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Models for grinding HSS Lathe Tools

DHarris

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Hey Barry, Glad they showed up - - finally - - 10 days to get to you!

Now that you have them in hand & mike's write-ups it's going to be a piece of cake!

Glad I could help!

Dave
 

q20v

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Tell me about it, my wife normally checks the mail during the day and I was often going in the evening in case stuff got delivered late for some reason. Just the other day she asked what I was all excited about and when I told her (tried my best to explain) what I was expecting she rolled her eyes and shook her head. Today I showed her the tools and she had a good laugh "You've been waiting for those three little things?!?!"
Some people just don't get it! :D
 

Z2V

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Well, tonight I ground a left hand square tool to put in my small flycutter. It cut great and the finish was more than acceptable. I started with a small nose radius and will add to that tomorrow to see that what effect it will have. The tool is about 2" diameter and I was spinning it at 400 rpm cutting mild steel. I will also try different spindle speeds while I'm at it tomorrow just ran out of time tonight.

IMG_3750.JPG
IMG_3754.JPG
 
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mikey

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Keep us posted on your LH tool, Jeff. A square tool should work, especially since the relief angles are increased. It may help to increase your back rake to focus the forces at the tip; I would try 18 degrees and see if it helps. In fact, I would try increasing back rake and see if it alters the finish. Then try increasing the nose radius after that. I will bet that increasing the back rake will do more than increasing the radius will.
 

Z2V

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Will do Mike, I'm thinking of trying different spindle speeds then going to the tool. I'll grind the 18* and give it a shot, then adjust the nose radius.
 

q20v

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Hey guys,

I finished my copies of the turning and knife tools today. Gotta say, Mike's instructions were pretty clear and easy to follow. While the process was simple, it still took me a bit of time to get the setup correct on my grinder. I have a small 6" grinder with basic tool rest, which I modified slightly to make work. There are locking teeth on the rest which secure it at ~15* increments, but using Mike's tool as a reference I found it wasn't close enough. So I put a washer between the teeth to allow for unlimited adjustment.

I also used a ball point pen for layout lines on the tool rest surface, which cleaned up nice using Dykem fluid remover.

Having Mike's tools in hand made replicating them very easy. I used them to compare side by side with my tools as I progressed, and to setup the tool rest angle (15*). Also, for getting the layout lines established.

The next steps for me are to replicate the grind using HSS, which I may try tonight after the kids go to bed, and then try it out on various materials. I have some DMT credit card sized diamond sharpeners on order from Amazon, based on Mike's recommendation.

Mike, thank you very much for taking the time to make these tools for us to look at. As mentioned, having them in hand was extremely valuable and educational! Thank you thank you thank you!

Jeff, thank you very much for organizing the distribution of the tools! I'll package Mike's tools up and have them out tomorrow. I'll drop you a PM once they're gone.

Dave, thanks again for sending them to me!

DSCN0125.JPG

DSCN0127.JPG

Knife tool: Mike's on the left, mine on the right. I don't have a radius on the nose yet.
DSCN0128.JPG

Turning tool: Mike's on the left, mine on the right.
DSCN0129.JPG

Another angle of the turning tool. Mike's on top.
DSCN0130.JPG

Turning tool, Mike's on the left.
DSCN0131.JPG

Knife tool, Mike's on the left.
DSCN0132.JPG

Barry
 

Z2V

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Great job Barry, I can't tell the difference in the two
I agree, Mikey's write up is so easy to follow
 

mikey

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I agree, Barry, its hard to tell which one is mine - you did a great job! It took me a long, long, long time to get my tools to look like yours and I am totally stoked that you guys are able to do this so fast. I've written a lot of stuff about tool grinding but it wasn't enough; it took the models to make it gel, or at least it looks that way.

Thank you for your kind words, Barry and Jeff, but more than that, I am thrilled with your success!
 

bfk

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After some time off to deal with a nasty allergy, I tore open the package of the sample tools last night and decided to try my (totally inexperienced) hand at grinding some tools. It didn't take long to realize that I need a much more stable and secure grinding situation. Resting the grinder on my lap was apparently a bad idea. Just kidding.

The rest on the grinder only adjusts in one direction, so setting it to 15 degrees was impossible. I have another grinder that does adjust in two planes, but the wheel on it is the one that was there when it came from craigslist. It seems to be made of uncuttium.

