# Sharpening Micro 100 bars



## dpb (Jun 27, 2020)

What material/ grit grinder wheel will give the best results for touching up my Micro 100 solid carbide boring bars?  I have an 8” grinder, and several Micro 100 bars with small chips, that I think would clean up easily with the right wheel.


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## mikey (Jun 27, 2020)

You would need a diamond wheel for that. One option is to send it back to Micro 100 for resharpening; it would be cheaper than a diamond wheel. For touching them up, a simple diamond stone will keep them razor sharp.


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## dpb (Jun 27, 2020)

The wheels for brazed carbide wouldn’t work?


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## benmychree (Jun 27, 2020)

Using green or dark grey wheels would invite chipping of the cutting edges.


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## mikey (Jun 27, 2020)

You mean those green wheels? Maybe, if the chips are tiny, but a diamond wheel will be safer. I use an Accu-finish wheel for this job but if I were you I would send them back to Micro 100.


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## mmcmdl (Jun 27, 2020)

Green silican carbide wheels would do the job , but I wouldn't recommend it . Diamond is the way to go , either a wheel or a file as Mikey said .


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## dpb (Jun 27, 2020)

Thanks guys.


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## Z2V (Jun 28, 2020)

mikey said:


> One option is to send it back to Micro 100 for resharpening; it would be cheaper than a diamond wheel.



Nice to know that they offer this service. I have chipped a couple myself, need to drop them an email.
Thanks


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## mikey (Jun 28, 2020)

I have not sent boring bars to Micro 100 but was told they would do it. I would contact them and see. Borite is another company that provided this service for their tools. They didn't advertise it either but they would completely recondition a boring bar for $6.50 each, which is cheap considering what one of their bars cost. Micro 100 will create custom boring bars on request so I would guess they will recondition a bar, too. 

Their website has been brought  into the 21st Century and is so much easier to navigate now. Check them out.


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## mikey (Jun 28, 2020)

Just thought of another option. Maybe one of the guys on the forum who owns a D-bit grinder and has a diamond wheel might be willing to sharpen a chipped tool for a fair price ... ??


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## mmcmdl (Jun 28, 2020)

mikey said:


> Just thought of another option. Maybe one of the guys on the forum who owns a D-bit grinder and has a diamond wheel might be willing to sharpen a chipped tool for a fair price ... ??



Mike , I must have 150 or so bars . I always had to customize most of them for additional clearance when doing small internal profiles . I will honestly say that these are the best carbide bars around and they come from the factory with a great general purpose grind .


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## Z2V (Jun 28, 2020)

I sent an email to customer service and will report back on their reply.
I only have about 15 of these Micro 100 bars but I managed to chip the tip on a couple of them, rookie mistakes.


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## mikey (Jun 28, 2020)

I haven't damaged many but same here, rookie mistakes.


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## Tozguy (Jun 28, 2020)

mikey said:


> You mean those green wheels? Maybe, if the chips are tiny, but a diamond wheel will be safer. I use an Accu-finish wheel for this job but if I were you I would send them back to Micro 100.


mikey, can we have the particulars on the Accu-finish wheel that you use please.


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## mikey (Jun 28, 2020)

Tozguy said:


> mikey, can we have the particulars on the Accu-finish wheel that you use please.



I use a 180 grit Gator wheel from Accu-finish on my Series 1 Accu-finish grinder. Follow up is with a 600 grit wheel. Works good for small nicks and for honing an edge. I have Micro 100 boring tools that must be over 20 years old and cut like new.


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## dpb (Jun 28, 2020)

I recognize that there will be a significant range of answers but will those of you with extensive experience with the micro 100 bars, give me some insight into the speeds and feeds you use, in various materials, with an eye toward long tool life?


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## doc55 (Jun 28, 2020)

Before I built my carbide grinder I took care of chipped tools and sharpening with a dremel tool with one of their diamond wheel mounts. I clamped the Dremel in the vise and carefully hand ground them. Worked pretty good.


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## mikey (Jun 28, 2020)

dpb said:


> I recognize that there will be a significant range of answers but will those of you with extensive experience with the micro 100 bars, give me some insight into the speeds and feeds you use, in various materials, with an eye toward long tool life?



This is a good chart. Use the cutting speeds listed and plug it into the RPM formula at the bottom to get your speeds.

I only use the Micro 100 bars in tiny holes so most of the time I am running very near max speed in most materials. I highly recommend you use a carriage stop in blind bores because if you hit the bottom of the bore without one, you will snap that bar in a microsecond at the speeds you will be using. 

Feed fast enough to produce a spiral chip for best results. Again, in a blind bore, you need a carriage stop so you can feed with confidence.


