Try looking at the edge with a lens, amazing how rough they come off the wheel. Make sure the wheel cuts vertically, same direction the work will be turning if you grind the tool 'horizontally' it can weaken the edge. Yes, I am starting to think that these carbide tools might not be worth the trouble. I might give the green wheel a miss for now and buy some indexable carbide tools instead. The bench grinder will still come in handy for sharpening the HSS tools.
The only time I have had problems with them chipping and cutting badly is when I have ground too much clearance angle on them. It's best to keep that angle at around 7 degrees which means that the centre height has to be set with some care - over centre wouldn't be a good idea.
I don't have much of a problem getting a decent finish with a 60 grit green wheel but as I mentioned before I haven't used them for a long time now. It's mostly been on cast iron for tooling and parting off blades converted to screw cutting bits mainly for use on HSS. Are you turning aluminium and it's sticking to the tool? If so it's easy to flick it off with something - sharp knife. If you want to use carbide on aluminium you will probably be better off using inserts - some would say ground and uncoated ones but the more recent ones are uncoated and micropolished.
It can melt and stick even then. The easiest way round that is to reduce speed. No coating may seem odd but aluminium oxide is pretty abrasive stuff and aluminium oxidises very quickly.
Instantly is often mentioned. A bit of thin oil makes them cut more efficiently. Brian, from my limited experience green wheels are slower than diamond at dressing the brazed carbide tips. Another thing I noticed was that they were inclined to slightly round the cutting edge. That might have something to do with the soft bond on the green grit wheels. I'd keep an eye out for one that was box shaped with four different grit sizes along the 4 sides. Using the finest side, I think is fine for final dressing the edge and the tool cuts cleanly.
Personally I gave up on the green wheel for dressing tips after using the diamond stone. It has served me well and I use it regularly. I have also recently been given a set of 8 cutting bars with clamps to hold inserts.
The inserts are square and the tool bars are set at different angles both right and left hand. The inserts are both black and white and are in plastic trays and look like they are ceramic, Are they able to be used for turning metal or can they only be used for softer materials such as plastic? Can someone please advise! At the smaller, more economical, Model Engineer affordable end of the range the quality of the carbide can be very variable.
Seems to be some element of "whatever we can get this week" in the suppliers production plans. Certainly no active, focused, material development aimed at small lathe applications. As ever the problem with carbide is that its admirable strength and durability when kept under decent compressive loading is counterbalanced by fragility if it ever gets into tension.
The Sandvick "Why Climb Mill" paper which Neil very kindly linked to in another thread makes it clear that even today clearing the very fine exit end of the chip when normal milling can rapidly blunt cutters seriously reducing life. Fine chip. Short life. Sounds about where Brian came in. Of course the absolute sharpness that can be got on a cutting edge is heavily dependant on umpteen parameters like grain size, bonding and gawd knows what else.
Its fairly clear that as you approach the ultimate possible sharpness there is is pretty much nothing holding the carbide grains on.
Which obviously sets the limit to how sharp a usefully durable cutter can be before the edge crumbles away. Our smaller machines inevitably suffer more from vibration, minor deflection, speed instability etc than industrial types which clearly won't help as every vibe, however small, puts a tension load into the cutter. Worse for really tiny cuts as there is pretty much nothing to load up and stabilise things. Worth examining your methods to see if you can get good finish from deeper cuts.
If I go below 0. Generally 50 thou, 1mm ish cuts for pretty much every job works OK for me giving a reasonable balance between finish, cutting time and chip handing.
I rarely need to remove so much stock that the extra two or three passes at 1 mm compared to really exploiting the machine capacity are significant. What's new New media New media comments New downloads Latest activity. Log in. Install the app. Welcome back! Did you know you can mentor other members here at H-M?
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Joined Oct 24, Messages GarageGuy said:. Another cheap way to touch up brazed carbide cutting tools is a carbide saw sharpening blade from Harbor Freight. It is a 4" diamond wheel. It also works well for sharpening TIG tungstens. Click to expand Joined Feb 5, Messages It is a 4" diamond wheel Joined Nov 30, Messages 3. Thank you, a very useful and ingenious use of currently owned tools to help the shop to grow.
Joined Mar 10, Messages Hey thanks for posting Thought the same thing about making a cheap carbide grinder Thanks for confirmation. Does anyone use this method and what grit a did you find works well?
JimDawson Global Moderator Staff member. H-M Lifetime Diamond Member. My small lathes are limited to spindle speeds of and RPM, correct for HSS tooling, but like most of us I find uses for carbide cutters. The photo shows a hardened tailstock center with a neck, turned with an AR brazed carbide tool. In this photo, the cutting surfaces of the broach at upper right was finish machined with a carbide end mill after hardening.
There were no issues when cutting the hardened O-1 material. There are other applications and the need for carbide cutting tools will likely be obvious at the time. But the main utility of carbide tooling is that it can remove material quickly leaving a good finish. This of course assumes that the spindle speed of the lathe is high enough to be effective.
Generally, for steel, this would be around — SFM and about twice that for most non-ferrous material. A Typical Method Of Sharpening Carbide Cutters One might get lucky and buy a brazed carbide tool that is sharp and has reasonable cutting geometry.
The reason for this is to better expose the actual cutting edges of the brazed carbide for sharpening. The AL cutter in the second photo has been stroked with the diamond lap on the cutting edge.
A fine-grit diamond grinding wheel is probably the best tool for dressing carbide cutters but that is a rare commodity among the HSM community. Sharpening the cutting edge the left side face of an AR tool for turning applications certainly lessens the requirements of motor horsepower and machine rigidity and may improve surface finish but the cutting edge may become fragile and break down in an interrupted cut or when encountering a shoulder. It depends. Space might be the limitation for many of us so now we come to the point and thank you for being patient.
Joined Mar 25, Messages 3, The drill press is a great idea! I had an old Sherline Lathe and did the same kind of thing.
Joined May 13, Messages Great idea, thanks. Click to expand Joined Feb 1, Messages 6, I keep one of those little guys next to the lathe for touchup. Joined Jul 14, Messages 7.
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