Jaager

Book binders PVA is a choice.  It dries clear and if slightly diluted should mostly soak in and not produce a film layer.
Titebond works well for wood, but it has a pH that is about as acidic as vinegar  ~ 3.0.  Another option would be to use
black ink to dilute -
You could get a larger supply of the tan and dye it with a walnut dye and have something that is closer in color to
rope treated with pre-petrol age tar.
Is your rope cotton or linen?  If it is a synthetic polymer, I have no suggestions.  The only synthetic or polymer that I
am willing to use at all is the PVA itself. 

You could make up the keel off the boat.  Using a jig - plywood or glued up scrap cut and sanded to match the inside of the keel.
- a second piece that is the shape of the outside of the keel.  The wet layers of the keel sandwiched and clamped between the inside and outside jigs
until dry, The keel should then lay naturally on the hull. 
When the keel is dry from the wet clamping - you could fit the bottom two layers on the hull and drill holes for pins or bamboo dowels
thru the keel layers into the hull spine.then glued up and clamp the layers  to set.  After the glue up - the pins fit into the holes and used to site the keel.  The outside lamina would hide the pins and keel would be more secure than if using glue alone.

Book binders PVA is a choice.  It dries clear and if slightly diluted should mostly soak in and not produce a film layer.
Titebond works well for wood, but it has a pH that is about as acidic as vinegar  ~ 3.0.  Another option would be to use
black ink to dilute -
You could get a larger supply of the tan and dye it with a walnut dye and have something that is closer in color to
rope treated with pre-petrol age tar.
Is your rope cotton or linen?  If it is a synthetic polymer, I have no suggestions.  The only synthetic or polymer that I
am willing to use at all is the PVA itself. 

Book binders PVA is a choice.  It dries clear and if slightly diluted should mostly soak in and not produce a film layer.
Titebond works well for wood, but it has a pH that is about as acidic as vinegar  ~ 3.0.  Another option would be to use
black ink to dilute -
You could get a larger supply of the tan and dye it with a walnut dye and have something that is closer in color to
rope treated with pre-petrol age tar.
Is your rope cotton or linen?  If it is a synthetic polymer, I have no suggestions.  The only synthetic or polymer that I
am willing to use at all is the PVA itself. 

You could make up the keel off the boat.  Using a jig - plywood or glued up scrap cut and sanded to match the inside of the keel.
- a second piece that is the shape of the outside of the keel.  The wet layers of the keel sandwiched and clamped between the inside and outside jigs
until dry, The keel should then lay naturally on the hull. 
When the keel is dry from the wet clamping - you could fit the bottom two layers on the hull and drill holes for pins or bamboo dowels
thru the keel layers into the hull spine.then glued up and clamp the layers  to set.  After the glue up - the pins fit into the holes and used to site the keel.  The outside lamina would hide the pins and keel would be more secure than if using glue alone.

You could make up the keel off the boat.  Using a jig - plywood or glued up scrap cut and sanded to match the inside of the keel.
- a second piece that is the shape of the outside of the keel.  The wet layers of the keel sandwiched and clamped between the inside and outside jigs
until dry, The keel should then lay naturally on the hull. 
When the keel is dry from the wet clamping - you could fit the bottom two layers on the hull and drill holes for pins or bamboo dowels
thru the keel layers into the hull spine.then glued up and clamp the layers  to set.  After the glue up - the pins fit into the holes and used to site the keel.  The outside lamina would hide the pins and keel would be more secure than if using glue alone.

For the trunnels:  bamboo skewers are easy to find.  There are very long ones and shorter ones
in most grocery stores. I have gotten a supply recently that is a softer species,  will split straight down end to end more readily, and pulls better.  The negative - they do not standup to much push force, so the hole needs to be a gauge larger.
 
 
I have wire drawplates, and they work a champ for drawing wire - can get any wire gauge that there is
 a hole for.  They are not so good at sizing bamboo.
 
I got my setup before Jim Byrnes became a source so I use a General  No. 15
 
                                                   
 
 
I find that drawplate tongs work pretty well - with or without the addition of a sandpaper gripper layer.
 
                                                  
 
for #61 down, a General No. 13 works well.
 
                                                  
 
Here, 220 grit sandpaper and my fingers are enough.

