Tool life

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nzlowie

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Oct 22, 2021
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Hi all, just starting to get to work with my myford ml7. Had a small project with some 1045 and killed 4 carbide tips. First was when I got a bit too aggressive with my cut and stalled the lathe. (Belt slip) in fact might have done a couple this way before adjusting the belts ... I was trying to be aggressive as I've always been told these tips like to be worked hard.
Next was when I tried to face right to the center of my job, pushed in a bit hard and lost the tip.

Just seems these tips are too brittle for a learner like me.....

Any tips on using carbide tips for a beginner? Or are you going to say, sick with tool steel?

Cheers Dave
 
I use both HSS and carbide. the aggressiveness you use depends on the geometry and grind of your carbide.

Using carbide tooling intended for aluminum can easily result in tool failure if the pressures get even a little too much. Formed carbides that are not ground are intended for higher pressures, but pisitive rake tools require less.

The short story is 'it depends': on your exact geometry, the grind, the rake, the composition and the coating. so it gets complicated quicker than you think. HSS is easier to explain...
 
Thanks mate. Getting to appreciate that the tooling is another area to learn. All my previous machining was in a shop that was all setup so I didn't have to think about that.
So.... Where do I go to get info on what tips to look for? Material and angles, that sort of thing.

Also will start looking at hss and getting familiar with that as well.

The other question I had which I'm sure you'll have an answer for, when I brought may tool holders the boring bar (round with flats) sits a lot lower in the tool holder so needs a lot more shims to bring tip to center line. Also points down at the tip. Normal?

Cheers
 
www.hobby-machinist.com

Models for grinding HSS Lathe Tools

In a recent thread by @Darkbluesky, http://www.hobby-machinist.com/threads/lathe-accessories-tools-ideas-of-what-to-buy.62043/#post-511618, @ttabbal joked about sending me blanks to be ground into lathe tools ... he was joking! But it got me to thinking ... yeah, I know it's not a good thing...
www.hobby-machinist.com www.hobby-machinist.com

Here you go ! Thank Mike , it's a great deal of information which took plenty of effort . :encourage:
 
nzlowie said:
Where do I go to get info on what tips to look for?
Click to expand...
For HSS, +1 on the link above.

There are a lot of tutorials in youtube, and lots of advice from guys here about carbide. My most reliable resource is the distributors (that have training or experience) or the manufacturer's technical reps, which are all available by phone. You also have to 'tune' your own mill through experience (read broken carbide inserts and poor performance).

About advice: everybody has their biases. I only learned about 15 years ago that I'd been using the wrong insert (triangle) for doing the work I do, instead of CNMG inserts, because my mentor had a hate on for CNMG. sigh. Always listen for both the positive and negative in any advice you are given - even a novice can have insightful observations.
nzlowie said:
Also points down at the tip. Normal?
Click to expand...

in a word, no. a picture will solve at least 8 or 9 questions I'd have to ask becasue I can't see what you are seeing.
 
I’m trying to imagine a lathe stalling with a carbide cutting tool = not a good combination. The carbide would most likely fracture.
High speed and heavy loads makes my carbide lathe tools happy.
 
nzlowie said:
The other question I had which I'm sure you'll have an answer for, when I brought may tool holders the boring bar (round with flats) sits a lot lower in the tool holder so needs a lot more shims to bring tip to center line. Also points down at the tip. Normal?

Cheers
Click to expand...
You didn't specify which insert this is for. For double-sided inserts (zero clearance) the insert is tipped downward to create clearance. Even more so for a boring bar where the curvature of the bore requires more clearance.
 
When you broke the tip heading to the center your tool was set to low the nubbin rode over top and broke the tip Just part of learning process
 
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