Bandsaw - How Much Wobble is OK

[DLB]

I would like to get back to the Headrest mounting holes but not right now. The picture I included was only meant to convey how much worse the holes looked visually compared to the base. I need to see if I can find a way to photograph what I think the issue is.

These BS eccentrics are new to me, my Magna BS has straight tubes and my Magna Jointer has a completely different design of eccentric. (I'm a couple of years older than them, but they are pretty old.) When I aligned the drive hubs the "new" BS eccentrics did not go all the way into the BS, that was one of the things that I contrasted with the straight tubes. Mine look like this:

Bandsaw Eccentric Tube Mounts

IMG_7934.jpg (614.92 KiB) Viewed 11475 times

Not only does it not engage the stop, it's kind of marginal on engagement of the upper collar. (There is ~1/8 inch of bevel at the top of the tube and hidden in this photo, but not adding much stability.) Not saying this is good, but it's what I ended up with when I thought I followed the instructions. Clearly, we did not all do it the same way OR do not have the same eccentric tubes. (Dimensions of mine are at the beginning of this thread.)

The BS manual I used is dated 2003. There are seven steps in that alignment, I'm going to paraphrase them for relevance/brevity, which leaves some out:
1) Set the tubes in the SS long side up, clamp/lock left loose.
3) Back out the BS setscrews and set the BS on the tubes.
6) Horizontally align the hubs by hand rotating the tubes. Tighten the accessory mount lock. (Emphasis added)
7) Vertically align the hubs by lifting the BS. Hold it and tighten the setscrews.

In an earlier post in this thread, JPG said he did not think the eccentric tubes were long enough at either end. I completely agree, and this (photo) is what I think/thought he meant.

Despite all of the things I didn't/don't like about how the eccentric mounts in the BS compared to the straight tube, I don't think it is rocking up there. I think it would get worse is I fully engaged the tubes in the BS, because I'd lose something like 1/2 inch of engagement in the headrest.

EDIT: I'm using a smart-phone level app, almost certainly not as accurate as a wixey, which I don't have. It measures in two axes and has a zero function, which I used each time I moved the BS. My numbers are loose / tight:
520 Headrest 0.9 / 0.6
Greenie Headrest 0.9 / 0.3
520 Base 0.9 / 0.2

-David

[reible]

A few more data points. I have the dual tilt and the castings are reasonable new.

The bandsaw is lined up with the tube shoulders pointed away from the headstock. The manual mentions that they both should point the same way and right off hand I don't see how else they could be but I guess that is something to check.

bsa2.jpg (118.86 KiB) Viewed 11465 times

The tubes as you might have expected do not reach the stops in the casting.

bsa1.jpg (118.29 KiB) Viewed 11465 times

With the locks disengaged and gauge zeroed with the bandsaw top pushed towards the headstock then moved to the left or away from the headstock I see 1.1 degrees. If I really push on the top of the saw I can get as much as nearly 3 degrees. Keep in mind this is total movement from extreme to extreme.

With the lock engaged and again pushing towards the headstock and zeroing the gauge then pushing left the most I can get is .65 degrees.

I have no idea if this is normal or not but I have yet to wreck a coupler going back to 1976. I have had no cutting issues that I could remotely view as being caused by the movement.

There is enough room to add a stop collar and I might do that to see how much difference that might make with the wider amount of support. BTW the tail stock used in lathe work moves a LOT when stressed. For me that is a lot more of an issue then the movement of the bandsaw.

Ed

[algale]

Reible, is the long end of your eccentric tubes installed in the band saw case? That’s how I understand it should be done.

[algale]

Four of us have now documented the existence and quantified the amount of our band saw wobble (me, Dusty, reible and DLB) before connecting the band saw to the headstock via the coupler.

But the original question was how much wobble is ok?

To answer that question, I go back to my first post in this thread. Once I have clamped the band saw, attached the power coupler to the band saw and pushed the head stock firmly against the power coupler and locked it into place using the headstock lock, there is no appreciable slop; I didn't bother to try to measure wobble after coupling because I know from experience that it feels tight once the head stock is firmly against the coupler and locked into place . I assumed this was simply part of the design and perhaps it is. But regardless of whether it is by design or by accident, it works. Like reible, I don't believe wobble has ever contributed to any of my occasional band sawing errors because, in use, it isn't wobbling appreciably.

The simple fact is that because it has to transform from a table saw to a drill press to a lathe, to a disk sander, etc., there are a lots of places on the Shopsmith where things tend to flex or move under heavy load or force or if the Shopsmith wasn't set up properly. It is good to be aware of these movement points since some of them can have a practical effect on our woodworking and others can have at least a theoretical effect.

In reality, however, I find that if I set up and calibrate the Shopsmith as it is supposed to be set up and calibrated and if I remember to properly tighten the locks on the things I'm supposed to lock, and if I use proper human technique that I would be expected to use on any power tool, the Shopsmith gives me all the accuracy I need to make accurate woodworking projects even if it sometimes doesn't feel as solid as an industrial stand-alone machine.

