1. Topics
  2. making the case for self-tapping screws

making the case for self-tapping screws

Andy Carlson
 

Many of us STMFC'ers have moved on beyond machine screws for fastening trucks to plastic or resin bolsters, for the simple reason that they fail due to their lack of clamping which causes the m.s. to rock back-and-forth, eventually totally loosening and falling out. A much better solution is to use sheet metal self-taping screws, which because of their design, attach much better without the need of the clamping forces from snugging a screw down real tight. Resin is particularly vulnerable to the m.s. loosening, for reasons I believe lay at the semi-lubricating properties polyurethane has on threads.

I buy boxes of about 100 screws at the hardware store for about $5.00.

-Andy Carlson
Ojai CA
Steve Lucas <stevelucas3@...>
 

I first dip the tip and first thread or two of the screw in
carpenter's glue before insertion. So far, truck screws treated this
way seem to stay in place without backing themselves out. But they
are still easy to remove.

Steve Lucas.

--- In STMFC@..., Andy Carlson <midcentury@...> wrote:



Many of us STMFC'ers have moved on beyond machine screws for
fastening trucks to plastic or resin bolsters, for the simple reason
that they fail due to their lack of clamping which causes the m.s. to
rock back-and-forth, eventually totally loosening and falling out. A
much better solution is to use sheet metal self-taping screws, which
because of their design, attach much better without the need of the
clamping forces from snugging a screw down real tight. Resin is
particularly vulnerable to the m.s. loosening, for reasons I believe
lay at the semi-lubricating properties polyurethane has on threads.

I buy boxes of about 100 screws at the hardware store for about
$5.00.

-Andy Carlson
Ojai CA

[Non-text portions of this message have been removed]
pierreoliver2003 <pierre.oliver@...>
 

I use machine screws for all the resin cars I build for my customers
and for myself and have noted that the brass screws one finds in the
local hobby shop can be a little undersize in the shank diameter,
causing the problem as described by Andy.
I buy my 2-56 machine screws from a fastener supply outlet and pay
about $2.50 a hundred. I find that machine screws are just the right
level of snug when going into a tapped hole. Presuming that one has
used a decent quality drill and tap in the hole in the first place.
I've never been comfortable with self-tapping screws because of the
material they displace and thus may split a bolster.
Pierre Oliver

--- In STMFC@..., Andy Carlson <midcentury@...> wrote:



Many of us STMFC'ers have moved on beyond machine screws for
fastening trucks to plastic or resin bolsters, for the simple reason
that they fail due to their lack of clamping which causes the m.s. to
rock back-and-forth, eventually totally loosening and falling out. A
much better solution is to use sheet metal self-taping screws, which
because of their design, attach much better without the need of the
clamping forces from snugging a screw down real tight. Resin is
particularly vulnerable to the m.s. loosening, for reasons I believe
lay at the semi-lubricating properties polyurethane has on threads.

I buy boxes of about 100 screws at the hardware store for about
$5.00.

-Andy Carlson
Ojai CA

[Non-text portions of this message have been removed]
Earl T. Hackett <hacketet@...>
 

There is a wide variety of "self tapping" screws available for plastic
assembly. They fall into two classes, self tapping that cuts threads,
and thread forming that displace material as they enter the predrilled
hole. The common sheet metal screws are of the thread forming type.
The material displaced by the thread forming screws creates internal
stress in the plastic. Some plastics tolerate this well, others
develop stress cracks. It can be quite important to provide some
place for this displaced material to go.

Rather than me yammering about this, go to the McMaster Carr web site

http://www.mcmaster.com/

search on "screws," and check on the various "About ..." topics. Not
all of the designs are available in the small sizes we use, but many
are.

Be careful when replacing a self tapping screw in a hole that you
engage the original threads. Turn the screw backwards (counter
clockwise) until you feel the threads click into place then as you
turn it clockwise you should note that it enters the hole with almost
no resistance. If you don't follow this procedure, after a few
changes you may find that the hole has grown to be over sized and the
screw will not hold at all.
Larry Jackman <Ljack70117@...>
 

Lock tite will do the same thing.
Thank you
Larry Jackman
ljack70117@...

