Thread: Indexed Tungsten-Carbide tips

Originally Posted by savage

Hi! All,
I have a question that I hope someone can answer for me, when I bought my lathe I also bought a set of basic cutting tools. They are of the indexable T/C type, due to my beginners capabilities, I managed to break the T/C tip of the cut-off tool and now I can't get the right angle to resharpen with my diamond files. Am I wasting my time, or can it be done by hand, if so what are the optimum angles it should be sharpened to.

I have got it to a stage where it just scrapes off a powder (fine metallic dust) that can be seen in the lube-oil but I can't get it to perform an actual "cut", can anyone help me please.?...

You may need to grind it on a silicone carbide wheel .( green)
Angles will depend on if you have a negative rake tool holder or not .I guess that your tool tips are the disposalble type ,just toss the tip and replace with a new one.
Make sure your tool is on or a poofteenth below centre .

Thank you Woodlee, I'll give it a go tomorrow and let you know how I go!....

P.S. a greenie for your help and quick reply, as I'm in the middle of a job and it's a real bugger without it.

You can sharpen them by hand with a diamond file, but it will take a very long time. Head down the local supplier and get a box of tips. Even if you have a silicon carbide wheel on hand to sharpen with, you'll find it extremely difficult and quite genuinely not worth the effort. Used power hacksaw blades make outstanding parting tools. Tomorrow, I'll take a picture of the hacksaw parting tool holder we made at work a few months back for you.

When you use the parting tool, as Woodlee mentioned, run it on or just below centre. (1/4mm MAX.)

As for your speed, assuming you're working with mild or annealed steel, about 200rpms for stock below 20mm in dia is the rough rule of thumb. Gentle feed, retract every now and then to break the chips if you start to bite off more than you can chew.

Thank you Article99, I am doing O.K. with the diamond files, and have thought about the power hacksaw blades but didn't know how to fix them securely nor how to fabricate a holder. It would be great if you could put up a picture of one, it would get me into Idea mode to come-up with one of my own if your one didn't fit my machine.

A greenie to you also for the soon to have picture, thank you.

O.K. I had a fiddle around today with the recommended angles and I now have a parting tool that actually parts. I found that I had to put slight angle on the sides to give clearance and it stopped squealing and chattering and started to cut. I got it down to about 0.5mm stub, which is a lot better than the original, so I am a "Happy Chappie". Thanks to all who responded with information and looking forward to the picture of the power hacksaw blade tool. I have found that even though my parting tool now works fine I need one with a narrow cut so the blade idea would be great!....

Hey Savage,

Forgot to take the sucker out of the QC holder when I took the photo, so I made a quick sketch up to better illustrate it. 'Twas milled from 4140 and then heat treated, IRCC.

The four bolts force the hacksaw blade into the slot nice and snug like. Rather than using a tricky slot cutter, like we did, you could simply use an endmill on an angle to make a v groove that it'll fit into. Provided they're square to each other, she'll still hold.

(Note for Grahame Collins: Buy / Borrow / Steal / Or get time, on a mill to make one of these. One of the best accessories a lathe owner can have. )

EDIT: You'll notice the blade picture has snapped. Be extra gentle on feeds and speeds when performing 1.5mm or smaller grooving and parting, or you'll wear the consequences.

The trick to eliminating the pip when parting using homemade tools is two-fold.

1) The rake face needs to be square to the rest of the tool.
2) Obviously, the tool needs to run on centre height.

When you filed the rake face angle on the tool, you may have done it on a bit of a sideways slope, which is where some of your pip will be coming from. (Two different centre heights.)

I'll do another drawing soon to better explain the angles on the parting tool for you in the next hour or two.

Here's the average angles used for parting tools in an illustrated form. Apologies for the rough drawing, I'm not terribly skilled at freehand drawing with a mouse.

One extra angle I neglected to mention is that you can completely eliminate the pip on the parted job by adding a 3-5deg taper to the cutting edge, with the higher side adjacent to the part. See second drawing (top down) for that one. You must still ensure that the rake face is square to the tool, however, otherwise it won't work.

Edit: You've already discovered side clearance, so my botched drawing won't confuse you on that, I hope.

Thanks fellas,
Now that I have committed to this lathe I shall be like a kid waiting for Xmas.Ordered it over the phone Friday and will pay for it on Monday.

I will have to get my finger out and prep a place for it

Article 99 ,you can be sure one of the first accessories I will make will be that part off /tool tool holder.

We have a big mill at school but it only has has a surfacing indexed carbide cutter ( 60mm diam) and some end mills.

