Milling a flat straight edge on an aluminum sliding table saw table

[Bobby Robbinett]

So who ever the prior owner of my Griggio sc3200b slider was, they apparently ran the blade or something into the right edge of the sliding table a few times. It made that edge rough on almost half the length of the sliding table.

This is making it difficult for me to set up the sliding table parallel with the saw blade as I can’t very easily get my dial indicator to read perfectly throughout the travel of the table because the edge is so rough. It bounces the tip of the dial indicator and messes up my reading. Tried going really slow and it is worse that going fast.

My solution is to mill a straight edge on the aluminum sliding table on the blade side. I am thinking about using my Bosch Colt trim router with a .25” shank 1/4” straight bit and making a wide base with a fence or guide of sorts to register off the opposite side and slide all the way down the length of the table. It’s aluminum so this should work.

Any thoughts from you guys would be much appreciated.

[Kevin Jenness]

If you have to take much off you might want to build back with JB weld or similar before trimming to the original line. Your plan should work but has the potential for varying from a straight line. I would probably use a straightedge clamped to the table as a guide to insure against divots. I would want the new edge parallel to the table slot.

[Maurice Mcmurry]

I do not have a sliding table but I have used JB weld and a strip of high density Pionite to re create the surface on a standard fence. Could you use the saw its self to do the milling?

[Greg Quenneville]

Your plan sounds good. You could also make something to ride in the slider’s slot. I am planning the same thing on my old Felder combo rebuild project. I aim to re-install the slider closer to the blade to compensate for the 2-3mm of lost material. I am not quite clear on what technique causes the blade to deflect that much into the slider.

[Jim Becker]

Wow...someone must have "done a number" on a blade for that to happen...and i'm with Maurice on this one. Repair the edge with JB Weld and some flat sanding blocks/sticks, maybe aluminum angle with the abrasive on the inside, to make the fixes parallel to the real slider edge. Getting it machined would be a really big row to hoe.

[Patrick Kane]

This happens when a small offcut gets jammed into the throat opening and deflects the blade into the sliding table. Its why a zero clearance is a good idea. Its also why Martin designed their tables to have a replaceable aluminum strip closest to the blade.

Do you have a long straight end you can clamp to the table as a reference? If you get the table .001-.002" over 48", then id call that 'good nuff' and move on to squaring the crosscut fence.

[Bill Dufour]

I agree with Pattrick. Clamp on a good straightedge of something and use that as a reference. The actual edge on the table does not matter.
I assume this is a set once and forget deal that does not require periodic adjustments. At the very least do the clamped edge bit for now and verify no slide ways or bearings need replacing and readjusting before committing to machining the table edge.
Bill D.

[Dan Cameron]

So who ever the prior owner of my Griggio sc3200b slider was, they apparently ran the blade or something into the right edge of the sliding table a few times. It made that edge rough on almost half the length of the sliding table.

This is making it difficult for me to set up the sliding table parallel with the saw blade as I can’t very easily get my dial indicator to read perfectly throughout the travel of the table because the edge is so rough. It bounces the tip of the dial indicator and messes up my reading. Tried going really slow and it is worse that going fast.

My solution is to mill a straight edge on the aluminum sliding table on the blade side. I am thinking about using my Bosch Colt trim router with a .25” shank 1/4” straight bit and making a wide base with a fence or guide of sorts to register off the opposite side and slide all the way down the length of the table. It’s aluminum so this should work.

Any thoughts from you guys would be much appreciated.
Couldn't you just use that other side with some sort of jig to hold the dial indicator?

[Bryan Lisowski]

I know aluminum can be cut with normal woodworking tools, but you may want to use a router with a 1/2” collet.

[Rick Potter]

+1 with Dan. Assuming your table has no slot to measure from, I would try the other side edge of the slider table.

[Wes Grass]

Seems to me you should have the indicator on the slider, and align its travel to the blade.

A perfect edge, not aligned with the linear bearings, will never show as straight with the indicator on the table. And even if perfect, tells you nothing about its alignment to the blade. Which you true up by shifting the table.

[Patrick Kane]

The problem with that, Wes, is he is limited to the travel of the table across a 12-18" blade. .001-.002" across a 12" blade plate means his actual error could be 5-10x worse over an 8-10' stroke. Also, blades arent perfectly flat etc at times so they arent an ideal reference surface. To your point, he could put a 4' machinist straight edge up against the blade and then reference that edge with the indicator base on the sliding table.

