Improving the JET JBSW18 bandsaw.

[ken carroll]

I have owned a Jet jbsw-18 from new, must have had it for close to 15 years now. Despite the less than complimentary FWW
review of 2004 I have always found it a decent resawing machine but then I've never used anything else. One thing I've
never enjoyed is changing blades and resetting the guides so when my neighbor moved I bought HIS jbsw-18 too! To be honest
it was buried in the back of his garage, and seeing the sloped backbone frame (versus my straight backbone frame) I thought
it was a jbsw18X which had the shortcomings of my saw fixed. After paying the money I realized that it was not what I expected.
Oh well, I paid too much!

My "A" model - the brace is a simple piece of angle iron upside down.

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My "B" model - the brace looks much better, but really isn't. It needs to go the whole way.

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Of the shortcomings, there's not much I can do about the 10" vs 12" resaw capacity, or the 1.5 vs 1.75HP motor, but I thought I
would fix the main complaint of the FWW review - the "flexible frame". I've seen this "flexible frame" comment repeated
many times on this site, and actually even my jbsw18-A model 6x4 straight backbone is way more than adequate for a saw of this size, the "B" models frame is massive and way more than needed and it is carried over to today's "jbsw-18Q" saw. No, it isn't the frame, it's the upper wheel housing to which the upper guide bar of course is mounted. Other saws use heavier gauge steel or internal bracing to reduce the flex in the guide bar assembly.

On the jwbs18X, Jet finally got the bracing right, taking the heavy sheet steel brace all the way to the guide bar mount.
Interestingly, they also increased the guide bar from 3/4" square bar to 1" square bar - totally unnecessary but it doesn't
hurt. Jet TRIED on the "B" model, they really did. The frame is super strong but an unhelpful improvement, the guide bar is
massive but equally unhelpful, the top wheelhouse box brace looks way more useful, but they didn't extend it the whole way.

I decided to replace the sheet metal brace with one of 3x2x1/8" tubing extended all the way to the guide bar mount.

First up was to take some before and after flex measurements. I extended the guides to within 1/8" of the table
and used a spring to apply force to the guidebar while measuring the deflection with my digital depth guage. I got
0.114". Bear in mind this was a LOT of force and the guide bar extended to maximum leverage so it bears no resemblance
to real world use - just a relative score.

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Removing the JET brace was way more difficult than I expected. It's fixed with eight oval plug welds and one seam weld.
I thought I could cleanly remove their brace but after a while gave up and used every cutting tool I had to hack the thing out
to pieces like some Asian bandsaw pirate.

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I added many more plug welds to the wheel housing (not done in this picture) and added a 1/8" plate under the housing which is welded to the bar.

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I shaped the end of the bar to fit around the guide bar mount and boxed in the end. There are two plug welds right underneath the guide bar mounting plate
as well as the skip welds to the bar.
My welding is not too good, finally remembered I should have been wearing some reading glasses - being able to see would have made a difference! I used skip welds and plug welds to reduce the heat distortion over a seam weld. For strength though, I did seam weld the end of the tube to the frame.

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Hopefully, I can find the time tomorrow to clean it up, get some "Jet" type paint and re - measure the guide flex.


If there's any interest, I'll post again when I'm done.

ken

[Dan Hintz]

I have to wonder if extending that brace really makes that much of a difference... so much of that force is on that distant fulcrum point once you have the blade tensioned.

Looks like you've also created a real knuckle buster with that notched support and knob nearby.

[Frederick Skelly]

Man, that's quite a project Ken. Please let us know how it turns out. I'm interested in how much your mod reduces the flex and whether you notice a change in the saw's resawing performance.

Fred

[ken carroll]

I have to wonder if extending that brace really makes that much of a difference... so much of that force is on that distant fulcrum point once you have the blade tensioned.

Looks like you've also created a real knuckle buster with that notched support and knob nearby.

Where are you saying the flex is coming from then?

A sheet metal box has a lot of strength until you open a big hole in the bottom for the guides and guidebar to come out of, and remove an entire side of it (the door).
Now you are essentially mounting a 3/4" steel square bar to a flat piece of 14ga sheet metal. Any force on the rear guide bearing will flex the sheetmetal. Jet understood this, and added a brace, they just didn't make it long enough until their third attempt - the jwbs18-X model.

