Grinding Aluminum What Type of Finish Expect

[majohnson]

Wondering what I should end up with for a finish when grinding 6061. I need to make up some plates for customer but they need to be flat with just a few tenths of variance. On side of the plate has tensioners that are pushing on the plates face.

I’m using a Radiac RAA46 H800 VOS. Not having any problems with the wheel loading up from the aluminum, i have the coolant spraying directly into the wheel on the right side, so it gets coolant just before the work piece.

 

[Richard King]

I once had a customer who ground aluminum and he mixed kerosene and petroleum jelly and kerosene into a paste and painted it on with a brush. I assume he had a open wheel like a 46. Ask Buck...he should know.

 

[majohnson]

Thank you Richard.

 

[eKretz]

I posted this before, but here's an aluminum head I did a while back. This was purposely left a little on the coarse side by allowing the wheel to "self dress" a bit. I like a SiC wheel for aluminum but AlOx is fine if you're only removing a little material.

Are you sure that the wheel isn't loading? The finish in your picture looks a little weird, like there's a dotted appearance. Hard to tell for sure as it's out of focus. Looks somewhat like smearing from a loaded wheel. WD-40 can work okay as a grinding fluid for aluminum in a pinch too.

 

[Milland]

If you need flat to a few tenths I'd think that's a lapping job. Do you have anyone in your area that does that?

 

[majohnson]

I hate to send things out. My SIC wheel should be here on Wednesday. I ground a couple of other aluminum pieces and it seems like they looked better. Maybe I try again but traverse the diamond faster.

 

[eKretz]

Induced porosity wheels can help too. The AlOx wheel loading problem can usually be got 'round by dressing more frequently and only taking a very light dust grind after final dress. Running the dresser faster can help a little but it will hurt your finish.

Nailing flat within .0002" is possible but you need a grinder in good shape. Or did you really mean parallel within .0002"?

 

[majohnson]

The V ways on both plates meet with key stock separating them and the plate in front rides against Delrin keeping them under tension. Then it all presses against the back wall of main body. The tighter the tolerance the happier the customer.

Thanks for the input!

 

[SteveEx30]

I once had a customer who ground aluminum and he mixed kerosene and petroleum jelly and kerosene into a paste and painted it on with a brush. I assume he had a open wheel like a 46. Ask Buck...he should know.

We use to brush plain grease on pcs, use an open wheel, was pink. Been long time....

 

[michiganbuck]

I don't have any magic for aluminum, it is usually a bugger. Often an open wheel and slippery coolant, for one job soapy water proved best, but I have used soluble oil and other coolants, ground it dry, and with an oil wipe rag.
If it is a height-dependent part a diamond pre-set to the height so one can quickly dress with not going off size or far distance from the dress can be an asset.
Open white, pink, and sic wheels may be best..avoid brown and gray wheels. IMHO.
I would likely use a mask using WD-40, kerosine, or most chemicals.

 

[eKretz]

I usually get away with an extra rich coolant mix, that has always worked pretty well for me. The only time I resort to WD or those lube sticks is when there's no coolant. I really like the induced porosity wheels for both iron and aluminum too.

 

[majohnson]

Spent part of the day grinding part using the ruby wheel I have using kool mist coolant mixed 4oz to a gallon of water. With ok results but hoping for better. Ordered an SIC as I posted earlier. Here’s a plate I did, I’m using a Cutter vise I’ve has for 25 plus years, it a big grinding vise.

 

[eKretz]

Looking better. Might run that coolant a little richer yet. I was always around 10% on my mix. That's only for grinding, and more for aluminum. Don't need it that heavy for steel.

 

[majohnson]

Thanks! I will richen the coolant mix.

 

[majohnson]

The SIc wheel came in, never using one I had to see the results. I was surprised at how easy it made surfacing aluminum. My SG does not have a coolant tank just a KoolMist system. I had not changed my coolant mix for this, I wanted to see the wheel difference. That will be a follow up.

I am curious about how much step over you use for spark out? The picture is my first attempt with the SIc wheel. I did give it a fairly course dress.

 

[eKretz]

The SIc wheel came in, never using one I had to see the results. I was surprised at how easy it made surfacing aluminum. My SG does not have a coolant tank just a KoolMist system. I had not changed my coolant mix for this, I wanted to see the wheel difference. That will be a follow up.

I am curious about how much step over you use for spark out? The picture is my first attempt with the SIc wheel. I did give it a fairly course dress.

Looks even better yet. A little smoother dress for finishing and it should look great. The richer coolant will help keep the wheel unclogged, but isn't always necessary. I generally run about ¼-wheel-width stepovers with a dust cut.

 

[majohnson]

The slower redress was a bust, the finish changed and even took on slight green cast. With no other changes to the grinding set up. Not sure why the color cast. It not lighting, it had the color shift on the grinder. I use a popsicle stick to knock and loose grit prior to grinding. Any other suggestion?

 

[eKretz]

Looks like wheel loading to me. Give me a full rundown. What grit and hardness is your wheel? Did you try the richer coolant? How much did you remove after the dress and what depth of cut were you taking? Should be tenths after the final dress. Are you on a hydraulic machine? Table speed? I like a pretty high table speed for finishing. If it's a loading issue and you can't shake it you might need to push the wheel a little harder to get it to shed a bit of grit and/or self sharpen. I don't think you'll need to do that for such a small surface area though. Also, I'm assuming you've got a nice sharp dressing diamond... And how long did you take to cross the wheel on that final dress? I would not recommend any slower than about 2-3 seconds for a ½" wide wheel.

 

[majohnson]

Check the wheel I didn’t see any loading, I wonder if the streaks are from burrs coming off the edges. Before i do anything I will chamfer my edges again. Then redress the wheel at a much faster pace. Along with fattening the coolant mixture.

I am using a Harig 612 Autostep, it a low hour machine, I purchased it from the original owner. He bought it to sharpen his dies.

 

[eKretz]

Can't help eliminate problem possibilities without answers...What's the grit and hardness of the wheel? Depth of cut and stepover you were using? How much removed after the final dress? How long did you take to cross the wheel on that final dress you tried? I assume it's not an induced porosity wheel since you didn't mention that.