Personally, i didnt go nuts over calibrating the parallelism of my sliding table over the entire length. Its very close, and it has zero impact over crosscuts 36-48" wide. My table is only 80", and i havent yet had to marry up two pieces of that length yet where i would discern any error in my cuts. If its really out of whack, then you will chase your tail forever when calibrating the crosscut fence, but practically, i dont think you need it to be exactly dead nuts perfect over 8-10'.

[Kevin Jenness]

I've never cut into a sliding table, but every one I've used had some divots in the edge. My neighbor has one that occurred as a result of the blade getting pinched while crosscutting reaction wood, heating up and deflecting enough to ding the table. The blade was ok to use after cooling down.

I like a continuous edge as I often use it as a reference when lining up cuts, measuring out to the workpiece edge with a 6" rule.

You do want the table travelling parallel to the blade, which may or may not line up with the fixed table edge. If it is out by much it will cause tearout at the back of the blade as the teeth come up through the kerf.

[Patrick Kane]

I've never cut into a sliding table, but every one I've used had some divots in the edge. My neighbor has one that occurred as a result of the blade getting pinched while crosscutting reaction wood, heating up and deflecting enough to ding the table. The blade was ok to use after cooling down.

I like a continuous edge as I often use it as a reference when lining up cuts, measuring out to the workpiece edge with a 6" rule.

You do want the table travelling parallel to the blade, which may or may not line up with the fixed table edge. If it is out by much it will cause tearout at the back of the blade as the teeth come up through the kerf.

Same, and my table is virginal, but ive had a dozen experiences of offcuts getting pulled through the throat plate and exploding against the dust chute under the table. It makes a god awful noise. One of these days ill make a zero clearance insert.

[Rod Sheridan]

Make a wood jig to allow the dial indicator to slide in the table groove, make it snug….Regards, Rod

[Wes Grass]

The problem with that, Wes, is he is limited to the travel of the table across a 12-18" blade. .001-.002" across a 12" blade plate means his actual error could be 5-10x worse over an 8-10' stroke ..... dont think you need it to be exactly dead nuts perfect over 8-10'.

True. And the blade can only touch the wood over whatever length is engaged. So a couple thou', regardless of what the travel is. You set your crosscut fence to that, and parallel guides if you have them.

As a perfect example of the effect, consider a sliding table on a router table. Makes no difference what direction it's pointing if it only engages line contact, vertical, with a round cutter.

On the table saw, you'd get a cove shape to the cut if you ran it at an angle. But it would be straight along the length of travel. Of course, a thru cut would be a problem with the blade getting bound up in there. And that's what you're trying to avoid by aligning the table to the blade.

A dead straight edge on the table will read zero on the indicator no matter what the angle of travel is. You want it referenced to the blade.

An extreme example. Your indicator will tell you that's 'straight'.480669

What you need to do is this:480670

The indicator goes on the sliding table.

More.

Sorry ;-)

This is the opposite of a conventional saw. Conventional, you have to align the blade to the miter gauge slot. Unless you have the ability to put your finger in it and pull it over like Popeye moving a knothole so he could see the construction project ;-)

The sliding saw, in effect, has a moveable 'miter gauge slot'. Both the table and the fence get set off the blade.

[Bobby Robbinett]

Ok I will take these opinions into consideration. I never thought about taking a reading from the opposite side of the sliding table.

I do have a Freud setup and calibration disc that fits my slider (had to be modified by a machine shop) and I suppose that I could theoretically clamp a straight edge to it and place my dial indicator on the sliding table.

.i will give some of these suggestions a try and see how well I can get things lined up. I don’t have a track saw or router guide. I suppose that I could get a straight edge and use the router to flatten the inside edge of the aluminum sliding table. Only thing is that I don’t have a good way to use a point of reference to set my straight edge router guide relative to the travel of the table. I still think my idea of using a trim router with a plywood sub base and a guide or fence mounted on the sub base to follow the opposite side of the table will work best.

[Steve Jenkins]

I’m probably not thinking right but me slider has a slot the full length of the table. There is an adjustment point at each end of the main base to allow for adjustment toward and away from the cast iron top. I put the magnetic indicator base on the cast iron top with the indicator riding on the edge of the slot. Probably clear as mud.

[Wes Grass]

One last try ...

If your goal is to align a straightedge with the axis of travel of the sliding table, then mounting the indicator to the fixed (cast iron) table and running the sliding table back and forth is the correct method. It still tells you nothing about where the blade sits.