On Dec 24, 2008, at 8:45 AM, Steve Lucas wrote:

I first dip the tip and first thread or two of the screw in
carpenter's glue before insertion. So far, truck screws treated this
way seem to stay in place without backing themselves out. But they
are still easy to remove.

Steve Lucas.

--- In STMFC@..., Andy Carlson <midcentury@...> wrote:



Many of us STMFC'ers have moved on beyond machine screws for
fastening trucks to plastic or resin bolsters, for the simple reason
that they fail due to their lack of clamping which causes the m.s. to
rock back-and-forth, eventually totally loosening and falling out. A
much better solution is to use sheet metal self-taping screws, which
because of their design, attach much better without the need of the
clamping forces from snugging a screw down real tight. Resin is
particularly vulnerable to the m.s. loosening, for reasons I believe
lay at the semi-lubricating properties polyurethane has on threads.

I buy boxes of about 100 screws at the hardware store for about
$5.00.

-Andy Carlson
Ojai CA



------------------------------------

Yahoo! Groups Links
George R. Stilwell, Jr. <GRSJr@...>
 

I can't make a "case" for self tapping screws. Machine screws work perfectly if you add a drop of "Loktite" to the tip.

They're removable many times, they don't stress the bolster material, and they won't work loose if "Loktite" is used.

Ray
David North <davenorth@...>
 

I've had the same problem with the truck retaining screws coming

loose on styrene cars that don't have the collar for the screw to bind
against.

eg: MDC cars that don't come with one, or Athearn etc cars where I trimmed
the post

too short.



Using a self tapper runs the risk of splitting the bolster, so I choose not
to go there,

plus removal of the screw more than once or twice will create the same issue
-

each time you retighten the screw, it will turn in a fraction further
looking for the clamping point.



A while back I started using nylon screws to retain my trucks.

As they are screwed in, the thread acts like a nyloc nut and the screws stay


wherever I've screwed them to.



This allows very fine adjustment of the tighter truck of the 3 point
suspension system.

Plus the screws have a slightly larger head that fits the land on the truck
a little better IMHO.

Here is the link to the Micro Fasteners 2-56 screws I use.



http://www.microfasteners.com/catalog/products/NYLNBPP.cfm



cheers

Dave
James Kubanick <kuban@...>
 

Another technique is to use a bushing under the head of a machine screw. While I have made these from styrene tubing in the past, I now make these bushings by shaving the center bushing off of a Kadee #5 coupler box with a sharp, single-edge razor blade.

Jim Kubanick
Morgantown WV

----- Original Message -----
From: David North
To: STMFC@...
Sent: Wednesday, December 24, 2008 5:12 PM
Subject: [STMFC] Re: making the case for self-tapping screws


I've had the same problem with the truck retaining screws coming

loose on styrene cars that don't have the collar for the screw to bind
against.

eg: MDC cars that don't come with one, or Athearn etc cars where I trimmed
the post

too short.

Using a self tapper runs the risk of splitting the bolster, so I choose not
to go there,

plus removal of the screw more than once or twice will create the same issue
-

each time you retighten the screw, it will turn in a fraction further
looking for the clamping point.

A while back I started using nylon screws to retain my trucks.

As they are screwed in, the thread acts like a nyloc nut and the screws stay

wherever I've screwed them to.

This allows very fine adjustment of the tighter truck of the 3 point
suspension system.

Plus the screws have a slightly larger head that fits the land on the truck
a little better IMHO.

Here is the link to the Micro Fasteners 2-56 screws I use.

http://www.microfasteners.com/catalog/products/NYLNBPP.cfm

cheers

Dave





!DSPAM:4952b3e019795268152715!
Denny Anspach <danspach@...>
 

Creating bushings to compensate for disarity in size between 2-56 screws and the gaping truck bolster holes is one path to solution- but it can be a remarkably frustrating one. The depth of bushings needed from truck make/type to another seem to vary considerably, so that the bushing that you have fabricated may be too short for truck A, or too long for truck B, so that in the end although one has indeed stopped the infernal truck side-slip, instead he/she is left to deal with either a car body rocking like a drunken soldier, or a loose truck screw already working its way out.