So as a mature adult I decided to wait until I could get my setup fixed. Yeah, right. Tonight I went back down and cut the right hand tool using both grinders. It was a pain, but the alternative was waiting, and where's the fun in that? Anyway, I got it done. It's not nearly as pretty as Mikey's or Barry's, but I thought I'd give it a try. I had made a 1/4" version for use on my Sherline. All I can say is WOW! Either this really works or someone snuck into the basement softened the piece of aluminum I grabbed out of the pile.

As a total newbie I had bought a cheap set of indexable tools from eBay or Amazon, or wherever, thinking that this is the newer technology---it must be better. (I should know better at my age.) They work, I've made a few things successfully and learned to live within the limits of the machine and my lack of skill. Cutting 6061 T6, I could reliably take .020 cuts and get a decent finish. With my first attempt at Mikey's HSS tool I can take .050 cuts in the same material. Colour me amazed. And very grateful.

Now to get some grinding wheels of a known quality. I think my Santa is list is already full, so I don't think CBN is in my near future, but probably some Norton AO wheels will make this much easier. And a proper adjustable tool rest. Maybe I'll try making one, I know I saw some plans on this site somewhere.

Huge thanks to Mikey for a major chunk of my machining education.
 

Z2V

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BFK
I put this tool rest together after Mikey started this project so that I could get full benefit from it. Real simple and fully adjustable. It's aluminum except for the table that is steel.

Bf IMG_3727.JPG IMG_3726.JPG IMG_3725.JPG
 

mikey

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bfk, thank you for your kind words. I really appreciate the sentiments from you and all the other guys.

May I suggest you change from 1/4" tool bits to 3/8"? I think you will find that the Sherline lathe responds very well to a stiffer bit, and you will see this when you take fine finishing cuts; your accuracy goes way up.

The maximum depth of cut a tool will produce is great but quite honestly, I don't often cut that deep. I know the tool can handle it but why waste material? What really matters to me is how accurately I can turn with that tool. If you keep the nose radius down to about 1/64" or so, the square tool will size accurately enough to come in dead on size most of the time. The cool thing is that when you have a half-thou to take off, it will take that much off, too. Try interpolating your depth of cut to 0.00025 and, if the tool is sharp, it will take that off the diameter.

Cutting force reduction isn't just about how deep you can go; it is also very much about how that reduction enables very fine cuts. This is why I keep saying that for a small lathe, HSS is often the better option - accuracy!

Anyway, good for you, bfk! Keep grinding, experimenting and enjoying your lathe.

Mike
 

mikey

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I was corresponding with one of the guys tonight and mentioned how to hone a tool. I am reproducing that advice here. Please don't be insulted by this; it is simply my way and I thought you might find it useful:
  • Use an extra-fine diamond stone and water to lube it. Be sure the stone is clean; wash with Ajax or similar first and get it clean and flat.
  • If you can, submerge the stone in water and then place it on a solid surface.
  • Bring the side cutting flat into contact with the stone and make sure it sits dead flat, no rocking. Gently stroke towards you. Going back and forth will make you rock the tool and you will round the flat. Just pull and apply gentle even pressure. You are not trying to grind the surface; you are simply honing it.
  • Do the same to the end cutting face. Be careful not to tip the tool; just keep it flat and pull lightly. EDIT: I should tell you that your goal is to raise a burr at the top of the face you're honing. You will remove this burr in the next step.
  • Finally, hone the top of the tool. You MUST keep this flat. It usually only takes a few strokes per face to hone (EDIT: to remove the burr) the tool.
  • Do not touch the nose radius unless it is getting too small. If you need to recut it, go easy and try to keep the radius even from top to bottom and side to side.
You can cut all kinds of facets if you are careless in how you hone your tools. It doesn't take a lot of pressure to hone HSS. More strokes is better than heavy pressure. When an edge is sharp it will not reflect light. If you look at the side cutting edge and see a band of bright reflected light then your tool is not sharp; hone it until the light is gone.

Remember that it is easier to hone a tool at the end of the day than it is to let it get dull and have to regrind it.
 
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q20v

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Thanks guys. I've ground a few tools in the past using the SB "How to Run a Lathe" for guidance, but I never put that much time or effort into the grinder setup. I also used to just guess at the angles. I didn't get a chance to grind HSS last night but am excited to do so.

