So what actually causes the concave/convex faced cut when parting? I've found that with these thinner blades it is more pronounced. As a experiment I angled the tool a degree at a time until I was getting beautiful straight , polished, almost "pipless" parts in 1" 12L14 at about 2.5 degrees toward the chuck, But I know everything I read says this is a big no-no. The part lopped off is square, although the end in the chuck still has a convex face. Is this really so wrong if I'm getting good results? What else can I do to fix it, Or what am I doing wrong to cause it? Also, What is the likelyness of having success with one of those .120 wide parting tools like this? Mostly using 6061 and 12L14(the only steel that I'm gonna buy for machining from now on!) http://www.latheinserts.com/product.sc?productId=46&categoryId=82 I know this is much wider than most people say is appropriate for a 13x24 machine. Thanks in advance for the help, Todd
-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Parting off
- Thread starter Ed Hoc
- Start date
Yeah, I'm sure I will need something stronger at some point, I guess what I meant is it is the only thing I'm going to just buy chunks of to stick in the rack without a prior need. I'm sure I'll get more used to having to polish up some stuff, Its just so nice to have it looking so fine without.
Sounds like as far as the parting tools the .108+ stuff is just too wide? Unfortunate I can't seem to find any narrower stuff with inserts that is within a "Hobby" budget. I will go look at the HSS blades and see if I can find any nicks,etc. It sounds like youre saying the main reason for a concave would be that the tip of the tool is "steering" the blade that way with the tip? Todd
Sounds like as far as the parting tools the .108+ stuff is just too wide? Unfortunate I can't seem to find any narrower stuff with inserts that is within a "Hobby" budget. I will go look at the HSS blades and see if I can find any nicks,etc. It sounds like youre saying the main reason for a concave would be that the tip of the tool is "steering" the blade that way with the tip? Todd
Try dressing the end and top of the parting blade. It's gotta have a sharp edge, with no nicks and not rounded over. A stone and a few minutes to resharpen the tip will do wonders for the operation.
Also, as rigidity is extremely important, set the blade so it is just sticking out as much as you need to part off. So, with a 1/2 inch part, the blade should be sticking out about .550 or so.
Also, as rigidity is extremely important, set the blade so it is just sticking out as much as you need to part off. So, with a 1/2 inch part, the blade should be sticking out about .550 or so.
- Joined
- Jan 30, 2011
- Messages
- 39
Max, The blade should stick out of the holder minimum length as rleete stated. I try to keep the end ground square , as any angle will steer the cut. Watch the sides of the tool for wear, that will cause grief too; You may have to lose the first 1/4" or more to get good tool, if it's been abused.
On production jobs, do what you have to, to tune the cut-off piece as good as possible, then face the stub end in the chuck for the next part.
Paddy that looks like a primo Tool!
Ed Hoc
On production jobs, do what you have to, to tune the cut-off piece as good as possible, then face the stub end in the chuck for the next part.
Paddy that looks like a primo Tool!
Ed Hoc
Parting is the one operation I really dislike. But I think I might have it figured out, even though I still use the bandsaw mostly.
The first parting blades I bought had an angle ground on the top edge. I was having inconsistent results & breaking blades, even with minimal stickout & aluminum.
I bought new blades without the angle ground on the top & it works perfect. Put the old "angled" blade back in & stuck a piece of .030 MIG wire between the blade & holder. This blade cut ok too. So I figured out the angled top blade was sitting in just enough of an angle to cause it to cant to the side & grab the part.
1st time it happened, I had to change my pants.
The first parting blades I bought had an angle ground on the top edge. I was having inconsistent results & breaking blades, even with minimal stickout & aluminum.
I bought new blades without the angle ground on the top & it works perfect. Put the old "angled" blade back in & stuck a piece of .030 MIG wire between the blade & holder. This blade cut ok too. So I figured out the angled top blade was sitting in just enough of an angle to cause it to cant to the side & grab the part.
1st time it happened, I had to change my pants.
Last edited by a moderator:
Just wanted to report that Mark's technique was a winner for me. I took his advice and used a piece of .024 solid mig wire behind the bottom of the parting tool (blade) in the tool holder, and it was visually appearant that the tool was standing straighter. I used it and parted a small piece of pipe that I had tried to do unsuccessfully earlier. It worked like a champ!
I measured the top of the tool at .100" and the bottom at .050". The .024 mig wire was as close as I could find to lining up the tool vertically.
Thanks Mark. ;0
I measured the top of the tool at .100" and the bottom at .050". The .024 mig wire was as close as I could find to lining up the tool vertically.
Thanks Mark. ;0
- Joined
- Jun 17, 2011
- Messages
- 2,063
I'm parting off the bearing flanges for the SOSE build with a parting tool I got with a set. The 'bit' is held at a positive rake. I wouldn't cut at all until I had lowered it about 1/16", or until the top was pointing directly at the center of the work.
In this case, it works, because the piece is drilled to almost 3/8" inside, so it does part off. If it was a solid piece, that would never work. Why do so many tool companies design parting tools with positive rake if it doesn't work?
In this case, it works, because the piece is drilled to almost 3/8" inside, so it does part off. If it was a solid piece, that would never work. Why do so many tool companies design parting tools with positive rake if it doesn't work?
Last edited:
- Joined
- Sep 13, 2011
- Messages
- 271
[quote author=Hawkeye link=topic=3631.msg28568#msg28568 date=1317865923]
Why do so many tool companies design parting tools with positive rake if it doesn't work?
[/quote]
IIRC at this early hour, a positive rake takes less force and horsepower to cut than a negative raked tool..everything else being equal.
For doing cutoffs with a center hole I chuck up a piece of wooded dowel in the tailstock. Whatever size fits easily in the hole will work. I like this better than a piece of steel or brass because the wood will twist off without harming anything should there be trouble.
About the only time this won't work is when the center hole is tiny. Then a piece of fine copper wire sometimes will help. ;0
Why do so many tool companies design parting tools with positive rake if it doesn't work?
[/quote]
IIRC at this early hour, a positive rake takes less force and horsepower to cut than a negative raked tool..everything else being equal.
For doing cutoffs with a center hole I chuck up a piece of wooded dowel in the tailstock. Whatever size fits easily in the hole will work. I like this better than a piece of steel or brass because the wood will twist off without harming anything should there be trouble.
About the only time this won't work is when the center hole is tiny. Then a piece of fine copper wire sometimes will help. ;0