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Sliding Crosscut Table Made From Round Shaft Linear Bearing Assembly

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Project by John Veazey posted 09-26-2018 04:54 PM 4213 views 17 times favorited 10 comments Add to Favorites Watch

I made a pair of round shaft rail assemblies into a great-performing sliding crosscut table for my table saw. The table moves smoothly to provide crosscuts up to 42 inches. The hardened 16-mm steel shafts and the ¾-in. thick MDF table do a good job of keeping the fence steady with the direction of cut. The linear bearings keep the rails clean and there are no areas for saw dust to accumulate and restrict motion. For a panel that extends over the front edge of my saw, I hold it level just like I do when using a rip fence. Since the table is only 10-in. wide, I use a saw stand at the left of the saw for long boards. This paper describes the crosscut table assembly and a separate mounting structure that I used on my saw. A similar mounting structure with different dimensions can be used on many other saws; or you can design your own mounting for the table assembly using other approaches.

The rail assemblies I bought on ebay were 2000 mm (78.74 inches) in length. I had the choice of using the full 2000 mm length for a table that would extend past my outfeed table and provide a 52-in. depth of cut on a ¾”-in panel (Who would need this?) or shorting the rails for a better fit at the rear of my saw but only a 42-in. cut. I choose to shorten the rails. A 4-in. hand grinder with a face mask for protection and a steady hand was used to cut the hardened shafts. The cut doesn’t look too bad, even with all my birthdays!

My saw has some beefy front and rear rails that are used for the fence system. On each of these rails, I extended from the lower edge a piece of T-bar from my “gonna use this someday” collection. The T-bar was from a discarded garage door opener. I used ¼-in. hex head bolts, nuts and lock washers and some wood shims between the fence rails and the T-bars. The front T-bar was attached by threaded holes in the front rails because there was not enough room for nuts. The shims took the T-bars down to a level slightly below what would be needed to mount the crosscut table assembly. 1.5-in. angle iron, which is more common than the T-bar, could have also been used.

The 2×3-in. steel guide tube on my fence system was in the way of the sliding table. I elected to saw 6 inches off of it. By doing this, I give up six inches of fenced space on the left side of the blade. An alternative to the cutting would be to move the guide tube to the right by 6 inches, but its taped-on scale would have to be peeled off and re-positioned. I took the guide tube off the saw and used a metal cutting band saw for a clean cut. I left the tube off until the front T-bar was mounted. Then I drilled the bottom of the tube to clear two of the T-bar mounting bolts.

Here’s the construction sequence I used after deciding on the table length (Dimensions are provided in the “Numbers Section” below):

Table:
Cut the MDF table with edges exactly parallel.
Cut the rail assemblies to equal the length of the table minus the length of the rear stop.
Cut the slots for the fence T-tracks on the top of the table with a router so the top of the tracks will be proud of the table about 1/64 in.
Apply finish to the table, all surfaces. I used shellac.
Mount the rear stop on the rear bottom side of the table with 3 wood screws. (See picture.)

Mount the rail assemblies on the bottom side of the table, centered over the T-track slots on the other side. This is so any screw tip from the T-track installation will not interfere. Note that the rail assemblies must be parallel to each other and to the edges of the table. The rail assemblies mount with two wood screws in manufacturer-drilled holes every 6 inches. Carefully measure, center punch and drill the screw guide holes in the table or position the rail assemblies and use a self-centering drill bit to start the guide holes. Place a stop on your drill bit to prevent drilling completely thru the table.
The T-track on the top and the moving portion of the front stop will be installed later.

Cleat Assembly:
The cleat assembly provides the bearings, the stationary portion of the front stop and has four tee nuts for the assembly attachment to the saw mounting structure. The mounting structure tee-nuts should be positioned close to the bearings to provide maximum stability.

Inspect each bearing and verify that it operates smoothly on the shaft. The bearings support a force against the mounting side. There are two hex adjustment screws on the bearings. Mine seemed okay as delivered. I didn’t mess with the adjustment screws.
Decide where on the cleats you want to place the bearings and determine an approximate location for the mounting structure tee nuts. The bearings should be located so that the mounting screw heads will not interfere with the mounting structure below the cleats. I placed mine on 24.5-in. centers, inside and close to the tee nut mounting points. We will mount the bearings now but the holes for the tee-nuts will be accurately determined and drilled after the corresponding holes have been made in the mounting structure.

