Carbide burrs in die grinder

magneticanomaly · Dec 11, 2017

I often use a carbide burr in a die grinder (currently Bosch 27000RPM) to bevel cracks for welding (usually grey cast iron), remove (steel) rivet heads, etc. Never happy with short burr life A 1/4" diam cutter @ 27000RPM is cuttng at approx 1600SFM, so maybe that is not surprising. Cutoff wheels work well, but are unhandy in a lot of tight places and mounted points always seem to glaze or cut slowly.

What am I doing wrong? Does anyone make burrs that last more than a few minutes in this kind of service?

AlexO · Dec 11, 2017

magneticanomaly said:
I often use a carbide burr in a die grinder (currently Bosch 27000RPM) to bevel cracks for welding (usually grey cast iron), remove (steel) rivet heads, etc. Never happy with short burr life A 1/4" diam cutter @ 27000RPM is cuttng at approx 1600SFM, so maybe that is not surprising. Cutoff wheels work well, but are unhandy in a lot of tight places and mounted points always seem to glaze or cut slowly.

What am I doing wrong? Does anyone make burrs that last more than a few minutes in this kind of service?

You're running them too fast and with not enough pressure. Mine seem to last forever. Of course, cheap ones are just an imitation of carbide.

MattiJ · Dec 11, 2017

Your speed sounds about right for a small 1/4 burr.

I would try quality burr for example from Pferd.
They recommend 24000 to 40000 rpm for 6mm burr.
http://www.pferd.com/images/Prospekt_Fraesstifte_Steel_72_dpi_en.pdf

Tyrone Shoelaces · Dec 11, 2017

I had an old pneumatic " Dotco " die grinder ( we called them pencil grinders by the way ) and a solid carbide rotary file that I used for de burring and grooving for years. I couldn't wear it out. It's still in my box somewhere. I don't know what make it was but it was pretty expensive.

The salesman who was selling the rotary files/burrs asked for an big old flat file. He put the file in the vice and slowly cut the file in half with the burr.

Management bought a box full once they saw that. I kept a few for my personal use.

Regards Tyrone.

winger · Dec 11, 2017

Not sure what size wheel you are using but check the speed rating. 27k is over what my 3" cutoff wheels are rated (25K).
4" wheels I have are rated at 19k.

Dave

mmarquette · Dec 12, 2017

I use these in repairing equipment. Don't know what brand your using but have found that the more I pay for one the better they cut. The chatter is also greatly reduced. Am currently running a new style from Kimball Midwest. It is black. Cant recall the name and my catalog is outdated

adama · Dec 12, 2017

Get a metbo or makita die grinder with vari speed, the metabo's and i think the makitas both have a shoulder that lets you use a std pistol drill front grip, dial the speed back about 10K into the mid - high teens and they last so much better its unreal. Whats even more odd is they dont cut all that much slower with the reduced speeds. 3m rolloc stuff with the various backing pads is also far nicer to use on something with variable speed.

Like any carbide cutter, you don’t want to recut the swarf, hence generally more light passes works faster and also avoid chatter, try and pick a shape that lets you take multiple passes with out too much contact and that helps too.

Only thing i find really tough on burrs is slag inclusion or having them spin me up in a small hole anyone thats used a burr will know what i mean by that.

Now all i really want to know is how to use one and not spend the next day extracting the splinters out of me, thats the only bit i have never yet resolved! I swear new burrs should come with tweezers!

Gordon Heaton · Dec 12, 2017

I have a standard straight die-grinder with a lever type valve. I simply wedge a finger under the open end of the lever and operate it with my thumb which gives me a modicum of speed control. I'd rather have a vari-speed unit though.

I've also wondered if a simple restrictor valve like is often used on cup-guns for paint might work. Anyone tried that?

Milland · Dec 12, 2017

Check you grinder spindle for excess play, if the bearings are going you'll get chatter pretty quickly.

SilveradoHauler · Dec 12, 2017

I use 1/4" air die grinders and carbide burrs for wood work. Feed them with a regulator in the air line so I can control the top speed. 40 to 50 psi gives a nice speed.

Try it, slow those burrs down, 27,000 is way too fast.

Danny VanVoorn · Dec 12, 2017

The burrs are just like end mills and will start chattering when they get pushed in a corner, that will chip the teeth off of carbide in a hurry. I use them all the time and find if I try to keep my motions like climb milling and keep the tool moving as steady as I can they will hold up indefinitely.
I'm thinking the problem here is trying to groove out the cracks and trying to keep the groove as narrow as you can? When your grinding and feel it rattling in your hands and making a racket it's the cutter going to crap and a good idea to change direction.

