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Discussion Starter · #1 ·
Hello everyone,

I am building a setup for surfacing 4 x 8 glued up solid stock panels. I have purchased 4 pcs of linear shafting with the linear bearings on ebay (around $300) and instead of the usual way of using a wooden jig I plan to run the router on the linear slides with a 2-1/2" surfacing bit.

Anyone have any input on things I should could or how to add to this project to improve it. This is a common task and I want something that will be fast and clean. Budget within reason is not an issue.

Thanks,
-Eloy
 

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Hello!
Well , you can make nice piece of machinery out of your linear shafting!
You did'nt say what lenght you bought.
Like router-lathe , routing slots , universal precision sliding mitre for router and circular saw, a copiing 3d router,
Many things.
IMHO:But just for cleaning surface, i' ll consider Harrysin ski system, its costless, fast to make and quite efficient!

The only point that could make this design fail a litle precision is the router's base:
Some bases uses too thin steel bars, some give an angle, when you screw router lock
to the steel bars, then the router is not staying horizontal , needs a bit of adjusting.

http://www.routerforums.com/jigs-fixtures/23799-beginners-guide-making-router-skis.html

Regards
 

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Trying to make 4' X 8' panels from solid wood does not sound to me like it will be very successful. With any change in humidity the panel will change shape. It may be flat one day, but look like a potato chip the next. Wood changes it's size too much with moisture content changes for this to work out well.

In fine furniture and paneled room construction it has been common to break up larger areas into frame and panel designs to allow the wood panels to move with changes in moisture content. It's a lot more work to do this type of construction, but it works out very well. I would never try to make a solid wood panel larger than about 1' X 2' and expect it to remain very flat, unless it was built into a frame with provision for it to move within this frame for any changes in moisture content.

Charley
 

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Discussion Starter · #4 ·
Good point Charlie,

I have had to go to a three ply glue up to solve that problem. I A little trickey to get three levels thick by 4' wide but using cawl's it can be done. It takes work but these are very expensive projects. Thanks for pointing that out. I normaly just laminate to a pc of MDF but some clients insist on "solid wood"

-Eloy
 

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Discussion Starter · #5 ·
Hello Gerard, good tip. I am building the same principle as the ski's but more ridgid. By the way, on the linear slides I will have 12' x 6' of travel.

-Eloy
 

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I am working on a set of skis like Bobj3 has and pictured below. Mine is 24 inches long with a cut down phenolic router table insert plate for the router. Going to use a Milwaukee 5615-20 router with the handles removed and a 2-1/4 diameter drawer lock bit to plane the stock. Got the extrusion off Ebay for around $30.00 shipped. The holes in the ends of the extrusion are perfect for tapping 1/4-20 threads to attach knobs for height adjustments. As it stands I will have invested less than $60.00 when finished excluding the router of course.

I also have a Woodhaven planing jig that is a monster and as such will plane larger stock than the ski will. I wanted the ski to plane 50 or 60 boards that average 12 x 6 x 3/4 down to 5/8 or less depending on the application as well as being easier to take down and store when not in use.
 

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Without knowing the size and type of shafting you have, it would be hard to predict how it will act as far as deflection goes.

I used to design industrial machinery such as this, before I became disabled, and for the size of project you're going to do, shaft deflection will be a problem, unless you have some pretty big shafting and bearings. Shaft deflection can mean an uneven cut, and vibration.

Normally, for a project of this size, the shafting to be used on the longest length you have, which will be 8 feet, plus some for the carriage, should be the supported rail-shafting mounted down to a fixed and very sturdy table. This is the shafting that mounts down onto a solid aluminum riser, and goes completely under the shafting making it into a rail. If you tried to use, say two pieces of shafting only supported by its ends at around 9 to 10 feet long, it could cause a vibration when the cutter was mid-way in the work, especially if you took a very heavy cut. The other direction, or axis, will be a little over 4 feet, and you could probably get by with end supported shafting here, as long as its big enough.

An idea would be to take a look at a CNC routers construction of something this size, and see what was required to do it without vibration.
 

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Hello!
Interesting project!
can you send picts?
Are you making some sort of real heavy plywood or am I wrong?

My grand father made a table like that. still got it , he made a 45° frame around it.
It never did move, but at this time,They where patient.
I'm very sure he did use some 20 to 50 Years of drying wood.

Some of the best woods for difficult jobs are the wooden beams and framing took
out at destruction of old houses.

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Extrusions

I am working on a set of skis like Bobj3 has and pictured below. Mine is 24 inches long with a cut down phenolic router table insert plate for the router. Going to use a Milwaukee 5615-20 router with the handles removed and a 2-1/4 diameter drawer lock bit to plane the stock. Got the extrusion off Ebay for around $30.00 shipped. The holes in the ends of the extrusion are perfect for tapping 1/4-20 threads to attach knobs for height adjustments. As it stands I will have invested less than $60.00 when finished excluding the router of course.

I also have a Woodhaven planing jig that is a monster and as such will plane larger stock than the ski will. I wanted the ski to plane 50 or 60 boards that average 12 x 6 x 3/4 down to 5/8 or less depending on the application as well as being easier to take down and store when not in use.
If he used something similar to the 80/20 extrusions for the long rails, on the 8' axis, like the 2" x 4" sections, he would be better off, or I would think. They also have the nylon linear bearings to fit the extrusions, and the extrusions could be easily mounted to a table or level floor. He could then use the round rods and bearings for the other axis, but my guess is that he would need at least 1" diameter rods, or larger, to stop any vibration.

He's using a 2-1/2" bit, which takes a good size router, and it creates a good amount of cutting force, so I'm worried about him getting vibration, and sway or sag in the rods over a long distance. The idea of the tubing is a good one.
 

