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  #1  
Old Sun 14 September 2008, 10:26
waynec
Just call me: Wayne from White Salmon
 
White Salmon, WA
United States of America
Getting rails coplaner and straight

I'm not building a Mechmate at this point, but many of the mods to my old Shopbot PR are taken from ideas for the MechMate.

I read the thread about using angle aluminum as a backing for my Bishop Wisecarver rails, and I'm getting ready to do this. I have the BWC rails and wheels, and I'm ready to buy the aluminum angle.

My question is- How do I mount the angle to my existing structure so that its straight and level, and coplaner with the other rail? What sort of accuracy should I be trying to get here?

Thanks for letting me ask this sort of question here, even though I'm not a MechMate builder yet.

Wayne from White Salmon
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  #2  
Old Sun 14 September 2008, 12:54
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Wayne,

I didn't use aluminum rails on my machine but I still had to use a system for ensuring my steel rails were straight and level. Here is what I did.
1. Using a 12" machinist's level, I leveled one beam to the best of my ability by adjusting the feet below both ends of it.
2. Again, using the level, I leveled the other beam.
3. Rechecked the first beam to ensure the adjustments to the second beam didn't affect it.
--The beams should now be in the same plane although not necessarily level in the Y axis. Maybe the others will disagree but unless the Y axis is drastically out of level, I don't see that it will affect accuracy to the degree it is needed for cutting wood.
4. Next, I clamped one of the angles to a beam. Then I created a crude fixture for one end of the angle that held the end of a piece of very fine fishing line. I created a similar fixture for the other end of the angle and stretched the line tightly between the fixtures.
5. Using a jeweler's loupe (magnifier), I centered the fishing line over each end of the edge of the vertical leg of the angle. Then I examined the line, using the loupe, for it's entire length. If the line wasn't centered, I knew my angle wasn't straight at that point. You can also look at the line from the side to see if the angle needs to be shimmed. I used the leaves from some cheap feeler guages to shim the angle. Just cut them out with tin snips.
6. When you are happy with the first rail, drill and bolt it in place. Recheck for straightness.
7. Once I had finished straightening one angle, I cut a piece of metal conduit to act as a spacer for the other rail. This spacer kept the two rails at a constant distance from each other while I was positioning the second rail.
I tried to keep my accuracy to better than .010"

If my instructions were confusing, please don't hesitate to ask for clarification. Good luck.
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  #3  
Old Sun 14 September 2008, 23:39
waynec
Just call me: Wayne from White Salmon
 
White Salmon, WA
United States of America
Excellent!

Thanks so much for the reply. I have a machinists level that should get me going. I'll do just what you suggest, and rig up something so I can compare the position of the alum rail to a reference wire.

I guess I'm not sure how to get the reference wire exactly centered on the beam, but I can get pretty close with my dial caliper.

So, what if I string a piece of piano wire tightly instead of the fishing wire, and just sneak up to some small distance just short of the wire. I could measure that difference, and make sure its the same along the length of the rail. I guess the wire would have to be pretty tight for this to work.

I just watched a demo of a FARO laser measurement device at work that will let you measure to .ooo4" using a reflective ball that you hold against the surface. Only $120K for it, but it sure would let me mount the rails with great precision. I asked if I could borrow it for the weekend. He acted like I asked to date his daughter or someting. Oh well.

I'm sure before there were lasers, people made wonderfully accurate machines with methods very similar to your instructions.

Thanks for the very clear step by step. It gives me confidence to give it a try.

