1018 HRS vs 1018 CRS Machinability?

[MinnesotaHSM]

I am making a fly cutter per plans in other HSM threads. Picked up a 3" round of 1018 HRS. Chucked in three jaw with dead center supporting the other end in my Atlas 618 Model 2 (square head).

I am using the import Carbide Brazed tool bits from Enco with the cutting edge on the centerline. I am running at a speed about 200 rpm which equates to a SFM of 80, which is is the number found in the Atlas User Manual for this material and size. (of course that might be for HSS)

So what's my problem? I seem to be able to take very little feed. The chips are coming off small, but dark blue. The workpiece is heating up quite a bit. And it is slow. At the rate I am going I might be done in 5 years cutting from 3" to .75". Also, the cut is extremely rough.

Is the source of the problem the HRS 1018 or is it the size of my lathe? Your thoughts? Is there some other material that might be better suited for a fly cutter (4041, 1144, 1018 CRS)?

Your help is appreciated.

-T

[kmccubbin]

Use an HSS toolbit. The cemented carbide requires speed, torque, and ridgidity. Your 6x18 lacks 2 out of 3.

Kerry

[PaulT]

I am using the import Carbide Brazed tool bits from Enco with the cutting edge on the centerline.

In my experience those import cemented carbide tools are pretty much junk.

You can use carbide tooling on that lathe, but its got to be one of the modern "highly positive" carbide insert tools, I would recommend one that uses the CCMT type insert, search that string on this forum for more info.

The advantage of this insert is that its 80 degrees, so with the same tool you can both turn and face without remounting the tool, so you only have to buy one of these tool holders to get started.

If money is tight, the import ones from www.shars.com aren't that bad, if you want a nice one, look for the Hertel brand ones sometimes on sale at J&L/Msc, they are the same as the ones sold by Kennemetal and are really nicely made, you would need a tool holder they call the SCLCR type.

However, its possible you have some hardened steel instead of 1018, does a file mark it easily, if not its probably not 1018. If it has mill scale on the outside, its not 1018, which is a cold rolled steel (CRS), 1020 is the typical hot rolled steel (HRS) alloy number.

Paul T.

[camdigger]

Your choice of material is fine. The properties the other materials will give you are overkill for the application in the home shop IMHO.

As others have said, carbide tooling for small lathes has to be carefully selected. Positive rake and sharp edges are very important on smaller lathes.

A few minutes 30 or so teaching yourself how to grind an HSS tool will serve you well. This is an excellent oppotunity to teach yourself how to grind an effective tool from a blank. Grind one, try it, repeat until you're done

My experience is , I can spend $30 or so in different inserts for, say 30 cutting edges and spend 5 - 10 minutes changing them, or spend $5 - $10 on HSS blanks and spend an hour grinding and resetting them for 150 or more sharpenings.

My $.02 cdn. YMMV.

[beanbag]

I am using the import Carbide Brazed tool bits from Enco with the cutting edge on the centerline.

I think this is your problem.

I have found a Kennametal TCGT insert with the -HP designation (high rake, no land) and coated with something orange (forgot the designation) to work very well.

[Walter]

I am making a fly cutter per plans in other HSM threads. Picked up a 3" round of 1018 HRS. Chucked in three jaw with dead center supporting the other end in my Atlas 618 Model 2 (square head).

I am using the import Carbide Brazed tool bits from Enco with the cutting edge on the centerline. I am running at a speed about 200 rpm which equates to a SFM of 80, which is is the number found in the Atlas User Manual for this material and size. (of course that might be for HSS)

So what's my problem? I seem to be able to take very little feed. The chips are coming off small, but dark blue. The workpiece is heating up quite a bit. And it is slow. At the rate I am going I might be done in 5 years cutting from 3" to .75". Also, the cut is extremely rough.

Is the source of the problem the HRS 1018 or is it the size of my lathe? Your thoughts? Is there some other material that might be better suited for a fly cutter (4041, 1144, 1018 CRS)?

Your help is appreciated.

-T

Minnesoda,

A couple of thoughts for you.

Try slowing the lathe and picking up the feed, little lathes get grumpy with speed on larger stuff.

Brazed carbide can work ok, but smaller nose radius's and proper clearances help immensely. Chances are that your Enco bits have neither. While good quality carbide will tolerate higher speeds and feeds, the cheap stuff will not fare as well. In combination with your small, not so ridged lathe you have a fight on your hands, but you already know that..

