I found grinding the rails is alot easier when i used one of those sandpaper/grinding disc. It can be ground in less than 1/4 of the time and less cost, 1.5 discs for 3.6m worth of grinding. The normal grinding discs kept on glazing up even the grinding is done near the edge of the disc.

That is a great note that I don't think get's shared enough. Start with a 36 or 50 grit and finish with a 80 or 120 grit to polish.

For the new readers, make certain that you have a VERY stiff backer to the sanding disk unit. Some of the backing plates on the disks can be to flexible and not give repeated grinding results. I personally put the sanding disk ON TOP of an actual grinding disk as a FIRM back.

Thanks for sharing.
Sean

I set the skate so that it was grinding in the middle of the disc with the rubber backing where it is a lot stiffer, as can be seen in the photo with the grey mark. It is not the opitmum spot for grinding (cutting tip speed, what ever it is called it grinding terms?).
I think using a grinding disc instead of the rubber backing is a very good idea and would be far better.
I timed my self and it took 1/2 an hour to grind 3.6m and 1/2 an hour to cut with 1mm blade. It has gone from a painfull process to a painless process.

Allow me to add to your caution SEAN.

Cheep grinders ( like the one I used back then) have some “flex” due to cheep bearing or bushing to chaft tolerance making the “stiff” disc still “wobble” out of axis.
I remember to remedy this had to take VERY very light passes in order to achieve a respectable flatness ….and goes without saying I had to replace that “cheep” darn oem bearing after only one rail ( see this)!

Buy good tools once rather than a "cheep" making it hard on you !

Robert ;)

Anthony

I'm with Sean, the rubber backing pad will give a second class result in comparison to using a grinding disk as a backer.
I have really tried to get this method out there for all to see after reading it on the forum myself.
I asked Redboards to run some comparison tests before he did his rails and he is a convert of the technique.
As Sean says, run up the grits and by the time you get to 120 Grit, it polishes the rails.

Good luck with your build.

Ross

Ross
I don't disagree with you or Sean.
If I was to to it again I would do as you have explained. When I had read Sean's post I had alredy completed the grinding.
The local Hardware Store only had 36 and 60 grit, so did the main cutting with the 36 and finished with 60. The surface still had machine marks so I draw filed with a 12" finishing file.
If some can tell me a good reason(s) why I must have 'polished' rails (apart from me being able to see myself combing my hair) I will do it, I think it is acceptable.

Hi Anthony

The accuracy of the rails are the only consideration, everything else is really only cosmetic. Small scratches will not interfere with the operation of the machine.
The section of rail you have shown looks to be the goods - well done.

Regards
Ross

Not just for combing your hair, Polishing the rail is also a great way to kill time. :)

I need links to where others have talked about sanding pads instead of sanding disks.

I also would like to see the link where that skate bottom is discussed.

I will add content to this thread so we have this pointed out to new builders.

Mike - My experiences start at Post 186 in my thread.

Regards
Ross

Mike,
It all started kinda here:
http://www.mechmate.com/forums/showt...51&postcount=1

Then prototyped here:
http://www.mechmate.com/forums/showthread.php?t=479

Then more protype here:
http://www.mechmate.com/forums/showthread.php?t=19

And final built protype that ended up being the production version in the drawing package before the bolt cutouts were added for the roller option on this skate.

http://www.mechmate.com/forums/showt...?t=460&page=10

Mike my experience is here
http://mechmate.com/forums/showthrea...&postcount=128

and here
http://mechmate.com/forums/showthrea...&postcount=133

I highly recommend the Sanding disk over the grinding disk. Removal rate was incredible. I also recommend a face mask with eye protection as the sparks really fly everywhere.