QCTP projection

wawoodman

wawoodman

himself, himself
H-M Supporter Gold Member
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Mar 19, 2011
Messages
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Please take a look at photo 1. You can see the problem; the body of the tool post is going to hit the end of the work. In photo 2, I extended the tool farther out, so the post will clear. However, in photo 3, you can see how far the bit is cantilevered out. This doesn't look right to me. What am I doing wrong?

QCTP1.JPG QCTP2.JPG QCTP3.JPG
 
loosen the big nut holding the tool post and turn it, you can adjust it to where you want it. see how it's aligned in this pic
steve

QCTPBallBearing.jpg
 
The two positions on your QCTP are not for any specific holder only. Remove the turning tool holder from where you have it anr put it on the other dovetail. Put the tool bit in the end that faces the chuck. Now set the tool post angle and you will have all the cleaeance you could ask for.

"Billy G" :))
 
For general purpose work, I set my post square with the world, and develop the needed angle or clearance on the tool, whether it's a hand ground bit or a factory holder. You're quite right, that's too much tool hanging out for a healthy cut. I noticed that you have a lead angle on the tool. If you need a square shoulder on the part, that tool isn't really the right one for the job. It should be ground square enough to face off the shoulder. At times, it may take two different tools to do the job, because a good lead angle can help with chip loading. Then when you get near size, switch to a tool with little or no lead. Or if you really need a square shoulder, even a slight negative lead will help face.
 
I think I understand. I was grinding to match the profile of the Armstong style toolholders. If I reverse that grind (that is, just grind the leading edge enough to sharpen it, and then grind the tip to achieve an 80 or 85 degree angle, I would only have to cant the tool post a very little bit. The profile presented to the work would remain the same.

Bill, if I understand your idea, that would put the toolholder on the "trailing" side of the tool post. Is that right?

Thanks, all.
 
jumps4 said:
loosen the big nut holding the tool post and turn it, you can adjust it to where you want it. see how it's aligned in this pic
steve
Click to expand...

I think Jumps4 has got you covered, that pic tells you most all your doing wrong.
 
Yes, just the opposite of what you are doing now. Tony has set you straight also as has "jumps. There are many ways out of your predicament. It just takes a little thought sometimes.

"Billy G" :thinking:
 
I use this pic to help me with tool shape it may help you mike
steve

Machine_Machine-Tool_Lathe_Tool-bit-shapes.jpg
 
Very helpful, indeed, and I will work on that. It seems that my problem was following TubalCain's sharpening videos. He grinds a tool very similar to the right-cut/side facing tool, and uses it both for turning and facing. But if you look at the sketch, the bit is angled to present that face to the work, and that seems to be where I went wrong with the QCTP.

I'm going to try to grind that pattern, but much more upright. I think I want it to look more like the LEFT cut finishing tool. That would follow the angles of the inserts more closely, I think.

If someone would be so kind, could you post a top view of an insert bit, so I can see the angle?

Thanks to you all for putting up with me!
 
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