Checking Flatness

[algale]

Here's a more detailed explanation of how to make a reference bar using screws -- http://www.woodcentral.com/articles/pow ... _511.shtml

I built a set of these and posted about it here: http://shopsmith.net/forums/showthread. ... t=test+bar
The are cheap, easy to make. Due to the ribbed nature of the Shopsmith table I think for what Dusty is trying to do they will be of limited use.

I would go in another direction. Why not adapt the same method that would be used to square the table in drill press mode? Basically attach your auxiliary table/sliding table to the main table with the extension tubes and then place the Shopsmith in drill press mode. Mount the sanding disc and clamp a rigid arm or trammel of the required length (can be a length of wood, steel bar or aluminum) to the disc and clamp/attach your dial indicator (point down) to the other end. Rotate the disc and take readings along the aux table/sliding table at various point along the arc (if the aux table/sliding surface has ribs, lift the point of the dial indicator between the ribs so it doesn't get stuck). If all the measurements are all the same, its a pretty safe bet you are flat (enough).

I look forward to seeing the results of your experiments, Dusty

Al

[dusty]

I built a set of these and posted about it here: http://shopsmith.net/forums/showthread.htm?t=8933&highlight=test+bar
The are cheap, easy to make. Due to the ribbed nature of the Shopsmith table I think for what Dusty is trying to do they will be of limited use.

I would go in another direction. Why not adapt the same method that would be used to square the table in drill press mode? Basically attach your auxiliary table/sliding table to the main table with the extension tubes and then place the Shopsmith in drill press mode. Mount the sanding disc and clamp a rigid arm or trammel of the required length (can be a length of wood, steel bar or aluminum) to the disc and clamp/attach your dial indicator (point down) to the other end. Rotate the disc and take readings along the aux table/sliding table at various point along the arc (if the aux table/sliding surface has ribs, lift the point of the dial indicator between the ribs so it doesn't get stuck). If all the measurements are all the same, its a pretty safe bet you are flat (enough).

I look forward to seeing the results of your experiments, Dusty

Al

I have not clearly communicated my objective here. erify Main Table flatness is not my objective. Actually, I have not that as best I can using the recommended drill press/trammel method. It worked well only to show and convince me that none of my Shopsmith tables are perfectly flat. All three have slight dips (low spots); none of which impact my woodworking. Sometimes these dips do impact the free flow of an alignment procedure.

When I started this thread, I was doing the preliminary work for attaching my soon to arrive Ryobi Sliding Miter Table to the Main Table on my Mark V.

To complete this task, I have to develop the proper thickness shims to raise the SMT to match the Main Table. I am hoping to be able to move that SMT between tables without compromising fit and form.

Provoking discussions of this nature here on the forum almost always brings about good things for me and I hope for others. This one has certainly done that.

[dusty]

Additional Comments:

One thing that this thread and this self imposed task has taught me is that I do not know how to use my calipers correctly.

I sat yesterday for probably twenty minutes just measuring and remeasuring the delta height between the two top surfaces referenced in the first post.

I finally settled on a number but I cannot say that it was achieved in an accurate and scientific manner. Certainly good enough for wood working but not precise by any means.

[JPG]

Additional Comments:

One thing that this thread and this self imposed task has taught me is that I do not know how to use my calipers correctly.

I sat yesterday for probably twenty minutes just measuring and remeasuring the delta height between the two top surfaces referenced in the first post.

I finally settled on a number but I cannot say that it was achieved in an accurate and scientific manner. Certainly good enough for wood working but not precise by any means.

I seriously doubt that!:)

I can understand how getting an accurate caliper measurement of the height difference between the two tables would be difficult. The table edges are rounded and the caliper surfaces are extremely small.

Unless something additional is also used(flat bars to eliminate the effect of the edge irregularities of both tables) I would think impossible!:eek:

[Ed in Tampa]

Dusty
Here is how I would do it. I would use blocks and shims to raise or lower my Ryobi table until it is level with my main table as measured with a straight edge.
I would then place my hardware for attaching the table to the SS on Ryobi table and mark where it needed to be.

I have never had a lot of luck calculating and measuring things like this as tiny errors keep creeping in and making one big error.

Actually if you are thinking of using Ryobi table on a 520 using the connector tubes and existing SS fence rails the aluminum setup block would do the trick. Turn the Ryobi table upside down, place the setup block in place and put the fence on it. Mark the location of the holes and mount the rails.

[dusty]

Dusty
Here is how I would do it. I would use blocks and shims to raise or lower my Ryobi table until it is level with my main table as measured with a straight edge.
I would then place my hardware for attaching the table to the SS on Ryobi table and mark where it needed to be.

I have never had a lot of luck calculating and measuring things like this as tiny errors keep creeping in and making one big error.

Actually if you are thinking of using Ryobi table on a 520 using the connector tubes and existing SS fence rails the aluminum setup block would do the trick. Turn the Ryobi table upside down, place the setup block in place and put the fence on it. Mark the location of the holes and mount the rails.

Yes, your approach will certainly work and is probably the way it will happen with the single exception of the aluminum setup block. The Shopsmith rails do not work into the system in the same manner as they are used on the Shopsmith.