A question for the actual machinists here about tool pressure.

[tobnpr]

I don't feel that machine mass/rigidity is relevant here. It's about the setup, and that spider doesn't know whether it's on a 800 lb or 15,000 lb machine.

I regard 4 tiny points of contact as being tenuous given we need zero movement of the barrel. I see no reason to "risk" even a tenth of barrel movement by taking heavy cuts. Me, I limit turning to about .020 DOC.

JMOYMMV

 

[Alex Wheeler]

I have taken .100 with my spider setup. Dont see why I couldnt take .200 maybe more.

 

[JPB3]

You can certainly distort the ID of the barrel with that set up if you over tighten the screws..
Moderation is key, same with your tool pressure or cut.

 

[jackieschmidt]

In my business, we machine really large pieces with large cuts and heavy feeds. Production dictates that large amounts of shavings in the pan means good production, and profits.

In my little shop at my house, I don’t have to worry about that. I don’t care if it takes me 5 cuts to bring a 1.200 barrel shank down to 1.058. I can take my time, relax, and concentrate on getting everything just right.

 

[X Count]

Getting the OD down in 2 vs 6 passes is going to be a drop in the ocean compared to how long the rest of the process takes.

I'm happy with .040 or so as a balance of speed, risk and heat.

 

[ELR LVR]

In my little shop at my house, I don’t have to worry about that. I don’t care if it takes me 5 cuts to bring a 1.200 barrel shank down to 1.058. I can take my time, relax, and concentrate on getting everything just right.

Exactly what I'm saying too!
Production is a different story compared to home personal work

 

[LVLAaron]

The type of insert is going to have some effect as well. KC5010 grade is like a hot knife through butter; the chips just fall off and even a heavy cut, my machine doesn't bog/change pitch much at all.

On the other hand I have some iscar inserts that need the surface speed of a rocket ship, and if they aren't run hard the leave a huge nasty burr and sound like drywall screws in a dishwasher.

 

[SKWERLZ]

The type of insert is going to have some effect as well. KC5010 grade is like a hot knife through butter; the chips just fall off and even a heavy cut, my machine doesn't bog/change pitch much at all.

On the other hand I have some iscar inserts that need the surface speed of a rocket ship, and if they aren't run hard the leave a huge nasty burr and sound like drywall screws in a dishwasher.

I’ll look in to those inserts as I need to order more soon anyways.

 

[SKWERLZ]

Exactly what I'm saying too!
Production is a different story compared to home personal work

I do my barrels between jobs on the machines at work so I usually can’t lollygag about.

 

[ELR LVR]

I do my barrels between jobs on the machines at work so I usually can’t lollygag about.

Lol I would say also if it's somebody elses machines and they don't care
Go for it.
I have seen different brand lathes have MUCH more beefy reinforcements in the bedways
Acraturn I think was one of them
It was like twice as thick as mine, so some may be able to handle heavier cuts for higher production type environments.
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It is too hard to find parts for my own personal Lathe so I tend to lean on the safe and easy side
I might speed up the feed from time to time, but not the depth

 

[ELR LVR]

The type of insert is going to have some effect as well. KC5010 grade is like a hot knife through butter; the chips just fall off and even a heavy cut, my machine doesn't bog/change pitch much at all.

On the other hand I have some iscar inserts that need the surface speed of a rocket ship, and if they aren't run hard the leave a huge nasty burr and sound like drywall screws in a dishwasher.

I just did a quick research on that and found this from the "Practical Machinist Forum"
Kennametal has a good technical dept. for grade and coating recomendations. On their recomendation we used the 5010 for turning heat treated allen screws and hardened free machining stainless and it has gave very good results
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Another guy said they lasted quite a long time too
Good info man

 

[Walt Krafft]

KC5010 is the grade of the insert. It determines its wear characteristics. The geometry determines how it cuts and breaks chips. For doing barrel work on our small machines, positive rake with a chip breaker form is needed. CPMT3201LF is my usual od turning insert. CPMT is the shape, 3201 is the size, LF is the style of chip breaker built into the insert.

