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Tool Annular Cutter Accuracy
- Thread starter Susquatch
- Start date
Tool
After my last post I examined my other annular cutters. I don't have a set of them. Mist were purchased individually for different jobs. You are right. If you look closely, all the teeth are unique.
I won't say never, but I think you are right about that so I doubt that the odd tooth is the cause of my problem.
Ain't that the truth. I'd prolly enjoy that book especially given my love of math. Not that I love multi order diffy's, but to the extent that math helps us under stand the world around us, and to its fundamental beauty, I really do love math.
It's a good guess. Especially since i did use moderate pressure. Said pressure might amplify a stuck chip's influence on the cut. On the other hand, pressure usually reduces the chance of a stuck chip.
The cut itself was done with dripped on high sulphur cutting oil (vipers venom), and moderate cutting pressure. Basically a light pull on the quill arm. The cuttings were all nice curls of reasonable size. You can see them in the first few photos at the beginning of this thread. I am very highly tuned to the feel and sound of my machines. I don't have CNC, so I fly by what the part, cutter, and machine tell me. I think I can say that I have a very good feel for an unhappy process. At no time did it feel like a stuck chip. Again, I won't say never, but I doubt I had any stuck chips.
I have a 2HP Bridgeport Clone. I have cut 3" holes with an annular cutter - no problem. My older MT3 round column mill drill had a very definite rigidity limit. When I used it, I knew when I hit that limit. In fact, that's what caused me to upgrade to a Bridgeport Knee Mill. Also, I have a very rigid Gerardi Vise holding a solid bar of steel. I think I can very safely say that rigidity was not even remotely a problem in this situation. But I do hear where you are coming from on this. It's a good thought and would normally explain this quite well.
What a great idea. It wouldn't necessarily tell the story but it would provide some great insights.
I didn't save the plug. In fact I don't remember even seeing it. I do know it wasn't inside my annular cutter. Which is a bit of a surprise in and of itself! It's probably inside my swarf vacuum. I will try to recover it later today. Since it wasn't inside the cutter, it had to be loose - a very tell tale fact all on its own!
You also remind me that I didn't use the guide pin. And also that my annular cutter was 2" long.
The details are starting to add up......
historicalarms
Ultra Member
You mentioed that the work piece was solid in the vise, but does your table dovetail/gib setting have a small amount of play that could allow a small movement of the whole issue....1/32" total hole oversize oversize needs only a shift of less than 1/64"
The root cause of many issues. Maybe not to this extent but locking the tables is always best practice. Especially if you have something with high torsional load like drilling a big hole + repetitive axial pecking / hole re-entering, I can see this combination wanting to displace the tables within their backlash limits. Another measurement of interest is top surface vs bottom hole dimension, although for 1/2" it probably wont vary that much. If I recall the teeth are set so it makes a slight annular gap for plug clearance. I never thought to measure it before & maybe varies by diameter but guessing about 5 thou.
Both axis were locked down solid as a rock.
But I think you and @mbond are on the right path. Mike suggested that I look at the plug.
I looked everywhere for it. It's gone. I puzzled about that for ages. I was looking at the new part and it hit me..... THERE IS NO PLUG! I was cutting the perimeter of an existing hole! The existing hole was punched, not drilled. I don't have the original hole anymore, but the plate has other holes in them. Some look like they were torched through! Ugly holes to say the least!
I hate getting old. I feel like my brain is slowing down. It should have been obvious to me before I even started that you can't cut the periphery of an existing hole without some wandering. Especially not without a guide.
Everything makes sense to me now. I cut another hole with the cutter on clean metal. 1.002. All is well in my world.
Thanks to everyone who chimed in. Thanks especially for enduring the dottering stupidity of this old man and taking the time to lead me to the light.
Doggggboy
Ultra Member
Only showoffs get it right the first time.
Ya, it's actually a funny tale thinking back on it. Especially funny for those of us on the old end of life's journey.
Now that my ego has been badly bruised enough to see the light, I distinctly remember looking at that old hole and thinking I have to he careful to center the cutter over the hole. I didn't use an edge finder, I just eyeballed it from all sides, then touched off, then raised the tool to look at how well I did. It looked great so I started cutting in earnest. Never once did I look back at what might be happening. It looked good, so it will be ok. It did a great job so all my first thoughts were erased. When it fit sloppy on the post, I went "Huh?" How did that turn out so loose? This led to slurry of thoughts none of which related to my first concerns - that had been neatly forgotten - file 13'd forever. Instead I dove down the rabbit hole of how did this happen neatly forgetting the prior hole. I even chastised myself for not drilling a small hole for the pilot. When I file something in my mind's file 13 - it's gone. Prolly why I seldom hold grudges.
Another lesson learned - for a few days anyway.
Being old does have the advantage of being able to forget. You can't forget, if you have never learned
Very true. Nice saying.
I often say that I've forgotten more than many guys ever knew. That's supposed to sound great, but it all depends on how much you actually do remember. It's a sad day when what you have forgotten exceeds what you ever knew.... I'm gettin there....
Just wondering, if you put in in a weldon shank holder, was it a good fit or did the set screws push it off center.
Dabbler
ersatz engineer
@Maker Mike My Weldon holder is a very close slip fit; perhaps 4 tenths slop.
Ah yes, another deep rabbit hole. If manufactured properly, Weldon shanks and arbours are supposed to be deliberately designed to center with the use of two screws at right angles. All bets are off with one screw. In fact only one screw means they don't comply with Weldon standards.
That all said, my arbour is not a genuine Weldon. However, I did mount a 3/4 inch gauge pin in my arbour and got the same runout as the arbour outside diameter itself.
I'm quite happy with the idea that the original hole pushed my cutter enough to cause the errors I found. Not only that, but I did cut a new hole in an undrilled blank and got the desired results. So I'm quite happy after all the dust settled. Even my enlarged hole will be ok for the final project. It's destined to be split to become a 1" clamp and I'll just make the slot a little bigger to take up the extra ID.
In the end, the only damage was to my old ego.