Thread Bar Project, nothing is going right and I need help

Sorry about the flu.... no fun.

Second picture..... rotate the tool post 90 degrees counter clockwise and you won't need as much overhang.

Third picture.... I can't really make out the tip, but at the rear of the center gauge, it looks like you are nowhere near a 60 degree included angle.....
 
In addition to all the good stuff above my thoughts ran to the centers being out of line or a chuck jaw being defective. As you found swarf in the tapers. Hope you get your project completed as required.
Ray
 
The tip has a 60 degree included as you can see up in there. I know the rear doesn't but does it matter since it will only be cutting with that tiny portion on top? I drew in red where it touches the gauge.

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Your tool looks okay at the business end; the tip of the tool is contacting the 60 degree fishtail on both sides. However, when time permits, re-grind it so that the tip is a bit more to the left side of the tool and the right side is at the correct angle. You can see that the right side, the long side, is less than 30 degrees and the point of the tool is not aligned with the shank of the tool.

All of this stuff is not critical. What is critical is that the angle of the tip is right and that the centerline of the 60 degree tip is perpendicular to the work when you're threading; be sure you use the fishtail to carefully align your tool before you cut. You haven't ground a threading tool before so I think you're doing pretty well.
 
I have grinded all my tools. It's required. We're cutting 1018 Cold Rolled Steel with HSS bits that we have to grind. I made a left-right hand cutting tool and a 90 and 60 degree tool. Do you think I would be OK with this to try it or not. I can't afford a mistake at this point. Maybe I will just start over with a new one?
 
You will need to put a slight relief angle on the top of the tool so there is a negative cutting angle, 3-5* should be enough. Remember to work carefully, making sure you have your lathe and tool set up properly before you cut each thread.
 
Here is a link to a video on the angles of a thread cutting tool. This YouTube creator is a former High School shop teacher and he has hundreds of machining videos. In this case he explains the different types of tool holders and how you need to put a grind on the top of your tool depending on the type toolholder you are using. I would suspect you have the most common at school, which holds the tool at at 16* angle. As long as your off school you might want to watch this a couple times and study the diagrams he puts at the end of the video. This is a good as I can do to help you without being there.

I dont mean to kick a dead horse here but I can not stress enough the importance of paying attention to all the details when working. Even today after having been an apprentice in the late 70's I still check set ups before cutting. Stay with this and soon doing this 4 step threading exercise will become routine, the job is no less important but your ability and confidence will increase.


 
jlsmithseven said:
I have grinded all my tools. It's required. We're cutting 1018 Cold Rolled Steel with HSS bits that we have to grind. I made a left-right hand cutting tool and a 90 and 60 degree tool. Do you think I would be OK with this to try it or not. I can't afford a mistake at this point. Maybe I will just start over with a new one?
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I took a good hard look at the tool you made and I'm pretty sure it will cut threads just fine as it is. You do need be sure you are at center height and that the tool tip is aligned correctly. Put your fishtail against the work and make sure the long side of the gauge is held flat and rigid against the work. Align the tool tip so it perfectly aligns with the 60 degree notch in the side of the gauge. Use a magnifier is needed but make sure both flanks of the tool are aligned with the notch and it should work out just fine.

Next time you grind your tool, set your tool rest to between 12-15 degrees of downward angle. Now mark the tool by dividing the width of the blank into thirds. Then use a protractor set at 30 degrees and draw a line on the tool blank to intersect the first mark on the left. Grind to the line and match the grind to the 30 degree angle on protractor. Grind to get this angle perfect. Then grind the right side of the tool at 30 degrees to make a perfect 60 degree angle at the tip. A tool ground this way is easier to align quickly because the tool's cutting tip is aligned with the shank of the tool and you can get very close to where you need to be visually. You still need to align the tool with the fishtail but its much faster when the tool is ground properly.

Be sure to hone the tool after grinding so the edges are very sharp. I don't angle the top of a threading tool. I do hone it so it is dead flat. I also make a small flat at the very tip, being sure the flat follows the angle of the nose of the tool so that the flat is even from the top of the tool blank to the bottom. This flat helps to prevent the tip from cracking off. Do not forget this flat! It only needs to be very small - maybe 1/64" across - and it does not need to be rounded unless you wish.
 
Justin, Your tool should work fine for this application. What Mikey means by offsetting to the left is more like this.IMG_0785a.jpg This is a 10 mm tool bit. The left flank is about 3 mm long. You really only need to make the left flank 2-3 times longer than the depth of the thread you will be cutting. Its also easier to adjust for 60* grinding angle. If you grind the right hand flank, (long side) 1st. Then you only need to make small adjustments to the way you present the tool to the grinding wheel to get your 60* included angle, and because you are only taking off an amount over a shorter length a light touch is all that is required. I also hone all my tools with a stone after grinding, makes a big difference. And I put the radius on my tools with the stone too. Its much more delicate and you get a nice radius. Too easy to put a big flat on the nose if using the grinder. Good luck next week!

Cheers Phil
 
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