Rubber Baby Bumpers

[reible]

Keep in mind you have a moving target here. The center of one blade is not necessarily the center of the next blade, the body thickness and how wide the kerf is changes things.

Given the thinnest body and thinnest kerf will establish a blade center but as the body and kerg widen the center line will move to the right.

Are you really going to try and deal with this?

Like I said I have played with this in terms of being able to relocate a setup for repeatably and it is not easy, this would be just as difficult. Perhaps a shim that matches the blade to the center? Perhaps dialing it in every time you move something? I don't know, a lot of effort for little gain.

Ed

[JPG]

Keep in mind you have a moving target here. The center of one blade is not necessarily the center of the next blade, the body thickness and how wide the kerf is changes things.

Given the thinnest body and thinnest kerf will establish a blade center but as the body and kerg widen the center line will move to the right.

Are you really going to try and deal with this?

Like I said I have played with this in terms of being able to relocate a setup for repeatably and it is not easy, this would be just as difficult. Perhaps a shim that matches the blade to the center? Perhaps dialing it in every time you move something? I don't know, a lot of effort for little gain.

Ed

Well said IMHO.

Add the possible variation of the arbor/quill shaft interface and the quill stop 'bumper'(yes that is a bumper). Then there is blade wobble.

"Exact"(repeatable) centering is an elusive goal.

[dusty]

Keep in mind you have a moving target here. The center of one blade is not necessarily the center of the next blade, the body thickness and how wide the kerf is changes things.

Given the thinnest body and thinnest kerf will establish a blade center but as the body and kerg widen the center line will move to the right.

Are you really going to try and deal with this?

Like I said I have played with this in terms of being able to relocate a setup for repeatably and it is not easy, this would be just as difficult. Perhaps a shim that matches the blade to the center? Perhaps dialing it in every time you move something? I don't know, a lot of effort for little gain.

Ed

Well said IMHO.

Add the possible variation of the arbor/quill shaft interface and the quill stop 'bumper'(yes that is a bumper). Then there is blade wobble.

"Exact"(repeatable) centering is an elusive goal.

You may think so but I do not.

[dusty]

Keep in mind you have a moving target here. The center of one blade is not necessarily the center of the next blade, the body thickness and how wide the kerf is changes things.

Given the thinnest body and thinnest kerf will establish a blade center but as the body and kerg widen the center line will move to the right.

Are you really going to try and deal with this?

Like I said I have played with this in terms of being able to relocate a setup for repeatably and it is not easy, this would be just as difficult. Perhaps a shim that matches the blade to the center? Perhaps dialing it in every time you move something? I don't know, a lot of effort for little gain.

Ed

You make a good point except that all of my blades, except one, are Shopsmith thin kerf. I have not measured the plate thickness on all of them so maybe I need to do that. But, I still contend that replacing a part (in this case the Carriage Stop Ring (aka rubber baby bumper) 516667) should NOT introduce the change that it does.

The new bumper offsets the blade nearly a 1/8" to the right of center. I can't even bring it back with the quill. Sure, I can relocate the carriage but I should not have to do that. Just like I should not have to realign the Extension Table when I move it from one side of the machine to the other. This has become even more frustrating to me when I learned that Shopsmith declares that the purpose of the Stop Ring is to center the blade in the insert.

If you accept 1/8" offset to the right as center then I understand your content. I am not content.

Yes, I do intend to deal with this.

[reible]

As I have mentioned I have done some testing to see what effect re-setups has on control of placement. I can't find the data now nor do I real call the range but it was a lot more then I would find reasonable for what I was trying to do.

The test was quite simple, quill locked with blade in place. Then set the table up with blade in insert. A dial indicator attached to the table and and set with it centered in range. Dialed to zero and then called that the first point of data.

Then took reading by sliding the headstock and or the carriage to different locations and then returning to what I had hoped was going to be an exact reading of zero once more. Not only did it not happen often it had a good deal of variance from set up to set up.

When doing so I tried to be as realistic as I could, to the left to the right and all places between. Tried to just move the headstock and left the carriage in place, then the opposite, and it only proved to me that there is very unlikely a situation that is going to repeat with the parts involved.

Then played with using stop collars and making several variations of "bumpers" that were a lot more exacting then the existing design. It got better but never good enough for me.

To this end if you have ever turned an object and un-chucked it then tried to re-chuck even with it marked as to orientation it needs to be turned to get it back to round. Makes little sense but that is just how it is.

To me the repeatably is just not built in and trying to get it was not an easy path. Not one that was worth the efforts.

I have a wide selection of blades and like it that way, if I had to pick using only certain blades to achieve results that would not be acceptable and certainly prone to problems in the future when shopsmith or who ever makes some design changes. Perhaps the next blade you get is made by yet another manufacture with different tolerances...... There are just too many things that are out of our control.

Anyway I think I'm done here.

Ed

[dusty]

The rubber baby bumpers are an issue no more. This was one of the easiest fixes I could think of. I removed the new bumpers and reinstalled the old one. The old one is a bit hard but it is the correct dimension. I cut a new ZCI and it is right down the "center. There is a space of 1 7/16" on each side of the kerf and the kerf is 3/32" wide. This ZCI is just a tad narrower than I would have liked. A perfect ZCI for me is 3 1/64" wide; fits in the cutout with only a very tiny bit of play.

[JPG]

So 1 3/8" IS the magic length?

[robinson46176]

I took a few pictures of the carriage to headstock control rod on my old Mark VII Shopsmith. You can easily see how simple the basic concept is as well as how effective it is. You can loosen the both the headstock to way tube lock and the carriage to way tube lock and slide them from one end or the other or anywhere between and clamp them back down and they will be in the same relationship with each other. An example of that would be to mount a SPT like a bandsaw etc. without losing your setup. I have not dug out my Mark VII manual to see if it tells you which of the three notches are intended for what purpose. I'll try to remember to look for that.

Shopsmith Mark VII Carriage lock rod 1 rz.jpg (144.37 KiB) Viewed 9036 times

Shopsmith Mark VII carriage lock rod adjustment 2 rz.jpg (137.47 KiB) Viewed 9036 times

Shopsmith Mark VII carriage lock rod in first notch-red lock-release button at left 3 rz.jpg (154.62 KiB) Viewed 9036 times

Shopsmith Mark VII carriage lock rod in second notch 4 rz.jpg (137.25 KiB) Viewed 9036 times

Shopsmith Mark VII carriage lock rod in 3rd notch 5 rz.jpg (139.25 KiB) Viewed 9036 times

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[JPG]

According to the manual, the outer notch(near the pointy end) is for using the secondary blade slot(near the left edge of the table), the middle notch is for using the main blade slot, and the innermost notch is not mentioned(I assume it is for when the carriage/table and headstock need to abut.

The distance between the notches is 2 9/16 and 5 11/16 = 8 1/4 over all.

The Mark 5 secondary blade slot is 5 11/16" from the main blade slot. The Mark VII table is the same.

FWIW I am placing the lock nut on the inside of the carriage apron. Time will tell if it will work there. There may be insufficient threads on the rod to do that.

[robinson46176]

Thanks JPG, I know I have the manuals, I'm not just sure right now where I have them...



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