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Parting and Inserts on a Small Lathe

ksimolo

Aluminum
Joined
May 23, 2010
Location
NY, USA
To put things in perspective, I am definitely not a trained machinist. I have a SB Heavy 10 and a BP mill that I use to make the things I need.

Routinely I read about not using inserts with these machines while others say they are ok. In addition, I have read about the difficulties with parting. When I have done parting with traditional tooling, I have had to feed a little harder than I am comfortable with so that it does not screech.

A while ago, I decided what the the heck and I bought some cheap insert tools. They have worked wonderfully on steel, ss, and Al. The parting tool I got was MGEHR1616-2 for $13 delivered and that included 10 MGMN200 inserts. I am able to part very slowly if I so desire and it works well dry or with cutting oil. I can not imagine going back to traditional HSS parting blades for most things I do.

I have also used SCLCR tool holders with CCMT09T308-PM YBC251 and CCGT09T304-AK H01 inserts which worked really well for me as have traditional HSS tools. At $0.50 per cutting edge, it is usually not worth it to me to grind HSS. It is also nice that the cutting heights are always constant.

So far, on the Bridgeport, the only inserts I have used were some old discontinued roughing cutters that are very good at taking the shock load of heavy (for my BP) interrupted surfacing cuts on steel. I have a used helimill to try when I think of it but I do have lots of traditional mill bits so I am not in any rush.

I just thought I would mention it in case other neophytes like me are looking for some easy tooling to use. It is also a way of giving back for all of the helpful advice I have gotten from posts and people here. I am not implying that these are the best cutters to use. Watching a real machinist make machines and tooling do what he needs them to do is always a joy.

Ken
 
first off what type of material are you parting? Second unless your making a lot of pieces that require parting throw the insrt things in the scrap bin.
I make break pins or a job that require parting to create the groove where the pin will break. I don't recall the alloy but it is nothing special.
Those insert parting tools work for some guys but this one. Get some Hss and grind your own. Make sure your tool tip is on center line and tool is perfectly perpendicular to work piece. I find a slight relief on sides of the tool helpful as well. Use cutting oil, and a relatively slow RPM , I never power feed, get a much better idea of how the tool is cutting. chips should come off as curly bits. If your having to apply a lot of pressure to get it to cut and it is screaming bloody murder something is wrong. screeching says your RPMs are to high.
JMHO
 
I am not quite sure why you are saying what you are saying. The insert cut off tool works great for me on steel, stainless, and aluminum and they are very inexpensive. I see no reason to switch back.

With the HSS parting tool, it always cut well; the higher feed rate was to quiet the cutter down. I preferred the ones with side relief and a small groove in the top of the cutter I always feed by hand.
 
I am not quite sure why you are saying what you are saying. The insert cut off tool works great for me on steel, stainless, and aluminum and they are very inexpensive. I see no reason to switch back...

Yeah, my thoughts exactly. I use nothing but insert tooling on my 13 x 40 lathe--it works great!! My advice would be to throw the damn
HSS away. It's obsolete...
 
Your recommendation is inexpensive enough to give it a try, but this is not a replacement for a HSS cutoff blade because of its limited depth. I have used several of these type cutoff tools in the past. They cut initially well, but all failed with chipping issues after only limited use. Further, the replacement inserts were always too expensive to compete with a traditional HSS blade. In this case the cost restriction does not exist, so I have ordered this tool with 10 inserts. It is worth a try for at least grooving use.

I'm not against insert use, but their use is expensive. HSS tooling is much less expensive, but it takes tool grinding knowledge, skill and a correct grinder, but those are a one-time expense. Now if time is an issue and you're trying to make a buck, insert tooling and stiff, powerful machines are the only way today.
 
I've gone around the block about insert vs HSS parting tooling. At first I was astonished at how easily the insert tooling could part tough stuff like 316 stainless. However after a couple of chipped insert edges caused by the tool edge being a couple of thousanths below center at the end of the cut, I've gone back to HSS blades for most of that sort of work. I found that "T"-shaped blades cut as easily as the inserts and are much more forgiving of exact edge placement.

I never do parting or cut-off at high speed because when the inevitable jam happens, high rotation speed can cause serious damage to the work piece and the tooling as everything stops suddenly.

I still have the insert tooling but I hardly ever use it.
 
There be more than one way to skin a cat. At work we have a row of tool holders. One has an insert parting tool, the one right next to it has HSS. I use both, depending on what I'm doing. The first time I used the insert tool, I broke it. Not just the insert, but the whole tool. Thought it was the dumbest idea anybody ever came up with. I think maybe the insert wasn't seated or the tool wasn't aligned. Anyway, it works fine and is just the ticket for tougher stuff. I use the HSS parting blade where I want a narrow kerf or where I want to grind the end so a part comes off finished, something the insert tool doesn't seem to do as well. IMO, HSS tooling is pretty much obsolete in a commercial shop doing production runs of parts. In a home or prototype shop, you'd be nuts not to have some around and know how to grind it.
 
My experience with inserted parting tools was that, all too frequently, when something went wrong, the insert and the holder were roached. This was in a job shop, mostly manual machines, with 10-12 machinists. The initial enthusiasm for the inserted tools faded, and HSS (or carbide tipped) became the tool of choice again. We continued to use the inserted tools depending on situation, but the machinists became gun-shy of them and I got tired of replacing the blades.

It's not always obvious that the holder has been damaged. In a home shop, where you are the only person using the tool, there's no danger of picking up a tool that someone else has crashed (and failed to report) and having it crash as soon as you start the cut. I continue to use HSS when parting because I've become quite comfortable with it and it causes me no problems. I've just been given a small Kennametal parting tool. I may order some inserts if I can find them at a good price.

While inserted tooling may be a good work-around, it teaches you nothing. I'd suggest that it's important to learn how to grind and use HSS.
 
We don't have a single high speed steel cut off blade in our shop, and we don't miss them a bit. We part off tens of thousands of workpieces a year. We machine stainless, several grades of aluminum,hardened and annealed steels, Delrin, brass, UHMW et.al. With the proper set up and cutting parameters, we have no use for HSS parting blades.
 
I can part perfectly well with HSS, but it's just a heck of a lot more convenient with an insert tool

(using a SB 10L, and an HLV-H)

For little stuff, if I want a perfectly clean back face on the part, sometimes HSS is preferable because I can bevel the cutting edge to ensure that the part is perfect. Often times, this means that flex in the HSS blade has resulted in a remnant bar that requires re-facing prior to another operation, however, this may not be too high a price to pay.

On the other hand, if I'm turning 2.5" 304, It's just not a question.
 








 
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