# Dust pickup for a Shars tool grinder



## Larry$ (Nov 2, 2020)

Since grinding dust from carbide is bad for you, I made an adjustable bracket to hold a shop vac hose close to the wheel. Sits on the bench but is held in position with two magnets I let into the aluminum angles so they would be close to the casting. The magnets were out of hard drives. I put an aluminum sheet backstop on to stop the dust from flying past. With no real mechanical attachment I can just move it easily to change wheels.


----------



## matthewsx (Nov 2, 2020)

Sounds great, did you take pictures?

John


----------



## NC Rick (Nov 3, 2020)

This is a future project I am reminded of every time I fire that thing up!


----------



## pontiac428 (Nov 3, 2020)

I usually post cautionary health info regarding chemical exposures, but this time I'm going to say that the risks of tungsten carbide grinding in the home shop are quite a bit less than using a can of spray paint.  Cemented tungsten carbide is 80-90% WC by weight, the remainder is cobalt, nickel, and titanium with trace amounts of metal oxides and fluorines.  Tool steel has cobalt, chromium (4+), vanadium, and some less toxic metals.  Grinding a few bits a week shouldn't hurt you.  I just keep my work area vacuumed so I don't get it on my skin (cobalt will cause skin sensitivity eventually).  What I'd really like to see people use ventilation for is welding fume control and paint vapors.  Good on you for putting something together, and it certainly won't hurt, but controlling the tool grinder is like going after the midget in the ring.


----------



## ThinWoodsman (Nov 3, 2020)

I found one of these home depot spring clamps has a hole on one arm that is the perfect size for the peg of a snug on one of those import magnetic dial indicator bases. Put the shop-vac extension of your choice in the clamp, and stick the magnetic base somewhere handy.


----------



## NC Rick (Nov 3, 2020)

Dressing the aluminum oxide wheel is messy.  If I sent get silicosis my machines certainly will


----------



## pontiac428 (Nov 3, 2020)

Silica is SiO2 and the bad version is crystalline (formed deep in the earth).  Aluminum oxide (as insoluble aluminum) isn't any worse than house dust.  

All I'm saying is that some hazards are worse than others, and the T&C grinder used on occasion to sharpen a couple of tools at a time is not a priority.  None of these metals are in the same category as, or even close to the exposure risk of lead, arsenic, chrome (6+), beryllium, cadmium, etc.


----------



## Larry$ (Nov 3, 2020)

I rarely use the AOx wheels because it seems like a lot of grit going every place. Not good for the machine or me.  But the Diamond & CBN wheels still give off some. I'm not even sure it is cheaper to use the AOx wheels since they wear away a lot faster. 
This brings up a point about what grit do you use. Diamond is offered in at least 3. 100, 120, 150. Just doing a touchup grind the 150 seems like the choice. But if there is a serious chip to be dealt with, a coarser wheel seems better. But then do you change wheels to get that shinny finish from 150 or just call 100 good enough? 

On our profile grinder we never change grits, The wheel is dressed to shape and used at a slower RPM for the primary grind and then spun at a considerably faster rate for the secondary grind to get a finer finish. I think the wheels are 60 grit and give a very smooth finish. The secondary grind is at a less steep bevel and only about 1/32" wide. It is also at 90 degrees to the edge giving the strongest edge possible. Honing is not permitted as it will always affect the edge geometry. A very minor burr that occurs is wiped away with a piece of hardwood.  Cutting wood @ SFM of about 11,000.  (7" dia. x 3.14 x 6000 rpm/12.) DOC , 3/4"+-, feed rate assuming single knife finish (2 knife head) of about 40 -50'/min. This is on a small 5 head machine with only 20hp on the main profiling head. 

I've done woodworking most of my life and there have been some minor differences when I started doing metal. Our primary saw is programed for one meter per second, I think! Our bore & insert machine drills, blows the dust out, injects glue, drives a dowel and moves to the next location in about 1.2 seconds. We use a very conservative 600"/ minute feed rate on the router. The bander @ 1'/second. These are all sort of slow compared to state of the art. Slowing down to manual metal machining has been -- difficult.


----------



## Skierdude (Nov 4, 2020)

I’ve been experimenting with a dust chute for my grinder. 





So far I have a cardboard dust hood with outlet for the shop vac. For now it’s held in place with a bar magnet. 
I’m trying to determine if a hood this size will have sufficient airflow to pull in the dust through the chute. So far I’m seeing quite a bit of dust still settling on the work holders so I might try a directed nozzle that can be nearer the action. 
Anyone got photos of their solutions?


----------



## pontiac428 (Nov 4, 2020)

@Skierdude, that is a decent capture hood design.  The ideal flare angle is 30 degrees.  There are two air flow characteristics to consider: capture (entrainment) velocity, measured at the source of generation (wheel) should be around 100-150 linear feet per minute; and transport velocity, which is the duct air speed that moves particulates to the filter, which should be around 3000 fpm.  You'll meet the transport velocity with that tiny shop vac duct, but I doubt the shop vac provides enough volume for entrainment and capture.  A 3-4" duct at 300 cfm would be in the ballpark.


----------



## pontiac428 (Nov 4, 2020)

Here is the professional reference for a partially enclosing hood.  Looks like my memory is close enough.


----------



## Skierdude (Nov 5, 2020)

pontiac428 said:


> Here is the professional reference for a partially enclosing hood.  Looks like my memory is close enough.
> View attachment 343117


Thanks John that’s a great reference. I can the see I need to extend the lower part of the hood forward as far as the external diameter of the wheel to ensure capture of the particles that typically come off the wheel more or less directly downward from the point of grinding.
The airflow from the shop vac is probably not sufficient to draw particles into the hood and through the vac but I might try a small centrifugal fan I have to draw the air through the hood. It’s around 350 cfm and has good static pressure.


----------



## pontiac428 (Nov 5, 2020)

Here's one that you can apply to the capture vent you already have.  It's based on capture distance and wheel surface speed.


----------



## Larry$ (Nov 5, 2020)

If you want to take it a step further put generous rounds on the edges. Improves the flow.


----------



## Larry$ (Nov 14, 2020)

Today I used the tool grinder to make a carbide tipped scraper blade from junk. I have some broken carbide molder knives and some worn out files that I made into a scraper. Silver soldered a piece of the carbide onto a file I had ground a flat on. Then ground the end to a curve on the diamond wheel. Just had to try it to see if it actually worked. I've never scraped anything before. Found a piece of cast iron in my junk collection. Didn't have any of the oil based ink but did have an art brayer and some artist oil paint. I didn't want to goober up my surface plate so I used the ground top of my mill vice. It worked! I think I need more of a curve on the scraper and the file isn't an ideal handle. My technique wasn't good and I got longer cuts than ideal. I did get the iron fairly flat. The carbide scraped the iron easily. 

I didn't know if the solid carbide would silver solder or break. I know that the carbide on brazed tools is a different composition.  I've got some extra pieces of carbide and some dull solid carbide bits if any one wants to use their tool grinder to do some experimenting with the carbide. The shanks can be used to make single lip profile end mills. Contact me through this site.


----------

