order of operations 60* cones?

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mr fixit
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order of operations 60* cones?

Post by mr fixit »

The RPC is up, the Lathe runs now. About to start on some of the stamps I have.

As I get started, what is the recommended way of making cones? I'm thinking drill bore, cut inside of cone, then cut outside of cone letting taper cut into bore parting cone off.

Suggestions?
this will be on a 12" Logan, cones will be 4140.
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Re: order of operations 60* cones?

Post by T-Rex »

You've almost got it. Don't push the taper all the way in. You want a little snout on the cone tip, not a sharp lip.

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Re: order of operations 60* cones?

Post by crazyelece »

Similar related question, what tool (or cutting profile if you will) is preferred to cut the interior 60 deg profile?
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Re: order of operations 60* cones?

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Obviously, it's not the preferred tool as you requested, but I used an SCLR insert, in an applicable sized boring bar, for all internal work on this build. Used the same insert for the entire build and I think I changed cutting edge once. Before inserting a tool into the QCTP, I'll hit it with a Carborundum stone, even inserts. Feeds and speeds make a world of difference :D
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Re: order of operations 60* cones?

Post by 1rflman »

I would suggest omitting the reaming operation but instead, bore the hole after parting the cone to achieve a "better-centered" hole. FWIW
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Re: order of operations 60* cones?

Post by fishman »

crazyelece wrote:Similar related question, what tool (or cutting profile if you will) is preferred to cut the interior 60 deg profile?
a generic 1/4" boring bar
1rflman wrote:I would suggest omitting the reaming operation but instead, bore the hole after parting the cone to achieve a "better-centered" hole. FWIW
+1
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Re: order of operations 60* cones?

Post by mr fixit »

T-Rex wrote:Obviously, it's not the preferred tool as you requested, but I used an SCLR insert, in an applicable sized boring bar, for all internal work on this build. Used the same insert for the entire build and I think I changed cutting edge once. Before inserting a tool into the QCTP, I'll hit it with a Carborundum stone, even inserts. Feeds and speeds make a world of difference :D
fishman wrote:
crazyelece wrote:Similar related question, what tool (or cutting profile if you will) is preferred to cut the interior 60 deg profile?
a generic 1/4" boring bar

I have a set of boring bars like this:
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I assume (yes I know) those would work in a boring holder using the compound?
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Re: order of operations 60* cones?

Post by T-Rex »

Yes.
If you're unaware, those cemented carbide bits should be dressed before use. Factory angles are not set for cutting.
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Re: order of operations 60* cones?

Post by mr fixit »

T-Rex wrote:Yes.
If you're unaware, those cemented carbide bits should be dressed before use. Factory angles are not set for cutting.
Thank you very much, I wasn't aware.
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Re: order of operations 60* cones?

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1rflman wrote:I would suggest omitting the reaming operation but instead, bore the hole after parting the cone to achieve a "better-centered" hole. FWIW
No, bore the hole before parting, not after. Drill undersized and bore to final dimensions if you want it perfect, otherwise just drill and ream if desired.

Boring the hole in a second op will make the hole less centered, not better. No matter how well you dial in the part for the second op, it won't be as good as the perfect concentricity you get from doing everything in one operation.

As to the rest of it, T-Rex covered the process well. And yes, dress those brazed carbide boring bars; a diamond lap is a must if you own a set of those. They can leave great finishes though if dressed right.
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Re: order of operations 60* cones?

Post by mr fixit »

yondering wrote: As to the rest of it, T-Rex covered the process well. And yes, dress those brazed carbide boring bars; a diamond lap is a must if you own a set of those. They can leave great finishes though if dressed right.
T-Rex wrote:Yes.
If you're unaware, those cemented carbide bits should be dressed before use. Factory angles are not set for cutting.
I guess I need to ask 'how' to dress the edges.
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Re: order of operations 60* cones?

Post by T-Rex »

A few good threads, from my bookmarks.
1
2
3
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Re: order of operations 60* cones?

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T-Rex wrote:A few good threads, from my bookmarks.
Some good info in there, but lots of bad info too; tread with caution. #3 for example has a nice picture showing the relief angle, but his sharpening method is crap. Don't do that to your cutting tools.
mr fixit wrote: I guess I need to ask 'how' to dress the edges.
I use one of these diamond EZE-LAP tools like a wetstone. It generally doesn't take much time and is easy to keep the edges straight and the corners sharp.
Don't round off the corner like that #3 link above (if you have to fix a corner, grind a bevel, not a curve), and rub the stone perpendicular to the edge like you'd sharpen a knife, not parallel to the edge like that guy.

I mostly just use the purple medium grit, you could buy just that one if you wanted.

https://www.amazon.com/EZE-LAP-PAK-Colo ... HVK5ADNZJG

Keep the tops of those brazed carbide tools flat, and just make sure there's enough back clearance for the cutting edge to actually cut. On a boring bar, that clearance angle depends on the diameter you're cutting; obviously smaller ID holes need more angle to provide adequate clearance.