Not just trunnels, Titebond II -  I apply a thin coat to both surfaces.  I just read something else that I have incorporated.
End grain to end grain does not make for a strong bond.  No big deal for deck planking, but can be for frame timbers.
The new technique:  apply a thin coat of PVA to the end grain surface and let it dry.  Then when gluing up the stick,
only one surface needs any fresh glue.  For decks, a separate supply of glue can be used that has burnt senna,
walnut,or similar dry pigment added to simulate caulking.

For the trunnels:  bamboo skewers are easy to find.  There are very long ones and shorter ones
in most grocery stores. I have gotten a supply recently that is a softer species,  will split straight down end to end more readily, and pulls better.  The negative - they do not standup to much push force, so the hole needs to be a gauge larger.
 
 
I have wire drawplates, and they work a champ for drawing wire - can get any wire gauge that there is
 a hole for.  They are not so good at sizing bamboo.
 
I got my setup before Jim Byrnes became a source so I use a General  No. 15
 
                                                   
 
 
I find that drawplate tongs work pretty well - with or without the addition of a sandpaper gripper layer.
 
                                                  
 
for #61 down, a General No. 13 works well.
 
                                                  
 
Here, 220 grit sandpaper and my fingers are enough.

Not just trunnels, Titebond II -  I apply a thin coat to both surfaces.  I just read something else that I have incorporated.
End grain to end grain does not make for a strong bond.  No big deal for deck planking, but can be for frame timbers.
The new technique:  apply a thin coat of PVA to the end grain surface and let it dry.  Then when gluing up the stick,
only one surface needs any fresh glue.  For decks, a separate supply of glue can be used that has burnt senna,
walnut,or similar dry pigment added to simulate caulking.

For the trunnels:  bamboo skewers are easy to find.  There are very long ones and shorter ones
in most grocery stores. I have gotten a supply recently that is a softer species,  will split straight down end to end more readily, and pulls better.  The negative - they do not standup to much push force, so the hole needs to be a gauge larger.
 
 
I have wire drawplates, and they work a champ for drawing wire - can get any wire gauge that there is
 a hole for.  They are not so good at sizing bamboo.
 
I got my setup before Jim Byrnes became a source so I use a General  No. 15
 
                                                   
 
 
I find that drawplate tongs work pretty well - with or without the addition of a sandpaper gripper layer.
 
                                                  
 
for #61 down, a General No. 13 works well.
 
                                                  
 
Here, 220 grit sandpaper and my fingers are enough.

Not just trunnels, Titebond II -  I apply a thin coat to both surfaces.  I just read something else that I have incorporated.
End grain to end grain does not make for a strong bond.  No big deal for deck planking, but can be for frame timbers.
The new technique:  apply a thin coat of PVA to the end grain surface and let it dry.  Then when gluing up the stick,
only one surface needs any fresh glue.  For decks, a separate supply of glue can be used that has burnt senna,
walnut,or similar dry pigment added to simulate caulking.

Being old school - Davis/Underhill - it is sort of a belt and suspenders sort of philosophy  - using both glue and pegs.
The deck would be clamped using brass pins with a small piece of wood between the head of the pin and the plank.
The pin bent to apply pressure to the piece of wood.  With brass, if the pin is stuck, it can be cut off and filed. I have
been calling this "hutchocks".  When the glue dries the pin holes are then drilled for bamboo trunnels.  Working at
1:60 - a #70 is about 1 3/4" dia. in scale  
I find that the hole needs to be at least #68 or #67 or #66 to get a push fit without the bamboo getting stuck and breaking.
Before driving home the dowel, a smaller steel pin that has been deeply dipped in 9 parts Titebond III -1 part water is run thru the
hole a couple of times to provide the knotting. The peg is cut off using a sharp single edge razor blade.
Then the planking is sanded and scraped.
 
A problem with this when at 1:72 or smaller is that it starts to get to #80 dowels to keep the trunnels within anything close to scale and
#74 - #76 is as fine as pins get. And things are sort of fragile.

Being old school - Davis/Underhill - it is sort of a belt and suspenders sort of philosophy  - using both glue and pegs.
The deck would be clamped using brass pins with a small piece of wood between the head of the pin and the plank.
The pin bent to apply pressure to the piece of wood.  With brass, if the pin is stuck, it can be cut off and filed. I have
been calling this "hutchocks".  When the glue dries the pin holes are then drilled for bamboo trunnels.  Working at
1:60 - a #70 is about 1 3/4" dia. in scale  
I find that the hole needs to be at least #68 or #67 or #66 to get a push fit without the bamboo getting stuck and breaking.
Before driving home the dowel, a smaller steel pin that has been deeply dipped in 9 parts Titebond III -1 part water is run thru the
hole a couple of times to provide the knotting. The peg is cut off using a sharp single edge razor blade.
Then the planking is sanded and scraped.
 