Wayne from White Salmon
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  #4  
Old Sun 14 September 2008, 23:48
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Instead of the taught line/wire, we used an alu extrusion as our reference. The alu is about 100x3mm [4x1/8"] and we used it like a big straight edge ruler vertically and horizontally, checking for gaps with a feeler gauge. Because that alu is rather floppy, we d-sided taped another small alu tube to it, but wood would also be okay as a stiffener. To get confidence in the straightness of that extrusion, we flipped it over, and end for end, to check for repeatable results.
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  #5  
Old Mon 15 September 2008, 06:02
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
My suggestion uses Steel fishing leader (strong [100 lb test] and cheap) 2 bolts about 1 1/2" longer than needed to bolt down the rails. Put a nut on the bolt leaving about an 1" of threads, this nut becomes the new head of the bolt. Drill a very small hole (1/16" and ease the hole with a 1/4" drill bit, both sides) through the bolt 1/2" above the nut toward the head . Lay the rail on the beam insert the bolts in the end holes. Feed the wire through the small holes and twist the ends (this can be done before putting the bolts in place just leave it a few inches long). now snug the bolts, turn the real bolt head and tighten the wire. As close as possible to the bolts, between the wire and the rail insert a 3/4" gauge block, you will need 3 blocks the exact same size. The 3rd is used to slide up and down the rail, in and out between the wire and rail. Insert shims as you go until you are satisfied with the results. Get the height of the rail right first. Then this same principal works by routing the wire around the ends of the rail to the outside. put gauge blocks 1/4" thick as close as possible opposite the end bolts, and adjust until your heart is content. Adjust the opposite rail for height using this principal and then use Doug's suggestion to adjust the proper distance between rails. If my instructions were confusing, please don't hesitate to ask "Gerald" for clarification, because I'm totally lost.
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  #6  
Old Mon 15 September 2008, 17:15
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Wayne,

The vertical leg of my angle iron is sharpened so that's why I chose to center the line above the middle. Since the vertical leg of your angle irons will be flat, I would probably place the line slightly above one edge of the leg. When you look at the line through a magnifier, you can accurately locate it in relation to a reference edge and easily see where the angle needs to be adjusted.

I haven't used wire but I can tell you that fishing line works great. It is super thin, dirt cheap, strong, and will stretch a tremendous amount. The fixtures I created were simply thin "off the shelf" metal brackets held in place with C clamps. The thin metal brackets can be easily bent with your fingers to align the reference line over the reference edge of the angle.

Ignore everything J.R. has written. If you follow his advice, you'll end up with a machine that is all shiny and perfect. No one will believe you built it. They'll think you bought a Rolls Royce gantry router and slapped a Mechmate sticker on it.
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  #7  
Old Mon 15 September 2008, 17:40
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
I have a better idea. Take the mono fishing line and go catch a nice fish, cook it for supper, enjoy the meal, sit back in your easy chair and smoke a good cigar.............. and then take steel leader along with the bolts and do it the easy way.







Doug, you know I'm just kidding.
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  #8  
Old Mon 15 September 2008, 18:21
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
...or. you do like I did and just sit the gantry on top and realize after test cutting that you got it right without touching a thing!
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  #9  
Old Mon 15 September 2008, 19:46
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Doug, JR,
Since Sean didnt have to do much to his rails I will ask this question of you two. How much did you actually have to shim and or staighten the angle iron? I could see a bit of straightening being needed but the height I would think would be pretty close once the rails were bolted to the main beams? Or are the beams out more than I would think?

Sean, Have you gotten to that point with Nils machine? Was it any better or worse than the angle iron version for aligning?
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  #10  
Old Mon 15 September 2008, 20:08
waynec
Just call me: Wayne from White Salmon
 
White Salmon, WA
United States of America
Thanks all. I'm starting to get a clear idea of how to do this. If these methods produce acceptable accuracy here, I'm sure it will be adequate for me. At work I use a $150,000 Biesse CNC with accuracy to about .002 or so. I'd be happy with much lower accuracy, but after dealing with the Shopbot PR design inaccuracy, I want to do the best I can.

I'm wondering if I can use and Eyebolt mounted on a piece of angle iron to provide an adjustable end for the wire.

Also, where can I get gauge blocks for a reasonable price?

Again, thanks for all the help.