When machining with these, go by how the finish looks, not what the chips look like. My best results are when the chips are crumbly rather than pretty spirals or 6 and 9 shapes.
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Re: order of operations 60* cones?

Post by jnjproto »

This is how I have done it. Drill .02-.03 undersize. Rough bore id of cone. Finish bore id of cone and bore. Rough and finish od of cone. Part off cone. The advantage of doing it this way is everything is done in one set up, guaranteeing that concentricity is maintained. Every set up you make adds to error. It may only be tenths, or thousandths, but it is something.
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Re: order of operations 60* cones?

Post by mr fixit »

yondering wrote: As to the rest of it, T-Rex covered the process well. And yes, dress those brazed carbide boring bars; a diamond lap is a must if you own a set of those. They can leave great finishes though if dressed right.
T-Rex wrote:You've almost got it. Don't push the taper all the way in. You want a little snout on the cone tip, not a sharp lip.
I need help, or advice...

I have round stock, but it is larger than my spindle ID of 1.375" on the Logan. I will have to bandsaw off a section to make cones. Obviously the section will have to be longer than the cone will be when finished. How do I keep waste to a minimum? Or will each cone result with a short section of steel left over?
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Re: order of operations 60* cones?

Post by T-Rex »

Use a steady rest (and center for exterior)or flip the chunk around and profile the exterior in another setup. No, you don't need to worry about bore concentricity, we trust your indicating skills :wink: :wink:

I did the same thing for my recent 5.56mm build. Had the bar cut into chunks, for my smaller lathe, but ended up using my larger machine with the smaller pieces. Bore was aligned perfectly, even after 11 circumferential welds.

Yes, it's an extra step, but it will get you where you need to be :D
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Re: order of operations 60* cones?

Post by yondering »

mr fixit wrote:
yondering wrote: As to the rest of it, T-Rex covered the process well. And yes, dress those brazed carbide boring bars; a diamond lap is a must if you own a set of those. They can leave great finishes though if dressed right.
T-Rex wrote:You've almost got it. Don't push the taper all the way in. You want a little snout on the cone tip, not a sharp lip.
I need help, or advice...

I have round stock, but it is larger than my spindle ID of 1.375" on the Logan. I will have to bandsaw off a section to make cones. Obviously the section will have to be longer than the cone will be when finished. How do I keep waste to a minimum? Or will each cone result with a short section of steel left over?
As T-Rex said, hold the back end of the stock in the chuck and the working end in a steady rest, with enough sticking out to cut a cone completely in one setup. You'll need to move the steady towards the chuck after cutting a cone or two. You don't need to cut the stock into small sections, just make it short enough that you can reach the working end on your lathe; don't be afraid to use the entire bed.

You'll have to use the same type of setup for threading the tube as well.

I had to do the same thing when I just had a 9" South Bend lathe. As I'm sure you've realized now, a larger lathe with at least 1.5" spindle bore makes things a lot easier for suppressor work. After working with my little SB lathe a bit, my #1 priority when buying the next lathe was a larger spindle bore of no less than 1.5".

Something you could consider (but proceed with caution) is boring your spindle out to a little over 1.5". A friend of mine did that on his lathe with good success, although it was a smaller lathe and he was only boring from 7/8" to 1". With yours, you'd only be removing ~1/16" of wall thickness, so it may be feasible depending on the spindle OD. Also, another option to boring (because that requires a really long boring bar) is to buy or make a reamer and an extension.
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Re: order of operations 60* cones?

Post by fishman »

Yeah, what they said ^^^

This is what I do because my lathe is ridiculously tiny. You shouldn't have to waste any material really.

Image
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Re: order of operations 60* cones?

Post by sizulku »

fishman wrote:Yeah, what they said ^^^

This is what I do because my lathe is ridiculously tiny. You shouldn't have to waste any material really.

Image
small lathe? whats brand?
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Re: order of operations 60* cones?

Post by 3strucking »

looks like a sherline
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Re: order of operations 60* cones?

Post by fishman »

3strucking wrote:looks like a sherline
Yep
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Re: order of operations 60* cones?

Post by mcrump »

fishman wrote:Yeah, what they said ^^^

This is what I do because my lathe is ridiculously tiny. You shouldn't have to waste any material really.

Image
Not necessary to run the lathe backwards. Simply get or grind the lathe tool to the angle you want. Plunge in whatever cut depth of cut you want and manually crank the saddle from headstock to tailstock, blending as you go. This operation takes me about 30 seconds to complete and you're not constantly rotating your compound rest or changing spindle rotation.

Also, use a 60 degree 6 flute countersink, running slow rpm's. The goal is to hog out material quickly, then finish up with a boring bar for final bore diameter.
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Re: order of operations 60* cones?

Post by fishman »

mcrump wrote:Not necessary to run the lathe backwards. Simply get or grind the lathe tool to the angle you want. Plunge in whatever cut depth of cut you want and manually crank the saddle from headstock to tailstock, blending as you go. This operation takes me about 30 seconds to complete and you're not constantly rotating your compound rest or changing spindle rotation.
I don't run it backwards, the cutting tool is upside down.
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