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  #31  
Old Mon 30 June 2008, 09:15
orotemo
Just call me: orotemo
 
Warburg
Israel
Just watched the Brazil video,
This is one sound technique to grind rails. We need some impressions from the cutter, if he could make the measurements in several places along the rail and post it, I'll bet he got the best results yet.
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  #32  
Old Tue 08 July 2008, 23:06
Valdir Fernandes da Cruz
Just call me: Valdir
 
Curitiba - Paraná
Brazil
grinding rail

Hi all, we improve this method, my brother Wladimir will put a second video for information.
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  #33  
Old Wed 09 July 2008, 00:23
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Thanks Valdir, we are looking forward to it!
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  #34  
Old Tue 22 July 2008, 23:29
William McGuire
Just call me: Bill
 
Weiser, Idaho
United States of America
Does anyone know if channel iron comes with 1 inch legs? You could then possibly just cut off the spare leg and grind the 45s. It seems as though it would be sturdier than the angle iron and not have any give...

I almost thought of doing it with mine, but the channel legs are 1 3/8 inch
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  #35  
Old Wed 23 July 2008, 00:39
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
You might find a 1" leg channel in your part of the world, but remember that you are looking for a parallel leg if you want the skate to work.
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  #36  
Old Wed 23 July 2008, 20:07
liaoh75
Just call me: David
 
Taibao
Taiwan
I watched the video several times from post #30 but still don't fully understand what I'm looking at. Is the cut being made all way through on a single pass? Is a standard cutting disk being used? Here in Taiwan, there are cutting disks that are made specifically for cutting metal that are just like the saw blades that are used in the "Steel Max" style of saw but made just for an angle grinder. It looks kind of funny and I don't know about the safety factor.

I cut my rails using a home-brew style of contraption similar to several I saw posted by other builders; nothing fancy but I did get some strange measurements after the cutting. One end was almost an entire millimeter taller than the other. I used a 4 meter piece of 7" Channel as my working surface. My Angle iron was well clamped to one edge. I moved the angle grinder and the angle stayed stationary. Another thing I noticed was that there is about a 0.75mm play on the head of the angle grinder I was using which leads me to believe that between the flex in the cutting disk along with the play on the angle grinder head attributed to the variations. The strange thing is the differences were very consistant from one piece of angle I was cutting to another (4 in all). If I were to re-cut I would lean toward moving the angle iron to get a more even cut along the length of the entire angle. Is there anybody that had the same results?
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  #37  
Old Tue 07 July 2009, 08:22
KenC
Just call me: Ken
 
Klang
Malaysia
No Cutting, Just grinding the V

Hi,
Just a idea flashed, What if we bolt + glue a 25 x 25 x 6mm angle on a 60~65 x 6mm flat bar? We'll have 31mm raw height, use the V skate to bring it down to final height of 28mm? (Or other more convenient angle and flat bar sizes would do)

Drilling CSK holes on the angle and tap to get it done correctly.

Edit, Maybe this had been discuseed, please forgive me.

Last edited by KenC; Tue 07 July 2009 at 08:24..
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  #38  
Old Sun 12 July 2009, 13:50
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
One challenge is that the inside of the 25 x 25 x 6 angle is only 19mm tall (3/4")

Based on my recent use of the skate, I'm not sure I could make the eccentric bushing/bearings/bolt head fit in that space and still have adequate contact between the inside surface of the angle and the bearings.

...Particularly when you consider the boltheads holding the angle to the bar. You could grind the angle without the bar attached, but then there's no guarantee that the assembled pieces will actually be 28mm.

Also, the rail will still need to be surfaced flat before using the skate to grind the bevel.

Otherwise, IMHO, the idea has merit.

FWIW, because I couldn't get my cutting disks to run true on my hand-me-down grinder, I used a harbor freight metalcutting saw, then surfaced the cut angle to finished height with the angle grinder using a grinding disk.

If I build another, I'm sure I could do better. Adjusting the fence to allow the saw to cut true was a fiddly process with much trial and error. The fourth rail looks great.

The first three? Less so, but I think they're serviceable, they'll simply require shimming.

Once this one is done, I NEED to build another. This education should not go to waste.

Last edited by lumberjack_jeff; Sun 12 July 2009 at 13:56..
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  #39  
Old Mon 13 July 2009, 01:44
KenC
Just call me: Ken
 
Klang
Malaysia
Jeff,
Thank for sharing your experience. Wasn't aware of the clearance as I'd yet to start construction for practical reasons.......

Its true all stock M.S. Angle & Flat bar does have their fair share of tolerance. I'll ditch this idea and concentrate on the MechMate Rail Cutting & Grinding Methode exclusively developed here.

I was impressed by the advance in metal cutting circular saw. Yet to find one off the shelf here... Fortunate for me... or else I would have already dug deep into my retirement fund...

I doubt the circular saw will ever replace the MechMach Rail Cutting proceedure with just one pass. Being more at home with metalworks, I am obsess with a god sturdy datumn, which is difficult with the circular saw... A finishing grind is mandatory is one wish to see accurate and flat finishing.

As such, I'll just have to look away from tha sexy SteelMax circular saw and live with my Bosh grinder...

Damn... Really WANT that toy...

OT, is there anyway I can transform my SkillSaw into a flaming metal chewing mean machine?
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  #40  
Old Mon 13 July 2009, 12:15
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
Here in the US, the Chinese metalcutting saw is about $90. They also sell replacement blades for $18.

The arbor size is the same as my circular saw and the blade is rated for a max speed which would make it compatible with my circular saw. The only reasons I didn't give it a try;
a) my local Harbor Freight store didn't have any of the replacement blades in stock
b) my circular saw has only the most rudimentary fence. The metalcutting saw has a much better one, which runs the full length of the saw's base. A good fence is not something you can do without when cutting angle.
c) the metalcutting saw has a pretty sophisticated set of shrouds/shields. I think an unguarded circular saw would throw chips (often hot chips) everywhere.

Although others have reported limited success with this, if they had any metalcutting blades in stock, I would have tried using it on my tablesaw.

With good technique, the surface finish was almost, but not quite adequate to use as a skate datum. By the time I cut the fourth rail, I found that if I ripped the rail about 29-30mm, the rail cleaned up very close to 28mm.

A true-running grinder and Pferd disks is probably the best, but having neither, this worked okay.

Last edited by lumberjack_jeff; Mon 13 July 2009 at 12:17..
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