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carbide inserts query for a confused wannabe user

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savarin

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#1
I'm in a "bit" of a quandary and desperately need some help.
I would like to try some carbide inserts but have absolutely no idea which ones to purchase.
I have come into possession (free) of a bunch of holders but with no inserts in them.
The internal threading holder is new and uses a torx screw fixing. From the centre fixing screw to the flat edge of the recess is around 4mm give or take a tad.
The other 6 use a cam lock except the end one that has been drilled out for some reason.
What from the gigantic selection of weird numbers would long time users suggest I should try?
most of my materials are mild steel, aluminium, stainless and brass.
Also any ideas what each tool should be used for? ie, facing, turning boring etc.
Thanks
tool-bits.jpg
 

GoceKU

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#2
Savarin, those are almost all for cutting in both directions, the first next to the boring bar is for cutting on the side of your material those usually have negative rake i use them for heavy cutting, the very last one with the hole is for facing off, for cutting across the chuck's face the shape of insert for the last three is "WCMT", my general rule is the smaller the cutting edge i take small cuts, for inserts i recommend sandvik seem to last longest and don't chip easily on a beginner's mistake, lastly i would like to ask how have you survived without insert tooling?
 

q20v

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#3
I just started using carbide inserts (cheap brand, like $60 for a set of 5 with the holders) and find them fantastic for roughing, but I turn (ha!) to my HSS for finishing when a nice surface finish is desired. Not sure if this holds true for higher end carbide inserts, though. The other day I was removing 70 thou DOC on heat treated 4140 with my 1224 busy bee lathe. That produced some desk-art worthy chips.
 

savarin

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#5
lastly i would like to ask how have you survived without insert tooling?
Well, I havnt been doing it for long (just realised its been 5 years, wow thats gone fast) so its been hss so far except for some brazed carbide boring bars (that I dont like much)
q20v, I dont think my flexi 9x20 could handle a 70 thou cut in steel somehow.:laughing:
 

GoceKU

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#7
Savarin, i've been doing this since february of this year and first cutter that i bought was an insert type cutter, i only use HSS on aluminium, brass and plastic, dependent of the insert angles and holder angle, you may need to spin the workpiece much faster to get the mirror finish with you smaller, less powerful machine, my lathe with 13,5 hp motor, relay doesn't care negative, positive rake, i'm sure other members will have more experience with less powerful lathes.
 

savarin

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#8
Okay, still confused. Been through the charts and can work out some of the codes but I still cant make head nor tail of the sizes.
How do I work out the size of cutter from the measurements I get on the holders.
Particularly the trigon and internal threading bar.
I am assuming this square one will fit my square holders for size SCMT09T304 Square,1-Side,IC 9.5mm, Sick 3.9mm, R0.4, Taper hole 4.4mm
 

Dave Paine

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#9
The trigon insert size is based on the inscribed circle of the insert. What is your measurement?

For the threading insert, I would look on a site which shows the same bar diameter as yours. Likely will be the same threading insert. The insert should state the tpi range it will cover. Often a different insert for coarse threads.
 

shooter123456

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#10
I have some WNMG inserts that are .5" inscribed circle and measure .613" across the widest points.
Well, I havnt been doing it for long (just realised its been 5 years, wow thats gone fast) so its been hss so far except for some brazed carbide boring bars (that I dont like much)
q20v, I dont think my flexi 9x20 could handle a 70 thou cut in steel somehow.:laughing:
I wouldn't be so sure. I have a PM1030v and messing around with RPM, angle of engagement, and feed, I can get mine cutting .1" in steel running .0025"/rev. I prefer that for roughing because it makes nice chips and drops them right below instead of flinging the chips everywhere or making a long string. Give it a go, I was surprised at what my machine was able to do because I usually kept the cuts light without ever trying heavier ones.
 

savarin

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#11
The comment regarding depth of cut possible with my 9x20 set the bells ringing so I thought a few experiments were worth while doing to set my mind at rest.
The material is stainless, HSS tool
First cut at 10 thou"
10-thou.jpg
No problems

Second cut at 15 thou"
15-thou.jpg
Nice tightly curled chips and again no problem

Third cut at 20 thou"
20-thou.jpg
Hmm, chips starting to string out but again no problem.

Fourth cut at 25 thou"
25-thou.jpg
Danger Will Robinson, these chips or should I say strings were lethal but it cut it ok.
I didnt have the nerve to go thicker as I felt this was more than enough for what I will do.
So, end of experiment..... I wont worry about the lathe being able to handle any thing I will throw at it.
 

Wreck™Wreck

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#12
A bit of insight from someone that has been doing general lathe work for a living going on 30+ years, take it for what it is worth.

In general lathe work such as is often found in job shops and hobby shops there are only a handful of insert shapes that will cover the majority of common turning operations, pictured below are what I use the most on a daily basis.

WNMG Trigon for OD roughing and facing. Very tough, excellent for roughing down flame cut edges.

CNMG 80º diamond shapes of various sizes and edge shapes, turning, facing and boring.

VNMG 35º diamond shapes of various sizes and edges, finish turning and boring, working close to a center and shallow undercutting, they do not face well.

Internal and External lay down threading inserts. I also use some end mounted internal thread tools for small holes when needed.

Parting, in this case Kyocera.

Kennametal Top Knotch inserts, internal/external full radius grooving, internal/external straight grooving and internal/external threading, the inserts fit in the same holders, one can use the same holder to turn Acme, 60º V, Whitworth, metric 60º and metric trapezoidal threads just by changing the insert.

Assorted triangle inserts which I rarely use.
 
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