Of course, if the overly long bushings can be made easily shorter, and if the security of 2-56 screws in the body bolsters can be assured, then the use of bushings is certainly one pathway to A solution.

Truck makers make bushings peculiar to their truck bolsters?

Denny

Denny S. Anspach, MD
Sacramento
Donald B. Valentine <riverman_vt@...>
 

Hi Denny,

Gather you are back in your "normal" habitat as I see "Sacramento"
at the end of your post rather than "Iowa". But with regard to truck
screws, and without wishing to open a new thread for endless
discussion, it does seem to me that this is another standard that the
NMRA could/should have addressed long, long ago. It seems that each
individual manufacturer of rolling stock has just chosen a method of
truck attachment that seemed convenient at the time the process was
set up. For my own purposes If I don't like what is presented I
usually fill any exisitng holes with five minute epoxy and then do
things "my way", which in the end only adds to the disparities
already out there. A single standard would better serve everyone.

Happy Holidays, Don Valentine




--- In STMFC@..., Denny Anspach <danspach@...> wrote:

Creating bushings to compensate for disarity in size between 2-56
screws and the gaping truck bolster holes is one path to solution-
but
it can be a remarkably frustrating one. The depth of bushings
needed
from truck make/type to another seem to vary considerably, so that
the
bushing that you have fabricated may be too short for truck A, or
too
long for truck B, so that in the end although one has indeed
stopped
the infernal truck side-slip, instead he/she is left to deal with
either a car body rocking like a drunken soldier, or a loose truck
screw already working its way out.

Of course, if the overly long bushings can be made easily shorter,
and
if the security of 2-56 screws in the body bolsters can be
assured,
then the use of bushings is certainly one pathway to A solution.

Truck makers make bushings peculiar to their truck bolsters?

Denny

Denny S. Anspach, MD
Sacramento
Dennis Storzek <destorzek@...>
 

--- In STMFC@..., Denny Anspach <danspach@...> wrote:


Truck makers make bushings peculiar to their truck bolsters?

Denny

Denny S. Anspach, MD
Sacramento
Doc,

I fail to see why truck makers need to be responsible for other
manufacturers' poorly designed body bolsters. The de facto standard in
the hobby for the last forty years has been a clearance hole for a
1/8" dia. boss, so the truck doesn't pivot around the threads, and the
screw can be tightened solid without binding the truck. If it wasn't
for the fact that Kadee persists in adhering to the outdated and
obsolete NMRA standard, the available trucks would have matched this
standard 100%, at least before the recent wave of designed in China
stuff started diverging again.

There is no reason why resin kit makers can't mold the boss on their
parts; I was even able to have it included on white metal parts. The
fact that it might need to be removed to accommodate a few trucks is
no excuse; it's easier for the modeler to carve it off rather than
cobble it up from nothing.

That being said, If you buy Accurail trucks, you get the added value
of someone actually giving this some thought during the design
process. Accurail trucks come with the clearance hole for the 1/8"
boss, and so will fit most any other injection molded kit. The inside
diameter of the screw head recess is designed to be a decent running
fit on the ANSI standard dimensions for the pan head on a #2 screw;
either a wood screw, type AB thread cutting screw (sheet metal screw)
or machine screw. So, if you use pan head screws, the O.D. of the head
should give acceptable results, although the standard for pan heads
does provide wider tolerances that the molded bosses are usually held
to. You can even trim the bushing off the ubiquitous Kadee #5 box, and
you will find that the thickness of the Accurail truck bolster is such
that the Kadee bushing is the proper length.

