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Boring on VMC to tight tolerances.

SIM

Titanium
Joined
Feb 19, 2004
Location
Staten Island NewYork USA
Usually within .001 we can interpolate bores not too deep.
.001 to .0005 a boring head is the go to.
.0005 and under the 10thSet boring head is what we use.


My issue is with boring heads the tools are a bit finicky. I found cermented carbide work best as they can be sharpened sharp enough not to push off, but honed to leave a nice finish and last. The problem is trying to have others grind, hone and set size without going thru a pile of otherwise good parts.

Add some depth to hole and it just gets to be too much hit and miss or way too much time...and I mean way too much time.

Is there a better way to hold tolerances tighter then .0005 then using boring heads. Or a better tool the cemented carbide. Ream is nice, for ream size holes.
Thought about honing machines...but have no experience. Keep coming up with cylinder honing.

Hole sizes 1"-several inches...although larger where head fits in hole is not so bad...it's when using bar to get in deep, like 1.732 x 4" deep +\-.0002

I have used burnishing tools with good results, but at several hundred a pop with a couple tho range...not great for short jobs.

Thanks for any input.
 
Chuck that cemented carbide and get some real tools. Kaiser makes some of the best boring tools money can buy, and it takes a lot of money to get much. You can get boring heads that take CCMT inserts or something similar and you can get any kind of insert you want, including super sharp inserts for aluminum.
 
Hello Simm,
Most of the bores that I bore are under .75" dia.. I use a 4" Criterion, and use solid carbide boring tools that are held with my own heat treated alloy tool holders. I bore at the same speed and feed regardless of material (1000 RPM/1-2" per min feed), and I use G76 bore cycle with a .0025" retract. I also use G60 to improve position accuracy. I learned years ago from a Jig Borer pro to always retract the tool tip before removing tool from bore.
To date, I have over a two dozen holders that can hold any tool at various lengths.
otrlt
 
Usually within .001 we can interpolate bores not too deep.
.001 to .0005 a boring head is the go to.
.0005 and under the 10thSet boring head is what we use.


My issue is with boring heads the tools are a bit finicky. I found cermented carbide work best as they can be sharpened sharp enough not to push off, but honed to leave a nice finish and last. The problem is trying to have others grind, hone and set size without going thru a pile of otherwise good parts.

Add some depth to hole and it just gets to be too much hit and miss or way too much time...and I mean way too much time.

Is there a better way to hold tolerances tighter then .0005 then using boring heads. Or a better tool the cemented carbide. Ream is nice, for ream size holes.
Thought about honing machines...but have no experience. Keep coming up with cylinder honing.

Hole sizes 1"-several inches...although larger where head fits in hole is not so bad...it's when using bar to get in deep, like 1.732 x 4" deep +\-.0002

I have used burnishing tools with good results, but at several hundred a pop with a couple tho range...not great for short jobs.

Thanks for any input.
.
.
rules i follow to bore to +/-.0001
.
1) i use inserts made for material. (for example cast iron). when insert replaced it can easily not be in perfect and needs test cut. does not take much to put insert in .001 different
.
2) boring bar length to diameter ratio keep under 5 to 1. short and more rigid is better
.
3) sfpm and feed, longer length to dia ratio you have to run slower due to vibration
.
4) leave test cut then -.005 and bore full depth. this evens out rest of boring and boring bar deflection will get more consistent
.
5) take -.002 test cut (.001 to .003 range) and if ok then bore full length. any deflection will show bore say -.0018" instead of -.0020". next bore should be even more consistent
.
6) final bore amount should be between .001 to .003" if under .001 many materials will not bite in and cut but merely skate over. then next adjust it will finally bite in and take too much. many materials have minimum cut you can consistently cut and it can be different amount for different materials
.
7) boring bar always adjust bigger. if you got to go smaller go 5 turns smaller then come back bigger the 4 or 5 turns you need to take out backlash. also push bit to smaller size when you tighten as it has sloppiness and just releasing lock it can spring bigger size diameter. if you loosen lock push smaller dia when you tighten.
.
8) always use indicator bore gage set to ring gage or gage blocks. inside mic, caliper, etc cannot trust finer than .001". watch indicator bore gage hold in rags to insulate from heat of hand . i often keep ring gage in machine so it is same temperature as part.
vertical or horizontal does not matter much
.
9) cnc may not repeat position. if you move in x and y to measure then come back it can easily be .0002 to .0010" different position and if bored again small amount you would be cutting a slot. best to stay in x and y position even when measuring
 

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Chuck that cemented carbide and get some real tools. Kaiser makes some of the best boring tools money can buy, and it takes a lot of money to get much. You can get boring heads that take CCMT inserts or something similar and you can get any kind of insert you want, including super sharp inserts for aluminum.

