Shopsmith Forums

I use Premium MDF and have very high confidence in it as flat surface (when verified). I have used plate glass for a reference too on smaller projects when I had access to 1/4" Plate glass, but that is not frequent for me.

I have more often used Machinists Square or Machinists Level to verify that MDF is a material that is stable, and uncompromisingly flat.

If you don’t have a Machinists level or large Machinists square, but have a ‘known’ machined flat surface you trust such as a cast iron band saw table (after you upgraded) or something similar you can lay that down on the MDF surface and slide it across to achieve essentially the same results.

One example in most anyone’s reach is a high quality level. The Craftsman 48 in. Heavy Duty Level model 880-48 is just under $30 and has a guaranteed accuracy to .0005 inch. Now if you use it in construction and drop it off the roof that can change. You can sweep it over the MDF in question in a variety of directions to insure you are working with a flat surface. (.0005 x 48" is still 0.024 over 4 feet.) I realize there is a separate thread that discussed Green MDF which is 25-30% stronger than standard MDF. One of the most interesting specifications properties that often accompanies Green MDF is the fact that is a material that can be machined to tight tolerances, with no sanding.

1/4" plate glass is a nominal thickness of 0.230. It varies from 0.219" to 0.244" giving it a tolerance of 0.025" That is relatively flat, and a Machinists level and a set of feeler gauges will still find some high and low spots across the surface.

If one compares 1/2" Premium MDF to 3/4" Premium MDF generally they are listed at 0.500" and 0.750" because they are manufactured to very exacting tolerances and the resins they are made with are dimensionally stable. They are sensitive to moisture absorption to some extent if not sealed. Seal them.

I live in Lubbock which is semi-arid climate and has low humidity at most times, but like anywhere it rains, that humidity will go to 100% from time to time. Even in those times, I have not noticed any variances to the MDF work surfaces I have used in the past.

A very stable, strong and very flat workbench can be achieved by gluing two 3/4" MDF panels together. Covering it with a slide over furring strip band and topped with 1/4" Masonite makes a durable and easily replaceable work surface and will take a lot of abuse with no effect to the MDF beneath it. Other areas which are more out-feed table, than work surface may need nothing at all to protect it other than some sealer.

It is important to see how one verified adjustment enables the accuracy of the next and that things need to be done in an order that sustains that outcome.

My point in all this is that there are a variety of things you likely have in your possession or can reasonably obtain, that will help you develop the methods that work best for you to insure your Shopsmith (or anything else similar) is properly aligned and ready to produce quality results, and it isn’t hard to do.

Everett,

Good info, thanks!

About that MDF . . . is this the same material as what I've always called "Particle board"?

I've got an 1.5" thick slab of polished marble, 3' X 2' as my most used workbench surface.
I'll have to recheck it for level with the ways you suggest.

Terry

Thanks! Interesting read and I always enjoy reading tips and tricks on keeping these machines tuned up!

Another trick you can do if you have dial indicator that mounts in the miter slot is to set/calibrate your miter gauge to 0^. Not sure if this works on the Shopsmith dial indicator, since it looks like it has a limited reach, but this works perfectly if you have an A-Line-It dial indicator jig, which will reach nearly from one miter slot to the next.

Just mount the dial indicator pointing toward the other slot then put your miter gauge in the other slot set to what you think is 0^. Clamp a machinist's square to the base of gauge and put the tip of the dial indicator against the tip of the square's blade. Push the gauge forward until the tip of the indicator is at the base of the blade, all while watching the indicator If the dial indicator doesn't move off the initial setting, your gauge is set to 0^.

I used this method to set up my v120 miter gauge and my standard Shopsmith miter gauge.

TooTall wrote:Everett,

Good info, thanks!

About that MDF . . . is this the same material as what I've always called "Particle board"?

I've got an 1.5" thick slab of polished marble, 3' X 2' as my most used workbench surface.
I'll have to recheck it for level with the ways you suggest.

Terry

Medium-density fiberboard or, MDF, it is much denser than particleboard. Premium MDF, even more so.

Like particleboard, it is a composite wood-based manufactured material pressed together from a combination of residual wood fibers, wax and a formaldehyde resin (YES formaldehyde resin) just like particleboard.

Because of its density, MDF is extremely consistent throughout, far more than and much heavier than particleboard.

Some manufacturers of MDF are moving away from formaldehyde, moving to polyurethane resins.

If you have (or had) one of the Craftsman 10” Radial Arm Saws in the last few decades, the table top was made from MDF as an example, so you have probably been around it for years.

Everett

algale wrote:Thanks! Interesting read and I always enjoy reading tips and tricks on keeping these machines tuned up!

Another trick you can do if you have dial indicator that mounts in the miter slot is to set/calibrate your miter gauge to 0^. Not sure if this works on the Shopsmith dial indicator, since it looks like it has a limited reach, but this works perfectly if you have an A-Line-It dial indicator jig, which will reach nearly from one miter slot to the next.

Just mount the dial indicator pointing toward the other slot then put your miter gauge in the other slot set to what you think is 0^. Clamp a machinist's square to the base of gauge and put the tip of the dial indicator against the tip of the square's blade. Push the gauge forward until the tip of the indicator is at the base of the blade, all while watching the indicator If the dial indicator doesn't move off the initial setting, your gauge is set to 0^.

I used this method to set up my v120 miter gauge and my standard Shopsmith miter gauge.