 

[LVLAaron]

These are the inserts I use on steel:

10pcs Kennametal DCMT11T304LF KC5010 DCMT3251LF CNC Carbide Inserts Original | eBay

Find many great new & used options and get the best deals for 10pcs Kennametal DCMT11T304LF KC5010 DCMT3251LF CNC Carbide Inserts Original at the best online prices at eBay! Free shipping for many products!

www.ebay.com

They're miles apart from anything else I've tried, Although I have some ingersol inserts on the way (They actually have a very nice easy to decipher website)

Most importantly they dont mind being run slow.

 

[WSnyder]

KC5010 is the grade of coating not the profile. Both profile and coating influences how the insert works.

https://www1.mscdirect.com/images/solutions/kennametal/grade_system_for_cutting_materials.pdf

I use this Kennemetal insert with the KC5010 coating. They will take very small cuts at pretty slow speeds on a manual machine but they are fragile. They were recommended to me by gunsmith Bill Myers years ago who had a friend that worked for Kennemetal at the time. I met him but I don’t recall his name. Bill needed an insert to work with the Ti he was machining at the time for his actions. They work very well on other materials as well.

 

[ELR LVR]

KC5010 is the grade of coating not the profile. Both profile and coating influences how the insert works.

https://www1.mscdirect.com/images/solutions/kennametal/grade_system_for_cutting_materials.pdf

I use this Kennemetal insert with the KC5010 coating. They will take very small cuts at pretty slow speeds on a manual machine but they are fragile. They were recommended to me by gunsmith Bill Myers years ago who had a friend that worked for Kennemetal at the time. I met him but I don’t recall his name. Bill needed an insert to work with the Ti he was machining at the time for his actions. They work very well on other materials as well.
View attachment 1656699View attachment 1656700

what do you consider slow speeds?
I usually turn at 300 rpm, its a nice comfortable speed that turns 416 very well and leaves a very nice fnish at my feed rates

 

[LVLAaron]

Yeah, 200-300 range. Nice and comfortable for the type of work we do on barrels.

 

[WSnyder]

what do you consider slow speeds?
I usually turn at 300 rpm, its a nice comfortable speed that turns 416 very well and leaves a very nice fnish at my feed rates

I run them faster than that mainly because my lathe is an easily adjustable variable speed. I can go from a higher speed profiling a tenon to slow speed threading very quickly. I’d have to try them at 300 to see how they do. I don’t doubt they they’d work fine though. I can skim cut a couple of tenths with just a little finger pressure pushing on the tool holder with them.

 

[WSnyder]

I’ll add that two coatings that work well for what we do on manual machines are:
Iscar IC908
Kennemetal KC5010

Not every profile with those coatings are going to work but the right profile with those coatings will do well.

No coating generally works well for slow speed machining but the manufacturers quit making many of the profiles in an un-coated version. I used to use an un-coated insert from Iscar that was great but the un-coated was discontinued. That’s where the rep came in and recommended the IC908. It works just as well as the un-coated version did.

 

[shortgrass]

Why not run a high speed bit. Positive rake, can grind a chip breaker in. Much less tool pressure than carbide. There seems to be plenty of Mo-Max for sale on ebay.

 

[WSnyder]

Much less tool pressure than carbide.

If I can skim cut a couple of tenths with finger pressure on the carbide I’d think there is very little tool pressure. I use carbide because it’s just one less thing to do and I know what to expect from the tool every time. Carbide threading inserts gives you perfect thread profiles every time too. I can also swap an insert just as fast or faster than I can re-grind my HS tool. I’ll add that I learned to grind HSS in high school in the 70’s so I do know how to do it. I do use HSS for some things. Now and then I need to custom grind a profile so HSS is the option there. Not disparaging HSS use at all I just like my carbide better for most of my work

Oh yeah, I do have a bunch of useless carbide where the profile doesn’t work at all on a manual machine. BTDT