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## dpb (Jun 28, 2020)

@mikey Thank you for the chart.  I’ve been running too slow on rpm, and taking too large a DOC.  My feed rate has been at the high end of what’s recommended.  If memory serves, I picked the rpm to keep the bar from “singing” as it cut.  I’ll revisit.


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## mikey (Jun 28, 2020)

dpb said:


> @mikey Thank you for the chart.  I’ve been running too slow on rpm, and taking too large a DOC.  My feed rate has been at the high end of what’s recommended.  If memory serves, I picked the rpm to keep the bar from “singing” as it cut.  I’ll revisit.



In my neck of the woods, "singing" of a boring bar is called chatter. Either your speed is too high, feed too low or depth of cut too deep. Deep depths of cut is a relative thing. What is moderate for a normal bar can be a honking big cut for a mini-bar. Micro 100 bars are able to cut deep but the smaller ones have their limits. You sort of have to experiment to see what the max depth of cut is.

I normally ignore feed rates from tables or calculations and let the bar tell me what it wants. For a given speed and depth of cut, feed will vary and it is easier for me to feed at whatever rate is needed to produce spiral chips. If I get spiral chips then I know the bar is cutting optimally, even if the speed and depth of cut are not dead on by calculations or tables. Quite frankly, I don't even calculate speeds, either. For these smaller bars I start out at max speed and lower it if the bar complains - chatter. If it cuts then I just feed to get the chips I want and focus on coming in on size. 

Unlike inserted carbide boring bars, you will find that Micro 100 bars cut more like HSS tools in that they can take relatively heavy cuts but can also take micro-cuts. You will not find an insert that can take a 0.0005" depth of cut but a Micro 100 bar definitely can if it is sharp. If you need maximum performance, take an extra-fine diamond stone or card and lightly hone the top and end of the bar; just make those flat surfaces flat again. It will cut like new and be much more accurate for you. 

Much of machining, especially manual machining, is based on touch, feel and sound. When the cutter is happy it will hiss sweetly and there will be a slight resistance to the feed transmitted through the hand wheel. More than numbers, I stay in touch with the lathe and let it tell me what it wants. It takes some time to learn how to respond the way the lathe wants but it will come if you pay attention.


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## Z2V (Jun 29, 2020)

Z2V said:


> I sent an email to customer service and will report back on their reply.
> I only have about 15 of these Micro 100 bars but I managed to chip the tip on a couple of them, rookie mistakes.



I received a reply that said they no longer offer repair services.


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## mikey (Jun 29, 2020)

Okay, well, that sucks! @dpb, you can try honing out those nicks with an extra-coarse diamond stone, followed by a fine and then extra-fine stone to try and rehab those bars. Of course, a powered diamond disc would be much faster but they are costly. A simple diamond stone will cut carbide quickly - why not try that?


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## bill70j (Jun 29, 2020)

mikey said:


> Just thought of another option. Maybe one of the guys on the forum who owns a D-bit grinder and has a diamond wheel might be willing to sharpen a chipped tool for a fair price ... ??


dpb:
I just reground a 6mm carbide bar this morning.  

We live l pretty close.  So if you like, I can run your Micro 100 over a green wheel, diamond wheel, then follow with a fine diamond hone.  PM me and I'll send you my address.

I would use my semi-converted bench grinder for the job.


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## mikey (Jun 29, 2020)

Alright, Bill!

Love this forum!


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## pontiac428 (Jun 29, 2020)

Bill's Delta grinder ought to do it.  I have a D-bit grinder with a cubic boron nitride wheel and a lathe bit fixture if plan A doesn't work out.  That's assuming you have a few to sharpen and not a few dozen...


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## ddickey (Jun 29, 2020)

mikey said:


> I use a 180 grit Gator wheel from Accu-finish on my Series 1 Accu-finish grinder. Follow up is with a 600 grit wheel. Works good for small nicks and for honing an edge. I have Micro 100 boring tools that must be over 20 years old and cut like new.


Bought a Cold Grind at an auction a week or so ago. Everything is in storage for my move so will be able to try it this winter.


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## dpb (Jun 29, 2020)

I’m going to take @bill70j up on his kind offer.
Thanks Bill!


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## chips&more (Jun 30, 2020)

Not sure what is meant when you say boring a small hole? What is small? My boring bars are typically 0.010’’-0.032” in diameter. If I tried to sharpen one of my bars on a green wheel it would disintegrate under tool pressure and the rough ride. I don’t like green wheels for anything! A diamond wheel is my choice, but not even for my bars, because of the small fragile size. I made a jig that supports the business end and I diamond stone to make like new. Only takes a few strokes and the jig holds the bar so it will not flex and break under sharpening pressure.


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## dpb (Jul 23, 2020)

Received the bars back from @bill70j.
Perfect.  This place is great!


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