For a light final grinding pass, the disk wear is practically zero. That applies to all grinding operations, eg. surface grinders, knife grinders, cylindrical grinders, etc.

remove gearbox screws?
 

I've been reading all the posts on the angle grinding as thats the bit thats got me most worried about starting my build. I grabbed my dads grinder to see if it will fit on the skate. It looks like it wont. Its an old Makita...
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I thought the skate attached to the equivalent of the 3 screws that held on the safety guard. So then i went down to the local hardware store here and had a look at a few there.
But then i re-read this:
So do I understand now the skate attaches to the 4 screws that hold the shaft bearing? So do you remove these screws then attach the skate with longer screws? Is there any issue comprimising the grinder doing this? (will it void my warranty if i buy a new one?)

So do I understand now the skate attaches to the 4 screws that hold the shaft bearing? Yes

So do you remove these screws then attach the skate with longer screws? Yes

Is there any issue comprimising the grinder doing this? (will it void my warranty if i buy a new one?) Your warranty will be voided if they find out that you have removed the screws. It is not as if you are doing open-heart surgery to the grinder, but you certainly would be using the grinder in a manner it was not designed for.

Matt just go on, I had to do it in the same manner. Also i was unable to fix my grinder to the small fixing dia on the original skate plate so i had to bore them and cut the end to enable my grinder to sit. I did a small ring washer with a PCD holes of the grinder and screwed them. No problem till the end of the grinding. Lot of R&D is not required just keep going you will learn in a few minutes. Love to see you grinding soon :)

I need someone to look at this drawing to see if my modifications will work or interfere with the workings of the skate. My idea is to use 2 bearings like Joe is shipping with the skate (now we need 10 instead of 8). Cut a length of 12mm rod 1" long insert it through the bearing, then spot weld the ends of the rod to the top of the plate. This will leave 1/16" of bearing protruding under the plate to ride the rail. Now all adjustments will need to be made by adjusting the upper plate in and out on the lower plate.
I also have some ideas about fine adjusting the plate, but I would like to know first if the modifications will even work.

I haven't decided yet on how I am going to grind my rails. With the skate or other guiding method.
I think this idea of yours will work. It will eliminating the damage to the riding bolt.
What did you had in mind for adjusting the height, J.R.?

Johan it will be easy, we will just adjust the top plate more toward the center.

I need help identifying the purpose of the 6 holes circled. Thanks

If you look at Sean's pics in earlier posts in this thread, you will see a pair of "all-thread" rods lying at 45 degrees to the base of the skate. They are for fine tuning the 45 degree angle when bevel grinding.

The remaining pair of holes (out of the 6 marked above) are a place to screw on handles.

Hi JR,
My boss left me alone last week so that I could enjoy my coffee during my lunch times. I was playing a bit with your new idea for the skate.:) Hope it it is ok?;)

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The existing plates are shown as per dxfs and I only removed the piece for the existing bolt - height adjustment.
It seems that the best position for the new bearing shaft center could be at the center of the bottom plate.
Only one bolt is shown in position for the bolting the two plates.
The two plates might have to be altered to allow for more adjustment towards the centre.
What do you think?

We could put a notch into the skate ends to accommodate the roller bearings. . . . . or the bolt, that is relatively simple and doesn't remove any functionality we have now.

However, that aspect of the skate (sliding bolt head vs roller) is not the highest concern for me. I would rather make a mod that stops the glazing of the face of the grind disk, ie. to make the grinder "attack" the rail at a more aggressive angle. This could involve swivelling the upper plate instead of a straight left to right adjustment.

A snag with the left/right/swivel adjustment is to get a fine control (that we have with the rubbing bolt head now)

Johan, that looks good, only one issue - on image 3 I see the lower bearing sets are set at different heights, this will cause problems when turning the skate around to do the inside, its best to have both sides set to the same height. I know that as you drew it would give the best support but everytime you turn around you would have to change bearing positions.

When grinding the bevel, you do one side, turn the skate around and do the other side, when it moves up and down without making anymore sparks, the skate is adjusted for more "bite" then the process repeated again and again and again...etc

The skate's "grip" or "pinch" on the vertical part of the rail will also be firmer if the roller pairs are opposite each other. ie. set at the same height.

Thanks Gerald and Alan. That make sense.
I received a quote for R45 per bearing. To buy the 8 to 10 bearings for grinding only seems to be expensive. I do not have a long flat surface on the other hand to grind like Hennie did his.

Your'e being ripped off, those bearings should cost no more than R8.00 - R10.00 each, find another supplier (Bearing Man or Bearing Distributors are two I can think of)

Thanks Alan. I will phone around.

Alan, some feed back on those bearings. One of the well known bearing manufacture - suppliers gave me a price of R11.55. Bearingman was the expensive one.
It is the old Zululand way of doing business again. If it is not a shelve item that someone use a lot then they charge 3 to 5 times the price.
The only time that I wish I lived in the city! :)
I was just lucky that the other supplier had some left over from a large order.

Johan I don't know how much trouble it is to redraw this thing (by the way it looks great) but here are some more mods. It is a DXF file so change the ext. from TXT back to DXF. Thanks

Not to much work JR. Geee did I say that! One will never hear words like that from a draughtsman!:D Please don't tell my boss!

By the way, these last modifications are based on the ideas from the last few post by Johan and Gerald. I said it once and I'll say it again ...... "none of us is as smart as all of us" or something like that. You get my drift ... right. ;):cool:. Thanks

JR, my AutoCad refuses to open that. (after changing txt 2 dxf)

It opened in mine Gerald. It might have been save in a newer version?

Johan, can you mail me a dwg or dxf compatible to AutoCAD 2005?

I only put some bolts in JR. I still have to tweak the roller heights and positions

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Thanks for trying Johan, but I still get this error message:
Unknown value "AC1021" encountered in drawing version.
Invalid or incomplete DXF input -- drawing discarded.

Good job! You nailed it. Thanks

JR,
Silly question but how are the rail rider bearing held in the skate? I dont see a way to get a bolt in there?

Tack welded. If you ever needed to modify the thing or change bearings, just cut the weld. What do you think ... keep it simple

I know ... I know ... keeping it simple was leaving it alone. I just couldn't do it. Sorry :o It's that type A personality. ;)