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View Full Version : High Speed Rotary Burrs (Dremel) - Diamond, Carbide, HSS



PStechPaul
08-29-2014, 01:05 AM
Quite some time ago I bought a set of 20 diamond burrs for less than $10, and they seem to work pretty well:

http://enginuitysystems.com/pix/tools/Diamond_Burrs_1316.jpg

More recently I got a set of HSS burrs, 6 pieces for $6: http://www.ebay.com/itm/290923628254. They are "OK" but not very sharp. Here they are with some better ones that came with my B&D "Wizard" rotary tool:

http://enginuitysystems.com/pix/tools/Cutting_Tools_HSS_1484.jpg

I think I used the smaller one on the left and the cutting edge seems to be damaged. I also bought a set of 10 carbide bits for a bit more than $10, and they seem to be much better: http://www.ebay.com/itm/230981252873

http://enginuitysystems.com/pix/tools/Cutting_Tools_1477.jpg

There are also two of what appear to be small two-flute milling bits that I found under the monitor on the desk at the class I took. The instructor said I could have them. They seem very well made and quite sharp, probably carbide:

http://enginuitysystems.com/pix/tools/Cutting_Tools_1478.jpg

darryl
08-29-2014, 01:52 AM
I like the carbide set- the hss ones I could do without. I have some like those and mine are useless.

Boostinjdm
08-29-2014, 03:04 AM
Show and tell thread?

vpt
08-29-2014, 08:08 AM
I bought a used snap on set of carbide bits a long time ago and they have served me very well threw the years.

Old Hat
08-29-2014, 08:23 AM
High Speed burrs arn't for steel. Or not realy for any metal.
Use them in model-making or pattern-making for non metals.

Even in wood they won't last long.
About the only place they serve a purpose is in refining hand work
where it's imparative that no carbide contaminates the work
from tips of the burrs braking off and becoming lodged in the part.

Alistair Hosie
08-29-2014, 09:04 AM
The hss are primarily for plastic work we used to use them on making dentures, braces atc.Even then, they were mostly superceded by the tungsten which just about everyone uses today.The diamond tend to clog up and again they do work very slowly on metals but were really designed for work on fine porcelain crowns teeth again keep them wet wherever possible they work better and last longer however as said they don't work at all well with any heavy deep cuts.IMHO only buy the tungsten and for goodness sake don't use the tungsten on porcelain they will blunt almost immediately.I can say they are good though, for light metals and plastic, mild steel etc wood not so good as they tend to burn through the wood. Alistair

Frank K
08-29-2014, 02:28 PM
I've also made a few special purpose Dremel cutters from both HSS and carbide cutters designed for the Roto-Zip tool although you'll need a diamond wheel to reshape the carbide cutters.

Black_Moons
08-30-2014, 08:33 AM
Iv found the diamond coated burrs work wonders on plastics, although its more of a friction melting cut at times, the high RPM throws strands of plastic around to keep it from building up and the closed grain structure of the diamond burr lets you easily peel the left over plastic off the bit when you are done.

Abrasive stones work well for hardened steels, but anything softer a carbide burr will chew through 10x faster. That said the abrasive stones dig in and skitter around your work a lot less and tend to give a smoother finish, so they can be nice to smooth out the carbide burr marks or for when you need to be more precise.

Carbide burrs, more in the 1/4" style for bigger die grinders, will throw really nasty sharp needles everywhere off some mildly hard steels, very annoying but does not happen too often.

HSS dremel burrs are rather useless and just dull instantly unless used at lower RPM with extreme care in very soft (Soft wood, plastics) materials.

Glug
08-30-2014, 10:25 AM
Abrasive stones work well for hardened steels, but anything softer a carbide burr will chew through 10x faster. That said the abrasive stones dig in and skitter around your work a lot less and tend to give a smoother finish, so they can be nice to smooth out the carbide burr marks or for when you need to be more precise.

One of the best things I ever bought for die grinder grinding was a router speed control. I love that thing. It allows me to get the speed down very low and have great control. One place where that is absolutely critical is when grinding inside a smaller ID. In that situation I find the carbide tends to snag when run at too high a speed, then it bounces around the ID of the part in a very angry and unfriendly way. That tends to chip the cutter, possibly break it, or damage the part.

Another thing I really like about the speed control is an electric die grinder run at low speed has way more low speed torque and controllability than an air powered die grinder. It holds that low speed rather than bogging. A decent control allows the die grinder to be run extremely slow - in the low hundreds of rpm. I think the low speed torque may be due to a feedback loop in the circuit.

Soap or wax also help with die grinding. It especially helps keep aluminum from loading up burrs.

While grinding cast iron cylinder heads I once had a sliver of cast iron stick in the white of my eye. Those shards bounced off the wall of the ID I was grinding, giving them a trajectory that wants to go around glasses. Really a time you need full goggles (tricky over glasses). Cast iron in the eye rusts and leaves a rust mark in the eye if it is not quickly removed.

J Tiers
08-30-2014, 10:45 AM
The problem with the HSS is that it is running too much SFM for any steel, and most other metals.

A 0.25 diameter burr at 20,000 rpm is 0.78 inch per rev. At 20,000 rpm, that is 15,700 inches per min, which is 1308 SFM, a tad high for even 1018... A 1/8" burr is half that, getting into the top end of the aluminum area. yes, it slows under load, but there are limits to that.