A problem with this when at 1:72 or smaller is that it starts to get to #80 dowels to keep the trunnels within anything close to scale and
#74 - #76 is as fine as pins get. And things are sort of fragile.

Being old school - Davis/Underhill - it is sort of a belt and suspenders sort of philosophy  - using both glue and pegs.
The deck would be clamped using brass pins with a small piece of wood between the head of the pin and the plank.
The pin bent to apply pressure to the piece of wood.  With brass, if the pin is stuck, it can be cut off and filed. I have
been calling this "hutchocks".  When the glue dries the pin holes are then drilled for bamboo trunnels.  Working at
1:60 - a #70 is about 1 3/4" dia. in scale  
I find that the hole needs to be at least #68 or #67 or #66 to get a push fit without the bamboo getting stuck and breaking.
Before driving home the dowel, a smaller steel pin that has been deeply dipped in 9 parts Titebond III -1 part water is run thru the
hole a couple of times to provide the knotting. The peg is cut off using a sharp single edge razor blade.
Then the planking is sanded and scraped.
 
A problem with this when at 1:72 or smaller is that it starts to get to #80 dowels to keep the trunnels within anything close to scale and
#74 - #76 is as fine as pins get. And things are sort of fragile.

Bob,


With a free 1/2" shaft you are potentially golden for options for the machine.


1.  You loose the table, but for free hand - if you wish to save on the cost of the sanding medium:


There are sleeveless drums - they use sheet sandpaper:
 
 
                                             
            06P14.jpg    



Woodcraft has 3" x 3" , 2.5" x 3" , 2" x 3"  drums with a 1/2" set screw socket mount. They have a 1/2" rod for a chuck to grip.
Peachtree Woodworking Supply  has 3" x 3" , 2"x 3"
they also have 4.5" x 3"  and 6" x 3" for a large surface.
Both also have 1" x 3"  and 3/4" x 3"  but the socket mount is 1/4" -  they have a 1/4" rod

As far as 1/4" tools:

There are shaft arbors that mount on a 1/2" shaft:
 
 
                                               
            3ZN03_AW01 s.jpg

They are available from multiple sources, but low quality will likely not run true.

Granger has arbors that are 1/2" x 20 (fine) threaded at the business end as both RH and LH.
They can mount buffing and grinding media - with a 1/2" hole.

I am guessing that your machine turns CCW -  I confuse myself with LH vs RH,
but Grainger has a 1/4" chuck - it is only 1/4" though - that threads on the 1/2" x 20 shaft and tightens down with CCW rotation.
 
                                                      
            1F612_AS01 s.jpg


With this chuck, the 3" x 1"  and  3" x 3/4" drums can be used.

In addition 1/4"  carbine burrs can be mounted.
 
 
                                                      
            259700_F.jpg

Wood Carvers Supply has a wide variety of choices available.  For our uses, the fine carbide seems coarse enough.

There is a Jacobs chuck that will mount on the 1/2" x 20 rod at Harbor Freight
 
                                                 
            image_18878 s.jpg

Again, CCW holds it down.

With this chuck you can use the Microplane tools  1" x 2.5"  and 2" x 2.5"
 
 
                                                  
            828821 s.jpg

These cutters are designed to use CCW rotation and have a 5/16" rod for a chuck to grip.

If you find a tool with a 1/2" rod and want to mount it, Grainger  has a 1/2" shaft coupling:
 
 
                                                
            6L013_AS01.jpg



 I have just made my own version of this machine, but with inspiration from Jim Byrnes - his machines are 1/3 HP - 2 pole - but are ~ 3400 RPM - twice what a sander wants - I bought a 1/3 HP self cooling 2 pole 1700 RPM motor and wired it with a drum switch so it will rotate CW as well as CCW.  I am right handed and prefer working on the right side of the drum.  But when sanding the rail end of a frame on the left arm - the drum tries to throw the work.  Flipping a switch to reverse the rotation solves the problem.  But with CW rotation, the chuck wants to walk up the threaded rod.  Set screw mounted tools work either rotation.  I will have to think about how and if I want to add the belt sanding option.  I had not thought of that possibility until your post.

