Are lathe tool carbide inserts supposed to be sharp?

[ajoeiam]

I think we were responding to someone who has very little experience of machining.

Without the backstory - - - - well your post reads as though you 'are' suggesting against using one's own developed tooling.
Dunno how many times I've read on this forum of people muttering about sharpening tooling.

Machining is not a solitary skill.
It is necessary to combine a bunch of other skills (likely also new) together to effectively practice machining.

 

[Shaun free]

As far as tooling goes the Carbide inserts generally have a radiused nose and specific angles for different types of material and as mentioned earlier are generally used on CNC machines that have much tighter tolerances and are more rigid allowing for deeper more controlled cuts with feeds and speeds calculated with the surface feet per minute adjusted with the diameter changes. For a home manual lathe you will get better results cheaper with the brazed carbide and high speed steel.

I really suggest getting the Machinist handbook. It will have any information you may need and then some. Its the bible for machinist and I use mine all the time.

 

[Ozwes007]

As far as tooling goes the Carbide inserts generally have a radiused nose and specific angles for different types of material and as mentioned earlier are generally used on CNC machines that have much tighter tolerances and are more rigid allowing for deeper more controlled cuts with feeds and speeds calculated with the surface feet per minute adjusted with the diameter changes. For a home manual lathe you will get better results cheaper with the brazed carbide and high speed steel.

I really suggest getting the Machinist handbook. It will have any information you may need and then some. Its the bible for machinist and I use mine all the time.

Shaun, I would have to disagree on this whole heartedl, at least in Australia. I have been a machinist for close on 50 years and in the last 15 to 20 years I can count on one hand the number of times I have used HSS at home or in a workshop. In CNC always carbide, in piece work lathes always carbide, on my little TAiG always carbide. You get 6 to 8 hours of cutting from the correct grade and type of tip on 90% of work in a mill, lathe, CNC machine. Consider that you have 3 to 6 minimum tips per insert, that equates to 18 to 48 hrs of cutting per insert. If you buy the best quality at $21 per insert! (Not talking diamond or super inserts) it works out pretty cheap. I have probably used silver steel more often then M2, M35 or M45 HSS. Just my humble opinion. And yes, get a copy of the the Machinist Black book, or download an app. I use FSWizard ( Pro Version) , there are many others.

 

[wazrus]

Depending upon the insert, the cost of replacements can be more than 'a factor', especially for amateurs. Then there are inserts and 'other' inserts. There are very clear quality issues. Insert clamping should also be considered. With my larger lathe, I couldn't find an negative rake insert holder SMALL enough for the centre height and I had to make one. Not a huge issue, but it sure held up the works. If you're OK with paying for inserts, then go for it: as I said, I do use BOTH carbides and HSS and, BOTH have their place. Grinding wheels/grinding machines? Cheap as chips on the 'net and usually come with a couple of wheels. Not necessarily a 'green grit' wheel, but they're not at all pricey, either. Practice is the key: experiment with reliefs and rakes until you arrive at the stock removal/finish you want. Other than some very specialised and expensive insert types, why is it that most drills are made in HSS? And I'm far from being opposed to carbides, but am very aware of the costs and benefits of one vs the other. The 'throw away' bit, for a hobbyist, isn't all that appealing.

 

[Richard Hed]

Depending upon the insert, the cost of replacements can be more than 'a factor', especially for amateurs. Then there are inserts and 'other' inserts. There are very clear quality issues. Insert clamping should also be considered. With my larger lathe, I couldn't find an negative rake insert holder SMALL enough for the centre height and I had to make one. Not a huge issue, but it sure held up the works. If you're OK with paying for inserts, then go for it: as I said, I do use BOTH carbides and HSS and, BOTH have their place. Grinding wheels/grinding machines? Cheap as chips on the 'net and usually come with a couple of wheels. Not necessarily a 'green grit' wheel, but they're not at all pricey, either. Practice is the key: experiment with reliefs and rakes until you arrive at the stock removal/finish you want. Other than some very specialised and expensive insert types, why is it that most drills are made in HSS? And I'm far from being opposed to carbides, but am very aware of the costs and benefits of one vs the other. The 'throw away' bit, for a hobbyist, isn't all that appealing.

On my small Enco, I broke a lot of carbides, but on the much larger, sturdier Grizzly, I hardly ever break a carbide. Also, I still use HSS on the Grizz for certain operations, esp. tiny threads which I have made quite a few for small bolts on the Coles/Ray Corliss. I ruined the half nut on the Enco when cuttin 8TPI which were just too much for that Enco. The enco just could not go slow enough to cut threads, at least for me. The slowest speed is 130 rpm. The Grizz gets down to 70. For some operations, I wish it was 50. What a bear (not a Grizzly) to get at the half nut to remake the it. If Enco were still in biz, I could probably buy one.

 

[Bazzer]

Different cutting tools as much as anything else have their place, I was taught in a formal apprenticeship how to sharpen HSS and I still do this on custom tools but given the choice I go carbide inserts every time.