Dennis Storzek
Accurail, Inc.
armprem
 

Weelllllll,I just couldn't resist.Model makers?...............With the flood of ready to run cars what's the issue?Are there that many of us model makers left to have to worry about screws? <G>,Armand Premo

----- Original Message -----
From: "Dennis Storzek" <destorzek@...>
To: <STMFC@...>
Sent: Saturday, December 27, 2008 1:32 PM
Subject: [STMFC] Re: making the case for self-tapping screws


> --- In STMFC@..., Denny Anspach <danspach@...> wrote:
>>
>>
>> Truck makers make bushings peculiar to their truck bolsters?
>>
>> Denny
>>
>> Denny S. Anspach, MD
>> Sacramento
>>
>
> Doc,
>
> I fail to see why truck makers need to be responsible for other
> manufacturers' poorly designed body bolsters. The de facto standard in
> the hobby for the last forty years has been a clearance hole for a
> 1/8" dia. boss, so the truck doesn't pivot around the threads, and the
> screw can be tightened solid without binding the truck. If it wasn't
> for the fact that Kadee persists in adhering to the outdated and
> obsolete NMRA standard, the available trucks would have matched this
> standard 100%, at least before the recent wave of designed in China
> stuff started diverging again.
>
> There is no reason why resin kit makers can't mold the boss on their
> parts; I was even able to have it included on white metal parts. The
> fact that it might need to be removed to accommodate a few trucks is
> no excuse; it's easier for the modeler to carve it off rather than
> cobble it up from nothing.
>
> That being said, If you buy Accurail trucks, you get the added value
> of someone actually giving this some thought during the design
> process. Accurail trucks come with the clearance hole for the 1/8"
> boss, and so will fit most any other injection molded kit. The inside
> diameter of the screw head recess is designed to be a decent running
> fit on the ANSI standard dimensions for the pan head on a #2 screw;
> either a wood screw, type AB thread cutting screw (sheet metal screw)
> or machine screw. So, if you use pan head screws, the O.D. of the head
> should give acceptable results, although the standard for pan heads
> does provide wider tolerances that the molded bosses are usually held
> to. You can even trim the bushing off the ubiquitous Kadee #5 box, and
> you will find that the thickness of the Accurail truck bolster is such
> that the Kadee bushing is the proper length.
>
> Dennis Storzek
> Accurail, Inc.
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>
>
> --
> No virus found in this incoming message.
> Checked by AVG.
> Version: 7.5.552 / Virus Database: 270.10.0/1864 - Release Date: 12/25/2008 9:40 AM
>
>


--------------------------------------------------------------------------------
Richard Hendrickson
 

On Dec 27, 2008, at 7:35 AM, Donald B. Valentine wrote:

....with regard to truck
screws, and without wishing to open a new thread for endless
discussion, it does seem to me that this is another standard that the
NMRA could/should have addressed long, long ago. It seems that each
individual manufacturer of rolling stock has just chosen a method of
truck attachment that seemed convenient at the time the process was
set up.








Gee, Don, are you just noticing that the NMRA is fifty years behind
in updating their standards and recommended practices, and that many
of the ones they established way back in the last century are
routinely ignored by manufacturers? Periodically, a new NMRA
standards chairman is appointed and a vigorous program to upgrade
standards and RPs is announced. Then nothing happens. Meanwhile,
NMRA membership and attendance at national conventions steadily
diminishes. NMRA standards? As the French say, it is to laugh.

Richard Hendrickson
Didrik A. Voss <davoss@...>
 

--- In STMFC@..., "Dennis Storzek" <destorzek@...> wrote:

--- In STMFC@..., Denny Anspach <danspach@> wrote:


Truck makers make bushings peculiar to their truck bolsters?

Denny

Denny S. Anspach, MD
Sacramento
Doc,

I fail to see why truck makers need to be responsible for other
manufacturers' poorly designed body bolsters. The de facto standard
in
the hobby for the last forty years has been a clearance hole for a
1/8" dia. boss, so the truck doesn't pivot around the threads, and
the
screw can be tightened solid without binding the truck. ...
Dennis,

Your recommendation to change the NMRA RP-23 to include a boss on the
bolster seems like a good idea to me. I am willing to carry your
suggestion forward.