I expect my brace will dramatically reduce the flex, I can already feel a huge difference by pushing and pulling on the guide bar mounting plate.
What I don't know is if this really makes any difference to resaw performance. FWW made a big deal out of it, but I am not so sure. We'll see.

As to the knuckle buster, well if that turns out to be true I will simply make a new knob with a longer shaft on my CNC mill.

[ken carroll]

Man, that's quite a project Ken. Please let us know how it turns out. I'm interested in how much your mod reduces the flex and whether you notice a change in the saw's resawing performance.

Fred

Fred,
You're right - it's the resaw performance that really counts, the rest is just theory. :D

[Tom M King]

Looks good! I've been eyeing my Centauro 600 and have several "improvements" in mind-like the method of mounting the guide assemblies, and giving it the same resaw capacity as a MM24. The trouble for me is finding time to do that sort of stuff for myself. I'll probably wait until I find a good buy on a 36".

[Gene Takae]

Wow-props for having the ability, knowledge and tools to take on a mod like that!

[Jeff Monson]

Ken, I'd love to know the outcome, I see these for sale in my area from time to time. Have always stayed clear since the bad reviews of the saw in the past. If the resaw performance was up to par I would consider one and modifying as you did. BTW, are you reusing the old brace?

[Allan Speers]

I've always envisioned a much simpler bandsaw stiffening solution: (Assuming your shop has a strong ceiling)

Bolt the saw to your concrete floor.

Put a large eyebolt into the top of the frame.

Now run a heavy chain from the eyebolt to the ceiling, and tighten it up using a ratchet or some other means.


Done. :)

[ken carroll]

Thanks for the comments Guys. Just waiting on a can of Rustoleum gloss canvas white to arrive before I finish assembly.

Jeff: No, if you look at the fourth picture you can see I had to destroy the old brace to get it off.

I remember when the FWW test came out and a good number of owners posted on this site that we really liked the saw and had no issue with the resaw ability, it was only people who didn't own, hadn't used, and probably had never even seen the saw who berated it on threads from that time onwards.

I am only making the mod because I enjoy doing things like this, and maybe it will make it a better resaw machine, since I've never used a real top end bandsaw maybe I am missing something with my trusty ol' jwbs18?

[ken carroll]

Good point Allan...... unfortunately, I would like to keep my saw mobile!

[Allan Speers]

I am only making the mod because I enjoy doing things like this, and maybe it will make it a better resaw machine, since I've never used a real top end bandsaw maybe I am missing something with my trusty ol' jwbs18?

If nothing else, this mod MIGHT allow you to use a thicker blade (A good carbide one, for instance) at the saw's maximum width.

It certainly is an interesting project. - but I'm glad it's YOU doing it, not me !

[Allan Speers]

Good point Allan...... unfortunately, I would like to keep my saw mobile!


Here's another way to go:

One really needs frame strength when resawing, as this entails the thickest blade you can get away with. Blades for crosscutting and curves don't usually require much tension.

OK, so when is the last time you ripped something on the bandsaw, and it overhung the "right" side of your table? Pretty much never, correct?

So, on a saw with questionable frame strength, why not just make a vertical brace, out of thick MDF, which attaches from the saw's base (or the floor) to the upper wheel housing, going past the outside edge of the table. (With enough clearance to work the trunnions.) You could make it removable, for when you need to crosscut or do curves.

Another simple solution. Heck, the MDF would even absorb some vibration.

[Frederick Skelly]

Ken,
A follow on question to Jeff's, above....... You clearly show that you had to destroy the old brace. I get that. But in the last picture, the new brace has a rectangular cross section that looks like it was originally the same color as the saw. Like Jeff perhaps, that made me wonder if you'd reused part of the old brace to create the new one.

So what are we seeing - why is the rectangular brace "JET White"? Did you reuse some other part or something? (Purely curious.)

Thanks Sir!
Fred

[ken carroll]

Fred,

When the Gym I went to closed, the owner said I could have some of the old weight benches etc - I'm always on the lookout for scrap steel - so what you see is part of the upright to a "bench press" bench. It was a maxicam brand I think, it just happened to be white.

