if you take equal depths of cut and keep speeds and feeds the same you can ignore the deflection. those repeated spring passes are a major waste of time in most cases. when you load the machine on the first cut it will remain the same as long as you dont change the variables. your following passes will have the same deflection, so all you need to know is how much that is and you can take heavier finishing passes to get a good surface while holding a few tenths( assuming the rest of your process is reliable anyway).
Depending on the overhang, material, deflection, DOC, cutting edge, tool rigidity, tool pressure......... you gotta pay attention & feel what you're doing & constantly stay on top of your dimensions...... I like to compare the entire experience to treating a lady.
I don’t how anyone else does it, but I square my tool post up with the centerline by placing a 123 block between the chuck face and the tool post. Just run the tool post far enough in to enable placing the 123 block squarely between them, run the carriage to the left until it squeezes the block and squares up the tool post, then lock the tool post down. Takes about 20 seconds!
"We are gonna be boring!" Dude, u were already boring a long time before that. "Touch the inside of your hole." Way to go dude, NOT BORING ANY MORE!! 😀
He was talking about why it cuts again when you take a "spring pass". As someone else already mentioned though, if you don't change the depth of cut and do the same feeds/speeds, then that deflection also remains a constant. What I do is when I start approaching the finished size, I alter the depth of cut a few passes away from final size so that the remaining cuts can all be the same depth of cut so you can still cut deep enough for a good surface finish which you typically don't get when making multiple spring passes. On my lathe (a 9" x 20", so not the most rigid of machines), I typically shoot for multiple passes between .010 - .025" for the last 2-3 passes, checking size each time. If I need to alter the last pass by .001' or so, then the change in deflection is rather minor.
This is delayed but I figured Ill answer anyway. To my knowledge it is not, I say this because this machine is 20 years old and we have always used it this way. Ill look more into it but the older guys told me "no its fine". I have seen it save a lot of tool posts in my career so far.
There are a number of reasons that "above center" is a good practice and recommended by cutting tool mfgs., usually .005 -.010". The tool is mounted off center of the tool post. As with end mills, where the deflection increases exponentially as the tool length increases, the greater distance off center increases the load and potential movement. Any particles in the dovetail of the tool post can allow movement under load. You mentioned length, this allows the tip to go below center. Lastly, the smaller the bar diameter, the greater the rotational (radial) movement of the tip downward, which increases as the tool edge starts to form a "wear land". One additional consideration, inserts for steel will have less back clearance, and as the bore gets smaller, the bottom of the insert can rub or "heel" on the bore, increasing the downward movement. Play with speed, feed, depth of cut, and edge geometry (more positive insert or rake) before "going low" for size and surface finish!
You can set your boring bar on center without issue. I routinely set a 2"/50mm devibe boring bar exactly on center and stick it out 20"/500mm and have no issues with clearances even when taking a cut that causes the bar to dive 1/8"/3mm down. Bars are designed to have clearance on center, and a lot of machines have no adjustment for tool height anyway. The only time I ever have a bar rubbing on the bottom of the bar from lack of clearance is when I am trying to deepen an already existing shoulder in a large bore and move my tool to a diameter smaller than the bar can allow (because the bore is large enough to accommodate being that far back without hitting on the back side of the tool) The most common inserts, *NMG (N=0 degrees), have no clearance and instead the bar will have the clearance built into it (usually -5 degrees), while Inserts in the *CMT (C=7 degrees) or *PMT (P=11 degrees) lines have clearance built into the flank of the insert (which is why you also only have one usable side of the insert opposed to both sides with the 0 degree clearance inserts). The distinction isn't whether it has a positive/negative chipbreaker , but the style of insert. The *CMT and *PMT insert styles and the accompanying bars are usually smaller bars (3/4" or smaller typically) and have less material to make the insert pocket and clearances with so they leave the pocket flat and grind the clearances into the inserts themselves. Long story short, if the bar fits in the hole, it's designed to have clearance in that hole on center with whatever insert fits in the pocket.
Super helpful, move up from a SB 9 jr. To a heavy 17 Lebond and learning the ropes, Thx, very helpful, as that today I have a piece of 2.75 DRM 0.375 wall hanging out 8 in off my 12in 4 jaw, with no follower,, a real bitch to only cut o.395 to fit a a sleve that will let me us the live center on in the tail stock ,🤐 building a center & follower rest in my future ♥️👍
What... is "Push Off"...? Can we please refer to this phenomenon with its actual name of "Deflection" and EVERY Boring Bar Manufacturer will specify the "Minimum Bore Diameter" that each one of their Bars is capable of. There should be no guesswork involved in selecting the right diameter Bar for the hole you use it in. If your Bar comes into contact with the material being Bored, you've either selected the wrong bar... Or the Machinest set it up incorrectly. You should also know if you need the Insert to be held in a Positive or Negative rake. The Insert Pocket dictates that nomenclature. Any information on the correct speeds, feeds or correct bar selection can be easily found by contacting a reputable Boring Bar Manufacturer of which there are many. Been selling Industrial Tools for over forty years.
if you take equal depths of cut and keep speeds and feeds the same you can ignore the deflection. those repeated spring passes are a major waste of time in most cases. when you load the machine on the first cut it will remain the same as long as you dont change the variables. your following passes will have the same deflection, so all you need to know is how much that is and you can take heavier finishing passes to get a good surface while holding a few tenths( assuming the rest of your process is reliable anyway).
The material seems too much ductile...such long curly continous chips!
Anyway, great video and demonstration...thanks for this.
Depending on the overhang, material, deflection, DOC, cutting edge, tool rigidity, tool pressure......... you gotta pay attention & feel what you're doing & constantly stay on top of your dimensions...... I like to compare the entire experience to treating a lady.
after you center boring bar, how do you set boring bar parallel to work axis? do you use a square or eyeball it?