Mike, thanks for the honing tips. I've always dragged the tools across the abrasive so that a burr would be left on the dull end, i.e. the sharp edge leading the drag across the stone, if that makes sense.. No rhyme or reason for this, just what I thought was right. Should I drag the opposite way? Or does it matter?

Barry
 

Z2V

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I still have a set of Mikey's tool models in Canada. If there are any of you guys in Canada that would like to get in on this shoot me a PM.
Thanks
Jeff
 

mikey

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Thanks guys. I've ground a few tools in the past using the SB "How to Run a Lathe" for guidance, but I never put that much time or effort into the grinder setup. I also used to just guess at the angles. I didn't get a chance to grind HSS last night but am excited to do so.

Mike, thanks for the honing tips. I've always dragged the tools across the abrasive so that a burr would be left on the dull end, i.e. the sharp edge leading the drag across the stone, if that makes sense.. No rhyme or reason for this, just what I thought was right. Should I drag the opposite way? Or does it matter?

Barry
I try to raise a burr on the top of the tool, Barry. That way, when I hone the top surface I take that burr off, leaving a sharp edge behind. After shaping the tool on the belt sander, I hone really carefully with the coarse stone. I am looking to get the coarse grind marks off without changing the angles of the face, creating facets or grinding down an edge. When I go to the fine stone, all I want to do is remove the marks from the coarse stone. Same with the extra-fine stone, but here I am making sure that I have zero light reflecting off the cutting edges. Once I get that, I stone the nose radius on and hone the top surface again and the tool is ready for use. It normally takes me far longer to hone a tool than to shape a tool.

A tool sharpened this way will shave hair, cut meat and will definitely cut metal. If I shaped the tool with the right angles, it will stay sharp for a long time. As I work, I keep an eye on the edges. If I see reflected light (which I rarely ever do), I stop and hone it with a few strokes; takes all of 15 seconds to do. Most guys don't pay much attention to their edges but once you see how a sharp tool cuts you will begin to. When you're trying to come in on size on a critical part take the time to sight your edges because a dull edge will deflect and this affects your accuracy.
 

Bamban

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In support of the Junior shooting program Mike donated a couple of Rex AAA cutters he made, one knife and the standard turning to cuts 416R SS specifically. Following Mike's instruction on angle of attack of the turning tool, made turning 20 inch barrels a lot easier, played with the angle till i got the results. Pointing the cutter towards the chuck when roughing and the other way finishing is the key, which I never practiced before with indeaxble carbide bits.

The knife tool is excellent in cutting or finishing the tenon shoulder. I needed to adjust the headspace on one barrel 0.0005, decided to use the knife tool, touch off the tenon, monitoring the tool post with 0.0005 indicator, moved the carriage and cut. And it indeed shaved off 0.0005 on the tenon shoulder.

On Mike's suggestion I will grind my own and duplicate and save his for models to copy. The first one I will duplicate is the knife tool specifically for cutting crown



Mike, thank you.
 

mikey

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In support of the Junior shooting program Mike donated a couple of Rex AAA cutters he made, one knife and the standard turning to cuts 416R SS specifically. Following Mike's instruction on angle of attack of the turning tool, made turning 20 inch barrels a lot easier, played with the angle till i got the results. Pointing the cutter towards the chuck when roughing and the other way finishing is the key, which I never practiced before with indeaxble carbide bits.

The knife tool is excellent in cutting or finishing the tenon shoulder. I needed to adjust the headspace on one barrel 0.0005, decided to use the knife tool, touch off the tenon, monitoring the tool post with 0.0005 indicator, moved the carriage and cut. And it indeed shaved off 0.0005 on the tenon shoulder.

On Mike's suggestion I will grind my own and duplicate and save his for models to copy. The first one I will duplicate is the knife tool specifically for cutting crown



Mike, thank you.
Thank you, Bamban. With your consent, can I post the angles for the tools so others can duplicate them for working 416R? It will be a good exercise to show how we chose the angles we chose and thanks to you we know we have a working tool that others can duplicate for their work. What do you think?
 

mikey

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Okay, Bamban and I discussed his work before deciding on what tool geometry to use. He is turning 416R stainless steel rifle barrels. (I have not turned 416R before.) It comes prehardened to somewhere between Rc 24 to 36 so maybe semi-hard. Like all stainless steels, 416R will work harden so we needed a tool that would cut with lower forces to keep the tool from bogging down in the cut and producing heat. We also needed to clear the chips out fast to keep cutting temps low. Most of the work is general turning and facing but rather than just make a turning tool, we chose to make a general purpose tool and a knife tool.