My lathe is an EMCO 5, I am the only owner from new and it is nicely setup, recently I had a job where PCD inserts were recommended, so I bought one off insert at £30 (approx $42), this insert has taken the lathe into areas of accuracy and capability that I never thought possible, this insert cuts so well that it has for all intents and purposes removed spring back, I am able to wind on 2 micron cuts and see the tiny amount of material being removed - quite incredible.

 

[Jasonb]

The enco just could not go slow enough to cut threads, at least for me. The slowest speed is 130 rpm. The Grizz gets down to 70. For some operations, I wish it was 50.

have you tried threading away from the chuck, speed can be a lot faster as you start from the shoulder and don't have the worry of stopping before you hit it.

The internal threading insert tools are ideal for this as you can easily reach around the back of the part being threaded with the added bonus of correct angles and tip & root radius if you use a full form insert.

Other option is to turn the spindle by hand as many do.

Barrie, I've not had need to try the PCD inserts but I see quite a few of the performance engine makers using them, I assume that piston has quite a bit of Silicon in it.

 

[Bazzer]

Hello Jason

Yes the piston is 30% silicon, it is RSA444 material, although the setters were done from regular aluminium 6082 T6 more than likely and this machined equally well with the same characteristics from the lathe, you may notice that the compound slide is canted around at 1 degree to get micron level advances of the tool.

The finish is phenomenal, I was really surprised the inserts came from APT, they have an online store.

B.

 

[Steamchick]

Just looked-up PCD inserts... I didn't understand the jargon... The "D" stands for "Diamond"... but my wife would not wear this one!

PCD Turning Inserts | Cutwel - Lathe Tool Specialist

Shop online today for PCD Turning Inserts. Designed for turning high silicon aluminium, carbon fibre, glass fibre and abrasive plastics. UK next day delivery!

www.cutwel.co.uk

This page explains the quality, applications and costs.
You pay your money, and never get more than you pay for...
K2

 

[Bazzer]

DCMT 070202 PCD 1500 Diamond Turning Insert for Aluminium Alloys with >12% Si content Associated Production Tools (shop-apt.co.uk)

The best improvement I have ever made to any machine tool I have ever owned and all for £30.00 worked the same on 6082 T6 as well.

B.

 

[mu38&Bg#]

The finish is phenomenal, I was really surprised the inserts came from APT, they have an online store.

I'm surprised you get usable pistons with the standard bearings in that spindle.

 

[Jasonb]

I might just have to put one on my next APT order, tend to use them for most of the carbide milling cutters for the CNC.

 

[Richard Hed]

have you tried threading away from the chuck, speed can be a lot faster as you start from the shoulder and don't have the worry of stopping before you hit it.

The internal threading insert tools are ideal for this as you can easily reach around the back of the part being threaded with the added bonus of correct angles and tip & root radius if you use a full form insert.

Other option is to turn the spindle by hand as many do.

Barrie, I've not had need to try the PCD inserts but I see quite a few of the performance engine makers using them, I assume that piston has quite a bit of Silicon in it.

On the enco, it would have undone on the spindle if it stuck. I tried that at an earlier date. On the Grizz, I could do that but all I have to do is pay close attention to doing it the regular way. Pluss I don't have the set up for it yet. I'll get around to it some time

 

[Bazzer]

I'm surprised you get usable pistons with the standard bearings in that spindle.

Who said they were standard bearings?

No all joking aside, I have changed the bearings but they are only SKF Explorers with a slightly better than normal precision, I think they cost about £28.00 each. The lathe is turning super well, it is difficult to tell the pistons from MB supplied ones.

Ovality in the piston is sub 2 micron and it certainly feels very good in the bore, no cogging as it is rotated and the band forms up perfectly evenly. Malcolm Ross saw a piston cylinder set a couple of weeks ago and he said that is definitely going to run well.

The lathe is well setup and I am very crafty

B.

 

[willray]

Who said they were standard bearings?
...
The lathe is well setup and I am very crafty

You did say the lathe was an Emco, yes? I would not have expected it to have particularly poor bearings in the first place.

 

[Bazzer]

Agree, but it did have a poor spindle from new, kind of looked like a cam, I bought another off of Ebay which was really nice and changed the bearings at the same time.
Good bearings are very cheap now.
B.

 

[mu38&Bg#]

The Compact 5 uses standard grade deep groove bearings. They are not super precision spindle bearings. This is also the case for some of the small mills. Emco does make premium product, but these were built to a price. Taig and Sherline do the same with bearings, and people do get great parts. The mystical precision required for this specific application is what made me comment.

 

[Bazzer]

Maybe you summed it up as mystical precision and with care and good feeling/mechanical sympathy the mystique is smashed !!

 

[willray]

Agree, but it did have a poor spindle from new, kind of looked like a cam...

That makes me sad. Beancounters are the most corrosive force in the universe, and I realize that the smaller Emcos aren't Hardinge Super-Precisions, but it's still disheartening to see a good manufacturer choose to cut corners on quality control.

 

[Bazzer]

I think it was one of the last Compact 5's made and was probably done from the parts bin, excepting the spindle issue it is great. I paid £30 for a second hand spindle on Ebay.

The other spindle was fine if you were working down to 0.00075" (3/4's of a thou) but not finer as I always got foxed by the out of round.