Main Table Alignment to the Blade

[keakap]

...
When we are talking .003" a .001" change which only requires nothing more than a bump of sawdust on lock wedge throws the alignment off by 1/3.
....

Ed, I see one problem with your proposal for Dusty.
Dusty.

We've seen the pictures of his shop area and the equipment. His testing as you suggest will probably not show results that you'd expect. With Dusty, there is no "bump of sawdust"!

:-)

[keakap]

... to start with the best alignment you can get in order to avoid problems and the need to frequently realign.

...
And if you have one of those Shopsmiths that some members report having that loses another few thousandths of alignment every time they look cross-eyed at it, the importance of starting with excellent alignment would seem obvious to me.
... I break mine out only when I've got a result (burning/pinching/cutting on the back side of the blade) that suggests...

So I've been reading all this and realized it is with a different mood than usually afflicts me when considering this topic. I'm not on the edge of anger this time. Why, says I. I go back to the last major table alignment I did, and now I remember. (Btw, 520, 4 large trunnion holes.)
I went in to fix it, not to try and make it acceptable. Started by loosening all, and shifting to enable access to that one semi-blocked rail nut. Lost a little "slop" but there's enough left.
[I had already removed everything, smoothed down all the contact points (they were not good) including washers and added a layer of (hold onto something!) grease to the contact surfaces only, reassembled.]

So, all four light-finger-tight, then the standard procedure, snug the pivot, yada yada, and checking align with every breath. Any move was made in both directions until it settled. Snugged, then tightened, then tightened, checking with every move.

I'd been "sneaking up on" each bolt- a little tap, then a little more, etc., in the same direction til I hit 'zero'. The tighten a bit and watch it go back bad. This time I tightened a bit then beat on that dang table until it did NOT move.

Haven't touched it since.

Smoothing those pieces and adding the grease made it work. It aint smooth, but it's workable.

Btw, has anyone, in the history of the earth, ever come upon a worse mechanical incompatibility than the bolts SS uses with their various castings?

(Disclaimer: yes, I did exaggerate for effect.)

[JPG]

IMHO a flat washer ALWAYS should be between a screw head and the mating surface(especially for those used for adjusting/alignment) and more so with differing material surface properties(hard/soft). A splitring lock washer is an acceptable exception when locking is numero uno.

[Ed in Tampa]

Ed, I see one problem with your proposal for Dusty.
Dusty.

We've seen the pictures of his shop area and the equipment. His testing as you suggest will probably not show results that you'd expect. With Dusty, there is no "bump of sawdust"!

:-)

The point I was trying to make wasn't to challenge Dusty or his opinion. But to offer my opinion that because of so many variables, so may potential places for slight variations and the fact the SS is movable thus commonly exposed to differing forces and stresses that worrying about .001" really isn't needed.

I have proven to myself that I can make up to nearly .020" difference in the parallelism of my table simply by pushing on it without effecting the quality of the cut.

[dcottrill]

I have 3 SS. The one that I purchased new back in 88 has a table that I can't get it to any better than 0.015". It takes me over 2 hours to get it down to 0.015". The other two tables I can get to 0.005" or better with in about 30 minutes using the method that Nick demonstrated in a saw dust session on line. I've always had problems with the SS I bought new. It has been a point of frustration ever since I purchased it.

I spent 3 hours on it yesterday and there is not enough freedom of movement in the trunnion holes that attach the them to the table to be able to adjust the table.

A jig would be very nice, especially if it holds the table stable when tighten up the bolts.

[JPG]

I have 3 SS. The one that I purchased new back in 88 has a table that I can't get it to any better than 0.015". It takes me over 2 hours to get it down to 0.015". The other two tables I can get to 0.005" or better with in about 30 minutes using the method that Nick demonstrated in a saw dust session on line. I've always had problems with the SS I bought new. It has been a point of frustration ever since I purchased it.

I spent 3 hours on it yesterday and there is not enough freedom of movement in the trunnion holes that attach the them to the table to be able to adjust the table.

A jig would be very nice, especially if it holds the table stable when tighten up the bolts.

Have you checked the rear trunion mounting hole size?

[dusty]

I have 3 SS. The one that I purchased new back in 88 has a table that I can't get it to any better than 0.015". It takes me over 2 hours to get it down to 0.015". The other two tables I can get to 0.005" or better with in about 30 minutes using the method that Nick demonstrated in a saw dust session on line. I've always had problems with the SS I bought new. It has been a point of frustration ever since I purchased it.

I spent 3 hours on it yesterday and there is not enough freedom of movement in the trunnion holes that attach the them to the table to be able to adjust the table.

A jig would be very nice, especially if it holds the table stable when tighten up the bolts.

I would suggest, as an experiment, that you remove one of the rear trunnion bolts and with it removed perform an alignment. If you can get closer that the previous best (.015"), then it would be my recommendation that you drill out that one hole. Theoretically, you would not be able to reinstall the removed trunnion bolt because the holes will not align.

Does anyone know that actual dimension of an original trunnion bolt hole. For my calculations, I have been assuming that it is 3/8" while a trunnion bolt measures .370". This would allow only .005" of table movement. That does not seem right to me.

[billmayo]

Please do not take this too seriously. I had to switch to a steel Total Shop main table for my drilling/tapping/milling Shopsmith. The aluminum table would just deflect too much when doing milling operations. The miter gauge slots are different (narrower) than the Shopsmith so I have front side of the table cut off at the first miter bar slot and machined the back miter bar slot for the Shopsmith miter gauge. I did not need the front part of the table for any of the operations I was doing and it was in the way for having clamps and jibs attached to the table. This table does not flex. I use short 2X4s under this table to the table top for the more precision operatons and only move the headstock with a bottle jack for adjustments.

I still have two Total Shop steel main tables, each with a front table extension. These are very heavy tables and the miter bar slot is narrower than the Shopsmith. If anyone is in my area, I will be happy to donate you one of these as they will make my scrap pile some day. Shipping would be expensive. The table trunnion bolt layout is the same as the Shopsmith.

[JPG]

I would suggest, as an experiment, that you remove one of the rear trunnion bolts and with it removed perform an alignment. If you can get closer that the previous best (.015"), then it would be my recommendation that you drill out that one hole. Theoretically, you would not be able to reinstall the removed trunnion bolt because the holes will not align.

Does anyone know that actual dimension of an original trunnion bolt hole. For my calculations, I have been assuming that it is 3/8" while a trunnion bolt measures .370". This would allow only .005" of table movement. That does not seem right to me.

Seek here and ye shall find the answer!:D

I'd give a higher karma rating to both you and Ed.

[dusty]

Since none of you jumped in here to help, I was forced to dismantle a table to see for myself. The holes on a set of old trunnions are in fact 3/8" (rear trunnion) and 1/2" (front trunnion).

The front trunnion moves freely approximately 3/16" while the rear trunnion (with the smaller hole) moves freely about 1/32".

BTW - News Flash: Movement of the rear trunnion IS RESTRICTED by the presence of the bolt and nut that secures the center screw for the rear rail. To resolve this potential issue, I used a lower profile nut and a star lock washer.

I had previously believed and stated here on the forum that I did not believe the nut restricted movement of the trunnion but it does (or could).

Thanks JPG for linking me back to SSUG (pointing me to one of my own posts to answer the size question). I thought that they had gone defunked for lack of participation.