Screws for the old screw bottm cars

[gtx6970]

Anyone know what the proper term is for them . They are kind of a weird thread .

I have several of these cars missing them and was looking around McMaster Carrs site to see if I can find a reasonable replacement

[Ace-Garageguy]

In general, they're referred to as "thread-forming" or "thread rolling" fasteners (or screws), and are specially designed for use with thermoplastics to minimize required installation torque (and therefore lessen the chance of snapping a stud or damaging a molded boss), but to still provide good resistance to backing-out.

As you know, they have an entirely different thread from self-tapping screws made for metal, or sheetmetal or wood screws.

Plastite 45 pan-head screws are a modern type-PT replacement, pretty close to some of the old screwbottom kit designs. They're available in a variety of diameters and drive styles.

        (enlarged for clarity)

As you see, these are very similar in thread appearance to the old-style screwbottom parts.

There is also the Hi-Lo type point, often specifically selected for plastic.

                                     

 

Edited November 26, 2016 by Ace-Garageguy

[StevenGuthmiller]

"floyd426rt" has a lot of 80+ chassis screws, axles & hood clips for sale on ebay right now.

Should take care of you for a while if you want originals.

Probably quite a bit more expensive than a modern replacement if you can find a good one, but he has them anyway.

 

Steve

[gtx6970]

thanks Steve.

I am currently high bidder on them 

But was thinking backup plan.....just in case

[Ace-Garageguy]

thanks Steve.

I am currently high bidder on them 

But was thinking backup plan.....just in case

You're welcome...not that you bothered to say "thank you" to me for answering your particular question in depth.

[disabled modeler]

I have the same problem with mine....they always seem to be missing and everything else I have tried just breaks the mounting posts or.?   I could use any originals anyone could spare for my restoration projects.

[Ace-Garageguy]

I have the same problem with mine....they always seem to be missing and everything else I have tried just breaks the mounting posts or.?   I could use any originals anyone could spare for my restoration projects.

And they break the mounting posts because :

1) The posts have been over-stressed previously by ham-handed screwers and / or

2) Whatever you're using isn't designed specifically for thermoplastics and is taking too much torque to drive in, which in turn snaps the post off.

See my post explaining the right replacement screws above. (NOTE: If the post has already been over-stressed, you're going to be SOL no matter WHAT kind of screw you use)

Just any-old-screw you happen to have that looks like the right diameter won't work right in plastic.

[gtx6970]

You're welcome...not that you bothered to say "thank you" to me for answering your particular question in depth.

ace. Thanks 

 

But my reply was because i was aready high bidder in the ones Steve mentioned. But ive tried that route before only to get outbid. And i am thinkng of a backup plan ahead of time 

I do appreciate all the  replies

[1930fordpickup]

Bill I will not bid on these just to help you out, I have enough for now anyway. Just no extra's . The rust remover works good on these little rusty parts, just paint after the process. 

 

[StevenGuthmiller]

You can always just "nix" the screws & do some pins too Bill.

I don't worry much about the screws.

If I have them, I use them.

Otherwise a plastic pin, or whatever, will work just as well.

That is unless you're planning on disassembling later on.

I don't do much of that.

 

Steve

[GLMFAA1]

Ever notice JoHan were thinner and deeper pitch than the others AMT,SMP,Hubley etc They screwed in faster. There were crazy kids like me that used glue to help set them in the posts so that destroyed the idea of backing them out.

greg

I only have a few to my name, can't help ya , sorry

[gtx6970]

You can always just "nix" the screws & do some pins too Bill.

I don't worry much about the screws.

If I have them, I use them.

Otherwise a plastic pin, or whatever, will work just as well.

That is unless you're planning on disassembling later on.

I don't do much of that.

 

Steve

Steve

I saw on the mcmaster carr site there is nail looking  pin with looks like splines that would work for that . sort of like the pin in the later reissue series Johan promos of the 80s

 

I have enough for my upcoming builds...but sooner or later i will need something.  As i  have a couple cars with nothing.

Maybe ill win these and wont have to worry about ths later down the road. These would be more than enough for my needs...now and later. IF i wn .