That Magnetic Machinists Square etc. that I stick on the 12" Sanding to Check the table, when turned sideways will allow you to run the miter gauge up to it to confirm / adjust the miter gauge.

I you have a miter gauge extension and an even longer square, it can quickly get you dead on, when coming off the Sanding Disk, once everything else is aligned.

Those earlier steps that verify the table slots are parallel and that the table edge is square to them, is a one-time verification. Once you know they are square and true, they stay square and true and don't have to be re-proven in your next alignment.

It is something I do when I acquire a new system as I rebuild / restore it, but from then on, it is a known quantity.

The table still has to be verified flat, and the connecting tubes properly aligned within the extension tables as they can get bounced about and can be damaged or otherwise thrown out of adjustment.

If you have more than one system, as many of us do, be careful mixing and matching as these table and extension components, while aligned to each other on the same system, may well not be 'between' different systems, even though aligned for the respective system. Marking them in some useful way to identify sets, is helpful even if it is just a color dot stuck somewhere.

Been there, not done that, and had those minor issues personally. It's also helpful if you decide to sell a system to have all the mating pieces easily identifiable between what you're finding a new home for and what you are keeping.

Equally, if you need to mix and match between systems regularly (as some will), do so with one reference table, align all the extension tables and tubes properly for both (or all other) systems, then remove the reference table, and insert the other tables one by one, adjusting them to the same plane of reference as the now 'matched' extension tables.

Keep and use the main table with the Carriage of the proper machine afterwards, and if the adjustments aren't perfect between systems, suspect carriage or way tube variances which can exist.

If you had those Bench and Way Tubes out for de-rusting / polishing, a quick roll over the verified flat MDF can show you where something you might never believe is off, truly is.

I don't think I want to explain in words how long it took me to arrive at that conclusion. You can guess how absolutely thrilled I was to find that issue existed.

It is what it is, only after you prove what it is; Otherwise it's only what you presume.... and yes, I avoided the word 'assume' for the reason we all know to be true.

Everett

Gotta squeak again Everett.

Agreed the disk was predetermined to be flat.

However my 'point' was that gauging the disk as it rotates only verifies that flatness, not that a 90° angle exists.

I alluded to that being the same thing and in retrospect have to admit that if not 90° the disk surface would wobble as it is rotated.


Consider horns retracted(gun ports closed unless you are a Babylon 5 fan).

If I understand the mdf spec right they are saying it will be less then 1.5mm/m and if I did the conversion right that comes in around .018in/foot.

Regular glass is also not flat, you need to look for optically flat glass. Not even float glass makes the grade..........

If you are looking for flat then granite plates are the only thing that even comes close to flat and that is after they are processed.

This is a class A version with the right tolerances to measure what you might expect top see with a shopsmith table.

https://www.zoro.com/starrett-granite-s ... /G7160447/

Back in the day this was the gold standard now it is done optically or who knows maybe some other magic has happened since I retired and stopped keeping up with this stuff.

Ed

reible wrote:If I understand the mdf spec right they are saying it will be less then 1.5mm/m and if I did the conversion right that comes in around .018in/foot.

Regular glass is also not flat, you need to look for optically flat glass. Not even float glass makes the grade..........

If you are looking for flat then granite plates are the only thing that even comes close to flat and that is after they are processed.

This is a class A version with the right tolerances to measure what you might expect top see with a shopsmith table.

https://www.zoro.com/starrett-granite-s ... /G7160447/

Back in the day this was the gold standard now it is done optically or who knows maybe some other magic has happened since I retired and stopped keeping up with this stuff.

Ed

This is great reference and if I ever want/need a reference plate that is flat to within .0001" I will go there. For now, .0001" is a bit of overkill. I'll just stick with my bench top which is a lamination of two sheets of 3/4" MDF with a couple bad spots where it got wet.

A flatness of .018"/ft over 4' (.072") is not bad.

[quote="dusty"

This is great reference and if I ever want/need a reference plate that is flat to within .0001" I will go there. For now, .0001" is a bit of overkill. I'll just stick with my bench top which is a lamination of two sheets of 3/4" MDF with a couple bad spots where it got wet.

A flatness of .018"/ft over 4' (.072") is not bad.[/quote]


Now remember that is if the mdf is sitting on a flat surface, if you have two sheets with glue(??) and or nails or screws involved this is no longer true. Unless the mdf has been sealed to keep out moisture it will be a moving target with how much can be absorbed at any given point. I'd be really impressed if it were anything near the .072".

I was taught that to measure something accurately you need to have an order of magnitude better equipment. So to measure to .001" the equipment must be at .0001". To measure .0001" you would need equipment to .00001". This is what allows us to guess at the next digit by where it comes between lines.

As an example, if a ruler has 1/8" marks I can get pretty close to 1/16" readings by seeing where the item falls in the space between marks. However if I then had a rule marked in 1/16" marks I could know, and perhaps again guess at the 1/32" and so on and so on. This assumes the rule is accurate to one level better then you are trying to read.

If you try to use a "level" surface that is worse then the one you are trying to measure which numbers are you seeing? The error in the surface that is "level" or the item you are trying to measure?

OK I'm going to leave this post now and go and do some yarding. Now how deep do those seeds need to be, was that 1/4" or 1/8" and where are my gardening calipers?? Oh yes better level that bed first......

Ed

Everett, thanks for the great procedure and explanation. Since the flatness of the MDF (.018"/ft) is an integral part of your process and most dial indicators measure to .001", what reading variances should be acceptable during your procedure?