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What kind of boring bar is this?
- Thread starter FlyinChip
- Start date
- Replies 20
- Views 3,798
moonlight machine
Diamond
- Joined
- Nov 19, 2007
- Location
- marysville ohio
I made the one I have, easy peasy.
Oldwrench
Titanium
- Joined
- May 21, 2009
- Location
- Wyoming, USA
Tool Bit Holder Sets | MSCDirect.com
MSC #00228270 el cheapo "boring tool bit holder" set. You didn't say what diameter, but start with this @$68.00. Just get a matching square tool bit and grind it to do your keyway.
MSC #00228270 el cheapo "boring tool bit holder" set. You didn't say what diameter, but start with this @$68.00. Just get a matching square tool bit and grind it to do your keyway.
what material to make the boring bar with? I would think that anything soft enough to drill crosswise (if thats what you do), would not be rigid enough. I did find "double end boring bar" on ebay with 3/16" square tool holding (set screw holds the hss).
i'm pretty new at this, as is pretty obvious. but already starting to understand this one. so thanks for the info
I have a 1/2" diameter boring bar holder for my qc toolpost, so 1/2" bar.
lathe is a SB Heavy 10
i'm pretty new at this, as is pretty obvious. but already starting to understand this one. so thanks for the info
I have a 1/2" diameter boring bar holder for my qc toolpost, so 1/2" bar.
lathe is a SB Heavy 10
Gordon Heaton
Titanium
- Joined
- Feb 19, 2007
- Location
- St. George, Utah
Cold-rolled (1018) works ok. 1/2" diameter is pretty thin if you are trying to cut a long keyway though. If it is a wide keyway you can use a narrower cutter and do it in two sections which will cut down on the cutting and bending forces. I've use such on a mill with a rapid feed handle but it seems to me it will be a tough go on a lathe without a long-throw carriage motion.
I have cut 3/8" keyways on the mill, in two passes and it takes a lot of strokes and a fair amount of pressure. You'll need a sharp cutter with adequate relief on both sides. If your lathe has a high geared carriage like the smaller South Bends it will take a lot of force on the handwheel. I personally would probably not attempt to use power feed for that.
I have cut 3/8" keyways on the mill, in two passes and it takes a lot of strokes and a fair amount of pressure. You'll need a sharp cutter with adequate relief on both sides. If your lathe has a high geared carriage like the smaller South Bends it will take a lot of force on the handwheel. I personally would probably not attempt to use power feed for that.
Bobw
Diamond
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- Feb 8, 2005
- Location
- Hatch, NM Chile capital of the WORLD
My terms may be totally wrong.. But. HARDNESS or SOFTNESS of a STEEL bar has nothing to do with
how much force it takes to deflect it.. Modulus of Elasticy or something (8am Class, I slept
through materials)..
How far you have to bend it to permanently deflect it, or how much it wears, or how much torque
it can take before you rip the threads out, that's a different story...
Spruewell
Hot Rolled
- Joined
- Sep 8, 2015
- Location
- Northern California
Get a broach and an arbor press. You will be done quicker and cheaper without scrapping a bunch of parts
steve-l
Titanium
- Joined
- Mar 2, 2012
- Location
- Geilenkirchen, Germany
My preferred steel for bars is 8620.
Anthony
Aluminum
- Joined
- Aug 6, 2003
- Location
- rural upstate NY
To answer your question, I like just about any cold rolled steel for the bar although toughened alloy is probably best. I've cut keyways in a lathe but never really liked it. I have to concur with Spurewell on his suggestion.
johnoder
Diamond
- Joined
- Jul 16, 2004
- Location
- Houston, TX USA
dsergison
Diamond
- Joined
- Oct 23, 2003
- Location
- East Peoria, IL, USA
hardness has nothing to do with rigidity. all steel has the same rigidity. it all deflects the same amount when loaded with the same force. up to the point it bends permanently. hardness determines how much force it takes to permanently bend (yield)
irrelevant for you since your going to be taking very light cuts just scraping your way to depth.
use the biggest, shortest bar practical. drill a hole through it, and put a bit in it. a broken endmill properly ground would be perfect. start scraping away. about .001" at a time Don't brute force it.
reversing the bit and cutting on the retract stroke will go better on a flimsy setup because it will not tend to dig in.
irrelevant for you since your going to be taking very light cuts just scraping your way to depth.
use the biggest, shortest bar practical. drill a hole through it, and put a bit in it. a broken endmill properly ground would be perfect. start scraping away. about .001" at a time Don't brute force it.
reversing the bit and cutting on the retract stroke will go better on a flimsy setup because it will not tend to dig in.
I'm not sure I understand this statement. Rigidity by definition is the measure of resistance to the force required to "yield". Saying that 2" x 6" long piece of 4140 has the same Rigidity as a piece of 'same dimensions' 1018, is hard to believe.
So if it isn't hardness that makes a thing more Rigid, than what is? Density maybe? IE, a solid Carbide Bar normally for me is a 6-1 overhang ratio, and Steel is 4-1 ratio, very different Hardness'. Not asking about set-up or any other variables, just simple chunks of Metal.
I'm asking out of ignorance.
R
This is very common confusion.
Stiffness or rigidity for different steel grades or hardness is the same as long as the part or "bar" doesn't bend permanently. (AKA elastic deformation)
With 200lbs load a 1" diameter and 2' long dead soft 1018 bends same amount as HRC 60 hardened carbon steel. But you are able to put more load on the hardened rod without making permanent bend.
"Young's modulus" or elastic modulus is the property you are after if you want to make something very "stiff" (and its practically the same for all the steel grades and hardnesses)
Young's modulus - Wikipedia
List includes some other suprises also like that titanium is less "stiff" than copper: titanium 110GPa vs. copper 117GPa
steve-l
Titanium
- Joined
- Mar 2, 2012
- Location
- Geilenkirchen, Germany
I think your confusion is in your understanding of yield. Yield is the point of permanent deformation.
Okay, thanks. Now lets talk about Machining, the biggest challenge with Boring as an operation, is vibration. Based on teh above information and Young's Modulus, in a Boring operation a Bar made of 1018 is going to deflect the same amount as a Hardened Bar of 4340. Obviously we aren't making Bars out of A36 or 1018 for that matter--why not? It would be cheaper.
It seems to me, on a molecular level that all things "yield" to a degree, right? The Atomic construction changes if the Bar's molecules are altered (flexing IE) Interesting stuff here, to me at least.
R
It seems to me, on a molecular level that all things "yield" to a degree, right? The Atomic construction changes if the Bar's molecules are altered (flexing IE) Interesting stuff here, to me at least.
R
I have made couple of ad-hoc boring bars out of cold drawn 1018 and they perform just the same as hardened 4340 withing limits.
-toolpost screws leave dents on soft boring bar
-if insert tooling the insert pockets won't hold size for long. Less of a problem if you use stick of HSS on the end of the boring bar but the hole can still bell-mouth in frequent use.
Young's modulus is the "reason" to use solid carbide or heavy metal boring bars.
Terry Keeley
Titanium
- Joined
- Oct 18, 2005
- Location
- Toronto, Canada eh!
You need a broach and arbor press for that...
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