into the holes and weld them together. This does not require tight tolerance. The diameter is not important as I will turn the diameter of the post to match. But, every project is a learning exercise and I'd like to make it right.
I just bunged up the first 1-1/8 inch hole in the square tubing. I used a Lenox hole saw that I had sitting, unused, in a drawer. The saw made short work of cutting at 300 RPM. However, as soon as the cutter bit into the metal it went eccentric, very obviously. The mill was rock-solid. The cutter went sideways. The result is a nasty looking mess (photo). Oversize with a non-uniform diameter top-to-bottom. Clearly this was the wrong tool or technique.
How would I better approach this? I see 3 options.
1) A better hole saw. Which one?
2) An annular cutter. Which one would work with PM833TV? 2HP with VFD?
3) A boring head. I don't own one, yet.
4) ??

FYI, I do own a set of taper shank drills up to 1 inch. Those would fit in the drill press. However such large holes in the drill press usually results in exciting oscillations and oval holes due lacking rigidity. I view those drills as "lathe tail stock only"

I'll go make another 2x2 tubing section now.

I can't tell from your picture but did your hole saw have a twist drill to guide it at the center? If yes I really don't have any suggestions beyond getting an annular cutter or boring after the hole is cut.

But, your hole doesn't look right compared to holes I've cut with the same hole saws. Those Lennox hole saws are good in my experience, also did you use any cutting oil?

John

 

[jwmay]

John beat me to it.

Should have been a pilot drill mounted in the center of that hole saw.

 

[Huub Buis]

You could use a hole saw for the rough portion and a fly cutter to bring the hole on spec. Using a fly cutter is a slow process but it can give good results.
If dimensions are tight, I drill a 12..20 mm pilot hole using the mill and finish the job on the lathe in the 4 jaw chuck.

 

[Jake M]

I used a Lenox hole saw that I had sitting, unused, in a drawer. The saw made short work of cutting at 300 RPM. However, as soon as the cutter bit into the metal it went eccentric, very obviously. The mill was rock-solid. The cutter went sideways. The result is a nasty looking mess (photo). Oversize with a non-uniform diameter top-to-bottom.

I think that's how they're supposed to work. It's probably in the directions somewhere. Take a look at your bollixed hole, see if you're getting the same results- I use those in a drill press frequently. (Well, not "unfrequently" at least). I usually grab a hole saw that's an eighth inch under (depending on how deep they are, more or less), and let the drill press and the hole saw do their worst. When I'm done there's some randomness about the inside wall, so I buzz through it with an air die grinder and a carbide burr. It makes a fairly nice hole for fabrication purposes, and pretty round as the burr "stops" when the wall of the hole gets to full depth.

Those hole saws are good for metal, and cheap enough to be viable for that, but fabricating was not really what they had in mind....

1) A better hole saw. Which one?

About all of the prosumer brand bi metal hole saws act about the same. The arbor on the other hand.... Most are fine, some not so much so. I have better luck driving thoough the threads with a firmly planted arbor, vs using ones that stay loose and have drive dogs/pins/ Better result without the locking/easy release feature, at the expense of a shorter lived arber, as the threads do wear.

2) An annular cutter. Which one would work with PM833TV? 2HP with VFD?

A proper annular cutter is an amazing thing. Still not "precision diameters" by some standards (Pretty good by my standards....) but they give you a beautifully cut and very round hole.

Something to consider if you're not familiar- I'm not sure how these might fit your "big picture", as they are limited. These are less "machinisty" and more "mechanicy / fabricatey, but check out "Blair Rotabroach". They have a "standard" and a "large diameter' kit, your current project would need the large kit. 11091. They are a "piloted" anular cutter, glorified hole saw, they use a spring loaded point center. The depth of cut is NOT that deep, as a more machinisty tool might be. But thse are ground somewhat different from those, and can actually (with care) be used in a hand drill.

3) A boring head. I don't own one, yet.

There's one way to solve that.

Obviously that is the best way to make a precise hole. such as you're doing. You could probably approximate that with option 4.

4) ??

Can you fanagle a way to spin that part on your lathe and bore it there?

FYI, I do own a set of taper shank drills up to 1 inch. Those would fit in the drill press. However such large holes in the drill press usually results in exciting oscillations and oval holes due lacking rigidity. I view those drills as "lathe tail stock only"

I'll go make another 2x2 tubing section now.

A drill thgat size won't typically do well in such a (relatively) thin piece of metal. If you were making this out of solid bar stock, they'd probably do fine in a floppy old crooked drill press. At least they do in mine. But in quarter inch stock, I give up on "visually round" after half or nine sixteenths of an inch. If the tube was 3/8 thick than up to 3/4 (usually) behaves pretty well.

 

[AllenV]

@matthewsx Hmm.. it does have the pilot drill installed. I used Relion cutting fluid. If you've used similar Lenox hole saws, perhaps I'll take this one apart and reassemble to be sure it's all tight. Then test on some 1/4 inch plate.

@Huub Buis @D.sebens The lathe is worth considering. I THINK I can get a 5-inch widget in my 8" 4-jaw. Then do all the drilling and boring there. I'd have to reach thru to the far side to get the two holes lined up. Now that I think of it, I am not sure I can get a 5-inch widget offset that far. Worth thinking about or putting the 4-jaw on a bench to test.

 

[DavidR8]

@matthewsx Hmm.. it does have the pilot drill installed. I used Relion cutting fluid. If you've used similar Lenox hole saws, perhaps I'll take this one apart and reassemble to be sure it's all tight. Then test on some 1/4 inch plate.

@Huub Buis @D.sebens The lathe is worth considering. I THINK I can get a 5-inch widget in my 8" 4-jaw. Then do all the drilling and boring there. I'd have to reach thru to the far side to get the two holes lined up. Now that I think of it, I am not sure I can get a 5-inch widget offset that far. Worth thinking about or putting the 4-jaw on a bench to test.

I've had very poor luck with that style of Lenox hole saws.
I have had excellent luck with the carbide tipped Lenox saws.
Recently I had to put two 44mm holes in 1/2" hot rolled steel.
The carbide saw went through it like a hot knife through butter.

 

[AllenV]

@Jake M thanks for all that detailed response. Some of what you mention was covered in my last response ( we were typing at the same time and your popped up after I hit "post")

From your description perhaps the rotabroach has been copied by HF? The one linked below looks pretty stout. but it specs a max depth of 3/16"

1-1/8 in. Carbide Tipped Hole Cutter

Amazing deals on this 1-1/8In Carbide Tipped Hole Cutter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[mattthemuppet2]

couple of tips. One, go slower, 300rpm is pretty quick for a hole saw. Two, drill a pilot hole to match your holesaw pilot drill. Then swap out the holesaw pilot drill with a blank rod the same size (ie. 3/16" rod for a 3/16" pilot). That stops the holesaw wandering when it starts the cut.

An annular cutter would be the bees knees, but holesaws are waay waay cheaper.