And it isn't just me. The proof is in the outstanding projects that have been made on the Shopsmith, many of which can been seen on this site or in the holiday catalog. I've never heard someone say "my project would have come out better if I used a different machine." On many occasions, however, I have heard folks say it would have been very difficult or impossible to do it on anything but a Shopsmith.

[BuckeyeDennis]

Four of us have now documented the existence and quantified the amount of our band saw wobble (me, Dusty, reible and DLB) before connecting the band saw to the headstock via the coupler.

But the original question was how much wobble is too much?

To answer that question, I go back to my first post in this thread. Once I have clamped the band saw, attached the power coupler to the band saw and pushed the head stock firmly against the power coupler and locked it into place using the headstock lock, there is no appreciable slop; I didn't bother to try to measure wobble after coupling because I know from experience that it feels tight once the head stock is firmly against the coupler and locked into place . I assumed this was simply part of the design and perhaps it is. But regardless of whether it is by design or by accident, it works. Like reible, I don't believe wobble has ever contributed to any of my occasional band sawing errors because, in use, it isn't wobbling appreciably.

I agree, Al. As a portable, multi-purpose tool, light weight and fast changeovers had to be key design goals for the Mark 5/V. I think that the designers did a fine job of achieving sufficient rigidity in areas where rigidity is of high importance. In other areas, such as the SPT mount/clamp, the other factors were given priority. As Dusty pointed out, it would be easy to use individual set screws in the SPT tube mounts to eliminate play in that direction. Or to stiffen everything by using heavier materials. But those mods would add weight and setup time, without significantly increasing performance.

I also agree with Paul that more stiffness in the tailstock would indeed be beneficial. I haven’t studied it in detail, but my impression is that my tailstock itself does most of the flexing.

The following is fodder for an entirely different thread, if I ever get around to it, but I’ll share it while I think of it. A couple of weeks ago I needed to mount my Nova live center to a special-purpose fixture. I happen to own an inexpensive set of #2 Morse taper reamers, purchased for a vintage-lathe rebuild project. So I thought “what the heck, let’s try making a #2 MT bore in wood”. I grabbed a piece of osage orange, drilled a 5/8” hole, and reamed the taper using nothing but an end wrench to turn the reamers. It was quick and easy, and the resulting bore was perfect. When I insert the live center, the shank locks in rigidly, and I have to give it a whack with a mallet to release it. So a rigid, shop-made, way-tube mounted tailstock for a Mark V looks eminently feasible.

[JPG]

The tailstock deflection is indeed due to slop in the mounting tubes to spt mount bore. It is also undesirable and a design deficiency.

We have traveled over this road before and IMO have not come up with a viable 'fix'. Dennis's suggestion deserves consideration even though it would decrease maximum spindle length.

BTW ever hear of anyone complaining about Model 10 tailstock deflection?

[rpd]

BTW ever hear of anyone complaining about Model 10 tailstock deflection?

Can't say I've ever noticed any, But, as you are alluding to, the tailstock is cast iron and mounts directly on the way tubes, so not a lot of latitude for flex.

[algale]

Regarding a fix for too much slop, has anyone tried self-adhesive, stainless steel shim tape?

https://www.mcmaster.com/shim-tape

[DLB]

First and foremost I want to thank everyone for their help on this. This forum is amazing, both for people's knowledge and experience but also your willingness to go the extra mile and spend your time helping with someone else's problem.

In looking at the data everyone provided I conclude that my setup is within the normal range and not wobbly enough to worry about. As stated, it is much more stable when coupled to the headstock. At the same time, earlier testing had left me with the conclusion that most of my wobble came from the relatively poor clamping action on the front mounting hole. So I also felt that it could be improved upon, and I modified a set of eccentrics to try to do that.

I retested the BS with straight tubes to get a more objective comparison, 520 only. I also experimentally modified a set of eccentrics, details to follow. Again, checking with mount lock loose / tight:
520 Headrest
Eccentric: 0.9 / 0.6
Straight: 0.4 / 0.3
Modified Eccentric: 0.7 / 0.3

520 Base
Eccentric: 0.9 / 0.2
Straight: 0.3 / 0.2
Modified Eccentric: 0.8 / 0.2

The straight tubes are inherently more stable in the unlocked state, that is probably true on any BS in any mount. They extend farther into the BS and farther into the SS and have a larger diameter, thus more stable. In a relatively nominal mount, my 520 base, they gave no appreciable improvement over the eccentric when locked (which surprised me). In my 520 headrest, however, the straight tubes are much more stable.

I modified a set of eccentrics specifically targeted to my headrest and what I believe to be its 'problem.' In doing so I significantly compromised the intent of the eccentric design. It is not something that others should necessarily do, but it is interesting. Like the straight tubes, it made no significant difference in my base mount. But it made a significant, to me, improvement in my headrest. I should have tested it in my Greenie so I will do that later, right now it is disassembled so I can photograph it for a follow-up in this thread. If I can find some peel shim that I used to have I will also incorporate algale's shim idea with my approach and see if it is more universal, user friendly, and requiring no permanent change to the eccentric.

[reible]

I had a few minutes today so I added a couple of collars to the bandsaw to see if that made much of a difference. Results were just a tiny bit better but not worth the effort, at least on my machine.

collars one on each side

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Ed