[Frederick Skelly]

Fred,

When the Gym I went to closed, the owner said I could have some of the old weight benches etc - I'm always on the lookout for scrap steel - so what you see is part of the upright to a "bench press" bench. It was a maxicam brand I think, it just happened to be white.

Ah, my mystery solved. Makes good sense to me. Thanks Ken.

[Jeff Monson]

Ken,
A follow on question to Jeff's, above....... You clearly show that you had to destroy the old brace. I get that. But in the last picture, the new brace has a rectangular cross section that looks like it was originally the same color as the saw. Like Jeff perhaps, that made me wonder if you'd reused part of the old brace to create the new one.

So what are we seeing - why is the rectangular brace "JET White"? Did you reuse some other part or something? (Purely curious.)

Thanks Sir!
Fred

LOL, I thought I was crazy. Thanks for asking. The matching paint is what really threw me off.

[ken carroll]

Realized that I hadn't continued the saga so I'm adding a few more pictures. I ended up replicating the factory reinforcement internal to the upper wheel house. Mine's made of sturdier stuff - minimum 1/8" plate. Two triangular boxes, one running from the guide mount to the backbone and fits behind the wheel. The second larger box is as large as it can be without interfering with the wheel. In an attempt to make the machine more capable of higher tensions I added 1/4" plate at the guide mount and the upper wheel mount - welded together and welded to the long internal box section.

Sorry, this pic taken with an iphone and this site doesn't seem to know up from down!

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Shows both boxes and the 1/4" plate stiffener. Machine painted with a 50-50 mix of rustoleum as noted previously. No, it doesn't match factory, but I sprayed the whole thing.


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Other angle

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Also added a gusset of 1/8" plate underneath the wheel house to the backbone.

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Well, I have to admit that all of this only offered a 33% improvement in my testing. So my assumption that the 3/4" square guide bar is adequate looks flawed. Either that or the sheetmetal plate used to "cap" the guidebar to the guidebar "gearbox" is inadequate. One day, I'll make up a thicker one, but not today.......
The reality is that for proper resawing heights - remember, my test was done with the guidebar almost to the table - the effect of the guidebar flex will be much reduced. There's no doubt that this bandsaw is stiffer than before, quick resaw testing has given me what I consider to be good results - but then I've never owned a European $4K bandsaw to judge against.

[Frederick Skelly]

Just saw your update. 33% better is still better, as you said. And it has been an interesting project.
Thanks for the follow up!
Fred

[ken carroll]

Fred,

I wish I had taken "before" deflection readings at more appropriate heights for resawing - say 8". I'd be willing to bet that the improvement is quite a bit better than 33% at those heights vs 1/2" above the table. Fun project.

[Allan Speers]

Not bad, really.

Probably not worth the effort, but perhaps you enjoyed the process?

[Michael Kulikowski]

Yes I know this thread is a year old, but the engineer in me is chuckling as I am about to buy an older Jet JWBS 18; what the poster calls "A". The frame in this particular situation does almost nothing, the tension is being held almost entirely by the box the wheel mounts to (very little pulling of the weldments of the box to the frame bending the upright tube, my beam analysis shows it wont move at all). They could have the frame be half the size. and if they just welded a gusset (like a long isosceles triangle, flat steel vs the posters open box) I would imagine you would all but eliminate ANY flex in this design. The new "triangle" tube does relatively little, they increased the size of the support welded to the back of the box which actually did the trick.

[Frederick Skelly]

Yes I know this thread is a year old, but the engineer in me is chuckling as I am about to buy an older Jet JWBS 18; what the poster calls "A". The frame in this particular situation does almost nothing, the tension is being held almost entirely by the box the wheel mounts to (very little pulling of the weldments of the box to the frame bending the upright tube, my beam analysis shows it wont move at all). They could have the frame be half the size. and if they just welded a gusset (like a long isosceles triangle, flat steel vs the posters open box) I would imagine you would all but eliminate ANY flex in this design. The new "triangle" tube does relatively little, they increased the size of the support welded to the back of the box which actually did the trick.

To paraphrase a famous movie, "pretend I don't know anything about mechanical engineering". What the devil did you just say? :confused:

Patrick! Where are you dude? I need a translator. ;)

[Mike Hollingsworth]

56 chevy back there?

[Malcolm McLeod]

He said "it's strong".