On 5/11/2022 11:05 AM, David Billington wrote: > On 11/05/2022 18:59, Bob La Londe wrote: >> On 5/11/2022 9:20 AM, David Billington wrote: >>> On 11/05/2022 16:41, Bob La Londe wrote: >>>> Yesterday I found myself cleaning up a bit of square tube in >>>> preparation for welding and later paint. It was outside, but in SW >>>> Arizona, that just means it has developed a small amount of >>>> protective rust over the mill scale. >>>>
>>> I started with an angle grinder and a flap disc. It made short work >>>> of the light loose rust, but would hardly touch the mill scale. It >>>> also showed some rust down "in the" the mill scale. I probably >>>> could have stopped there, but I got carried away with myself. This >>>> stuff welds really nice if you have bright shiny metal and takes a >>>> good paint coat as well with an etching primer, and proper cure times. >>>>
>>>> I probably I could have just used extend or some other rust >>>> neutralizing primer after knocking off the loose rust, but this >>>> construct will be going into a humid environment. >>>>
>>>> I noticed a fresh flap disc stripped rust, and mill scale amazingly >>>> fast. It did more work with less effort in the first minute or two >>>> than it did in the next ten. Now the flap disc was still nearly >>>> new, but it was performing like one that was half worn away. There >>>> was still plenty of grit, but the edge was mostly the flaps rather >>>> than the grit, and the face was the same, but also gummed up with >>>> mill scale. >>>>
>>>> I am NOT trying to get longer life out of a flap disc. I am trying >>>> to get more time performing like the first minute or two of a new >>>> disc. I don't care if the total life of the disc is less. Is there a >>>> practical way to dress these so that you can expose more grit >>>> quickly. I tried spinning it against a wire wheel on a bench >>>> grinder. The result was less than amazing. >>>>
>>>> Sans the solution I am looking for is there a better disc for >>>> stripping metal than an abbrasive flap disc? I can do the work with >>>> a grinding wheel, but its much more skilled to avoid gouging the >>>> base metal and doing damage. I tend to only use a grinding wheel to >>>> make the bevels before welding. >>>>
>>> I know what you're experiencing with flap discs and have used this >>> type of disc to good effect >>>formatting link. I've seen many >>> of this type for sale on ebay and most don't have a high enough speed >>> rating for use on a 4.5" grinder so check what you get if you try one. >>>
>>
>> I looked at that. I've seen those type of wheels before. How well >> does it work on mill scale. >>
> In my experience they deal with the mill scale on box section I've > cleaned up very well. >
They are a little pricey, but I think I'm going to give them a try If the actually work ok it may be worth it in time saved. If not then I'll know. I'll start with one for now and if they work ok, I'll probably buy a box of them from one of my industrial suppliers the next time I am flush. I'll keep you guys posted on whether or not I think they are enough better to be worth it.