Tools For Lathe And Mill From Shars And Enco

[mikey]

I second Dan S.'s suggestion on insert tools - the SCLCR (Right hand) and SCLCL (LH) tools work fairly well. It is unlikely that you will use most of the tools in the Grizzly set. Well, maybe the boring bar. This geometry allows for both facing and turning when the tool is perpendicular to the work and is probably the single most popular tool holder amongst hobby guys. With a max lathe speed of only 1800 rpm, they are not better than a properly ground HSS tool but they do work, especially until you learn to grind tools.

Most 1/2" SCLCR/L tool holders take a 32.5X insert; the Grizz tools take 22.5X inserts. CCMT is the standard insert for these tools but they will accept a CCGT insert, which is sharper at the nose (cornerpoint). The X in 32.5X is the size of the nose radius; this affects your depth of cut and finish. The smaller the number, the smaller the nose radius. Be clear that a tool holder will accept only one size of insert - 32.5X or 22.5X - so you need to know which size insert your tool holder uses. You can use either a CCMT or CCGT insert in these tools.

The CCMT inserts are good for most work and the CCGT-AK inserts work well for aluminum. The AK inserts are very sharp and have a very positive rake so they are very, very good for aluminum. However, be aware that the nose radius can greatly affect the finish in aluminum (and any other material you cut) and a CCGT 32.52 is better than the 32.51 in this regard due to the larger nose radius. AK inserts also work well in softer steels and plastics.

If you need to learn about the differences in the various inserts, I suggest you download and peruse the catalog from Seco or Iscar. Once you know which insert you need you can cross reference it on the Carbide Depot site and either buy it from a supply house or go to ebay, which will be cheaper. Seco, Iscar, Korloy, Kennametal, Valenite/Walter, Mitsubishi are all good brands.

Not all tool holders are created equal regarding the precision of the insert pocket where the inserts sits. One cheap but very good tool holder is made by Tool Mex; they are as good as my Seco and Iscar tool holders at 1/3 the cost. You can find them on ebay. For a 12" lathe, a 1/2" tool should fit and will be much stiffer than a 3/8" tool.

With all that said, these carbide tools are intended for much higher speeds than your lathe can achieve. The geometry and chipbreakers will not be as effective but they will work. When you can, learn to grind a good HSS tool. They will work better in the speed range your lathe can handle.

 

[Dan_S]

With all that said, these carbide tools are intended for much higher speeds than your lathe can achieve. The geometry and chipbreakers will not be as effective but they will work. When you can, learn to grind a good HSS tool. They will work better in the speed range your lathe can handle.

Mike, that's not exactly true, as it depends on the material being turned and it's diameter. Even on my little 8" lathe it very easy to get into the sfpm operating window for inserts, specially in steel.

The ak inserts are rated at 984 sfpm maximum. at 1800 rpm anything over 2-1/16" diameter is going to be over the sfpm limit.

 

[65Cobra427SC]

Anyone happen to have a coupon code for Grizzly?

And yes, I've been keeping up with the posts

 

[mikey]

Mike, that's not exactly true, as it depends on the material being turned and it's diameter. Even on my little 8" lathe it very easy to get into the sfpm operating window for inserts, specially in steel.

The ak inserts are rated at 984 sfpm maximum. at 1800 rpm anything over 2-1/16" diameter is going to be over the sfpm limit.

Okay, let's see if I understand. Say we're cutting something soft - 1215 mild steel maybe, with a work piece 1" OD and a moderate feed rate of 0.008 ipm with a common grade of insert like TP200. The suggested cutting speed is 1575 so the calculated RPM would be over 6000 RPM. A similar sized work piece in 6061 with the same cutting conditions might have a cutting speed of 1775 sfm, for an RPM of about 6800. These cutting speeds are from Seco but they are similar for most inserts with similar grades and geometries. Korloy lists the AK insert at 984-2625, with an average recommended cutting speed of 1640 sfm so 984 is the minimum recommended speed.

I agree that the material and size enters into the picture but, in general, most of our hobby shop lathes will not get into the speed range these inserts are designed for. That is not to say they won't work but they will not work as intended. This speed thing affects insert life primarily and in a hobby shop that may be less important but I've used an AK insert at the proper speed on a high speed lathe and believe me, that is an awesome insert when used in the recommended speed range. At over 6000 rpm that insert will equal or better the best HSS tool for surface finish, will cut more accurately and size better. At purely mortal speeds in a hobby shop, I think HSS has the edge.

Let us also not overlook depth of cut. A carbide inserted tool on an 8" lathe will limit your depth of cut more than a HSS tool will. Similarly, a HSS tool will take a finer sizing/finishing cut than a carbide tool will if the tool is properly ground. Don't get me wrong; a carbide tool can cut accurately but you must know how that nose radius cuts at a given DOC to bring it in on size. A HSS tool is less finicky, at least it seems so to me.

My point is that HSS will work better for most hobby class lathes but you have to know how to grind a tool and that takes time. Carbide tools will enable the new owner to get up and running so he can learn to use his lathe and they will work but we should acknowledge their limitations, don't you agree?

