Seam Fillers....

[FLHCAHZ]

Anyone have any tips on what to use to fill seams, such as after gluing an engine and transmission together, or putting seat backs on seats.  Can anyone recommend a product to use as sort of a putty to add then sand to male it look like one piece? 

[David G.]

Hello Chaz. For filling seams such as you describe I use Bondo Spot and Glazing Putty.

What I've done is to cut the bottom of the tube off and squeeze it into a wide mouth jar. If kept in the tube, it will most likely dry out in a couple of weeks. Since this material is essentially lacquer primer with some kind of filler, probably talc or clay, It can easily be reconstituted by adding lacquer thinner. I have a pump bottle of lacquer thinner at my desk and add a splash about every week or so.

It cures through evaporation so works well enough for seams and other irregularities but not so much for larger areas as it tends to shrink and crack. I have had some luck building it up in thin layers smoothing each out as I go, but that's a slow process.

Hope this helps.

David G.

[FLHCAHZ]

1 minute ago, David G. said:

Hello Chaz. For filling seams such as you describe I use Bondo Spot and Glazing Putty.

What I've done is to cut the bottom of the tube off and squeeze it into a wide mouth jar. If kept in the tube, it will most likely dry out in a couple of weeks. Since this material is essentially lacquer primer with some kind of filler, probably talc or clay, It can easily be reconstituted by adding lacquer thinner. I have a pump bottle of lacquer thinner at my desk and add a splash about every week or so.

It cures through evaporation so works well enough for seams and other irregularities but not so much for larger areas as it tends to shrink and crack. I have had some luck building it up in thin layers smoothing each out as I go, but that's a slow process.

Hope this helps.

David G.

Thanks David.  Ill pick some up.  I had been to every auto parts store near me looking for a similar product that we used to call Nitro-stan, but cant find in.  this looks like the same type of stuff 

[Plowboy]

I use Tamiya Gray Putty. 

[espo]

I have also been pleased with using Tamiya Putty. I would first sand the joint as smooth as I can before applying the putty. Usually takes a few hours before it's hard enough to sand, but then just spray it with primer and sand smooth before color coat. There have been times on engines as an example where I had to remove the mounting pins that are in the casting so that the parts will line up better.  

[hedotwo]

I generally just put a decent bead of tube glue on the full perimeter of one of the two engine halves.  As it begins to set I give it pressure and try and move it back a forth a bit (I cut off the locating pins, if any) to try and "squish" the melting plastic together.  After dry I just sand well.  Works for me and I also use it on other two piece joins.

[tbill]

I use liquid glue for joining block halves and seat parts, I have found after getting the best fit possible while joining the parts, I can usually sand the seam ‘away’ with no filler needed, and not destroy or lose any detail.

 

Edit, granted I didn’t answer your question, but tried to show another way around having to use filler.

Edited September 1, 2021 by tbill
Added info

[Mark]

I now use a method suggested by one of the regulars here, Bill Geary if I remember right.

Cement the parts together with solvent cement (not CA or epoxy).  Let dry, then sand the seam smooth.  Then brush liquid cement over the seam, let dry, sand smooth.  I've done four of the MPC 1/25 scale three-wheel chopper bodies that are split right down the center, three of them are primed and painted...no problems.  Did a few engine blocks with molded-in oil pans too...again, no problems.

[SfanGoch]

If you use a solvent cement, such as methylene chloride, there's no need to brush a liquid cement over that seam. Brushing the solvent over the area accomplishes the same result without softening the seam because of its fast evaporation rate.

[Mark]

My past experience has been...

Cemented seam, let dry, sand, primer over...visible seam.

Cemented seam, brush cement over, sand, primer over...no visible seam.

Your results may vary...

[TransAmMike]

I lay sandpaper on a hard surface (I have a small cutting board) and drag each mating surface of the engine back an forth a few times to flatten them uniformly. Put liquid brush on glue (Tamiya) on each surface, squeeze them together then brush the glue (immediately after putting them together) on the seams. After drying, sanding the seams are usually not visible after priming or painting......I say usually😊

[SfanGoch]

44 minutes ago, Mark said:

My past experience has been...

Cemented seam, let dry, sand, primer over...visible seam.

Cemented seam, brush cement over, sand, primer over...no visible seam.

Your results may vary...

Brush solvent on both mating surfaces; this acts as sort of a primer and increases the bond strength. Clamp the parts together tightly and, using a hypo applicator, apply the solvent along the joint. This will allow the solvent to flow into the joint by capillary action. Repeat the process along the entire joint. The resulting bond will produce an almost invisible seam requiring little to no sanding. It's the same technique used by fabricators when constructing multi-part clear plexiglass display cases.

[Rodent]

Pretty much the same. I sand and put on a coat of automotive primer-surfacer and maybe rinse/repeat. If there is any noticeable seam, then I use filler.

[FLHCAHZ]

Thanks for all of the replies.  Some great tips for sure.