Carefully measure the bearing mounting hole pattern and transfer it to an L-shape sheet metal template. Punch small holes in the template and place it against the edge of the cleat to aid in center-punching the 4-hole pattern at each bearing location. Use a drill press to drill the holes in the cleats for the bearing mounting screws. The holes must be perpendicular to cleats and accurately placed. I drilled them oversized so the bearing would self-align on the shafts before the screws were tightened.
Place the bearings on the cleats with the mounting screws loose. With the table upside down on the work bench, carefully slide the bearings with the attached cleats over the shafts. Carefully tighten the bearing mounting screws (See note 2 below.) I noticed that the bearings do not operate smoothly when they are upside down.

Using 4 wood screws, mount the moving portion of the front stop on the front bottom side of the table between the rail assemblies and behind the front bearing. (See picture.)
Position the stationary portion of the front stop on the rail assembly and mark the location of the two mounting screw holes on the stop. Drill the screw holes in the stop piece using the drill press. Now, with a hand drill, use the drilled stop piece as a drilling jig to drill two perpendicular holes in the cleat assembly at the correct position.
Attach the stationary portion of the front stop to the cleats with two 10-24 R.H. screws and tee-nuts. The tee nuts will seat as the screws are tightened. The stationary portion of the front stop is now easily be removed from under the table when it is necessary to remove the table from the saw.

Fence:
Construct a fence with a ¼-in. slot for angle cuts. I used large knobs tapped for ¼-20 bolts. The floor mounting bolts for toilets have heads that fit the standard T-tracks. Use a hack saw and vise to cut the two bolts to length. I used a router table to cut the slot in the fence. Cover the front edge with sandpaper for a non-slip surface. Use contact adhesive to hold it on.

Mounting:
The mounting structure you install on your saw will need to provide four mounting points at saw table height minus the height of the crosscut table assembly. Install it a little bit lower so shim can be added for an exact position. Your structure will need to secure the cleat assembly at the mounting points with ¼-20 hardware. The structure should not interfere with the protruding screws from the bearing mountings. It should not interfere with the screw driver removal of the stationary portion of the front stop when the table is removed from the saw. Ref. 1 contains an example of a style of mounting that does not attach to the saw fence rails.

Install and level the mounting structure without mounting bolt holes.

Set the crosscut table assembly on the mounting and align its table with the saw top and the saw fence. Use a square to position the table parallel to the fence and add shims to place the table in the same plane as the saw top. Identify hole locations for 4 bolts through the mounting structure. Mark the centers for the four required bolt holes in the mounting structure.
Record for later use the thickness of the shim required at each bolt position and remove the assembly.
Drill 4 oversized holes in the mounting structure at the marked centers. I used a 5/16-in. bit.
Set the assembly back on the mounting structure and align the table with the saw fence but don’t install shim.
Using a 5/16-in. transfer punch, tap through the mounting holes and into the cleat assembly to mark the centers.
Remove the assembly.
Remove the table from the assembly and drill four 5/16-in. holes at the marked location using a drill press.
Drive four ¼-20 tee nuts into the holes from the top side of the cleats.
Reassemble the table and set it back on the mounting structure.
Using the recorded shim amounts, prepare shim with holes to slip over the mounting bolts between the table assembly and the mounting structure.
I used a leather punch to cut the ¼-in. holes.
I used ¼-20×2 in. socket head bolts to mount the table assembly to the mounting structure.
The socket head screws accept a 3/16-in. T-handle hex wrench and the heads have no flats to catch on the T-bar.
Install/remove shim to place the table top in the same plane as the saw top and align the table edge with the saw fence.
“Snug” the mounting bolts.
Verify the table alignment by using a square to confirm the same perpendicular distance of a point on the table to each end of the fence. Tighten the four mounting bolts.
On the top of the table, install the T-track with wood screws using a centering bit to drill the holes.
You are done. Enjoy!

