T6-6061 Aluminum sanding questions

[wagspe208]

I have searched and am sure it has been answered, but with some questions...
I am building a drag boat. All Alum is T6-6061. Most starts out as bar, plate, or angle.
I will be using (I think) a Dewalt orbital sander to remove tooling marks, etc.
Should I start with 80 or 120 grit, then 220, 320, 400? How fine do I need to go before going to a sisal wheel and emery compound?
The polishing is just going to be the prep for anodizing. Needs to be damn nice, though.
What are your favorite wheels? Just sisal, spiral sern, then loose? or any new tricks?
Thanks
Wags

[baz]

Originally Posted by wagspe208

I have searched and am sure it has been answered, but with some questions...
I am building a drag boat. All Alum is T6-6061. Most starts out as bar, plate, or angle.
I will be using (I think) a Dewalt orbital sander to remove tooling marks, etc.
Should I start with 80 or 120 grit, then 220, 320, 400? How fine do I need to go before going to a sisal wheel and emery compound?
The polishing is just going to be the prep for anodizing. Needs to be damn nice, though.
What are your favorite wheels? Just sisal, spiral sern, then loose? or any new tricks?
Thanks
Wags

i don t think you would need to start with 80 grit. you should always start with the finest grit that will remove the imperfections on the material you are working on.i dont use sisal on aluminium , (you dont say for anodize if you want a brushed , satin or mirror finnish so i figure it s a mirror finnish ),i would sand down to 600 then a sewn spiral with a tripoli compound

[mpierich]

Yup, burn down any giant goobers like welds with 80-grit (or even an angle grinder); if there are still scratches you can feel with a fingernail, go to 120 or else start with 220, then 320, 400. I usually stop there but some go further...it's a matter of how much time you want to spend for diminishing results. For me buffing is more fun than sanding, so I skip the 600-up and go to spiral/emery, _maybe_ tripoli (leaves a haze for me usually), then finish with white for a mirror polish. I don't anodize so I don't know what finish you should have - ask the boys over on that board.

Sisal can gouge and make a lot of heat. It's good for stainless, though.

You should have on hand both spiral and loose wheels for each compound - if one doesn't do what you want, try the other.

[jrow]

Wags,

It sounds to me like you are going to be TIG welding some smaller aluminum parts together prior to anodizing. 6061-T6 is a hard aluminum. What I would suggest is that you use a 3" pneumatic cutoff tool to grind down your welds. Stack two blades on it and run the blades perpendicular to the welds to grind them smooth. When you run the blades perpendicular to the welds it doesn't heat up the surrounding aluminum. After that use a flap disk to smooth the rest of the area. They make flap disks especially for aluminum. I would then use your Dewalt orbital sander with 400 grit paper and clean it up with that. I would then try buffing with a sewn wheel and some Emory then on up the ladder to loose and white.

John

[baz]

Originally Posted by mpierich

Yup, burn down any giant goobers like welds with 80-grit (or even an angle grinder); if there are still scratches you can feel with a fingernail, go to 120 or else start with 220, then 320, 400. I usually stop there but some go further...it's a matter of how much time you want to spend for diminishing results. For me buffing is more fun than sanding, so I skip the 600-up and go to spiral/emery, _maybe_ tripoli (leaves a haze for me usually), then finish with white for a mirror polish. I don't anodize so I don't know what finish you should have - ask the boys over on that board.

Sisal can gouge and make a lot of heat. It's good for stainless, though.

You should have on hand both spiral and loose wheels for each compound - if one doesn't do what you want, try the other.

to be honest with you many times i do the 220 grit sanding then go straight to 600 grit , (with a bit of practice and a bit more pressure on the sander it will get the 220 grit scratches off) andthen directly to a tripoli on 14 inch airflex buffs

[wagspe208]

Well, there we go. You guys are a helpful bunch.
I am looking for an anodize over polish sort of finish.
I was working with some rough cut pieces the other night. I started with a used 80 pad because the tooling marks were pretty big. Went to 220, 320, 400. Now it is ready for the polishing attempts. I used to do this years ago, but just trying to remember the procedures.
My confusion is whether I need to start with sisal. It sounds like it is a matter of personal preferernce.
Also, I need to do some inside corners (just a few..I guess the felt bob..things??)
I am making my list and checking it twice this week. Still cutting and fitting, the polishing comes after the first assembly.
OH, recommended wheel widths? Total width of stacked wheels. I have a 3/4 hp buffer.
Thanks again
Steve

[mpierich]

Originally Posted by baz

to be honest with you many times i do the 220 grit sanding then go straight to 600 grit , (with a bit of practice and a bit more pressure on the sander it will get the 220 grit scratches off) andthen directly to a tripoli on 14 inch airflex buffs

Wow, seems like quite a jump...but you're right. When you think about it, you _could_ start with 600 on a rough casting, LOL...but I'd get bored with that. Total time might not be much different! Or if you want to take a Zen approach, put it in a babbling brook and wait for the water to do the work...

[baz]

Originally Posted by mpierich

Wow, seems like quite a jump...but you're right. When you think about it, you _could_ start with 600 on a rough casting, LOL...but I'd get bored with that. Total time might not be much different! Or if you want to take a Zen approach, put it in a babbling brook and wait for the water to do the work...

you should give it a try on a scrap piece of aluminium once you reach the 220 grit go to 600 with a jitterbug air sander, put a good pressure on the sander then go to a airflex with a tripoli if you have a strong enough buffer you will be surprised how fast you get a part done
i know you are an experienced polisher but give it a try anyway

in your post you say you get haze from tripoli ,don t you have the same with
emery

[mpierich]

Originally Posted by baz

you should give it a try on a scrap piece of aluminium once you reach the 220 grit go to 600 with a jitterbug air sander, put a good pressure on the sander then go to a airflex with a tripoli if you have a strong enough buffer you will be surprised how fast you get a part done
i know you are an experienced polisher but give it a try anyway

in your post you say you get haze from tripoli ,don t you have the same with
emery

I might try it, it's just that I enjoy buffing more than sanding...plus I have no 600-grit tools for the tight areas. What do you do about that? Or don't you...?

As you know there are a multitude of aluminum alloys. Most of the time the white colors up the little bit of haze from the emery OK for me, if it's a good hard type of aluminum. But I do use tripoli occasionally as an intermediate step if necessary. There's no way to tell (before you start) exactly what will work. Right now I'm working on a set of HD shovelhead cases which are poor quality caveman-type castings. It looks like I'll have to use the tripoli in this case since the black is leaving a lot of haze.

[baz]

Originally Posted by mpierich

I might try it, it's just that I enjoy buffing more than sanding...plus I have no 600-grit tools for the tight areas. What do you do about that? Or don't you...?

As you know there are a multitude of aluminum alloys. Most of the time the white colors up the little bit of haze from the emery OK for me, if it's a good hard type of aluminum. But I do use tripoli occasionally as an intermediate step if necessary. There's no way to tell (before you start) exactly what will work. Right now I'm working on a set of HD shovelhead cases which are poor quality caveman-type castings. It looks like I'll have to use the tripoli in this case since the black is leaving a lot of haze.

i havn t done shovel head cases for a while but caveman castings is probably an understatement i that case . for the tight areas i make my own cartrige rolls
i have different size and shape mandrels with a split opening so i insert and roll my abrasive paper on it , might sound caveman type way of doing but i get the roll the size and shape i need in the grit that i want . have a look at my vrod engine in the member galery .i dont like working with real cartrige rolls
the tips wear out too fast i go through a box of 100 in no time