You get what you pay for with boring heads, no doubt about it. Kaiser, D'Andrea, Sandvik, super precision heads with 2μm increments. They are in a different league and you need to use them to appreciate the difference.
 
the worn gear fine adjust .0001 easier to adjust than simpler .001 with just screw adjust
.
but still with both when you release lock they can spring ahead bigger diameter. always push bit to smaller size when tightening lock. there is a technique to follow when adjusting if you want consistent results
.
i use head band magnifier to see numbers when adjusting.
 

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IMO inspection is as, if not more important than the actual machining process, having good equipment to do it is the right answer. I agree Kaiser makes some REALLY nice boring tools $$$$, I agree solid carbide bars make life a lot easier $$$$, I agree ditch the cemented carbide and use indexable tools, use as short a bar as possible, rigidity. rigidity, rigidity. Below .0005" everything starts to come into play, so the best thing to do is start eliminating or minimizing the possibilities for error.

R
 
IMO inspection is as, if not more important than the actual machining process, having good equipment to do it is the right answer. I agree Kaiser makes some REALLY nice boring tools $$$$, I agree solid carbide bars make life a lot easier $$$$, I agree ditch the cemented carbide and use indexable tools, use as short a bar as possible, rigidity. rigidity, rigidity. Below .0005" everything starts to come into play, so the best thing to do is start eliminating or minimizing the possibilities for error.

R
.
.
i often bore to +/-.0001" but it is never easy.
 
Tom I don't know if you are old and senile or just stupid. Having good equipment IS IN FACT important okay, you never "mentioned" "taking care", and NOONE ever said anything about any part of any of this being "easy".
 
What is meant by "cermented carbide".
Carbide brazed tip bars or cermet carbide inserts in a holder?
Sort of different tooling, I'm so confused.....pardon me , I get lost easily in this stuff.
Bob
 
Thought about honing machines...but have no experience. Keep coming up with cylinder honing.

Hole sizes 1"-several inches...although larger where head fits in hole is not so bad...it's when using bar to get in deep, like 1.732 x 4" deep +\-.0002
If I had that to do, I'd use a sandvik vari-set boring bar and head, they use Micro bore type inserts and cover a wide range of sizes.

You might look into Superior hones. They make floor machines and also make this setup that can be chucked in a drill press or mill

md-1.jpg
 
We recently purchased one of these boring heads and I would highly recommend. 1 micron adjustment and very versatile for the $$$.
Micron Precision Boring Head Set MariTool


Thank you. I looked at this very kit several years ago before going with Ericson 10th set.


Looked at kit again last night after researching some others...4k for a Kaiser kit.




I think issue was hit on the head with using Cemented Carbide Bars. Yes, Brazed Tip...just habit we got in calling them that. Anyway the bars can be had beefy to slender for not a whole lot of coin and if sharpened correctly they did a great job for me...even HSS for alum and real short runs. But not being on the floor as much, the problem is they are not being sharpened just right so they are no longer working well. Indexable bars I had used were good for roughing to just under a thou...but tighter cuts I found they pushed off so went to using sharp cemented for real light tight tolerance jobs. That was me, that was then...this is now...Thanks for wake up call on that...

I am going to have to get better bars for sure. Indexable sharp positive cutting tools otherwise, I'll need to plan on staying on the floor.



I tryed looking for Sandvik Vari-Cut...I kept finding Valenite Vari cut heads...I have some of those, and yes they work well. Just not easy to set under .0005...but when we hit it, it did stay nicely.


Appreciate the advice and help.
 
My mistake - Valenite vari-set, not Sandvik. But I think they are discontinued, so you have to find them on the second hand market

.1111.jpg
 
My mistake - Valenite vari-set, not Sandvik. But I think they are discontinued, so you have to find them on the second hand market

.View attachment 190458


Thanks, your right they are great bars. Bought one in 1-1/4" dia that I stuck right into a CAT 40 holder; worked like a charm boring 10" deep. Wasn't an overly tight tolerance and my bar does not have a fine adjustment, but recall I went from playing to running soon as that bar went it. Better bars...
 








 
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