I sent you offlist the Word version of RP-23 for your review. Please
make whatever changes you feel appropriate. Do not worry about the
format of the document. I will take care of that. However, a revised
drawing would be very helpful. Please, also provide the new drawing
as a CAD file (or whatever drawing program you are using) and a jpg
file. The CAD file will be helpful for future revisions if necessary.
The jpg file can immediately go in the Word document.

Once you and I agree on the final version of the revised RP, I will
share it with other manufacturers for their comments.

Thank you for making this recommendation. We need people like you who
are looking at these RPs and Standards in critical detail.

By the way, I will be at the Amherst RR Show in West Springfield, MA,
January 24-25. I hope to see you there.

Didrik Voss, MMR
Manager, S&C Dept.
NMRA
Didrik A. Voss <davoss@...>
 

--- In STMFC@..., Richard Hendrickson <rhendrickson@...>
wrote:
Gee, Don, are you just noticing that the NMRA is fifty years behind
in updating their standards and recommended practices, and that many
of the ones they established way back in the last century are
routinely ignored by manufacturers? Periodically, a new NMRA
standards chairman is appointed and a vigorous program to upgrade
standards and RPs is announced. Then nothing happens. Meanwhile,
NMRA membership and attendance at national conventions steadily
diminishes. NMRA standards? As the French say, it is to laugh.
Richard,

You are correct. NMRA S&RPs are up to 50 years old and need to be
revised. My problem is finding people who are knowledgable, willing and
able to do the revisions. Our volunteers do run out of energy after a
few years and want to get back to doing just modeling. Therefore, we
need new people that have built up a head of steam and are willing to
help.

Therefore, I challenge you and everyone else on this list to do a
critcal review of the Standards and Recommended Practices. Throw darts
at them, make changes in red, and send them to me.

The manufacturers association, HMA, wants to become more involved with
NMRA to revise the S&RPs. Your critical reviews will be very helpful in
this endeavor. Turn your complaints into honest and helpful suggestions.

I am listening.

Didrik Voss, MMR
Manager, S&C Dept.
NMRA
Jon Miller <atsf@...>
 

Our volunteers do run out of energy after a
few years and want to get back to doing just modeling.<

Here is the problem, at least as I see it. A few years is just too long to change things. DCC can change without a membership vote, as I understand it, but even then it's seems to take a year or more. Talking to a cell phone rep the other day (we use many of those components in our decoders) his comment was that phones change every 6 months or less. This means the parts (and probably the software) change in that time period.
Changes need to occur much faster than the NMRA seems to be able to react. Maybe all specifications should be taken away from a membership vote (however that could be done) and allow those volunteers see their work take place in a reasonable time period.
I'm sure you would get more volunteers if they could see something happen with all their hard work. I know I tried with some DCC terminology some time ago. Lots of emails and compiling information and when presented I received an email that said "what's wrong with it now". Of course that ended my work in that area.

Jon Miller
AT&SF
For me time has stopped in 1941
Digitrax, Chief/Zephyr systems, JMRI user
NMRA Life member #2623
Member SFRH&MS
cj riley <cjriley42@...>
 

I think you'll find that the requirement for membership voting was done away with a while back (by membership vote), leaving technical changes in the hands of those who have (perhaps) appropriate knowledge of the subject.

CJ Riley

--- On Sun, 12/28/08, Jon Miller <atsf@...> wrote:
From: Jon Miller <atsf@...>
Subject: Re: [STMFC] Re: making the case for self-tapping screws
To: STMFC@...
Date: Sunday, December 28, 2008, 12:21 PM











>Our volunteers do run out of energy after a

few years and want to get back to doing just modeling.<



Here is the problem, at least as I see it. A few years is just too long

to change things. DCC can change without a membership vote, as I understand

it, but even then it's seems to take a year or more.





























[Non-text portions of this message have been removed]
Didrik Voss <davoss@...>
 

Jon,

Prior to earlier this year, Standards had to be approved by the NMRA membership and RPs were approved by the BOD. Approving changes to Standards did take up to two years. However, RPs changes could be approved every 6 months since the BOD met every 6 months. This has now changed. Changes for both Standards and RPs are now approved by the BOD which means they also can be updated and approved every 6 months. Changes to Standards will be published in Scale Rails so members can review and provide comments before approved by the BOD.

