Miter slot tight on ends of tablesaw

[Scott Goldthwaite]

I'm trying adjust my Incra Miter 1000 so there's no slop in the t-slot. I've got it adjusted so it's good for most of the length of the t-slot; but apparently my t-slot is a little narrower in the front and back of the saw (Powermatic 66). So the miter gauge binds up at the start and end of a cut. Any suggestions for how to fix my miter slot? I was thinking of taking some wet-dry sandpaper like 320 or 400 grit and trying to hone it or something.

[glenn bradley]

It could be narrow or just have some deviation from the cast iron continuing to cure after being machined. I would mill a strip of wood to fit the starting end of the miter slot well, cut off about a 1" long piece and slide it along the slot front to back. If it stalls at the far end, I would agree that a narrowing is present. If it moves along OK, then there is probably some deviation. Either way you will have to ease the slot. You just want to be sure you are curing the right problem as widening a crooked path can result in a bad feed path. High end miter gauges exist to assure a good feed path and we don't want to botch that up ;-)

As to how to ease it, fortunately cast iron is pretty malleable. Any abrasive that is suitable for working metal should do. I think you are wise to start at a finer grit and work down if you are not getting the result you are after rather than the other way around. If the deviation is severe I would consider taking the top to a machinist so things remain relatively true. JMHO.

[Phil Thien]

I agree w/ Glenn. If you have a decent set of calipers, you could take measurements at several spots and quantify and deviation in width.

[ian maybury]

Guess it'd be no harm to get an accurate straight edge along one side of the slot to check that it is in fact straight - and also aligned correctly.

It'd be advisable to stick self adhesive abrasive paper to a squared slip of wood if working the slot. It's possible that a nice new/sharp single cut fine flat file on edge with the no tooth edge down (the sort that gets used to clean up the edges of a card scraper) - perhaps stuck to a square sided parallel slip of wood with double sided tape might be a useful tool by which to adjust the slot. Especially if it needed a bit more work than was easily done with abrasive paper. It'd have the advanatge of reliably holding it's shape. It'd definitely need to be fine, and be handled gently as it could remove more material than was wanted very quickly...

[Andrew Hughes]

I'd check the bar first it's probably bent.

[Ralph Y Thorne]

I think this is a fairly common problem on the 66. The miter slots are wider towards the blade and narrow at the ends. This is a result of the manufacturing process. I purchased mine around 1999 and didn't notice this until I too bought an Incra gauge. I contacted Powermatic and was told the slots had a tolerance of +.015. I measured the slots and found them to be slightly more than .015 wider in the middle of the table. As Ian suggested I then used a Starrett 36" straight edge and found that on each slot one of the edges was not true. You would think that the tolerance would be for the entire width of the slot not for just a section.

After several calls, Powermatic sent me a second top which was to be checked to be within tolerance before shipping. It had the same bowed slots, but was only .014 out. At this point Powermatic would do no more. I chose to keep the saw and try to repair it.

I used a center punch to expand the metal in the affected areas, much like knurling a piston in an engine rebuild. I then used a file to true the edge. This may have not been the best approach, but it worked.

Several years ago I found a new in the box top here in the classifieds. It was better than the first two but still not perfect. I have not installed the third top yet.

[Frederick Skelly]

I'd check the bar first it's probably bent.

I think Andrew is giving excellent advice here. While it may be the miter slot based on what others are saying above, I'd DEFINITELY check the bar on your Incra first. We can argue why it couldn't/shouldn't be the bar - I sure understand that. But it costs you nothing to rule this out before starting to make slight-but-permanent changes to your tablesaw. And it should take less than a minute to rule out that bar.

Hope it helps.
Fred

[Joe Kaufman]

I found the same situation with a SawStop I purchased last month and the Incra Miter 1000. It was especially tight at the entrance on the left hand side of the blade. I found that it was the right hand side of the slot that was the problem for approximately the first half inch. I used a 4 inch mill file and my finger tips to carefully straighten out the surface. The slot on the rIght hand side of the blade wasn't as bad, but needed a little a little filing.
Joe

[Bryan Cramer]

This has been a helpful thread for me too. My 2 year old Grizzly 1023's left miter slot pinches at the end. I can't properly use the stock miter gauge let alone use my Incra or even jigs with shop made runners. The deviation is very bad. I might try to see if I can get a new top. I am worried that if I start messing with the slots and go too far I essentially wreck the top and then I am screwed.

