Keeping track of tool inserts?

All, I’ve got several lathe tool holders (straight, left hand, right hand etc) which all take the same geometry insert (DCMT/DCGT). I’ve also got Inserts with several tip Radii, and for cast iron, steel and non-ferrous materials.

I find that when I change an insert, I soon loose track of how much it’s been used, and whether it’s been slightly damaged or turned around in the holder.

How do you keep track of how much use your inserts have had, assuming a limited amount of holders and the need to swap them over quite often?

Also, is there a standard pattern on the inserts that tell you what type it is, ie cast iron or non-ferrous?

Thanks.

If I have to removed a partially used insert I mark all the unused or serviceable edges with a waterproof felt tipped pen.

I'm not sure if there are noticeable differences in the design of tips that would tell you what materials they are for. I would be inclined to keep them is separate boxes for each type.

Brian

Edited By Brian H on 10/03/2021 19:15:06

I tend to just do it on visual inspection. If I need a shaper insert than I'm currently using, the old one goes back in the insert box at the other end to the new ones. Then if I want to use one for some grotty roughing task that I don't want to bust up a good insert for I can use that.

Me too. I eyeball the new edge with a loupe. I inspect brand-new ones just to make sure it's not been chipped in transit. (Not found a dud yet apart from the seconds I foolishly bought cheap at an exhibition, and even they had up to three good edges.)

Dave

Thanks all. I sorted them into boxes, with the types and replacement order numbers etc stuck on. Putting used ones at the other end of the box is a good idea. I tend to get impatient and just put the old tips to one side to deal with later, but never get around to it.

On a related note, for a general purpose DCMT 0.4 radius insert used on, say, mild steel, about how many times would you use it for before replacing? I know it’s a vague question, but on something like a medium sized steam engine, could one insert last the whole model, or do you replace for each job where finish is important?

Its really difficult for me to know when a tip needs changing, unless it’s obviously damaged. I get the impression Im changing them way too often.

BTW my lathe is an ML7.

Ive also recently got a 4-insert shell mill from Arc, for use on the SX2P. That cutter is a bit of an animal - very impressed with it, although it does cover everything in the vicinity with a layer of blued chips.

Thanks.

I normally chip it through a silly error before I wear them out. Better engineers may be able to tell you!

Change it when the surface finish drops off

Once it gets a bit dodgey mark the bad edge with Tippex and turn it round. Of course you could be OCD like my brother and make up a spread sheet with hours run etc for each tool/tip.

regards

If it needs to be a good edge, I check with a mini microscope-40X I think it is. Just a cheapy, but allows you to see the cutting edge in great detail. Some new inserts are not as good as they appear either. I will often mark the edge I am using. If it is chipped or stuffed, I generally hit that edge on the linisher belt to make obvious not to use that particular edge. On double sided inserts, I use one corner, then turn over and use the other side of that corner. So if it ever fails for what ever reason, you have got to use both edges, particularly with TNMG inserts, or the VNMG inserts.

That's a good idea with the linisher - to make the insert clearly unuseable.

Good question and hard to answer because there are so many variables!

Assuming the cutter is used as the manufacturer recommends, it will last about 30 minutes on a tough abrasive material, and about 2 hours on, say mild steel. That's cutting time, not elapsed time, and how long the insert takes per cut is usually quite short. I suppose I average less than 10 seconds per cut, and because I rarely attack difficult metals, I don't change inserts that often. 720 cuts is quite a lot in my world, but I'm not a busy metal worker - my lathe hasn't been used at all for 10 days.

In hobby circumstances it's unlikely any of us run carbide as recommended, and that can either increase or dramatically reduce insert life in complicated ways. For example,

• taking relatively slow but deep cuts will increase tool life because the insert runs cool
• taking slow shallow cuts will reduce tool life because it concentrates wear on a small part of the cutting edge.

Unfortunately in amateur hands there are more ways of reducing insert life than getting the best out of them. Our machines tend to be underpowered and slow, which encourages over delicate cutting and greatly increases wear on the tool. We often sneak up on dimensions by taking a series of fine cuts rather than doing it in one. Swarf getting caught and minced under the tool will wear the edge quickly. Being brittle Carbide doesn't care for being bumped by clumsy operators. Nor is it happy to have coolant dribbled on it because thermal shock cracks it - all or nothing with carbide, either run it dry or flood cool it. Except a bit of coolant/lube is essential to stop low melting point metals like Aluminium welding itself to the cutting edge.

That said, carbide inserts are much tougher than HSS provided the pitfalls are avoided.

Got through a fair number of inserts when I was learning how to use my mini-lathe. Now the same inserts last for ages on my 1.5kW lathe, probably and counter-intuitively because they are worked much harder. Andrew Johnson deserves another thank you because it was he who drew my attention to the dangers of pussyfooting with carbide. Don't - carbide works best when pushed in a way that would ruin an HSS cutter. I think I've also got a little more skilled. For example, although I still sneak up on dimensions, there is usually only one light finishing cut at the end, not several. I guess my inserts last longer because the more confident me takes deep cuts at fairly high-speed and doesn't bump them into the job. Practice makes perfect.

Hard to generalise because the type of work, machine and materials used make an enormous difference. As it's tricky to predict how long an insert will last, might be worth buying a cheap USB microscope and checking for damage before an insert is used for anything mission-critical. (Damaged inserts are often still good for roughing out, just not for finishing.)

Dave

Edited By SillyOldDuffer on 11/03/2021 17:47:07

Thanks Dave. I don’t like taking deep cuts with my lathe because I feel like it’s struggling, and maybe even causing excessive load on things. I like to think I’ve got some mechanical sympathy, so taking deep cuts doesn’t sit well with me if I feel like things aren’t sounding right.

If I take a deep cut in the mill, in, say cast iron, it just makes a terrible vibrating racket, to the extent I’ll happily use shallow cuts and pay for more inserts if required...

It's counter-intuitive but chatter when milling can often be eliminated by increasing the feedrate, and hence chip load.

Andrew

Not on mine, believe me.

Out of interest, what’s classed as a “deep cut” on an ML7/SX2P sized machine?

My ML7 will happily take a 100 thou deep cut in mild steel under power feed. Using a HSS knife tool good and sharp and preferably with tailstock centre in place unless job is very short. It would probably take a bit more but never tried it. One full turn of the cross slide handle is my standard roughing cut, which is 100 thou. I think my recently acquired insert tooling will do about the same with xxGT inserts but at higher rpm so really speeds up metal removal.

Edited By Hopper on 12/03/2021 00:07:46

Me too. I've peered at the things through a loupe and invariably found there is a chip out when it starts behaving badly. Simpler and quicker just to change it.

Hopper -I'd be interested to hear how it goes with the xxGT inserts. Like many others I suspect I use them for finishing on steel as well as the non-ferrous they're designed for, but the tip seems quite fragile and not up to roughing steel- on my machine anyway.

Rob.

Presumably at a fine feed? I reckon my DCGT tips would snap on contact at that depth of cut in steel.