Parting / cut off tool

[mbond]

After some more work today, I have successfully parted a piece. The tool post rotates, but the scale is misaligned by about 1.5 degrees. So when I had it set at 90, it was not perpendicular to the work. I think that's why I broke the tool.

re the tool height, there is no direct adjustment, so I am using shims made from sheet steel (salvaged from HVAC duct work). Each shim is about 0.070". Using 4 shims, lifts the tool by about 0.280". Using 3 shims, lifts the tool by about 0.210". I have measured the top of the tool when sitting on the bottom of the tool post as being about 0.300" below center. Using 3 shims and a half shim cants the tool slightly, and puts the tip about 0.050" below center - and at a slightly different angle - and seems to cut well.

As an aside, this machine requires a ton of reconfiguration. Virtually every new cut requires the tool post to be repositioned. I sort of knew that when I bought it, but I want to both turn and mill and I can't really justify multiple machines

 

[YotaBota]

Good to hear you're making progress. Pop or beer cans make good shims, IIRC they are about .004 thick. Cheap feeler gauges make good shims as well.

 

[Susquatch]

re the tool height, there is no direct adjustment, so I am using shims made from sheet steel (salvaged from HVAC duct work).

Woooo Hoooo! Congrats on the accomplishment! Bet it feels GREAT!

Can you post a photo of your tool holder so we can see what you are working with? I'm pretty sure the collective experience here has dealt with your issue before.

The problem with shims is that they generally reduce rigidity. It's better not to use them unless you have no choice. Unfortunately, no choice happens often in the machining world and shims are a fact of life. I bought two sets of really cheap stainless feeler gauges and then took them apart to fine tune shim stacks. I also have a set of purpose made shims to get tool heights right on my tool post. You can use them to get your dimensions closer without stacking up a billion shims. I went looking to post a link for you just now, but failed to find them. Perhaps another member knows where to get them and can chime in.

 

[Upnorth]

When I got my first parting tool I had some issues. The first two were from those kits of 6 lathe turning tools that available in multiple places. Chinese made generic. All my tools are set on centre using an edge technologies tool setter. I also retested the position of the tools with multiple tests to verify the repeatability of the tool being on centre. I verified that the tool was being fed straight by using a dial indicator.

First try the tool cut great. Second try all went wrong. I was power feeding in almost all cases. Tool was causing the compound rest to pivot. Took me a few tries to realize the tool was not cutting at all just bulldozing the part. I noticed this when the material would deflect then it was not cutting. Insert broke and the tool went into the garbage. Second tool broke almost immediately. Into the trash it went. By now I was thinking parting must be some sort of black art.

I decided to try a better quality parting tool this time. I ordered one from KBC tools. It was one of the brands that they usually push in their sales (Dorian tools maybe?). It arrived with a couple of inserts. I saw "made in India" on the box and was disappointed. My experience with Indian made tools has been very negative. I set up the tool and tested the tool in aluminum. Success. I thought ok but that's just aluminum and decided to try tool steel which is what I mostly need to cut. 100% success. Cut like butter. Since then I have made hundreds of cuts with the tool with no issues. O-1 and A-2 tool steel in .500 and .625 inch diameters. Inserts last great.

The set up I use is a replaceable carbide insert in a blade holder with a BXA size tool holder. I can take a photo of it if anyone needs to see it. The lathe is a Harrison M300.

 

[Susquatch]

The first two were from those kits of 6 lathe turning tools that available in multiple places. Chinese made generic.

It's too bad we can't reach new machinists before they make that mistake. The outfits that sell them know how to sell them to newbies almost before their lathe/mill is purchased.

My very first word of advice to all new machinists is to avoid those sexy kits like they were covered in slimey maggots. I say it with conviction because I did it too.

The good news is that you can speak with experience and conviction now too. Hopefully you can save another guy the pain that you had.

So how come your tool post was rotating? That needs to be fixed!

 

[slow-poke]

It's too bad we can't reach new machinists before they make that mistake. The outfits that sell them know how to sell them to newbies almost before their lathe/mill is purchased.

My very first word of advice to all new machinists is to avoid those sexy kits like they were covered in slimey maggots. I say it with conviction because I did it too.

The good news is that you can speak with experience and conviction now too. Hopefully you can save another guy the pain that you had.

So how come your tool post was rotating? That needs to be fixed!

I have had mixed success with parting. Mostly when parting something less than small because the blade needs to protrude too far from the holder to remain rigid.

Suggestions for a non slimy but not too expensive tool please?

 

[Susquatch]

I have had mixed success with parting. Mostly when parting something less than small because the blade needs to protrude too far from the holder to remain rigid.

Suggestions for a non slimy but not too expensive tool please?

You will get LOTS of suggestions on here. Everyone loves spending your money.

Let's start with a question. What type and size is your tool post?

 

[slow-poke]

Let's start with a question. What type and size is your tool post?

AXA

 

[Upnorth]

It's too bad we can't reach new machinists before they make that mistake. The outfits that sell them know how to sell them to newbies almost before their lathe/mill is purchased.

My very first word of advice to all new machinists is to avoid those sexy kits like they were covered in slimey maggots. I say it with conviction because I did it too.

The good news is that you can speak with experience and conviction now too. Hopefully you can save another guy the pain that you had.

So how come your tool post was rotating? That needs to be fixed!

The compound rest was rotating because the tool was not cutting. I was power feeding the parting tool. It just kept pushing without cutting until the compound rest rotated. Luckily that happened before there was and damage to the lathe gear train. Since switching to a better quality parting tool the compound rest has never rotated again.