 

[gtx6970]

Ps. When i screwed them in my 59 Edsel for the 1st time. I put a little vasaline to help them go in easier...really didnt want to risk breaking the posts off .

 

[disabled modeler]

A wealth of information here gents....thanks!   I found out the hard way a long time ago to just be safe and use the original type screws if one needs to use some like me...I like trying to keep them as original as possible when restoring them when it comes to old models or promos.  I remember seeing those odd Johan metal pin type ones with no screw head too...they were interesting to have to mess with.  I found most original style chassis screws are close enough to work on most that had them whatever the brand of promo or kit it was.  Second thing is old plastic gets brittle...I have actually coated the mounting posts with 2 part epoxy glue to help make them stronger before just have to remember to let it set up all the way first before mounting the chassis.  The old screw chassis ones and promos are my favorites.

[BigTallDad]

If you're merely trying to repair the kit and originality is not an issue, replace the plastic posts.

Cut the post off, leaving about 1/4" at the base. Apply epoxy, then screw a tee-nut on the post remnant. After the epoxy cures, you have a threaded sleeve that uses machine-thread screws.

[Ace-Garageguy]

If you're merely trying to repair the kit and originality is not an issue, replace the plastic posts.

Cut the post off, leaving about 1/4" at the base. Apply epoxy, then screw a tee-nut on the post remnant. After the epoxy cures, you have a threaded sleeve that uses machine-thread screws.

Of course, if you elect to do that, be sure to measure the original length of the posts VERY CAREFULLY before removing them. You'll HAVE to get the new posts EXACTLY the same height as the old ones.

All the posts I've ever seen also function as standoffs that accurately position the chassis relative to the body, and are responsible for how the wheels fit up in the wheel openings on the body, and "stance".

A 1/32 or 1/16 inch mistake here can really ruin the look of a model...so be careful.

Edited November 27, 2016 by Ace-Garageguy

[GLMFAA1]

Another repair is to get evergreen tube and slide it over the post, if you can't get the right size, cut the tubing and slide it over the post. I used brass tubing before evergreen came along

greg

[gtx6970]

Another repair is to get evergreen tube and slide it over the post, if you can't get the right size, cut the tubing and slide it over the post. I used brass tubing before evergreen came along

greg

I'll have to look into this idea. Ive been fairly lucky in this regard as  I only have a couple of cars  with damaged posts but they're not easy kits to replace ( Johan 1959 Fury is one ) and this sounds like a  viable repair.

But for the most part I just need to replace missing screws ,,thus my original post.

 

[StevenGuthmiller]

I'll have to look into this idea. Ive been fairly lucky in this regard as  I only have a couple of cars  with damaged posts but they're not easy kits to replace ( Johan 1959 Fury is one ) and this sounds like a  viable repair.

But for the most part I just need to replace missing screws ,,thus my original post.

 

I built a '58 Buick kit a few years ago that came with both front screw posts twisted off.

I repaired them by simply gluing them back in place at final assembly & "pinning" them to the chassis.

worked just fine.

The nice thing about using pins is the fact that you don't have to worry about twisting off or breaking the posts, & if your pins fit tight enough, you don't have to glue them in either.

Just as a side note, as of the past year or so, one of my first tasks with any old annual with an engine, is to remove the front screw posts anyway.

They're just completely unsightly in the finished engine bay, so I get rid of them.

There are other ways to attach the chassis plate without screws.

 

Steve

Edited November 29, 2016 by StevenGuthmiller

[gtx6970]

Well, I got outbid on those....So  I will look at other options.

 

Steve, as far as removing them . MOST of the stuff I have in mind are kits where the hood doesn't open anyway. Remember I kind of loose interest after about 1962 or 63 . So its mostly late 50s and early 60s annuals builtups that I need the screws for anyway . Its not like I need a hundred of them ,,,,,,just maybe a dozen or 2 tops

If I have anything later 60s,,,,,Its a Mopar B body and I plan to use the AMT chassis under them  anyway so on them ,,,, they're not a problem.