HopefulSSer wrote: ↑Sun Jan 01, 2023 12:11 pm
So back to the original question then: Since this may be a common problem, is there a common fix?
I did a 520 table a while back. IIRC it was 'dished' over 0.030" to the left of the blade slot, with the worst deviation near the opening and aligned with the quill. I was able to bend it flatter, not flat, to <0.010". Perhaps could have gotten better with a couple more attempts, but suspect it would never have gotten truly flat. Basically I used some heavy walled steel tubing, C-Clamps, and steel plates for standoffs. I'll look for a pic, I did a post on it. I applied the clamping force near the miter slot, positioning the plates to limit the force to the area that needed it.
Very important, IMO, to quantify where and how bad the problem is. And on what kind of table, for example a 520 table has much less reinforcement to the left of the blade than to the right. My 500 style table is not handy for comparison. My recollection is that I primarily focused on the miter slot to the left.
I found the thread I referred to earlier. I see that some of my recollections were wrong... viewtopic.php?p=271020#p271020
Note that in some places in that thread there are references to contribution from the trunnion locks. I'm reasonably certain that this is a factor only on 510+ table systems.
This is not something I've seen on any 500 tables, and I have a bunch of them from old Shopsmiths that are sometimes in very condition overall. The strength of the 500 tables. I have several 510 main tables and many extensions, but I've only checked alignment on one of the main tables, and flatness hasn't come up so far. I do have at least one floating table that is not flat and can't be aligned with other tables correctly. Certainly alignment between tables on the 510 system is problematic, but flatness has not been the true issue there.
I'm guessing that tables like the one described in this thread result from manufacturing problems or user abuse. Even if the table was flat to start with then forcing it into misaligned trunnions could distort the metal. In this thread - viewtopic.php?t=31631 I found a right side tilt casting to have badly misaligned way tube holes. The machine was probably assembled with the way tubes forced into position, which means I probably have two bent way tubes from the machine it came with.
I think some peoples expectations are too high for 60 to 70 year old aluminum tables. We are not talking about something new from the factory. Who knows what previous owners subjected them to.
John & Mary Burger
Eagle's Lair Woodshop
Hooper, UT
This thread got me curious about my 1958 Greenie's table, so I just checked it. It has a dip of about 0.002" in the area in front of the saw blade. From the blade back it's dead flat (I'm just using a 2' rule - I don't have a precision straightedge). This doesn't count the table insert, which is a bit lower than the table itself.
I've yet to get my head around the trunnions. I need to watch the Sawdust Sessions video and see if what Nick describes might be contributing to what I'm seeing...
...which is a dip in the middle near the blade of around "typical sparkplug gap" -- i.e. I didn't measure it but it looked to be around typical plug gap of about 0.030". After my hydraulic press excursion it's reduced to probably half that, but that's still a fair amount. Yes, these machines are old but if a belt or bearing is worn out I don't say "Well, it is 60 years old..." and live with it. Instead, I fix it. If the table is distorted and I can fix it some how, then that's what I want to do. ;-)
Greenie SN 362819 (upgraded to 510), Bandsaw 106878, Jointer SS16466
HopefulSSer wrote: ↑Sun Jan 01, 2023 10:56 pm
I've yet to get my head around the trunnions. I need to watch the Sawdust Sessions video and see if what Nick describes might be contributing to what I'm seeing...
The 'trunnion thing' is unique to the 510 and on main tables. It may be worth watching the video anyway, but it is a potential feature of the dual trunnion locks present on 510 and on. With a single lock, I can't think of anything similar on 500 and earlier.