HSS can cut 416 but a tungsten cobalt tool would handle the heat and abrasion better. We chose a Rex AAA bit because it has 5% cobalt but 18% Tungsten, the highest tungsten content of any bit made by Crucible. This would allow the tool to handle high heat and abrasion.

Here are the specs we chose:
  • Side and end relief = 15 degrees
  • Side rake = 25 degrees
  • Back rake = 10 degrees
The relief angle of 15 degrees is about 50% more than called for in this material. I chose this to reduce cutting forces but also to improve the finishes. By lowering forces, the tool should cut more freely and this should reduce heat.

The side rake is 7 degrees more than the angle table calls for. The goal is to greatly improve chip clearance while also reducing cutting forces. Given that the relief angles are increased and side rake is also boosted, the risk of reducing edge life is a real thing so I encouraged Bamban not to hog with this tool.

Back rake is increased by only a few degrees. This is intended to keep the cutting forces focused juuust to the side of the nose radius. It would have been nice to increase back rake more but then we would need a larger nose radius to finish well and this would lead to deflection, less cutting action and more heat production so I opted for more side rake and kept back rake reasonable. Focusing the forces here will enable the tool to rough well and face very accurately.

We chose a general purpose shape and a typical knife tool shape but used the angles above for both tools. The nose radius on the turning tool was held at about 1/64", while the knife tool radius is smaller than that. The reasons for these radii are to reduce radial forces to improve accuracy first; finish is a secondary consideration. If a better finish is required, the nose radius can be increased.

This is an example of how we can take a general purpose turning tool shape and alter its geometry to accommodate the peculiarities of the material. I will admit that since I haven't turned this material myself, the angles chosen were a guess ... but it was an educated guess. We chose a tool blank with the desired properties so it should hold up under frequent use; I think we chose well. Here are the tools right off the belt sander:

IMG_5657.jpg

My thanks to Bamban for allowing me to share the specs on his tools. I wanted to show you how a tool blank was selected and how the angles were chosen. Bamban already told you how he altered lead angle to both rough and finish, which is helpful.

Now we have a tool that is proven to work with 416R. If you have a tool geometry you would like to share, please feel free.
 

q20v

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Hey guys,

I had a bit of time tonight to try the RH turning tool on a piece of Cleveland Mo-Max HSS that I had. I copied my copy of Mike's turning tool pretty much exactly, which took some time to accomplish considering my small grinder and Mo-Max is a tad harder than key stock... anyway, got it done and spent a decent amount of time honing, first by practicing on my key stock bit, then carefully on the HSS. Mike, I tried both honing techniques we discussed above and I felt I had better control doing it the way you suggested, basically piling up the burr (even though none really built up) on the cutting edge, then taking it off by honing the top.

The DMT plates I ordered arrived today and worked very well. (don't mind the shape of the back of the bit, I bought it used at a second hand store)
DSCN0133.JPG

This is the new grind next to my previous attempt, using the South Bend manual as a rough guide. It worked with mixed results.
DSCN0140.JPG

Please let me know if anything can be improved, particularly with the honing. I'm using a 6" grinding wheel so the hone is only really touching the edges.
DSCN0138.JPG

Looking at this picture now, I kind of see a band of reflected light on the top edge. Is this what you're talking about trying to avoid, Mike?
DSCN0139.JPG


I was almost going to stop there and go to bed, but I had to give it a try. The deeper cut is with very little lead angle (~10*) and the 1.25" piece of 6061T6 sticking out way too far. There are chatter marks on the surface as a result. Second cut (shiny one) is with a greater lead angle (as pictured) and the bar pulled into the chuck. Very very nice finish!!
DSCN0141.JPG

Then I tried a piece of 1.5" mild steel. Same increased lead angle as before. Same impressive result on the surface finish. Then I put it to the test and successfully took less than .0005 off the diameter. Barely a hair of material came off the bar. Wow! Can't say I've ever done that before.