The problem now is to get the manufacturers to agree to the changes. Without manufacturer concurrence, changes to Standards will make no sense. Your problem with DCC terminology changes was probably due to the manufacturers not responding in a timely fashion and not the delays caused by the NMRA bureaucracy. Maybe you could provide me with additional information off list that would help me understand where the problem lays.

Didrik

----- Original Message -----
From: Jon Miller
To: STMFC@...
Sent: Sunday, December 28, 2008 12:21 PM
Subject: Re: [STMFC] Re: making the case for self-tapping screws


>Our volunteers do run out of energy after a
few years and want to get back to doing just modeling.<

Here is the problem, at least as I see it. A few years is just too long
to change things. DCC can change without a membership vote, as I understand
it, but even then it's seems to take a year or more. Talking to a cell
phone rep the other day (we use many of those components in our decoders)
his comment was that phones change every 6 months or less. This means the
parts (and probably the software) change in that time period.
Changes need to occur much faster than the NMRA seems to be able to
react. Maybe all specifications should be taken away from a membership vote
(however that could be done) and allow those volunteers see their work take
place in a reasonable time period.
I'm sure you would get more volunteers if they could see something
happen with all their hard work. I know I tried with some DCC terminology
some time ago. Lots of emails and compiling information and when presented
I received an email that said "what's wrong with it now". Of course that
ended my work in that area.

Jon Miller
AT&SF
For me time has stopped in 1941
Digitrax, Chief/Zephyr systems, JMRI user
NMRA Life member #2623
Member SFRH&MS
Roger Robar <rrobar@...>
 

What has "making the case for self-tapping screws" got to do with the NMRA?
PLEASE change the subject line.

Roger Robar



_____

From: STMFC@... [mailto:STMFC@...] On Behalf Of
Didrik Voss
Sent: Monday, December 29, 2008 6:01 PM
To: STMFC@...
Subject: Re: [STMFC] Re: making the case for self-tapping screws



Jon,

Prior to earlier this year, Standards had to be approved by the NMRA
membership and RPs were approved by the BOD. Approving changes to Standards
did take up to two years. However, RPs changes could be approved every 6
months since the BOD met every 6 months. This has now changed. Changes for
both Standards and RPs are now approved by the BOD which means they also can
be updated and approved every 6 months. Changes to Standards will be
published in Scale Rails so members can review and provide comments before
approved by the BOD.

The problem now is to get the manufacturers to agree to the changes. Without
manufacturer concurrence, changes to Standards will make no sense. Your
problem with DCC terminology changes was probably due to the manufacturers
not responding in a timely fashion and not the delays caused by the NMRA
bureaucracy. Maybe you could provide me with additional information off list
that would help me understand where the problem lays.

Didrik

----- Original Message -----
From: Jon Miller
To: STMFC@yahoogroups. <mailto:STMFC%40yahoogroups.com> com
Sent: Sunday, December 28, 2008 12:21 PM
Subject: Re: [STMFC] Re: making the case for self-tapping screws

Our volunteers do run out of energy after a
few years and want to get back to doing just modeling.<

Here is the problem, at least as I see it. A few years is just too long
to change things. DCC can change without a membership vote, as I understand
it, but even then it's seems to take a year or more. Talking to a cell
phone rep the other day (we use many of those components in our decoders)
his comment was that phones change every 6 months or less. This means the
parts (and probably the software) change in that time period.
Changes need to occur much faster than the NMRA seems to be able to
react. Maybe all specifications should be taken away from a membership vote
(however that could be done) and allow those volunteers see their work take
place in a reasonable time period.
I'm sure you would get more volunteers if they could see something
happen with all their hard work. I know I tried with some DCC terminology
some time ago. Lots of emails and compiling information and when presented
I received an email that said "what's wrong with it now". Of course that
ended my work in that area.

Jon Miller
AT&SF
For me time has stopped in 1941
Digitrax, Chief/Zephyr systems, JMRI user
NMRA Life member #2623
Member SFRH&MS
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