Can't get mitre's right... need a new TS?

[Justin Florentine]

Sight it using a light and anything flat like the edge of a chisel or the but end of your steel rule.

With a little practice you can tell between .005" and .001" just judging from the light that gets under the edge.

So I did the chisel/light test, and it's way off. The mounting surface of the trunnion is irregular, I'm not sure by how much, but it's pretty clear. The surfaces of the mounting lugs in the deck are also mighty irregular, but they are also (partially) covered with paint. I suppose I could sand those down with steel wool, but I'm concerned that I would just be introducing new irregularities at a different depth.

I'd also be willing to take both the deck and the trunnions to a machine shop and have the mounting surfaces ground down, but I'm not sure how they'd get everything down to the same heights...

Can that be done, or am I out of options?

Thanks for all the help everyone, I feel a little better at least knowing what the (or at least this) problem is.

[Phil Thien]

I'd also be willing to take both the deck and the trunnions to a machine shop and have the mounting surfaces ground down, but I'm not sure how they'd get everything down to the same heights...

Can that be done, or am I out of options?

Well, anything can be done at a cost. I'd check the bottom of the table with a straight-edge (the blade from a Starrett comb. square is a great straight edge). And I'd check the trunion, too.

Now, if the table is good and the trunion is off, you can lap it using a large (18") tile covered with sandpaper. Don't laugh! You'd be amazed how fast you can cut cast iron with sandpaper, and how flat you can get it using a tile.

If the table isn't flat, then I kinda suspect a new table saw is in your immediate future.

[Justin Florentine]

So this evening, I broke down the entire saw, and spent about an hour's worth of elbow grease with some steel wool on the mounting surfaces. I cleaned off all the rust and most of the paint. I locked down one of the front trunnion bolts, and left the other 3 hand tight. I only installed PALS on the rear trunnion because I can't get to them in the front anyway.

The trunnion holes are oversized all the way around the post holes, allowing the trunnion to be adjusted forward and backward the same amount it is adjustable side to side. I have no idea how this design was intended to work, but it seems that there is a good amount of play towards and away from the arbor. So much that when it's broken down and I wiggle the works, I can see the trunnion rail slide in and out of the trunnion. I suspect that this is causing some of the problem here. If anyone has experience with these old Rockwell saws, I appreciate knowing if this is a known issue.

So now my front trunnion is locked down, and I'm out of play by about .040 when I crank it all the way to the right. I assume this means I'll need to adjust the front trunnion over more to give me more slack to adjust from the rear. I'll take one more crack at it tomorrow night before declaring "good enough" and moving on to make a mitre fixture sled.

Any idea what the tolerance is in a situation like this? Am I gonna frustrate myself trying to get a descent 45 mitre if I can't get the runnout under .010?

[Wayne Cannon]

In addition to the miter sled suggestions, use a sandpaper face on the fence surface (miter gauge or sled) and/or clamp your work to the fence. Otherwise, the work will frequently slip slightly while cutting at the miter angle -- enough to mess up an otherwise good miter joint.

[Howard Acheson]

Inaccurate miters is almost always an issue with the miter gauge.

Either the miter gauge is not set to exactly 45 degrees or the board is sliding along the face of the miter gauge as you make the cut.

First, deal with the slippage. Using a spray adhesive or double faced tape, apply 120 grit sandpaper to the face of the miter gauge. This will stop the slippage.

Next, are you sure your blade is set exactly (within 0.003" or less) parallel to the miter slot? If not, adjust the position of the trunnion until you get it right.

Now, put a 45 degree drafting triange against the blade plate and against the miter gauge face and set it to 45 degrees.

To make and accurate picture frame you must start with a two pairs of boards of exactly the same width and each pair must be exactly the same length. You should be cutting the boards to length as you cut the miter. Use a stop block on your miter gauge. Fit the pieces together and if they don't fit, slightly adjust the miter gauge angle to correct.

Finally, for picture frames it is much preferred that you use a crosscut sled so you don't have to adjust your miter gauge. Cuts are much more accurate and repeatable.

[Justin Florentine]

Inaccurate miters is almost always an issue with the miter gauge.