These tools work fine for free hand use.  For cutting the bevels on frames, the change is continuous so a table is not much use - free hand seems about it.  I am thinking that the 4.5x3 and 6x3 drums will give me plenty of room to work.

I also want to use the Microplane and 3" drums as an edger, to sand and true up boards that are too wide to fit my sanding planer.  The arbors and chucks are not turning as precisely true as I wish.   So, as much as I hate have to tear down my lathe to clean up the steel cuttings, I will probably bore my own shaft couplings from 3/4" steel rod,   bore a 1/4" hole in one end and 1/2" in the other and drill and tap for set screws in one and 5/16" by 1/2" in another.
 

Mike,
 
Unless you intend to model at 1:36 or something like that, the additional surface area with the belt over a 3" drum
may not offer that much more function, but that or the drum allows you to sand with the grain, while a disc or vertical
 belt sands across the grain.  For sanding end grain for precise match up , I trust the disc over any sort of belt because
a belt will have give in/out.

Bob,


With a free 1/2" shaft you are potentially golden for options for the machine.


1.  You loose the table, but for free hand - if you wish to save on the cost of the sanding medium:


There are sleeveless drums - they use sheet sandpaper:
 
 
                                             
            06P14.jpg    



Woodcraft has 3" x 3" , 2.5" x 3" , 2" x 3"  drums with a 1/2" set screw socket mount. They have a 1/2" rod for a chuck to grip.
Peachtree Woodworking Supply  has 3" x 3" , 2"x 3"
they also have 4.5" x 3"  and 6" x 3" for a large surface.
Both also have 1" x 3"  and 3/4" x 3"  but the socket mount is 1/4" -  they have a 1/4" rod

As far as 1/4" tools:

There are shaft arbors that mount on a 1/2" shaft:
 
 
                                               
            3ZN03_AW01 s.jpg

They are available from multiple sources, but low quality will likely not run true.

Granger has arbors that are 1/2" x 20 (fine) threaded at the business end as both RH and LH.
They can mount buffing and grinding media - with a 1/2" hole.

I am guessing that your machine turns CCW -  I confuse myself with LH vs RH,
but Grainger has a 1/4" chuck - it is only 1/4" though - that threads on the 1/2" x 20 shaft and tightens down with CCW rotation.
 
                                                      
            1F612_AS01 s.jpg


With this chuck, the 3" x 1"  and  3" x 3/4" drums can be used.

In addition 1/4"  carbine burrs can be mounted.
 
 
                                                      
            259700_F.jpg

Wood Carvers Supply has a wide variety of choices available.  For our uses, the fine carbide seems coarse enough.

There is a Jacobs chuck that will mount on the 1/2" x 20 rod at Harbor Freight
 
                                                 
            image_18878 s.jpg

Again, CCW holds it down.

With this chuck you can use the Microplane tools  1" x 2.5"  and 2" x 2.5"
 
 
                                                  
            828821 s.jpg

These cutters are designed to use CCW rotation and have a 5/16" rod for a chuck to grip.

If you find a tool with a 1/2" rod and want to mount it, Grainger  has a 1/2" shaft coupling:
 
 
                                                
            6L013_AS01.jpg



 I have just made my own version of this machine, but with inspiration from Jim Byrnes - his machines are 1/3 HP - 2 pole - but are ~ 3400 RPM - twice what a sander wants - I bought a 1/3 HP self cooling 2 pole 1700 RPM motor and wired it with a drum switch so it will rotate CW as well as CCW.  I am right handed and prefer working on the right side of the drum.  But when sanding the rail end of a frame on the left arm - the drum tries to throw the work.  Flipping a switch to reverse the rotation solves the problem.  But with CW rotation, the chuck wants to walk up the threaded rod.  Set screw mounted tools work either rotation.  I will have to think about how and if I want to add the belt sanding option.  I had not thought of that possibility until your post.

These tools work fine for free hand use.  For cutting the bevels on frames, the change is continuous so a table is not much use - free hand seems about it.  I am thinking that the 4.5x3 and 6x3 drums will give me plenty of room to work.

I also want to use the Microplane and 3" drums as an edger, to sand and true up boards that are too wide to fit my sanding planer.  The arbors and chucks are not turning as precisely true as I wish.   So, as much as I hate have to tear down my lathe to clean up the steel cuttings, I will probably bore my own shaft couplings from 3/4" steel rod,   bore a 1/4" hole in one end and 1/2" in the other and drill and tap for set screws in one and 5/16" by 1/2" in another.
 