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Discussion Starter · #10 ·
Thanks for the response Will,

You made some good points. I have 25mm supported shafting, The long rails will be mounted to a table so I am sure they will be fine. What is your opinion on the cross travel since it will only have the additional rigidity of the rail support. Since it will be inverted I will have spacing brackets over both ends over the long travel shafting. The plate to mount the router will be recessed to get the spindle down to the work. I would appreciate knowing what you think.

-Eloy
 

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Discussion Starter · #11 ·
Hello Gerard,

Plywood is a good guess. I am actually building out a law office and the workpeice will be one of three parts for a conference table top on this project, hence the solid stock. I have done a few jobs similar and decided to make something that is quicker than the way I have done it before.

-Eloy
 

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If I needed a 4 X 8' flat panel I would purchase a good quality veneered sheet of 3/4 or 1" plywood. It would be far more dimensionaly stable than trying to make a flat panel from solid wood. Add a ribbed frame or torsion box to the table design to support it and it would remain flat and stable for a very long time.

Charley
 

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Hello!

shaft mounting for a 8 feet travel on a 25mm steel round ?
IMHO:
No need to calculate, it will surely move too much.
Unless you go for a support in the midle and change the moving bearing for
a 3 bearings at 120° thus leaving possibility for supporting the sliding bar.
That makes 6 bearings with some kind of machined wheel to run on round profile.

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Design

Thanks for the response Will,

You made some good points. I have 25mm supported shafting, The long rails will be mounted to a table so I am sure they will be fine. What is your opinion on the cross travel since it will only have the additional rigidity of the rail support. Since it will be inverted I will have spacing brackets over both ends over the long travel shafting. The plate to mount the router will be recessed to get the spindle down to the work. I would appreciate knowing what you think.

-Eloy
Well, the 25 mm shafting is the same as 1", or very close to it, as 25.4 mm is one inch. I take it you have four linear bearings to mount to the router plate, one per each corner? If so, I would think it will probably be enough, as long as you don't go over about four to five feet in span for the shafting length. The rods will need to be a little over four feet, because the router plate will need to extend past the work somewhat on each side for the bit to cover a full four feet.

The main thing is, mounting the shafting at the ends, rigidly, where it will ride on the shafting for the long axis. This long shafting should be connected to the table at least every two feet or so to keep it as rigid as possible.

You might buy two pieces of heavy aluminum angle, maybe from 80/20's eBay site, to make the carriages for each end of the four foot cross shafting. You can mount two linear bearings under each angle to attach to the long axis shafts, or the eight foot ones, and mount two 25 mm rod clamps on the top of the angle to hold the four foot+ shafting. They have these made from aluminum castings, and are available on eBay for CNC builders.

The trick is to keep everything spaced a close as possible, as far as the distance between the linear rods, etc. go. This will give a minimum of deflection in the router plate, because it will be smaller, and in the carriages for the rods.

I think I saw some 3" x 3" aluminum angle on ebay the other day, with 1/4" thick legs, which would be about right for what you need. The rod clamps are available from a few places, mostly from the guys supplying home CNC building components. The clamps use a couple of bolts underneath to hold them, and the top is split, with a through-bolt to tighten it down onto the end of the rods. There's some others made from a block of aluminum, where the top comes off, and splits the rod hole in half, using that to clamp the rod with two screws.

Last, that shafting is very hard, and hard to cut or drill. To cut it, you will most likely have to use an abrasive cutoff to do it, as I doubt a band-saw will handle it, without quickly dulling the blade. To drill it, you may have to take it to a machine shop, as trying to drill it dry on a wood shop drill press may not be advisable. To mount the shafts, we used to grind a flat towards the ends, and use a set screw to hold it. We couldn't mill the flat, it had to be ground, as its just that hard.

I hope this helps, as it can be hard to explain what one envisions.
 

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Discussion Starter · #17 ·
Hello Charlie,

I agree with you but my client insists on solid wood. I agree with you I could veneer a panel myself having him select a grain that suited him. It would be stable, tons cheaper and no body would know. But it's his money so here I go.

-Eloy
 

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Please make a sketch.

Hello!
I'm carrefully reading everything here, and it's difficult.
WillMatney seems to know about it.
Think it could be time for a good litle sketch, just to figure out.
So i could input sizes and forces to my Tech calculator and output values for deflection.Its only a static calculator, but it's a start.
I could start with a wheight around 15kg on long travel.
And then vertical cutting forces my estimation would be to inputa minimum of 30 kg for ridgidity i even think 100Kg would be better.

What could be the distance betwen a bearing pair ? say 1 foot or 10 inches ?
If this travel holder is very ridgid it helps a bit .
As WillMatney said, the shaft would hold better if strongly hold at ends.
Like stuck in a concrete wall It goes for super- strong support.
I can see no need of drilling or grinding shafts, i' ll keep them as they are.
The holder could be two half cylinders with a pair of bolts.
Thats exactly how it is made in a Thermic motor, simple and strong.

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Hello!

Made a quick calculation:

lenght 2.4m
ends ridgid support
Travel is one bearing one point for force
Shaft 25mm steel Youg module: 210 000 MPa elastic limit 250 Mpa.
True steel but not hight grade.

Force: 115kg midle deformation 40 mm
Force 15 kg midle deformation 3.5 mm

Go for better steel:
steel 45 SCD6 young module 220 000Mpa
force 15 kg deformation 2.6 mm

If my calculator works, deflectionn is obsiously too big.


The design works with central ridgid support here with 15kg
deflection is 0.3 mm

Oups ! Been putting all force to one bar, means deflection is to be divided by two with two bars
Or you can think about 15Kg on each makes a 30 Kg total force.


Regards
 

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