Lubrication:
The SBR16-2000 mm rail assemblies did not come with documentation. On the web I located a catalog for PBC Linear bearings & shafting products. In a lubrication section it recommended “3-in-1” type oils and spoke against using most other popular lubricants. See Ref. 2 below.

The Numbers:

Table
3/4X10X72-in. MDF. The table length should be 2 inches longer than the rail assemblies.
Slots for fence T-tracks: 3/4X23/64X25-in. on 6 ¼-in. centers centered on the table
Two round shaft rail assemblies SBR16-2000mm cut to 70 in. mounted on 6 ¼-in. centers centered on the table
48 #8X3/4-in. F.H. wood screws to mount rail shafts. See note 5.
Rear Stop: 3/4X2X10 in. soft wood block attached to table with three #6X1 1/4 wood screws
Front Stop (moving portion): 3/4X2X4-in. soft wood block attached to table with four #6X1 1/4 wood screws
Two 3/8X3/4X24-in. T-tracks available from woodworker’s supply stores.
12 #6X3/8-in. F.H. screws to mount T-tracks

Cleat Assembly:
Two 7/8X2½X46-in. hardwood (my installation would also work with cleats 32-in. long) See Note 3.
Four ¼-20 tee-nuts, 2 in each cleat on 29-in. centers (my installation).
Four linear bearings (they were packaged with the rail assemblies) mounted on 24 ½-in. centers (use spacing appropriate for your mounting structure.
Sixteen M5X0.8X30mm hex-head screws with flat washers (they are installed with an 8-mm wrench) See Note 1. below on installation caution.
Front Stop (stationary piece) ¾ X1 ½X5 ¼ soft wood with 3/4X1 1/2X1 ½ block glued on top.
Two 10-24 tee nuts to press in front stop.
Two 10-24X2-in. R.H. screws with flat washers to mount front stop.

Fence:
1×2 ½ x 30-in Baltic birch, ¼-in. slot, 7-in. long. (See Note 4)
Two 2-in. plastic knobs with ¼-20 threaded inserts.
Two 1 ½-in. T-track bolts.
Sandpaper for front of fence (not too fine – not too coarse)
Contact cement to stick sandpaper on fence.

Mounting (My saw):
Rear Support: 20-in. T-bar cut from an old garage door opener to mount to rear fence rail.
Shim: 3/4X2X10-in. soft wood between T-bar and rear fence rail.
Four ¼-20 hex head bolts with lock washers and nuts for rear T-bar attachment.
Front Support: 18-in. T-bar
Shim: 3/4X2X8.5-in. softwood between T-bar and fence rail.
Four ¼-20 X2-in. hex bolts with with lock washers for front T-bar attachment (tapped holes)

Performance
The 3/4-in. MDF with the two attached round shaft rail assemblies was measured to be very stable in the lateral direction. I set up a dial indicator to the edge of the fully-extended table and pulled using a fish scale in the horizontal direction. My thought was that movement in this direction could disturb the direction of cut. Here’s what I measured: 5# .010”, 10# .022”, 15# .040”.

I clamped a drywall square to the fence with the table fully extended and set up a dial indicator at the cutting edge of the blade. With my brides help, I measured 5# .001”, 10# .005”, 15# .008”. This seems very good to me, but the “proof will be in the cutting.”

This table certainly won’t support much weight in the vertical direction when extended. You can’t set on it as shown by the builder of one made from extruded aluminum. For a heavy panel, you will need to use a stand or support the weight with your body. When you push a panel along the fence for a rip cut, you must view the fence and direct the force to keep the panel edge against the fence. Using the cross cut fence, you don’t have that distant alignment problem, you just keep the work tight against the crosscut fence in your hands as you push.

I’m getting the material together for the next project. I’ll use it for some useful cuts.