Steve: Whether the slot in the table has been machined in alignment to the surfaces for the guide bearings is another question. I never checked my KF-700. My guess is 'probably, maybe'. What I *DO* know is that the underside of the T-slot was not machined to make the shoulders parallel to the top of the table. Not normally a necessary requirement for simple T-nuts used for clamping. I made some custom pieces, and had to shim them to get them level. The main feature being a precision bore with a close fit to an insert I put into the crosscut fence so it repeats 'square'. It actually bound up a little without the shims, as the insert was tilted toward the table, I think, a fair bit.

[Mel Fulks]

Denatured alcohol on Al- U- Minium get rid of gummyness and makes for easier cutting, scraping ,and drilling.

[Bill Dufour]

Slop JB weld on the edge to fill any gashes. Then rip top to width on a tablesaw with an old carbide blade.
Bill D

[Michael Schuch]

Does it look anything like this:
480851

480852

My Casidia saw has some relation to Griggio. I am thinking of adding the shown T track to my saw (it does not have any T track) which would move the aluminum plate over 5/8". To mill a new straight surface on the plate I am planning on clamping the plate to the underlying support brackets and cut a straight edge on the plate half way using a saw blade on the sliding table saw. Then move the plate forwards on the supports, re-clamping then cutting a straight edge on the trailing half of the aluminum plate. From what I have read a wood saw blade should be able to cut an edge on an aluminum plate with no problem. I think this will result in a MUCH straighter edge than a router.

I had also considered using a track saw to cut a new straight edge.

I have used carbide router bits on aluminum previously and they cut the aluminum very well leaving a good finish.

[Michael Schuch]

So who ever the prior owner of my Griggio sc3200b slider was, they apparently ran the blade or something into the right edge of the sliding table a few times. It made that edge rough on almost half the length of the sliding table.

This is making it difficult for me to set up the sliding table parallel with the saw blade as I can’t very easily get my dial indicator to read perfectly throughout the travel of the table because the edge is so rough. It bounces the tip of the dial indicator and messes up my reading. Tried going really slow and it is worse that going fast.

My solution is to mill a straight edge on the aluminum sliding table on the blade side. I am thinking about using my Bosch Colt trim router with a .25” shank 1/4” straight bit and making a wide base with a fence or guide of sorts to register off the opposite side and slide all the way down the length of the table. It’s aluminum so this should work.

Any thoughts from you guys would be much appreciated.

Just curious if you made any progress?

[Bobby Robbinett]

Just curious if you made any progress?

I got it as close as I could. What I ended up using was a set up and calibration disc in place of the blade. I then clamped my 96” Empire level to the back side of the setup and calibration disc and put my T-Track dial indicator in the slot of the sliding table. Then without moving the sliding table itself I slid the t track dial indicator from one end to the other registering on the edge of the 96” level. It’s not nearly as accurate as I would like. But it’s decent.

If I try putting a dial indicator on the sliding table and measuring travel by again referencing off the level that is clamped tight to the back of my setup and calibration disc (thus measuring the travel of the sliding table relative to the blade) then I get readings all over the place as if the table is not tracing straight.

It is what it is. I would love to have a new Felder but right now I can not shell out $10k for a new one. I have, however, considered ordering a Chinese slider that is pretty much a clone of the Grizzly and Cantec style of sliders. I can get one for under $3k and shipping is $875. So that is my plan. Would love to find a deal on a used Felder, SCM, MiniMax, Altendorph, Martin, Cantec, ect.

[Kevin Jenness]

You get what you pay for (usually). There's a Martin T71 listed in the classifieds here for $6k - it's in CT so not exactly convenient but saws like that do come up and in my opinion are a better bet than a no-name Chinese machine. Good luck.

You can measure all you want with a dial indicator, and you may need to use one to make adjustments. Before you do any thing though, does the saw cut a straight line? Cut two 8' rips and put the sawn edges together. If there are gaps between them relating to the indicator variations the table is thrashed and you may as well replace the saw. If not, relegate the level to building stud walls and get a reliable straightedge. If your saw cuts straight enough you won't need to buy one.

[Wes Grass]

If you get a good reading off the level by running the dial indicator down the t-slot, but it jumps and wanders moving the table, it's likely the table bearings are shot. In that case, I'd expect random readings off the t-slot with the indicator on the machine table as well.

What kind of bearings does it have on the table? Integrated linear guides like a Felder, or ordinary ball bearings running on machined rails? If the latter, there may be crud ironed onto the rails making it jump around.

A couple places I worked had Roll-in band saws that would do this on a regular basis. I pretty much had to scrape the rails with a scale every time I was going to use it.