Mike,
 
Unless you intend to model at 1:36 or something like that, the additional surface area with the belt over a 3" drum
may not offer that much more function, but that or the drum allows you to sand with the grain, while a disc or vertical
 belt sands across the grain.  For sanding end grain for precise match up , I trust the disc over any sort of belt because
a belt will have give in/out.

For a full size assembly I just used an epoxy to bond steel to wood. 
I have tried the syringe applicator in the past and I had a tendency to push one end more than the other so I had to express more than I needed to equalize the two components.  But that waste was of no consequence because  I use it so infrequently that most of it tried in the applicator before I used it all.
 
This time I used J-B Weld original - it comes as two   1 oz tubes and is < $5.00 US.
It has about a 5 hr set time so you have a while to play with it.  It takes 24 hrs to cure.  Then it can be filled, sanded, tapped, drilled.
It is ugly (dark grey)  and messy   and goes where you don't want it if you are not careful.  Wear gloves and mask any surface where it is not wanted.
It is cheap enough that mixing too much is not an issue.

Bob,


With a free 1/2" shaft you are potentially golden for options for the machine.


1.  You loose the table, but for free hand - if you wish to save on the cost of the sanding medium:


There are sleeveless drums - they use sheet sandpaper:
 
 
                                             
            06P14.jpg    



Woodcraft has 3" x 3" , 2.5" x 3" , 2" x 3"  drums with a 1/2" set screw socket mount. They have a 1/2" rod for a chuck to grip.
Peachtree Woodworking Supply  has 3" x 3" , 2"x 3"
they also have 4.5" x 3"  and 6" x 3" for a large surface.
Both also have 1" x 3"  and 3/4" x 3"  but the socket mount is 1/4" -  they have a 1/4" rod

As far as 1/4" tools:

There are shaft arbors that mount on a 1/2" shaft:
 
 
                                               
            3ZN03_AW01 s.jpg

They are available from multiple sources, but low quality will likely not run true.

Granger has arbors that are 1/2" x 20 (fine) threaded at the business end as both RH and LH.
They can mount buffing and grinding media - with a 1/2" hole.

I am guessing that your machine turns CCW -  I confuse myself with LH vs RH,
but Grainger has a 1/4" chuck - it is only 1/4" though - that threads on the 1/2" x 20 shaft and tightens down with CCW rotation.
 
                                                      
            1F612_AS01 s.jpg


With this chuck, the 3" x 1"  and  3" x 3/4" drums can be used.

In addition 1/4"  carbine burrs can be mounted.
 
 
                                                      
            259700_F.jpg

Wood Carvers Supply has a wide variety of choices available.  For our uses, the fine carbide seems coarse enough.

There is a Jacobs chuck that will mount on the 1/2" x 20 rod at Harbor Freight
 
                                                 
            image_18878 s.jpg

Again, CCW holds it down.

With this chuck you can use the Microplane tools  1" x 2.5"  and 2" x 2.5"
 
 
                                                  
            828821 s.jpg

These cutters are designed to use CCW rotation and have a 5/16" rod for a chuck to grip.

If you find a tool with a 1/2" rod and want to mount it, Grainger  has a 1/2" shaft coupling:
 
 
                                                
            6L013_AS01.jpg



 I have just made my own version of this machine, but with inspiration from Jim Byrnes - his machines are 1/3 HP - 2 pole - but are ~ 3400 RPM - twice what a sander wants - I bought a 1/3 HP self cooling 2 pole 1700 RPM motor and wired it with a drum switch so it will rotate CW as well as CCW.  I am right handed and prefer working on the right side of the drum.  But when sanding the rail end of a frame on the left arm - the drum tries to throw the work.  Flipping a switch to reverse the rotation solves the problem.  But with CW rotation, the chuck wants to walk up the threaded rod.  Set screw mounted tools work either rotation.  I will have to think about how and if I want to add the belt sanding option.  I had not thought of that possibility until your post.

These tools work fine for free hand use.  For cutting the bevels on frames, the change is continuous so a table is not much use - free hand seems about it.  I am thinking that the 4.5x3 and 6x3 drums will give me plenty of room to work.