!018 isn't worth wasting time with IMHO, 1144 is very nice stuff, comparable price wise and you'll like it a lot more, it's a harder material, not gummy like 1018. 12L14 machines similarly, easier than the 1144. It's very well suited to smaller lathes and both it and 1144 are quite usable for your stated purpose, but I'd look to 1144 first for that application.

For a lathe like the 618 I'd look to HSS, learn to sharpen and hone a good edge. You'll like the results a lot more. Please don't waste your time or money on cheap low grade imported HSS... the stuff just doesn't stand up. Although good quality stuff costs, you'll rarely need to come near it with a grinder once it's properly formed and sharpened. There's little reason for a good quality bit to not last 5+ years easily. The vast majority of the HSS I run in my shop has never been back on/near a grinder since it was made, just touch ups with a stone or diamond hone.

[Mcruff]

For carbide that material should be run at 800-885 fpm not 80 fpm and even for HSS it should be turned at around 125-215 fpm. With carbide and 800 fpm you should be turning roughly 1000rpm not 200rpm that would be for HSS. You need your feed rate set at about .004"per revolution.
Here is a decent source for turning and milling info for feeds and speeds.

http://littlemachineshop.com/Reference/CuttingSpeeds.php

[MinnesotaHSM]

Thank you for the suggestions.

I bumped up the speed as recommended in the LMS link using my original setup, but same result. Still couldn't take any kind of substantial cut.

Went to some 1/4" HF insert bits (I am sure you have all seen them). Still couldn't take any substantial cut.

Dug out a 1/4" Cleveland Mo-Max HSS bit that I had gotten in a box from my brother-in-law. Looked at the thread(s) on lathe grinding here on the HSM bbs. Fired up my old grinder that I had gotten from my Dad (it has a 4" stone wheel on it) and ground the bit according to the diagrams as best as I could without a protractor.

Then mounted in my lantern toolpost and was able to take .050 cuts (.10 per travel) without difficulty. Speed set at 200 rpm. The chip just curls right off.

The workpiece is still heating up over time, but I am able to make significant progress. I plan to try taking some deeper cuts and get additional HSS bits to grind some different rakes, etc.

- T

[Paul Alciatore]

Enco braised and HF inserts. I think there's your problem. And the blue chips which indicate a lot of heat. And you said the work is getting hot.

Look at the edges on them under 10X magnification. (Don't have a maginifyer, GET ONE! GET A GOOD ONE! And USE IT! I have not one, but two Hastings triplet magnifiers in my pocket at all times. They cost 35 to 45 dollars each, but are worth their weight in gold.) When you look at the tool's edges I will bet you will see dull edges and that is what is causing the heat and slow cutting. Just because it's carbide does not mean it is sharp. I have seen some very dull edges on new carbide tooling. A diamond stone will allow you to manually touch up carbide edges if the wear is not too much.

As for carbide and speed, speed is not a requirement for it to cut. Carbide ALLOWS you to use higher speeds which save time. This is of great importance in commercial shops where time is money and also in home shops where time is limited. But the cutting action depends on the geometry of the tool and carbide WILL cut at lower speeds. The surface finish it leaves may be different, but it will cut just fine. If you are hogging off excess stock, surface finish is not of much importance.

I do recommend HSS tooling as you can easily sharpen it to whatever shape is best for the job at hand. To do that with carbide you will need an expensive grinding set-up. Sharpening HSS tools is not difficult and only requires a standard bench grinder or even just a sander. I rough grind on my grinder and finish up on a 1" belt sander for flat facets and a finer finish. Between sharpenings I use a hand stone to touch them up.

Sharp tooling with the proper geometry is the key, not carbide vs HSS. HSS is just the easier way to get there.

[johnny o]

6x18 turning

Hello
I found this thread interesting as I am guilty of pushing my own 618 to the limit.I have had good success with the braze on carbide toolbits with more positive rake on them usually. I suggest you put together a drip con for cooling and improved finish. I made mine from a soup can with a small brass valve soldered to the bottom. A 1/4" cu. tube extends down to cutting area and can is mounted up out of youre way. Just pour youre favorite concoction in there and sat it to drip at desired rate. This works well on Ti also.
Good Luck