Either the miter gauge is not set to exactly 45 degrees or the board is sliding along the face of the miter gauge as you make the cut.

First, deal with the slippage. Using a spray adhesive or double faced tape, apply 120 grit sandpaper to the face of the miter gauge. This will stop the slippage.

Yes, I'll be attempting this first before I build a sled. Right now I'm still recovering from the 3 hours spent trying to get the motor pulley off the motor. It was cracked, warped, egged, and fused right onto that axle. A nice machined aluminum one is waiting to be applied once I clean off that axle.

Next, are you sure your blade is set exactly (within 0.003" or less) parallel to the miter slot? If not, adjust the position of the trunnion until you get it right.

That's a good one. Alignment of this table/blade has been an ongoing ordeal, and the best I have been able to get it is .015", and I constantly debate if that makes this a lost cause. I have a couple of new theories as to why this may be, and I'm hoping that putting new pulleys on further up their respective axle/arbor will keep this from falling back out of alignment so quickly.

Now, put a 45 degree drafting triange against the blade plate and against the miter gauge face and set it to 45 degrees.

To make and accurate picture frame you must start with a two pairs of boards of exactly the same width and each pair must be exactly the same length. You should be cutting the boards to length as you cut the miter. Use a stop block on your miter gauge. Fit the pieces together and if they don't fit, slightly adjust the miter gauge angle to correct.

Finally, for picture frames it is much preferred that you use a crosscut sled so you don't have to adjust your miter gauge. Cuts are much more accurate and repeatable.

[Bruce Wrenn]

Justin, I have rebuilt the same saw. I had to use two 24" clamps to clamp front trunion to rear trunion, before tightening down any of the bolts. This way, whole assembly moves as a unit. Wear in the curved grooves will allow for the parts to drop down. I had enlarge the bolt holes also. Do build a sled, or spring for a Dubby.

[Ed Gerken]

This thread inspired me to take another crack at aligning my Montgomery Ward TS. I inherited it from my dad, that alone makes it a keeper. It's old and underpowered but I've used it for 20 years, I'm used to it and it makes a good cut.

Last time I tried aligning it with the saw upsidedown so I could see what was going on. When I was done and righted it, the alignment hadn't improved at all.

This time, I loosened just one bolt and gave the works a nudge in the direction it needed to go. Success! The other bolts let it move without it slipping back, unlike when I'd tried it with all the bolts slackened.

Have you checked to see if the blade is warped or the arbor or washers bent? If you check alignment against the blade, then remove the blade to adjust and reassemble with the blade and washers in a different, random rotation, you might be measuring blade problems instead of trunnion.

If that's all square and true, perhaps you can align with the blade mounted and clamped to the fence with a board inbetween fence and blade. It may help hold things in position till you can evenly tighten the trunnion.

Try some brass shim stock on the trunnion mounting surfaces. Might take up some slack and give a better surface to adjust and tighten against.

I use a CMS for miters, but I like the idea of the sled shown earlier in the thread.

-Ed

[Justin Florentine]

Justin, I have rebuilt the same saw. I had to use two 24" clamps to clamp front trunion to rear trunion, before tightening down any of the bolts. This way, whole assembly moves as a unit. Wear in the curved grooves will allow for the parts to drop down. I had enlarge the bolt holes also. Do build a sled, or spring for a Dubby.

Positively inspired Bruce. I'm totally going to do that.

I think a lot of the problems I was having when cutting mitres were due to both technique and some insane vibration. I now have cleaned both the motor axle and the arbor and refitted with machined pulleys. I also built a mini torsion box on the cheap and am using that as a platform for the stand since my floor is not level at all (like 1/4" per foot in a lot of places). The blade is reading off by .020", but I seem to be able to get somewhat reliable mitres. I cut a bunch on the right side of the saw using a new gague + sandpaper and saw only a 1/32" of drift over about 26" once assembled into a frame.

I'm about to call that good enough, but I will try clamping the trunions together during adjustment. Thanks everyone for the advice, someday I'll get this thing sandblasted and will post pix after a proper paint job.

...the moral of the story, is that when you find a "deal" on a big old piece of iron on craigslist, noticing that it's been stored year round in a barn should probably be a deal breaker.