Wayne
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  #11  
Old Mon 15 September 2008, 20:13
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
I did not do any shimming to the height and only minor adjustments were needed to correct the other. The hardest thing for me was getting the rails parallel to each other even though I used the "Doug" method.
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  #12  
Old Mon 15 September 2008, 21:39
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
My experience was that the base table is very flexible. The four leveling feet are used to make the channels, which the rails attach too, level and flat.

Making the rails parallel wasn't that hard. I think your going to be surprised at the accuracy. I haven't run any "official" tests, but, it's certainly impressive.

I'm making a router table where I used the MM to machine the table top pocket for a "Mast R Lift" (jessem.com). The "Mast R Lift" fits the table like a glove.
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  #13  
Old Mon 15 September 2008, 21:55
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Greg J View Post
My experience was that the base table is very flexible. The four leveling feet are used to make the channels, which the rails attach too, level and flat.
And, if you think the table is flexible, look at how flexible the boards are that you want to cut to sub-millimeter accuracy.

Okay, the table is relatively flexible for twist, or for maintaining a flat plane. That's why we rely on the floor strength to ensure the flatness (coplanar) of the table. But, one can waste a lot of time adjusting feet to get a perfectly level table only then to go and cut very flexible material.
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  #14  
Old Mon 15 September 2008, 22:07
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
Quote:
Originally Posted by Gerald D View Post
And, if you think the table is flexible, look at how flexible the boards are that you want to cut to sub-millimeter accuracy.

Okay, the table is relatively flexible for twist, or for maintaining a flat plane. That's why we rely on the floor strength to ensure the flatness (coplanar) of the table. But, one can waste a lot of time adjusting feet to get a perfectly level table only then to go and cut very flexible material.
But don't forget, people are also cutting, PVC, Aluminum, etc. Allot of not so flexible materials.

The MM is capable of sub-millimeter accuracy.
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  #15  
Old Mon 15 September 2008, 22:10
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
PVC and Alu have to be rather thick before they will lift a table leg as you clamp them "down"
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  #16  
Old Mon 15 September 2008, 22:24
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
Yes Sir.
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  #17  
Old Mon 27 December 2010, 05:48
Red_boards
Just call me: Red #91
 
Melbourne
Australia
Are there any alternatives to using a machinist's level (also called engineer's levels) for levelling the beams?
They're a bit pricey. I'll get hold of one if I have to, but I was wondering if there were other smart methods out there.
I know a long clear tube filled with water and fixed to the beam at each end would do something, but could it be accurate enough at something like 1mm over 3000mm?
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  #18  
Old Mon 27 December 2010, 06:02
Polder48
Just call me: polder
 
Edam
Netherlands
Quote:
I know a long clear tube filled with water and fixed to the beam at each end would do something, but could it be accurate enough at something like 1mm over 3000mm?
Yes this will work accurate enough. If you use water, add to drops of Dreft or alike, to lower the surface tension of the water. This way the surface will be flat and your readings accurate.
My 2 cts.
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  #19  
Old Mon 27 December 2010, 06:50
AuS MaDDoG
Just call me: Tony #71
 
Brisbane
Australia
Hi

Water levels have been used for years and are very simple to use, they are also very accurate if used correctly.
The correct way to read the water level is always take your reading from the top of the bubble which generaly is flat or flatter than the bottom of the bubble and always make sure nothing is fouling the tube when being used.

Cheers
Tony.
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  #20  
Old Wed 29 December 2010, 01:37
Red_boards
Just call me: Red #91
 
Melbourne
Australia
Righto, I'll try this when I reassemble. and report back. I'll try to get an engineer's level to check results.
Thanks
Red
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  #21  
Old Thu 30 December 2010, 03:08
KenC
Just call me: Ken
 
Klang
Malaysia
Been there, done that...
Water level is a waste of time. Any carpenter level can fulfill the accuracy. (except a broken one...)
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