[Bob Wingard]

You could always easily modify your miter gauge bars by drilling some holes and inserting something like this into one side only ... they will automatically adjust to small dimensional variations, and keep the opposite side of the bar in firm contact with the slot it rides in.

http://www.mcmaster.com/#ball-plungers/=x4et7a

[Scott Goldthwaite]

Thanks for all the info. I'll do a little more checking to see exactly what is going on with my slot.

[Scott Goldthwaite]

I measured the miter slot with my calipers and the center is about 0.004" wider then the ends. I also put a straight edge on my incra miter 1000 bar and it looked good. I think I'll take it apart and put the bar on my granite surface plate just to make sure it's not contributing to the problem.

So it looks like I'll need to open up the ends of the slot a little bit. I'll probably attach some wet-dry sandpaper to a piece of wood and use that for a sanding block. What I don't know is if I should open up both sides of the slot evenly, or just one side. I have a long straight edge so I'm gonna see if I can figure out a little more about the slot's shape.

[Phil Thien]

I measured the miter slot with my calipers and the center is about 0.004" wider then the ends. I also put a straight edge on my incra miter 1000 bar and it looked good. I think I'll take it apart and put the bar on my granite surface plate just to make sure it's not contributing to the problem.

So it looks like I'll need to open up the ends of the slot a little bit. I'll probably attach some wet-dry sandpaper to a piece of wood and use that for a sanding block. What I don't know is if I should open up both sides of the slot evenly, or just one side. I have a long straight edge so I'm gonna see if I can figure out a little more about the slot's shape.

Where does the taper start? That is, the table saw is (probably) 27" front to back, so how far from the front and rear edges does the taper down to .004" begin?

[Brian Tymchak]

I had the same problem on my Ridgid 3650 TS. The last 1.5" of the miter slot narrowed by several thousandths and the miter bar would bind there. I took a small triangular metal file and slowly widened the end of the slot on both sides until the bind was relieved.

[Phil Thien]

I had the same problem on my Ridgid 3650 TS. The last 1.5" of the miter slot narrowed by several thousandths and the miter bar would bind there. I took a small triangular metal file and slowly widened the end of the slot on both sides until the bind was relieved.

Yeah, I think the key is just working slowly and sneaking up on the fit, as you did.

[Jon Nuckles]

My SawStop PCS was straight and true except for the last approximately 1/4" on one side of each miter slot, in mirror positions (that is, on the outside front of the right miter slot and the outside back of the left slot). It was a very small bump in each slot, but enough that my Kreg miter gauge noticed it. After calling SawStop customer service to confirm that they did not have a better fix to suggest, I ran my fine diamond sharpening plate over each area until the high spot was removed.

[Myk Rian]

What I don't know is if I should open up both sides of the slot evenly, or just one side. I have a long straight edge so I'm gonna see if I can figure out a little more about the slot's shape.
Wait until you find out what the straight edge tells you. It could be one side needs attention.

[Scott Goldthwaite]

The miter slot I'm having a problem with is the left one (I haven't checked the right side since I rarely use it). I put a long machinist's straight edge on the slot and found the right side of the miter slot seemed very straight. It's only the left side of the slot that's the culprit. It's about 0.004" narrower on the front and back of the slot. The narrow section is about 3 inches long at both ends.

To open up the narrow sections of the slot I used a fine file and held it square by holding it tightly against a wooden block. Then I used 1/2 x 1/2 x 6" stone. I didn't use the file very much, mostly the stone. I used a gauge block with feeler gauge to judge my progress - it's actually kind of hard to measure the slot accurately with calipers. So now it's good, but not perfect. The miter gauge still has a little resistance on the ends, but it's not bad. Tomorrow I'll go in with a stone an take a touch more off.