 

[mikey]

Cobra, I just came back and re-read my post and wanted to clarify this for you. What Dan and I are discussing is the RPM the lathe should turn at for the insert to work as intended by the maker. The most common formula for calculating turning speeds is: RPM = CS X 4 (3.82 is more accurate)/D, where CS is the recommended cutting speed for the material and feed rate and D is the diameter of the workpiece. This gives you the RPM the insert is intended to run at to produce a given insert life, usually rated in minutes.

For example, for a 1" diameter piece of 6061-T6 Aluminum, an AK insert run at about 0.008 ipm feed will have a recommended cutting speed of 984-2625. If you plug these numbers into the formula above we get an RPM range of 3900 to 10,500 RPM at a feed rate of 0.008 ipm. Your lathe has a top speed of 1800 RPM so you aren't anywhere near the range for optimal performance for these inserts. They will work and they will cut but the chipbreaker and cutter performance will not be as advertised. I wouldn't let that stop you from buying and using these tools. Just know that there are limitations to them and you need to learn how to use them to gain the accuracy you require.

 

[65Cobra427SC]

Okay, my ordering is finished. In the past week I placed two orders with Shars, and one each with Grizzly and Enco. I had to call Enco because for some reason the Cyber Monday codes didn't work. They couldn't modify the original invoice so I had to read off all the item numbers so they could construct a new invoice. At least the wait time wasn't long and the person was very nice. But when I went to check the new invoice there were 3 items that I still didn't get a ($26) discount for so I'm going to have to call them again tomorrow. I may just have them issue me a gift certificate if they can and I'll use it later. Unless you don't think I'll ever need any more tools???

 

[65Cobra427SC]

Thanks mikey for the explanation. I think I understand the situation you and Dan are talking about, but I plan to revisit it later this week since placing all these orders, and having to call Enco, wore me out. Both my back and credit card are killing me after spending most of the last 3 days sitting and reading things over and over again. But I'm glad I got it done. Although I may not be finished here, I really want to thank everyone for the help. This is a great forum.

 

[Dan_S]

Okay, let's see if I understand. Say we're cutting something soft - 1215 mild steel maybe, with a work piece 1" OD and a moderate feed rate of 0.008 ipm with a common grade of insert like TP200. The suggested cutting speed is 1575 so the calculated RPM would be over 6000 RPM. A similar sized work piece in 6061 with the same cutting conditions might have a cutting speed of 1775 sfm, for an RPM of about 6800. These cutting speeds are from Seco but they are similar for most inserts with similar grades and geometries. Korloy lists the AK insert at 984-2625, with an average recommended cutting speed of 1640 sfm so 984 is the minimum recommended speed.

I think the insert size plays a part as to how hard it can be pushed as well. Take a look at this photo On the left is the back of my 21.51 pack and the right is the back of a 32.51 pack. Maybe they are mis labeled, but i haven't found any listing sfpm over 1000 sfpm, and I checked several ebay listings.


It's the same with these Sandvik insets I use on steel, and I got these directly from a popular US retailer. I've actually smoked 2 of these, because I pushed them to hard. These are specifically designed for finishing.

My point is that HSS will work better for most hobby class lathes but you have to know how to grind a tool and that takes time. Carbide tools will enable the new owner to get up and running so he can learn to use his lathe and they will work but we should acknowledge their limitations, don't you agree?

I've never really had a problem grinding hss bits, I just looked up angles in the machinery handbook and went to town. In my shop, I use HSS for specialty stuff, like custom profiles, or tasks carbide isn't good for, or can't do. For example a few weeks back i needed to single point a center to ensure it was perfect, so I took 5 minutes and ground a quick tool to do it.

 

[Dan_S]

Both my back and credit card are killing me after spending most of the last 3 days sitting and reading things over and over again. But I'm glad I got it done. Although I may not be finished here, I really want to thank everyone for the help. This is a great forum.

wait to you spend several hours in your shop leaning over the lathe, your back will really love you then.

 

[mikey]

I think the insert size plays a part as to how hard it can be pushed as well. Take a look at this photo On the left is the back of my 21.51 pack and the right is the back of a 32.51 pack. Maybe they are mis labeled, but i haven't found any listing sfpm over 1000 sfpm, and I checked several ebay listings.

It's the same with these Sandvik insets I use on steel, and I got these directly from a popular US retailer. I've actually smoked 2 of these, because I pushed them to hard. These are specifically designed for finishing.

I've never really had a problem grinding hss bits, I just looked up angles in the machinery handbook and went to town. In my shop, I use HSS for specialty stuff, like custom profiles, or tasks carbide isn't good for, or can't do. For example a few weeks back i needed to single point a center to ensure it was perfect, so I took 5 minutes and ground a quick tool to do it.

Dan, I wonder if we might be talking about two different things here. Your responses imply that the listed cutting speed on the package is the RPM the insert is intended to turn at. If so, then you might want to look into this a bit more. On the other hand, I suppose it's a moot point since most lathes can't get that speed anyway.

Glad tool grinding is so easy for you. It took me awhile to get the hang of it and I'm still learning.