I don’t how anyone else does it, but I square my tool post up with the centerline by placing a 123 block between the chuck face and the tool post. Just run the tool post far enough in to enable placing the 123 block squarely between them, run the carriage to the left until it squeezes the block and squares up the tool post, then lock the tool post down. Takes about 20 seconds!
@@tomt9543 great, thanks for your explanation
nice vid. drills often are not straight
this is a great video and helped me a lot. Thanks!
"We are gonna be boring!"
Dude, u were already boring a long time before that.
"Touch the inside of your hole."
Way to go dude, NOT BORING ANY MORE!! 😀
Yup Ill add some fire to spice up my next video haha. Thanks for watching. I'm going to add better camera angles and information in my future videos.
Thanks for the tips about boring
No idea what pushoff means but you sure talked about it a lot. Would have been nice to understand why this mysterious phenomenon affects size
He was talking about why it cuts again when you take a "spring pass". As someone else already mentioned though, if you don't change the depth of cut and do the same feeds/speeds, then that deflection also remains a constant. What I do is when I start approaching the finished size, I alter the depth of cut a few passes away from final size so that the remaining cuts can all be the same depth of cut so you can still cut deep enough for a good surface finish which you typically don't get when making multiple spring passes. On my lathe (a 9" x 20", so not the most rigid of machines), I typically shoot for multiple passes between .010 - .025" for the last 2-3 passes, checking size each time. If I need to alter the last pass by .001' or so, then the change in deflection is rather minor.
Great video! One thought, if you use that stop block and power feed. Won't it damage the machine if the powerfeed runs into it?
This is delayed but I figured Ill answer anyway. To my knowledge it is not, I say this because this machine is 20 years old and we have always used it this way. Ill look more into it but the older guys told me "no its fine". I have seen it save a lot of tool posts in my career so far.
nothing on how to set for str8 bore hole. or centered up end to end. not found one video telling as such
This is a great tutorial but I made the mistake of getting an ancient lathe and I can't find the holder for a tool like this
Thanks, damn that was boring. Not in the bad sense though. :)
Very good video. Thanks.
Thanks for the support! Hope this information is helping someone out there.
Machining-Tutorials I’m in a machining program as part of my high school education, u are helpful
There are a number of reasons that "above center" is a good practice and recommended by cutting tool mfgs., usually .005 -.010". The tool is mounted off center of the tool post. As with end mills, where the deflection increases exponentially as the tool length increases, the greater distance off center increases the load and potential movement. Any particles in the dovetail of the tool post can allow movement under load. You mentioned length, this allows the tip to go below center. Lastly, the smaller the bar diameter, the greater the rotational (radial) movement of the tip downward, which increases as the tool edge starts to form a "wear land". One additional consideration, inserts for steel will have less back clearance, and as the bore gets smaller, the bottom of the insert can rub or "heel" on the bore, increasing the downward movement. Play with speed, feed, depth of cut, and edge geometry (more positive insert or rake) before "going low" for size and surface finish!
You can set your boring bar on center without issue. I routinely set a 2"/50mm devibe boring bar exactly on center and stick it out 20"/500mm and have no issues with clearances even when taking a cut that causes the bar to dive 1/8"/3mm down. Bars are designed to have clearance on center, and a lot of machines have no adjustment for tool height anyway. The only time I ever have a bar rubbing on the bottom of the bar from lack of clearance is when I am trying to deepen an already existing shoulder in a large bore and move my tool to a diameter smaller than the bar can allow (because the bore is large enough to accommodate being that far back without hitting on the back side of the tool)
The most common inserts, *NMG (N=0 degrees), have no clearance and instead the bar will have the clearance built into it (usually -5 degrees), while Inserts in the *CMT (C=7 degrees) or *PMT (P=11 degrees) lines have clearance built into the flank of the insert (which is why you also only have one usable side of the insert opposed to both sides with the 0 degree clearance inserts). The distinction isn't whether it has a positive/negative chipbreaker , but the style of insert. The *CMT and *PMT insert styles and the accompanying bars are usually smaller bars (3/4" or smaller typically) and have less material to make the insert pocket and clearances with so they leave the pocket flat and grind the clearances into the inserts themselves.
Long story short, if the bar fits in the hole, it's designed to have clearance in that hole on center with whatever insert fits in the pocket.
Super helpful, move up from a SB 9 jr. To a heavy 17 Lebond and learning the ropes, Thx, very helpful, as that today I have a piece of 2.75 DRM 0.375 wall hanging out 8 in off my 12in 4 jaw, with no follower,, a real bitch to only cut o.395 to fit a a sleve that will let me us the live center on in the tail stock ,🤐 building a center & follower rest in my future ♥️👍
Good video, thank you
What... is "Push Off"...? Can we please refer to this phenomenon with its actual name of "Deflection" and EVERY Boring Bar Manufacturer will specify the "Minimum Bore Diameter" that each one of their Bars is capable of. There should be no guesswork involved in selecting the right diameter Bar for the hole you use it in. If your Bar comes into contact with the material being Bored, you've either selected the wrong bar... Or the Machinest set it up incorrectly. You should also know if you need the Insert to be held in a Positive or Negative rake. The Insert Pocket dictates that nomenclature. Any information on the correct speeds, feeds or correct bar selection can be easily found by contacting a reputable Boring Bar Manufacturer of which there are many.
Been selling Industrial Tools for over forty years.
Did you say .."yeah I know my tool is dull, but i'm not going to change it"
Your making a tutorial SLICK !!!!
You're*
Great
This was so boring.
Jeff Vader are u a machinist?
@@imperfectperfectionist9853 it's a pun lol