# Router table surface options



## Analias (Oct 15, 2013)

I have a CRP-4848 CNC router table that I built a couple of years ago.  The table has performed well, but the one rough spot in the build was surfacing the table.  I know that most folks just bolt down a 3/4" piece of plywood or MDF, then simply fix their work to the table surface using wood screws.  This works fine for wood and where you are not too concerned with repeatability, but I would like more options.  I would like to handle aluminum and plastic.  I want to be able align the work parallel to the X and Y axis with some accuracy.  I want the option of using clamps.  The table size I'm trying to address is 57" x 54".

Most options I have looked at come at a substantial cost.  A 5/8" cold rolled steel sheet can be had for $560 and I could drill and tap a hole pattern for tools and clamps.  This is the most flexible for me, but the router would have to drill the holes - a problem since I have a 2.5Kw Chinese water cooled spindle with a minimum speed of 4K.  T-Slots would work, but they are priced in the same range if spaced 2" apart and 60" long.  I would love to have a aluminum surface with t-slots, but that's at the $1300 range.

As a short term option I created a 24"x24" tooling plate made out of 3/4" plywood and steel 1/4-20 steel wood anchors.  it's anchored to to the table using a couple 3/8" steel dowels. This has worked fine until the 1/4-20 hex socket bolts I'm using want to get cross threaded and get stuck.  Removing the munged anchor and bolt usually means destroying the anchor and the hole housing the anchor is shredded some.  I'd like a larger, more robust, permanent solution.

I guess I'm looking for some options that don't cost an arm and a leg.  The table is sitting idle until I can come up with a solution that doesn't cause frustration.  I would welcome any ideas that folks have.

I have some 50mm x 50mm extruded aluminum t-slot stock (think 80-20 stuff).  I could rip it in half if I could come up with a reliable way to do that.  I have 9 pieces at 75" each, 18 pieces total after ripping.  That's enough to cover the 54" x 57" surface by spacing the rails every 3" with a 1" wood spacer between them.  Ripping and mounting the rails would be challenge.  I would appreciate any ideas if this is even possible.  The image below is the profile of the extruded aluminum stock.






Here's what I'm trying to surface.


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## Codered741 (Oct 15, 2013)

A cool idea for clamping that i considered when i built a CNC router in Grad school, was to use an MDF/plywood buildup to create t-slots.  We ended up using a vacuum system instead, but it was very simple, and easy to build /replace.  

The idea is to cut up 3/4 or 1/2" material into strips, 3-4" wide (the width can be larger if desired).  Cut two sets of strips, say one at 3" and another at 4" wide.  Place the 3" strips about 1" apart, and lay the 4" strip centered on top, to make a T. Viola, MDF t-slots!  The idea was to use glue, no fasteners, so that you never have a problem cutting through, and can surface cut the entire area without worry.  When the top board gets too thin, surface it all off of the base strips, and lay down new top strips.  

You can make your own t-nuts with 1", or slightly under, wide strips of MDF with an insert in the middle, or tap a hole in a piece of aluminum.  

Its a pretty versatile system, and really cheap and easy to use.  

-Cody


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## DMS (Oct 15, 2013)

We'll here's my $0.02.

* MDF top, either just bare, or covered with melamine
* Drill holes with your router to form a grid 2" on center as you suggest, then drive threaded inserts such as these http://www.mcmaster.com/#92105a002/=oy9b2t. They are about $13 per hundred. If you do them every 2 inches, that could be quite expensive. If you get creative with spacing (some areas with higher hole density, some with lower) you could probably bring the total cost down lower to a more reasonable level. If you really need higher density, you could have a tooling plate that mates with this hole pattern.


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## bkcorwin (Oct 15, 2013)

My router table is similar to  as described by code red.  I took a sheet of 3/4 mdf, ripped it into 4" strips, then attached them to my substrate with 

http://www.ebay.com/itm/8020-T-Slot...701?pt=LH_DefaultDomain_0&hash=item5633441a7d

laying in between.  Then I just use the standard 8020 1/4-20 t nuts and 1/4-20 cap screws to hold down work.  

Also, with MDF you can surface the table to eliminate any warpage by cutting the table true to the axis plane.  Not sure how you would deal with this with a solid metal top?  I doubt it would come dead true unless you somehow got a giant blanchard ground piece of steel?


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## Analias (Oct 16, 2013)

DMS said:


> We'll here's my $0.02.
> 
> * MDF top, either just bare, or covered with melamine
> * Drill holes with your router to form a grid 2" on center as you suggest, then drive threaded inserts such as these http://www.mcmaster.com/#92105a002/=oy9b2t. They are about $13 per hundred. If you do them every 2 inches, that could be quite expensive. If you get creative with spacing (some areas with higher hole density, some with lower) you could probably bring the total cost down lower to a more reasonable level. If you really need higher density, you could have a tooling plate that mates with this hole pattern.



Wow, I really like this idea. The 1/4-20 are the cheapest. I am curious how well the flanged hex driven inserts stay in the wood? I know it's more expensive, but I am tempted to consider the steel high-strength hex drive 3/8-16 inserts. I could then standardize on the same hardware I have on my X3 mill. The only real problem is the insert length, they are 1 3/16" meaning I would have to double up bed material and give up a bit of Z axis. Any thoughts on using 3/8-16 over 1/4-20?

http://www.mcmaster.com/#90192A132


Sent from my Xoom using Tapatalk 4


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## Analias (Oct 16, 2013)

Ouch! That's 2256 inserts using a 48x47 checker board pattern. I better shop around for bulk pricing. 

