Jim Byrnes Thickness Sander

[Roger Pellett]

It’s probably the upcoming alignment of Jupiter and Saturn but dispite singing the praises of my home made thickness sander I am toying with the idea of buying one from Jim Byrnes.

 

looking at the photos it seems tall and narrow.  Since it works by sanding wood being pushed through it what keeps it from tipping over?  My home made one is built onto an integral stand, but it seems that many users here on the forum use theirs sitting on a bench top not bolted down.  

 

After cleaning up a number of non ship model model projects I am anxious to begin a new ship model that involves making a lot of saw dust and using up a pair of (real) boxwood planks that have been waiting in my stash for many years.

 

I am anxious to hear from forum members, pros and cons before making a buying decision.

 

Roger

[Jaager]

Roger,

Jim uses a 1/3 HP motor for many of his machines that is heavy enough that tipping over is an unlikely problem.

It is probably a good idea to set the distance between the table and the drum to remove a minimum layer of wood.

The force from the hand feeding the stock should be fairly low. Most of it is resisting kickback.  The push should not be enough

to tip over a much lighter unit.   The pull from the vac hose should be minimized.  A sky hook with a bungee or it being a horse shoe, with

down stream on the bench surface.

The only problem I have experienced is a weak spring holding the depth dial. It only wants the open, so I fit a 2" C-clamp to it and have it butt the table.

The media is easy to mount - not like me having to glue it to a Maple drum on my old NRJ plans homemade unit.

 

Get spare screws.  A plank fixed to the motor base floor with holes to hold the Allen wrenches and a contact lens type container with a lid to hold screws

will keep everything to hand and keep bits from going away while doing a media change has been good for me.

[gjdale]

Roger,

 

Like all of Jim’s tools, the thickness sander is a superbly designed, easy to use tool. I have had one for several years now and have never had an issue of it wanting to tip during use. It may have something to do with the slight upward angle of the feed table. Regardless, I guess the key would be to not try to take too much off in one pass, but you’ll quickly get a feel for what is “about right” for the particular species and thickness you’re using at the time.

 

Not sure if it’s included with the base package, but there is a separate 6” retainer bar iavailable n addition to the two 3” ones. The two 3” ones allows you to load two different grades of sandpaper onto the machine so you have a “coarse” and a “fine” without having to change paper. If you’ve got slight wider stock, you may want to replace these with the single 6” retainer bar and a single grade of sandpaper. I have found this to be a useful addition.

[Jim Rogers]

My only issue has been the occasional launching of stock into the wall at Mach 9.

[allanyed]

Roger, I have been using the Byrnes sander for many years.  If he had serial numbers on them (maybe there is one on there somewhere) mine is probably in the number 10 to 20 range.  I have never had an issue with tipping.  It weighs a lot and as said above, the main thing is to not take off too much wood at once.  I stand to the side just in case a piece does launch and cannot catch me, but rather connects with the  concrete wall.   Once of my favorite things about this sander is that I have a rough paper on one half of the  drum and finishing (400 grit) on the other side.   

 

Allan 

[Jaager]

4 hours ago, allanyed said:

finishing (400 grit) on the other side. 

Allan,

I have read that 220 grit is about the limit for the surface smoothness for components that will be joined using PVA.  400 grit may leave a surface with not enough tooth for the polymers to attach to efficiently.  

Like you, I progress - bulk 80 grit,  dress the 80 scarring with 120-150 grit - 1-2 passes. Finish with 220 grit.  On my old 11" drum, I had all three.

[allanyed]

Jaager,

You are correct.  I failed to mention I "smooth" sand the surfaces to be seen and not glued.  Great catch on your part!

Allan

[Bob Cleek]

3 hours ago, Jaager said:

I have read that 220 grit is about the limit for the surface smoothness for components that will be joined using PVA.  400 grit may leave a surface with not enough tooth for the polymers to attach to efficiently.  