I also want to use the Microplane and 3" drums as an edger, to sand and true up boards that are too wide to fit my sanding planer.  The arbors and chucks are not turning as precisely true as I wish.   So, as much as I hate have to tear down my lathe to clean up the steel cuttings, I will probably bore my own shaft couplings from 3/4" steel rod,   bore a 1/4" hole in one end and 1/2" in the other and drill and tap for set screws in one and 5/16" by 1/2" in another.
 

Bob,


With a free 1/2" shaft you are potentially golden for options for the machine.


1.  You loose the table, but for free hand - if you wish to save on the cost of the sanding medium:


There are sleeveless drums - they use sheet sandpaper:
 
 
                                             
            06P14.jpg    



Woodcraft has 3" x 3" , 2.5" x 3" , 2" x 3"  drums with a 1/2" set screw socket mount. They have a 1/2" rod for a chuck to grip.
Peachtree Woodworking Supply  has 3" x 3" , 2"x 3"
they also have 4.5" x 3"  and 6" x 3" for a large surface.
Both also have 1" x 3"  and 3/4" x 3"  but the socket mount is 1/4" -  they have a 1/4" rod

As far as 1/4" tools:

There are shaft arbors that mount on a 1/2" shaft:
 
 
                                               
            3ZN03_AW01 s.jpg

They are available from multiple sources, but low quality will likely not run true.

Granger has arbors that are 1/2" x 20 (fine) threaded at the business end as both RH and LH.
They can mount buffing and grinding media - with a 1/2" hole.

I am guessing that your machine turns CCW -  I confuse myself with LH vs RH,
but Grainger has a 1/4" chuck - it is only 1/4" though - that threads on the 1/2" x 20 shaft and tightens down with CCW rotation.
 
                                                      
            1F612_AS01 s.jpg


With this chuck, the 3" x 1"  and  3" x 3/4" drums can be used.

In addition 1/4"  carbine burrs can be mounted.
 
 
                                                      
            259700_F.jpg

Wood Carvers Supply has a wide variety of choices available.  For our uses, the fine carbide seems coarse enough.

There is a Jacobs chuck that will mount on the 1/2" x 20 rod at Harbor Freight
 
                                                 
            image_18878 s.jpg

Again, CCW holds it down.

With this chuck you can use the Microplane tools  1" x 2.5"  and 2" x 2.5"
 
 
                                                  
            828821 s.jpg

These cutters are designed to use CCW rotation and have a 5/16" rod for a chuck to grip.

If you find a tool with a 1/2" rod and want to mount it, Grainger  has a 1/2" shaft coupling:
 
 
                                                
            6L013_AS01.jpg



 I have just made my own version of this machine, but with inspiration from Jim Byrnes - his machines are 1/3 HP - 2 pole - but are ~ 3400 RPM - twice what a sander wants - I bought a 1/3 HP self cooling 2 pole 1700 RPM motor and wired it with a drum switch so it will rotate CW as well as CCW.  I am right handed and prefer working on the right side of the drum.  But when sanding the rail end of a frame on the left arm - the drum tries to throw the work.  Flipping a switch to reverse the rotation solves the problem.  But with CW rotation, the chuck wants to walk up the threaded rod.  Set screw mounted tools work either rotation.  I will have to think about how and if I want to add the belt sanding option.  I had not thought of that possibility until your post.

These tools work fine for free hand use.  For cutting the bevels on frames, the change is continuous so a table is not much use - free hand seems about it.  I am thinking that the 4.5x3 and 6x3 drums will give me plenty of room to work.

I also want to use the Microplane and 3" drums as an edger, to sand and true up boards that are too wide to fit my sanding planer.  The arbors and chucks are not turning as precisely true as I wish.   So, as much as I hate have to tear down my lathe to clean up the steel cuttings, I will probably bore my own shaft couplings from 3/4" steel rod,   bore a 1/4" hole in one end and 1/2" in the other and drill and tap for set screws in one and 5/16" by 1/2" in another.
 

Mike,
 
Unless you intend to model at 1:36 or something like that, the additional surface area with the belt over a 3" drum
may not offer that much more function, but that or the drum allows you to sand with the grain, while a disc or vertical
 belt sands across the grain.  For sanding end grain for precise match up , I trust the disc over any sort of belt because
a belt will have give in/out.

Bob,
How are the drums mounted to the motor shaft?
More to the point: what is the bare shaft like? 
Is it a 1/2" steel rod or a proprietary setup?
If it is proprietary, how is that attached to the actual motor shaft?

The unit on sale looks to me to be the same Asian generic that Harbor Freight sells.