DSCN0142.JPG

Maybe tomorrow I'll give the knife tool a try on some HSS. Gotta say I never thought I'd be putting so much time into grinding HSS, but I'm having a great time doing it now that I have some good direction!

Barry
 

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mikey

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Grinding HSS is a bit different than keystock, isn't it? There will be a tendency to push harder and grind faster but I suggest you not do that with a wheel. Take your time, dip the tool in water to keep it cool and it will get there eventually.

You need a larger nose radius on the tool, Barry. Try for a 1/64" to 1/32" radius and the tool will finish much better for you.

As for honing, yeah, when you grind with a small wheel it will tend to create a scallop on the flat. A belt will not do that. You need to flatten the entire side cutting edge, from the tip back to where the back rake curves up. This will give you the entire side cutting edge to work with. Same for the end face; you should catch the entire edge. The top should be honed so that the side and end edges are clean, sharp and do not reflect light.

The reflected light I was referring to will be on the edge created by two planes as they intersect, both the side and end.

Try honing the tool well, then align the shank of the tool perpendicular to the work to rough. If it chatters, which it won't, then turn it slightly more toward the chuck. If you want to size the work then turn it more toward the tailstock. You have to mess with it but the tool will tell you when its right; it will cut smooth and clean with a good finish.

As for taking a fine cut, yeah, this tool can take a very fine cut. I've dialed in a 0.0001" depth of cut (using a dial indicator) and cut it with the square tool so I know it can be done.

Good work, Barry! You went from newbie guy to tool grinder in a matter of days. It takes time to hone your skills so be patient and it will come.
 

mikey

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I just re-read my post above and it is unclear. Barry, you need to hone the faces but you do not need to flatten the face with the hone. Only the upper and lower edges will be honed and that is just fine but try to catch the entire cutting edge. Sorry, Barry.
 

mikey

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I was queried tonight about how a square tool cuts as you turn into a shoulder. As I stated before, most of the cut is made with the nose radius but the end cutting edge is also involved.

The tip geometry of a turning tool is actually rather complex but basically you have two cutting edges joined by a nose radius. You have the side cutting edge, which is comprised primarily of the side relief and side rake angles, and you have the end cutting edge that is comprised primarily of the end relief and back rake angles.

When turning normally, the side cutting edge is the primary edge used. However, when turning into a shoulder, the end cutting edge is primary. You can see this in the pic below; the side of the nose radius and the adjacent end cutting edge is in contact with the work:

IMG_5652.jpg

What actually happens is that the end cutting edge cuts like a facing tool and this has the potential to produce very good finishes. However, there is also a fair amount of edge in contact with the work so cutting forces increase. Therefore, when turning into a shoulder, lighten up on your depth of cut and you will retain your accuracy and finish. Go too deep and you get deflection and can produce chatter due to the edge contact. What I do is rough until I am about 0.005 - 0.010" from final size and then change my lead angle like in the picture so I can get into that corner. Then I can reduce depth of cut and sneak up on the final diameter; works good.

This is one reason why I recommend you make the side and end relief angles the same; doing this reduces cutting forces and it makes a difference when taking light cuts into a shoulder. While this is yet another thing to remember, you will eventually learn to reduce your depth of cut in this situation without even thinking about it. At least now you know why you're doing it.

Edit: the work piece in the pic is a prop and was not being turned. An actual cut would produce a mirror finish.
 
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q20v

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Mike,

Thanks for the feedback!

Nose rad: Definitely agree with you. It was awkward trying to put the small radius I have on the tool, as I'm essentially freehanding it on the grinding wheel. Although the surface finish is pretty good in the pictures, that was at the slowest feed rate and there is still a discernible line around the work piece (more evident in person). Embarrassingly, I never thought to re-adjust my grinder tool rest angle so that I don't have to freehand the initial cut (small flat) for the nose rad. I'll try that tonight and carefully round the cut with the DMT plates.

Honing: I think I'm honing just the point of the side cutting edge because that surface may not be perfectly flat (not talking about the grinding wheel scallop, but the length from the tip of the tool, back), the pressure I was putting on the tool while grinding was likely inconsistent as I moved across that surface (grinder wheel is about 3/4" thick). I'll put a straight edge across it tonight to see how flat it is.