I can rough most of it out with the miller and get my mate who also has a mill,but more mill tooling, to do the slots.
could you offer any clues where one could buy small amounts of 4140. I am not keen on having to buy 6 mmetres or so of flat. Would machine shops sell me some?
I have bought 4140 round bar as replacements for bent vice handles as the little strong men at school like to bend the older weaker ones.It was fun to watch the expression on one young mans face as he tried to wind it up with the expectation of a bent handle. He may have busted something, but it was'nt the handle.(grin)


Any clues on setting up the lathe correctly.I assume it will be checking that both the bed vees are are horizontal and not torqued out of alignment.I can get one engineers square,will it be sufficient?

Thanks
Grahame

Thanks again for the very interesting information and drawings, I will have a go at making my own and see how it works out.

Originally Posted by Grahame Collins

Thanks fellas,
Now that I have committed to this lathe I shall be like a kid waiting for Xmas.Ordered it over the phone Friday and will pay for it on Monday.

I will have to get my finger out and prep a place for it

Article 99 ,you can be sure one of the first accessories I will make will be that part off /tool tool holder.

We have a big mill at school but it only has has a surfacing indexed carbide cutter ( 60mm diam) and some end mills.

I can rough most of it out with the miller and get my mate who also has a mill,but more mill tooling, to do the slots.
could you offer any clues where one could buy small amounts of 4140. I am not keen on having to buy 6 mmetres or so of flat. Would machine shops sell me some?
I have bought 4140 round bar as replacements for bent vice handles as the little strong men at school like to bend the older weaker ones.It was fun to watch the expression on one young mans face as he tried to wind it up with the expectation of a bent handle. He may have busted something, but it was'nt the handle.(grin)


Any clues on setting up the lathe correctly.I assume it will be checking that both the bed vees are are horizontal and not torqued out of alignment.I can get one engineers square,will it be sufficient?

Thanks
Grahame

You will need to level the lathe with a machinists level ,to get it perfect .Mines a bench mounted lathe ,but some of the larger floor mounted jobd have jacking bolts
You watch the bubble in the level as you tighten the mounting bolts after you have it level as this is what will pull the bed out of alignment,if you get movement when tightening the bolts you have to shim that footing until any movement stops when you tighten the bolts..
I have to do the same with mine but I'm having trouble finding a proper machinists' level around here.
There used to be one at the power station where I worked a few years ago ,but since the big flood in 98 lots of things wet missing or were damaged beyond repair.

Wherever you put the lathe, make sure it's stable. Cracks in concrete are to be avoided at all costs. (Have had that headache at work with a 6ton NC lathe. Cracked floor behind it means the damn thing no longer runs on centre and is far enough away that it can't be adjusted onto centre height. )

http://www.hareandforbes.com.au/samp...working/42.jpg

Top left is a picture of a precision level. Very handy thing to have, albeit expensive. Have seen them used for setting weird and irritating jobs as well as machines. (A must have if you ever want to try centreless grinding, too. )

Basically, once you've got the lathe set level with true beds, use it for a week and then check again. (It will have moved.) Repeat the process for a month or so until it settles down good and proper and you shouldn't have any dramas.

You could use every day BMS if you wanted to save a couple of bucks and the headaches of finding 4140, but your holder won't be as rigid and might suffer from chatter a bit more than the next guy. My advice would be to just get some 140mm round stock and mill it square and true with your face cutter.

Hi,

I have attached a photo of how I set my parting off tool if I am doing aluminium, plastics or brass round bar that as a hole in it.

This way you can part off the piece you require without leaving a burr around the hole. When parting off large diameters I start by cutting longer than the finished size with only a little bit of the cutting edge protruding out of the holder and I gradually pull it out (a bit @ a time) until the item falls off. It also pays to cut a wder channel than your parting tip as if you don't have it quite square to the workpiece it is less likely for the blade to break.

When I said I cut it longer than the size required, on the final cut, I face to off to length. This allows for less deflection and a better finish.

If the hole is large enough (in the workpiece), you can place a smaller diameter bar in the tailstock chuck & place it in the hole while parting off. This removes any danger of getting your fingers cut tryin to grab it, as well as not marking the item should in fall into the collection tray below.

I apologize if I haven't made myself understood.

Regards
MH

Yes! I understand I think!...I have read a little on the pro's and con's of the angled grind of the tip, there seems to be merits and drawbacks of a square grind to an angled grind. I guess I'll just test both for myself. Thanks again for all of the information, certainly gives me something to think about. A greenie to you also MH, thanks for the picture.