As pointed out, backyard [shade-tree] methods work for those that see it fit for purpose, I'll go with technology every time, and yes i know, it always costs me money.
Something not pointed out when using abrasive tapes and cloths is its preparation for the job at hand. We were taught as apprentices when using these types of abrasives to prepare them by 'breaking their back' first, that is, with tapes and flexible abrasives running their back over an 90°edge first whilst holding the tape fairly tight, this introduces flexibility to the abrasive, also preconditioning the abrasive surface by stroking it over a piece of material before introducing it the the finished job to dull off the initial cuts.
My vice of forty+ years [and welding table] actually has an area on the back of the slide that has an edge worn away from doing this,[force of habit]. Back of tape on vice face of tape on table.
Cheers.
polishing a crank
Moderator: Team
Re: polishing a crank
This apples to almost all single layer of abrasive on a backing.......and many other abrasive processes also.
I have heard people ask time and time again...
"What grit do I use"???...... and that's not easy to answer because we don't know what the heck they are doing.
Just the "GRIT" refers to how many abrasive grains in a square inch area.
There are many other factors.
FACTORS
What the abrasive IS, the size of the grains, hardness of the material being worked, and the PSI pressure, as well as the density of the abrasive grains, and the shape of the grains themselves.
With any fresh abrasive "belt" or paper... at first, some of the abrasive grains stick up higher than others.
A "NEW" sanding belt, or a roughly dressed grinding wheel........is usually only suitable for ROUGHING. It's good for "making low spots".
UNTIL, the high spots of the abrasive are worn down... and most of the abrasive grains are sticking out an equal amount, THEN it is suitable for finishing and it is at this point that IMO, represents what kind of finish you get with a particular GRIT.....which still depends on the other factors just mentioned.
Eventually the belt will become dull and/or plugged up, to the point that it CANNOT make low spots anymore, but CAN knock down high spots.
And at this point the abrasive is no good for removing any material anymore, but still can do something.
"Stoning a surface", is just knocking down high spots, or the term "burnishing" means bending the high spots down.
OLD SCHOOL crank finish IMO
Base finish of a "broken IN" 320-400 grit belt, then burnished with a worn out belt. But it really varies.
I struggle to find belts mild enough for VERY soft steel cranks, and on the other end of the scale the hardened & nitrided cranks used in some engines.... I can barely remove any material at all before the belt is dead.
I have heard people ask time and time again...
"What grit do I use"???...... and that's not easy to answer because we don't know what the heck they are doing.
Just the "GRIT" refers to how many abrasive grains in a square inch area.
There are many other factors.
FACTORS
What the abrasive IS, the size of the grains, hardness of the material being worked, and the PSI pressure, as well as the density of the abrasive grains, and the shape of the grains themselves.
With any fresh abrasive "belt" or paper... at first, some of the abrasive grains stick up higher than others.
A "NEW" sanding belt, or a roughly dressed grinding wheel........is usually only suitable for ROUGHING. It's good for "making low spots".
UNTIL, the high spots of the abrasive are worn down... and most of the abrasive grains are sticking out an equal amount, THEN it is suitable for finishing and it is at this point that IMO, represents what kind of finish you get with a particular GRIT.....which still depends on the other factors just mentioned.
Eventually the belt will become dull and/or plugged up, to the point that it CANNOT make low spots anymore, but CAN knock down high spots.
And at this point the abrasive is no good for removing any material anymore, but still can do something.
"Stoning a surface", is just knocking down high spots, or the term "burnishing" means bending the high spots down.
OLD SCHOOL crank finish IMO
Base finish of a "broken IN" 320-400 grit belt, then burnished with a worn out belt. But it really varies.
I struggle to find belts mild enough for VERY soft steel cranks, and on the other end of the scale the hardened & nitrided cranks used in some engines.... I can barely remove any material at all before the belt is dead.