I'll try again tonight and report back with the results.

Barry
 

mikey

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Mike,

Thanks for the feedback!

Nose rad: Definitely agree with you. It was awkward trying to put the small radius I have on the tool, as I'm essentially freehanding it on the grinding wheel. Although the surface finish is pretty good in the pictures, that was at the slowest feed rate and there is still a discernible line around the work piece (more evident in person). Embarrassingly, I never thought to re-adjust my grinder tool rest angle so that I don't have to freehand the initial cut (small flat) for the nose rad. I'll try that tonight and carefully round the cut with the DMT plates.

Honing: I think I'm honing just the point of the side cutting edge because that surface may not be perfectly flat (not talking about the grinding wheel scallop, but the length from the tip of the tool, back), the pressure I was putting on the tool while grinding was likely inconsistent as I moved across that surface (grinder wheel is about 3/4" thick). I'll put a straight edge across it tonight to see how flat it is.

I'll try again tonight and report back with the results.

Barry
Barry, I suggest you not use your grinder to put a nose radius on your tools; it is very difficult to do this under power. Use your fine or extra-fine diamond stone to do it manually. Just grind an even flat at the nose that extends from the top of the tool to the bottom, making it just slightly narrower than the nose radius you want. Then gently round the sides of the flat and blend it into the side and end faces.

Maybe consider using a belt sander as a tool grinder. I will try to find the time to use ceramic belts on my 1/3HP Craftsman belt sander to see if they will allow that machine to grind tools. If it does then we have a cheap and readily available option for a machine that will work. I'll get on it soon.
 

q20v

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Hey Mike,

Okay, I follow you now. I'll give it a go manually. That edge is tricky to radius because it's curved (end and side faces are scalloped from the grinding wheel). And I hear ya about the belt sander. I will have to keep my eye out for one.

Barry
 

Bamban

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Mike,

I have to admit, I learned from your posts and the personal messages you sent me. In the past I always use the indexable carbide bits with the holder just butted up against the inside of the wall of the cut out, basically straight forward into the workpiece and just let the holder and the bit design do their thing.

I have a barrel in one of the lathes, the 1236, that has been sitting there since I encountered the anomoly of the QCGB. Just out of curiosity I played with the bit angle of attack. Here is a short video as I made the finishing pass, cleaning up the previous roughing cut. Notice the bit holder is kicked back towards the TS side. Did not move the QCTP, just adjusted the angle of the bit holder. Notice the finish.

Thank you for all the tutorials.


Nez

Watch "Finishing Pass Cutter Towards TS" on YouTube
 
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Randall Marx

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Hi Mike
Thanks again for taking the time and putting forth the effort to help all of us with this endeavor! I have a question regarding the grinding tool. I am currently stuck with a bench grinder to use for grinding my tools. Using the periphery of the wheel to grind, where do I need to set the angle in relation to the tool? Does the 15-degree tangent need to fall at the top, middle, or bottom of the tool? In other words, If I match your example to my grinder, would I set the table angle with the wheel actually touching the ground face on the top or what? I ask because the tangent location will change the apparent angle of the ground face as seen by the workpiece being cut in the lathe.
Thanks again for your guidance.
Randall
 

mikey

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Mike,

I have to admit, I learned from your posts and the personal messages you sent me. In the past I always use the indexable carbide bits with the holder just butted up against the inside of the wall of the cut out, basically straight forward into the workpiece and just let the holder and the bit design do their thing.

I have a barrel in one of the lathes, the 1236, that has been sitting there since I encountered the anomoly of the QCGB. Just out od curiosity I played with the bit angle of attack. Here is a short video as I made the finishing pass, cleaning up the previous roughimg cut. Notice the bit holder is kicked back towards the TS side. Did not move the QCTP, just adjusted the angle of the bit holder. Notice the finish.

Thank you for all the tutorials.


Nez

Watch "Finishing Pass Cutter Towards TS" on YouTube

Yup, lead angle is a real thing. Most guys who use inserted carbide don't even realize that just because the tool has clearance angles on the side and end, that doesn't mean you have to use the tool that way. Try using a CCGT AK insert turned toward the tailstock in aluminum - the finish will like to frost your eyeballs.
 
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