I would still recommend those 6 holder kits. I would also recommend tossing away the parting tool and replacing all the inserts with better quality ones. If you try cutting with the supplied inserts you may wonder what you are doing wrong. The inserts may chip and leave a finish that looks like you tried to cut with a blunt nail. Good inserts last a long time. Get the proper sharp inserts for aluminum.

 

[Bandit]

The only thing that parts easily for me is my money.

 

[Susquatch]

AXA

OK. I'll find something to spend your money on in the budget you suggested

In the meantime, both of the tools in your photo show tools that are upside down.

The top one will never work that way. Inserts must be used right-side up in the tool but the tool has to be flipped upside down. That's difficult to do with a tool holder that has screws to hold the tool down. So I can't recommend that. I'd only ever use an insert tool right-side up.

The second one with the blade is perfect for upside down parting. But I confess that's a very long stick out. If you are using it that way right side up, it's a guaranteed problem. It will squeal like a banshee and won't cut worth crap. Pretty sure you will burn the cutting edge in minutes too.

If I recall correctly, an AXA tool holder will take 1/2" tools and the blade holder you have will take 1/2" blades. But you should measure both dimensions and get the biggest tools that fit.

Here is a good blade for your holder. It is 8% cobalt. You might need to shim the blade so it sits vertical and it might need to be sharpened. The fat part (top of the T) sits at the top of the holder, not at the bottom for regular parting. It isn't a support, it's diberately wide where it cuts leaving clearance for the thinner support below it.

HHIP 2000-7025 1/8 X 1/2 X 4-1/2 Inch 8-Percent Cobalt Parallel Type Cut-Off Blade-P3S https://a.co/d/6N0plWL

You can get thinner blades, but I don't like them.

If I was @PeterT , I'd draw up the idea for you.

I also have one of these in 5/8 inch. It works great. You can also get inserts for cutting stainless & aluminium.

Accusize Industrial Tools 1/2'' Heavy Duty Indexable Grooving/Cut-Off Holder, Nickel Plated, with 11 Gtn-2 Tin Coated Carbide Inserts, 2415-5024INS https://a.co/d/9O2CkLQ

Again, @PeterT could draw something up to show you why insert tools don't work well upside down. Your wedge type blade holder will work fine because it supports the blade at both top and bottom. Both the blade holder in a regular holder and the blade in it has to be flipped.

None of the above are top quality, but you didn't want that. Nonetheless, I can say that the BXA versions of these work fine for me.

If any of the above isn't clear, I'll grab a pen and paper and make drawings for you.

 

[YotaBota]

The HSS blade looks like it's upside down in the tool holder or is that just the photo? The rake is wrong and it looks like the thick side is on the bottom instead of at the top of the holder.
@Susquatch - is that what you were talking about?

 

[Susquatch]

The HSS blade looks like it's upside down in the tool holder or is that just the photo? The rake is wrong and it looks like the thick side is on the bottom instead of at the top of the holder.

Yes, that's what I said in the post before yours. Easy to appreciate why you didn't read it though.........

 

[YotaBota]

Easy to appreciate why you didn't read it though.

Did you say something?lol
I had to read it twice to see we were taking about the same thing.

 

[terry_g]

I have always had a difficult time with parting My previous SouthBend 10K lathe lacked the rigidity I think. My Craftex CT043 is better but I still have trouble on occasion. I worked with a machinist that apprenticed prior to the carbide tool bit. He showed me how to forge a parting blade. He took the blade an American made Eclipse tool and put it in the vice heated the end with a torch and hammered ti to slightly swell the end. Then he ground it to shape. That create clearance between the side of the tool and the work.




For thinner parting jobs I use a small HSS tool bit I ground for cutting snap ring grooves. It can part 3/16" depth.

 

[Susquatch]

He took the blade an American made Eclipse tool and put it in the vice heated the end with a torch and hammered ti to slightly swell the end. Then he ground it to shape. That create clearance between the side of the tool and the work.

Very cool trick! That belongs in the tips N tricks sub forum.

I will try that first chance I get. Nice thing about HSS is that you can actually do stuff like that without ruining the blade.

 

[Susquatch]

Did you say something?lol
I had to read it twice to see we were taking about the same thing.

If you look closely at the other tool, you will see that the insert tool is upside down in its holder too. That's what led me to conclude it might have been done on purpose - which made it harder to discuss....... LOL! I can be quite the loser eh!

 

[Bandit]

Watch out for back lash also when parting, not just the stuff from SOWMBLT when buying tools.
Most of my parting is done with a hack saw and its dangers.
It seems lack of clearance on the sides can be a big problem too. Have to be a bit careful of grinding rake on tapered cutter as changes side relief at tip compared to farther back on cutter for deeper plunges. Some times I make 2 plunges overlapping abit on deeper cuts. Have to be careful of side flex when doing this. Probably should be useing wider heavier blade. See terry g post and Susquatch above

 

[Susquatch]

Some times I make 2 plunges overlapping abit on deeper cuts.

Although it's quite cumbersome to make, I ground a tool that has a forked tip for really deep parting. The fork digs in and pulls the bit a tad sideways when taking its turn on that side. You have to switch cuts back and forth between sides like you describe, but I find it does the job when needed.

Bottom line is that deep parting is hard to do. Sometimes it's just easier to take the part to the bandsaw - although I confess that I have used a hacksaw at the lathe a few times too....... (Insert face full of shame here).

 

[slow-poke]

The second one with the blade is perfect for upside down parting.

Thanks, that's actually how I was using it.

Will review the other parting tool, not sure how I was using it?

Thanks for the links.