Notes:
  1. The linear bearings came tapped for M5X0.8 screws. Check each hole for proper thread length. The aluminum threads are easily damaged if the screw is started crooked or is forced in too far. Use over-sized holes in the cleats so the bearings will adjust to the shafts before tightening. Use template and a drill press to ensure accurate holes. 30 mm screws with a flat washer provided about 7 mm of thread insertion in my installation with cleats that were .87 thick. If you use 3/4-in. hardwood for your cleats, 25 mm screws would be a better length. Another option is to use your mounting template and make ¼-in. thick spacers so you can use the longer metric screws if the 25 mm screws are not available.
  2. Aligning the table with the saw’s fence assumes that the fence was previously aligned with the blade. Check your saw user’s manual for fence alignment procedures.
  3. The hardwood cleats can also be made from 3/4-in. stock. I used what I had. The cleats will work for me at 32 in. but I made them longer for the possible installation of a latch.
  4. The fence offers an opportunity for a lot of variations, depending on your imagination. The 1-in. Baltic birch was in my scrap bin already cut.
  5. #8X3/4 worked on my rails. Check screw and go to 5/8 length if the screw tips will punch through the table.

References:
1. Woodsmithplans.com, Sliding Saw Table, 2016 August Home Publishing Co.
2. pbclinear.com, Round-Shaft-Technology-Catalog.pdf, Types & Effects of Lubrication, page 130.

Changes:
9/29/18 Added 3 pictures and section on Performance.
9/30/18 Rail mounting screws changed from #6 to #8. Added note 5.
10/6/18 2nd par. now 42-in. cut not 43.

-- John Veazey





10 comments so far

View fivecodys's profile

fivecodys

1228 posts in 1840 days


#1 posted 09-26-2018 05:40 PM

This is really interesting and very well done.
I hope that you will report back after using it for a while.
Thanks for sharing.

-- I always knew I would grow old, But I expected it to take longer!

View John Veazey's profile

John Veazey

8 posts in 85 days


#2 posted 09-26-2018 06:27 PM

Thanks. I’m getting ready to make a flip-flop tool stand similar to the one you made. Will probably use the new sliding table on some of the cuts. Maybe I’ll build a new bench. The cast iron top on my table saw was a great assembly spot for glue joints, but I can’t do that any more with the sliding table there.

-- John Veazey

View therealSteveN's profile

therealSteveN

1721 posts in 778 days


#3 posted 09-27-2018 12:13 AM

Looks like a lot of planning, work, and energy. If it delivers a smooth rolling, and SQUARE cut, it’s time well spent. I am thinking like fivecodys, report back to let us know if it continues being smooth, cause the test of time is important on items like this. I would think the attachment point of the table works to the saw itself, rather than just the table will be the part you could see issue with. Movement of anything can cause issues with alignment, loosened parts, and shifting. All of those will prove to be deal breakers.

I’m hoping it stays smooth, and does cut dead square. Thanks for posting.

-- Think safe, be safe

View John Veazey's profile

John Veazey

8 posts in 85 days


#4 posted 09-27-2018 12:23 AM

Thanks for passing along your thoughts. I’m looking for an old door to trim with it.

-- John Veazey

View Sta2lt's profile

Sta2lt

5 posts in 1892 days


#5 posted 09-27-2018 01:28 AM

Nicely done.

View Redoak49's profile

Redoak49

3670 posts in 2192 days


#6 posted 09-27-2018 10:55 AM

Well designed and nicely done.

View AJ1104's profile

AJ1104

609 posts in 1863 days


#7 posted 09-28-2018 02:32 AM

Wow. Tremendous effort and engineering. Well done.

-- AJ

View BburgBoy's profile

BburgBoy

40 posts in 706 days


#8 posted 09-30-2018 10:05 PM

thanks much for the ingenious design and for sharing all your detailed instructions. This clearly must win an award for the longest post ever on the LJ website…

-- Larry, SW Virginia

View John Veazey's profile

John Veazey

8 posts in 85 days


#9 posted 09-30-2018 10:38 PM

Well thanks (I guess). That’s not the award I want. I’m new to the forum and probably should have sampled the typical level of detail a little better.

-- John Veazey

View Mas's profile

Mas

70 posts in 2466 days


#10 posted 10-04-2018 02:43 AM

That looks like an excellent addition to your table saw.

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