Indexable parting blade woes

harrzack

Harrzack
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Mar 27, 2013
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Have always wanted to try a parting blade with carbide insert. I have a LMS 3536 8.5x16 lathe that has enough juice to handle it. The commercial versions are out of this hobbyist's budget, so went for a Shars combo pkg - http://bit.ly/2pmQtIi - AXA holder, blade & inserts.

Gave it a run today. Had a 3/4" bar of 1040 CRS in 3 jaw chuck, carriage all locked down. Started in - lots 'o chatter - tweeked speed/feed till I saw some nice chips coming out. Things were going well, and then (as you may have guessed), it dug in an popped the insert out - and holder appears bent as now insert just falls out.

Undaunted I flipped the blade around and tried again - with same results.

So - I'm thinking the heart of all this is the blade. The tool holder itself is typical QCTP stuff.
I'm hoping that the Shars blade was the culprit - appearing to be a bit light (AL?).

It would seem if I get a name-brand blade (and thinner inset) that I may get a workable system. I know - avoid this "BigBoy" tooling and stick with a standard HSS parting tool - but where is the challenge in that? Anybody else tried this?
 

Wreck™Wreck

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Sep 29, 2014
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I part off thousands of pieces per year in mostly 304 and 316 stainless material, flood coolant is excellent. 750 brass parts from hex stock last week alone.

Power feed the tool to a suitable -distance in the X axis if a solid, less then the ID if a part with a bore, hand feeding is inconsistent at best. Try .001" feed per revolution on steels as a starting place, increase if it works well.

Good Luck
 

harrzack

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Wreck - thanks for the ideas. Sounds like you are a real production shop!

I'm still puzzling over what the "secret" is about the parting blades Shars is selling. Now have found several others complaining about how flimsy they are.
 

carlquib

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Apr 26, 2015
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I think that sounds like a lubrication problem. I use several of the shars parting inserts and holders. The only time I've had problems was when I was pushing the holder too hard or didn't have enough lube on the cut. I guess there was the one time I let the insert get too dull. I'm with wreck, I prefer a good flood coolant. If everything is right you should get chips like this.


This is the tool I was using, I was parting some 2 1/2" 1045 cold rolled. This was pushing this tool a little but it did just fine and survived to part again.


Sent from my SM-G930P using Tapatalk
 

kd4gij

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Watch EBay I got a great deal on an iscar blade and inserts mine uses 3/32" inserts I think.
 

jbolt

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I have read other complaints about the Shars small cutoff blades bending. Not enough meat below the insert to resist the load.

I have this blade and have been using it for 3-4 years in materials up to 3" diameter.

I have found the GT inserts need .003" to .005" feed rate and 200+ SFM otherwise they can rub or chatter. Lots of lubrication.

HSS is more tolerant of speed & feed rate.
 

kioni5004

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I have found , even with some of the larger lathes of chinease origin the problem is spindle stiffness . The spindle flexes at the front bearing as the material tries to climb over the tip of the tool .once the chatter starts its gonna keep going . One way i have found to combat this problem is running the lathe in reverse with the parting blade mounted upside down . I cannot recommend this it the chuck screws on to your lathe though but if it bolts on try it . It's a much quicker trial than having to build a rear tool post

Sent from my SM-G935F using Tapatalk
 

NortonDommi

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Nov 15, 2016
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Hello harrzack,
I concur with kioni5004, if you can run the blade upside down then you will eliminate the tendancy to dig in. You may have to fabricate something as the couple of pictures I attach will show. Please excuse the unfinished appearance this was knocked up fast as all I had to hand was scrap.
The blade is a Widex 25mm, that means the blade is 32mm wide,(the 25mm is the measurment from the base of the blade to the cutting edge of the insert),my lathe takes 16mm tooling so I needed to hold the blade above the top of the toolpost.
Things of particular importance when parting are: Is the blade square to the lathe axis? Regardless of anything else this is critical! Set your toolpost holder by placing a tool holder in place and set it against your chuck. Quick, easy and the first thing to do WHENEVER you fit a parting blade.
Next thing that I'd recommend is when you have determined the place you are about to part LOCK THE SADDLE.
When using Carbide tips, Don't dawdle! They like to get stuck in and if you set up the right conditions they will last and give great servive.
If you do run upside down another advantage is that the swarfh just falls straight down. I've also found that I do not need to flood cool.
Hope this helps.
- Barry
 

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  • Parting Toolholder.zip
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GarageGuy

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Nov 9, 2013
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I have the same or similar carbide insert parting tool from Shars, and the exact same thing happened. I was watching a video on Halligan142's YouTube channel, and he had the same thing happen as well. I don't know for sure, but it seems like the holder is too soft and too easily bent. In my book that makes it a defective tool, but who am I to say?

My parting problem was so bad that I gave up trying to part steel at all. I would only part off aluminum and brass. Steel would get band sawed off. I finally got frustrated because the 14" Logan at work would part like a dream, and mine wouldn't. I went around and tightened up the gibs on the compound, cross slide, and the gibs on the carriage. Now it is much better. Still not perfect, but much better.

GG
 
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