AlexO · Dec 12, 2017

adama said:
Now all i really want to know is how to use one and not spend the next day extracting the splinters out of me, thats the only bit i have never yet resolved! I swear new burrs should come with tweezers!

For some unknown reason all my grinding tools throw towards me and not away. I wonder why.

brianweldor · Dec 12, 2017

Formax belt grease will triple your removal rates when cutting aluminum, and keep the flutes from gumming up with chips.

eKretz · Dec 12, 2017

All you guys taking about regulators and such to slow down your air die grinders need look no further than the little valve down near the air inlet. That thingie that looks like a flat head screwdriver would fit it just right? It's an adjusting valve and you can use it to throttle down your grinder a bit. From what I understand they are originally meant to be used at the factory to dial in the rated speed at standard 90psi on the assembly line.

As far as those dastardly slivers, if I'm going to be doing some heavy hogging with a carbide burr I usually wear nitrile gloves and long sleeves, with the sleeves duct taped to the gloves. I also make sure my pant legs are fully over the tops of my boots. Face shield to keep them out of my eyes and neck of my shirt. After all the work is done a quick air blast takes care of getting rid of most of them before unbundling.

garyhlucas · Dec 12, 2017

Slowing it down with a regulator is the wrong approach. Air pressure controls torque so reducing pressure also reduces torque. As you load the tool it may stall. Using a restrictor with the pressure kept high will slow the tool but keep the torque up so it doesn’t stall.

eKretz · Dec 12, 2017

I don't think that will help a whole lot either. A restriction in the line means a pressure drop on the other side. Basically, anything done to reduce the RPM will reduce the torque as well. I get around this by having a few different die grinders. My hogger is a 1 H.P. Dotco @ 18,000 r.p.m. that was designed as an air router - it's a beast, but not much bigger than the little 0.3 H.P. models most companies make. That baby has some serious power.

adama · Dec 13, 2017

Pretty sure the op is using a electric one, unless Bosch do air tools? Going to need to do a screw up awfully tight to get the speed down on the typical electrical cable!

eKretz · Dec 13, 2017

If you are referring to my post - reread it. It wasn't directed at the O.P. - it was prefaced with "all you guys talking about regulators to slow down *air* die grinders."

The O.P. might be well served by trying a router speed control or something. Not sure if electric die grinders use a universal motor.

Forrest Addy · Dec 13, 2017

1600 FPM is fast for carbide in cast iron but on the low end for a mounted point abrasive grinding wheel. Carbide burrs in cast iron poop out early because of the silicon. A "few minutes " does seem pretty short. I would think an hour or so. but YMMV depending on burr specifics, iron alloy and cast quality, technique, and die grinder RPM.

The hard reality is carbide burrs are consumable tooling. They're expected to wear out in use - a cost of doing business. I usually use the 3/8 dia tree-shaped burrs and sometime the ball shaped ones. The smaller diameter burrs costs les and run closer to acceptable FPM than the larger burrs and they cut at about the same rate. I wish they made lower speed die grinders just for carbide like 7000 RPM

BTW, Throttling or regulating may reduce the RPM it but it will have little practical operating torque. Fiddling the air pressure merely makes the die grinder easier to stall, Die grinders are built to run at a certain RPM either because of a teeny governor in the air valve or the design of the vanes. If you want the grinder to run slower you have to tweak the grinder itself.

MattiJ · Dec 13, 2017

Forrest Addy said:
1600 FPM is fast for carbide in cast iron but on the low end for a mounted point abrasive grinding wheel. Carbide burrs in cast iron poop out early because of the silicon. A "few minutes " does seem pretty short. I would think an hour or so. but YMMV depending on burr specifics, iron alloy and cast quality, technique, and die grinder RPM.

The hard reality is carbide burrs are consumable tooling. They're expected to wear out in use - a cost of doing business. I usually use the 3/8 dia tree-shaped burrs and sometime the ball shaped ones. The smaller diameter burrs costs les and run closer to acceptable FPM than the larger burrs and they cut at about the same rate. I wish they made lower speed die grinders just for carbide like 7000 RPM

BTW, Throttling or regulating may reduce the RPM it but it will have little practical operating torque. Fiddling the air pressure merely makes the die grinder easier to stall, Die grinders are built to run at a certain RPM either because of a teeny governor in the air valve or the design of the vanes. If you want the grinder to run slower you have to tweak the grinder itself.

You can get some models down to 12k rpm at least
But burr or die grinder recommendations are really high anyways compared to ie milling: ie 2000-2600fpm for non-hardened steel, 1600-2000fpm for hardened steel over 45rc. And another manufacturer ecommends 1200-2000fpm for stainless.

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