With a standard Dremel, you can't get any chip load without loading it down to a slow speed, and even the slow speed is too fast. So you are running it too fast, with hardly any chip load..... basically it is "rubbing" and burning up the burr.

Die grinders might go slower, and have more torque, but unloaded even they go pretty fast....

PStechPaul
08-30-2014, 09:25 PM
I have a cheap mounted stone that came with a HF air die grinder set, and when I tried to use it on a piece of stamped steel, it resulted in a deep groove in the stone and not much metal off the work. Possibly wrong speed, but more likely a "stone" molded from sand and glue. :rolleyes:

The small burrs that came with my "Wizard" tool seemed to work pretty well for cleaning up the inside of the square socket I made in a piece of 4140 for my chuck screw, but it was hard to hold it steady by hand, and at one point it caught a sharp edge and the tip broke off. It remained pretty sharp, and the other small burrs appear to be well made and sharp as well.

I originally used the diamond bits in my shop-made toolpost grinder which used a 12 VDC rotary tool that I controlled with a PWM device, and the main problem was tightening the collet. This was used to grind a slot in the walls of a thin taper of 1026 DOM tubing. I think I used the steel Dremel tool as well and it worked a bit better.

Thanks for the tips on HSS tool bits. I thought they would be more durable than the carbide, but they may be of poor quality and are not very sharp to begin with, so I may use them only for soft materials as suggested. Perhaps it is worth the $5-$10 each I have seen for genuine Dremel bits?

I have not tried the carbide bits yet. They feel quite sharp and look pretty good under the magnifier, but they appear to be "roughing" bits with the diamond-shaped pattern.

The two cutting tools I found in the shop class appear to be good quality 1/8" and 3/16" two flute end mills, perhaps used in CNC machines. I'm not sure if my sets of Weldon tool holders or MT2 collets will work with them, but I think they include those smaller sizes. I'll give them a try soon. The price for similar carbide end mills from McMaster is $8-$12 and more, so I snagged a good deal.

J Tiers
08-30-2014, 11:23 PM
the point may have been crappy quality....

There is also an issue with matching grit size, binder, and task..... soft wheels for hard materials, hard wheels for softer materials.... coarse grit for stock removal, finer for finishing.

Black_Moons
08-31-2014, 11:54 PM
One of the best things I ever bought for die grinder grinding was a router speed control. I love that thing. It allows me to get the speed down very low and have great control. One place where that is absolutely critical is when grinding inside a smaller ID. In that situation I find the carbide tends to snag when run at too high a speed, then it bounces around the ID of the part in a very angry and unfriendly way. That tends to chip the cutter, possibly break it, or damage the part.

Another thing I really like about the speed control is an electric die grinder run at low speed has way more low speed torque and controllability than an air powered die grinder. It holds that low speed rather than bogging. A decent control allows the die grinder to be run extremely slow - in the low hundreds of rpm. I think the low speed torque may be due to a feedback loop in the circuit.

Soap or wax also help with die grinding. It especially helps keep aluminum from loading up burrs.

While grinding cast iron cylinder heads I once had a sliver of cast iron stick in the white of my eye. Those shards bounced off the wall of the ID I was grinding, giving them a trajectory that wants to go around glasses. Really a time you need full goggles (tricky over glasses). Cast iron in the eye rusts and leaves a rust mark in the eye if it is not quickly removed.

I have found to just NEVER grind ID's with carbide burrs, they ALWAYS grab and spin around and snap, its the only way I have ever damaged carbide burrs. Also I think the diff between the cheap burrs and the $$$ burrs is the $$$ burrs have less runout and hence don't bounce and snag nearly as much.

Black_Moons
08-31-2014, 11:58 PM
The problem with the HSS is that it is running too much SFM for any steel, and most other metals.

A 0.25 diameter burr at 20,000 rpm is 0.78 inch per rev. At 20,000 rpm, that is 15,700 inches per min, which is 1308 SFM, a tad high for even 1018... A 1/8" burr is half that, getting into the top end of the aluminum area. yes, it slows under load, but there are limits to that.


Never done the math, but always suspected it wouldn't work out at those speeds. No wonder HSS does not handle well. Im not sure why you said a tad high when HSS vs 1018 is typically given around 100SFM. Even for aluminum at 1/8", that is 650~ SFM and that is really pushing it for HSS on aluminum I think, Hell, that is more like carbide on aluminum speeds. 1300SFM on steel is like "How does that bit survive anyway? I can't get away with those speeds on my mill"

k2man
09-01-2014, 12:48 AM
My experience with the diamond bits is that they overheat very easily. You can ruin one in a few seconds trying to engrave in mild steel. If you look at them under a magnifying glass, they diamonds are half buried in a soft base metal. The base metal heats up and the diamonds get buried all the way, or fly off.

I've used lots of carbide bits (from MSC) - bought many brands. I use 1/8" ball burrs to engrave lines about 1/16" wide, 1/32" deep in mild steel. They eventually get dull - probably get 100 ft. or less of engraving line out of one.

J Tiers
09-01-2014, 08:57 AM
Im not sure why you said a tad high when HSS vs 1018 is typically given around 100SFM.

It's irony.... in my case you could call it "old irony".... I'm old....