I might also want to fab a tool to help insert them straight. I was thinking a simple block drilled for the outside diameter of the insert to keep it perpendicular to the table surface. If the  outside diameter of the threads for the flanged inserts is smaller than the flange I may have to do something closer to tapping stand to hold the hex driver and insert perpendicular.


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## Maxx (Oct 16, 2013)

Analias said:


> Ouch! That's 2256 inserts using a 48x47 checker board pattern. I better shop around for bulk pricing.



What spacing? 2256 would be a tight pattern.
I'm too tired to do the math.

Edit: never mind, I got it


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## Analias (Oct 16, 2013)

Maxx said:


> What spacing? 2256 would be a tight pattern.
> I'm too tired to do the math.
> 
> Edit: never mind, I got it



Actually you're right. It's too many. The count would be 1152 for 1" spacing on a 48x48 table for a staggered pattern. It is too late for doing math. 

Sent from my Xoom using Tapatalk 4


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## bloomingtonmike (Oct 16, 2013)

I glued screwed 2 pieces of 3/4" MDF and fender washer and screwed from underneath through the unistrut table bed. Then I surfaced that second layer with the router and used the router to cut 1/6" deep channels to layout 8020 T Track. I then used 3" long thin (4mm maybe?) flat head screws, drill and countersunk the T track (8020 does not come with holes), and screwd it down using fender washers underneath - no way it is lifting and screws still slide along the T Track. Between the 8020 T Track I then layed plain 3/4" (3rd layer) MDF strips down  and used nylon bolts that were counter sunk - no glue and no danger of bits getting ruined. This 3rd layer sits above the t-track. Then in one spot I cut a grid for a vac table in one section and drill through all three sheets for the 2" PVC for the vac clamp. 

A hint in all this is to draw it all, including table web, in cad or vcarve so you know where the unistrut/base is and you leave room for washers and nuts. 

Also since the 2nd layer is the surfaced layer you can easily change out the 3rd nylon bolted on layers out.


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## astjp2 (Oct 16, 2013)

Why not use the rounter to build yourself a vacuum table from plate aluminum?  cut the slots on the bottom and top, mount a big vacuum pump to the bottom side. suck down some mdf and let it hold down your material with a board that is sacrificial?  Tim

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astjp2 said:


> Why not use the rounter to build yourself a vacuum table from plate aluminum? cut the slots on the bottom and top, mount a big vacuum pump to the bottom side. suck down some mdf and let it hold down your material with a board that is sacrificial? Tim



Another method is to use double sided sticky tape and tape down the material to a plastic sacrifical plastic board.  We built lots of parts that way at work.  Tim


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## DMS (Oct 16, 2013)

3/8" fasteners seem like waaay overkill. If you got anywhere near close to the fastener strength you would tear out. I was actually thinking about the 8-32 size, total length is a little over 3/8". You should not have much "up" force. I am imagining you are mostly doing sheet goods? Seems better to have more smaller fasteners than fewer larger ones.

I'm thinking that even with the zinc based inserts, if they wear out, or you cut into some, you can just pull them out and replace.


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## Analias (Oct 17, 2013)

DMS your probably right, I'll go with the 1/4-20 flanged inserts.  They come in 100 qty so they are the best deal.  Most manufactured tool holding for wood working is 1/4-20.

I took time to measure and draw up the a mock up of my CNC-4848 table, at least the parts that matter for this project.  If I go all out with a 1" staggered hole pattern It comes to 1387 inserts.  The price is not too crazy for such a dense hole pattern.  I had to take particular care to deal with the holes that have framing under them.  I shifted the pattern to align the holes with the slot in the 8020 1530 extrusion.  I'll sacrifice 16 holes for mounting the bed to the frame.  The rest should be available for work holding.  I have a bit of space on the left and right, I'm tempted to install a couple 8020 1575 t-slot to provide clamping for full 48"x48" stock.

Here's a couple of pics of the mock ups.


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## Analias (Oct 19, 2013)

If anyone is interested, I found a decent price for 1/4-20 threaded inserts in 1000 count for $112 for the flanged version and $102 without the flange.

http://www.drillspot.com/products/603679/approved_vendor_4kxu4_flanged_hex_drive_threaded_insert

http://www.drillspot.com/products/604039/approved_vendor_4kxr8_flush_hex_drive_threaded_insert


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## DMS (Oct 20, 2013)

Not a bad deal for that many of anything .
Your wrists are going to be sore installing all of those


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## Maxx (Oct 20, 2013)

Analias said:


> If anyone is interested, I found a decent price for 1/4-20 threaded inserts in 1000 count for $112 for the flanged version and $102 without the flange.
> 
> http://www.drillspot.com/products/603679/approved_vendor_4kxu4_flanged_hex_drive_threaded_insert
> 
> http://www.drillspot.com/products/604039/approved_vendor_4kxr8_flush_hex_drive_threaded_insert


Way cheaper here.
http://www.zorotools.com/g/Flush Hex Drive Threaded Inserts/00105676/


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## cjsamples (Nov 3, 2013)

Misumi has some flat extrusion that might offer some ideas.
http://us1.misumi-ec.com/us/ItemDetail/10302261820.html

250mm flat would cover almost 10 inches across. Price for a 3000mm piece is $180 so might only need 2 sticks @118 inches and a shorter to make up the last stick.

Chris

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Techno-Isel has some interesting profiles available too. I have yet to get a price on this table plate, but it might be worth checking on. Looks like their pricing server is down at the moment.
http://www.techno-isel.com/lmc/Products/TablePlates20375T1.htm

Chris


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