Nylon/Plastic Screws for DCC Conversions

QUOTE (Ian 47 @ 27 Jun 2008, 03:33) <{POST_SNAPBACK}>Hello

I have been attempting to obtain some specific information in order to convert a number of Hornby locomotives with tender drives to DCC, however, I am getting increasing frustrated because instead of answering my question and supplying the information requested (or being honest and admitting they don't know the answer) go on at considerable length about the need to isolate the brushes from the chassis when converting to DCC.

If they had bothered to read the question properly they should have realised that I am trying to replace some steel screws with nylon or plastic ones (i.e. insulated) with the same dimensions. I have even supplied details of the Hornby Part numbers concerned from their service sheets, and whilst I appreciate not all of them may not have access to the service sheets - unfortunately the fact that Hornby themselves appear unable to supply this information.

The screws concerned are shown on the relevant Hornby services sheets as part numbers S 1245 or S 1147 dependent on the type of cover plate used.

Obviously in order to try and obtain replacements I need to know the size of the screw in a format that is meaningful to a screw manufacturer

Hoping someone can assist me with this problem

Regards

Ian 47

PS - Locos types involved are 28xx, County 4-4-0, Schools and Duchess

*** There is no Nylon or plastic direct replacement easily available, however the Mfrs of Kadee couplers do a nylon screw that works - ie you can use a Kadee 2-56 nylon screw cut to length. Any Kadee stockist will be able to get them for you.

(Weshdiesel - the metal lug applies to only some versions of the hornby tender drive/power bogie motor - many variants are made simply with only long screws to a metal frame)

Richard
DCCconcepts

Hi

No bull and straight to the point. I used M3 Nylon 6.6 PA screws and did the following:

Once you remove screw get stiff piece of wire, measure depth of plastic to metal frame inside hole, screw came out of. In my case 7.8mm. Subtract 1mm to end up with finished size of screw. Measure hole diameter and find appropriate tap to suit. In my case M3.

Tap hole with intermediate tap first remembering this is a fine thread, you are tapping plastic so go easy. At the start go in 4 full rotations of tap and back off a 1/4 turn, then every 2 rotations and back off. This is to break the chip.

Once correct depth is reached gently remove tap, holding up side down insuring no swarf falls into the motor. Optional you don't have to do this, run a plug tap through.

Remove plug tap following above and cut Nylon 6.6 PA screw to size. Check size of pickup as you may need to file bigger. Put nylon screw in and away you go.

Where to get the stuff Nylon, Acetal Polyprop screws from any good hobby shop or electronic shop. Taps local hardware store or engineering tool supplies.



I didn't bother using a tapping wrench, as I really wanted to feel how the tap was going.



m

QUOTE (Richard Johnson @ 27 Jun 2008, 05:38) <{POST_SNAPBACK}>*** There is no Nylon or plastic direct replacement easily available, however the Mfrs of Kadee couplers do a nylon screw that works - ie you can use a Kadee 2-56 nylon screw cut to length. Any Kadee stockist will be able to get them for you.

(Weshdiesel - the metal lug applies to only some versions of the hornby tender drive/power bogie motor - many variants are made simply with only long screws to a metal frame)

Richard
DCCconcepts

Many thanks Richard, this is the answer I have been seeking.

Thanks also to welshdiesel and Martin71 for their suggestions.

Regards

Ian 47