 

This seemed to make sense, but I've only ever been concerned about "tooth" in adhesive applications when using epoxy adhesives. When a good epoxy bond is of paramount importance, I use a preliminary application of penetrating epoxy sealer (Smith's "CPES") and then the epoxy adhesive, not clamped too tightly to avoid "joint starvation." (The penetrating epoxy soaks into the wood and the epoxy adhesive then creates a molecular bond with the penetrating epoxy so long as the two are joined within 48 to 72 hours. (See: tech data at: http://www.smithandcompany.org/) I've used a lot of PVA in woodworking applications and, generally speaking, I'm a "planer," not a "sander." I was taught that "the tighter the joint, the stronger the joint."  I've never given a second thought to joining smoothly planed surfaces with PVA and I've joined a lot of them without ever noticing any problem. This got me thinking. Well, not thinking, as much as googling, and at the risk of falling victim to the comedy of errors known as the internet, I looked it up and found an interesting and credible answer in an excerpt from Popular Woodworking quoting the Senior Technical Specialist for Franklin International, the makers of Titebond PVA adhesives:

 

"Our work has shown that a smooth surface will always have higher strength than a rough surface.  Two-hundred grit or higher sanding to get flat or tight-fitting joints works well."

 

The Titebond tech expert gives one caveat: PVA will not bond well to burnished wood. While I doubt wood is intentionally burnished by many modelers, burnishing may inadvertently occur when wood is sanded with dull sandpaper and when sanding dust builds up between the abrasive sheet and the worked surface, especially with high speed power sanders, or when dull circular saw blades and other rotary cutting tools rub against wood surfaces, even to the point of burning. Titebond's expert says wood can be tested for burnishing by placing a drop of water on the surface. If he water soaks into the wood, it's not burnished. If water doesn't soak into the surface readily, the bonding surface must be sanded enough to remove the burnished surface. I have little or no experience with laser-cut parts, but I wonder if the heat to which laser-cut surfaces are exposed may create a burnishing effect which might extend to some depth below the "char" into the wood. Perhaps those using laser-cut parts might do the "water drop test" and report back on this question.

 

The article can be found at https://www.popularwoodworking.com/techniques/best-wood-glue-surface-smooth-or-rough/ and is quite informative. What I found of particular interest upon reflection was the fact that the strength of a PVA glue line is in great measure affected by high clamping pressure. This I knew, but never gave any thought to in the context of modeling. The general woodworking maxim is "except when using epoxy adhesives, glue joints should be clamped as tightly as possible until cured." The way I employ clamping in most modeling applications, when a part is clamped at all, is more to hold the part in place than to apply strong clamping pressure. I do try to mechanically fasten parts as much as possible, using pins and pegs, and I'm even more convinced now of the merit of that practice than before. In so many modeling applications, it's just not possible to clamp a part strongly because of its shape, location, the strength of the part itself, or a combination of the above. It would appear that without strong clamping pressure, PVA may not be any better than any other kind of "stickum."

 

As the saying goes, "Your mileage may vary." but I'm buying what Titebond's in-house senior tech says.   

Edited December 14, 2020 by Bob Cleek

[Jaager]

4 hours ago, Bob Cleek said:

"the tighter the joint, the stronger the joint."

Which just fortifies my compulsion that joints should be clamped as tightly as possible, but no crushing of wood fibers.

Planing and scraping produces a clean surface - good for gluing.  Sanding fills the pores, which is not all that good.

I think it was an old Sci Am, or the short lived popular edition of Science  article about either Stradivari or Guarneri that noted that their violins were probably scraped - the pores were free of wood flour under the clear finish.

Take home was that scraping was a good thing to do as a final step.

 

Edited December 14, 2020 by Jaager

[Bob Cleek]

10 hours ago, Jaager said:

I think it was an old Sci Am, or the short lived popular edition of Science  article about either Stradivari or Guarneri that noted that their violins were probably scraped - the pores were free of wood flour under the clear finish.

 

Being as sandpaper was almost certainly not available in their place and time, I'd say scraping was a safe bet.   

Edited December 15, 2020 by Bob Cleek