Cox Engine screw chart

We used to sell the socket head prop screws for about two years. Unfortunately, they were very poor sellers. We purchased two different lengths in black oxided steel as well as stainless steel in what we believed to be 3-months quantities (50 short / 550 long).

When we finally ran out about two years later, we did not replenish stock. This compares to about 4,000 - 5,000 slot round head ones sold in the same period.

However, we could offer them again in "long" black oxide; the short ones only sold 50 in two years and the SS sold 200 in two years. In the absence of a SS version, we should sell more black ones.

Thanks Bernie. I for one would certainly buy them. With the shoulder having no threads right under the head it would perfectly fit in the aluminum spinner thus eliminating vibration.

balogh wrote:Thanks for the comprehensive list Roddie.

I am encouraging Bernie and Matt to sell the socket head screws as replacement for the round head propeller screws for 049 and smaller size engines. Matt already sells them though, included with the 09 spinner only.
Round head screws are rather short lived. I am not sure how common the socket head screws of these sizes with Whitworth threads in US DIY and hardware shops are..they seem to be unobtainiums outside the US, at least in metric screw environments.

This guy claims to ship worldwide, I got 100 a while back. I can send you a few dozen if you like.

https://www.ebay.com/itm/5-40-x-1-Socket-Head-Cap-Screws-Allen-Hex-Bolts-Stainless-Steel-Qty-100-/263167561935

crankbndr wrote:


This guy claims to ship worldwide, I got 100 a while back. I can send you a few dozen if you like.

https://www.ebay.com/itm/5-40-x-1-Socket-Head-Cap-Screws-Allen-Hex-Bolts-Stainless-Steel-Qty-100-/263167561935

Thanks for the link, he really sells them in 100 lots, which is too many for me. Instead, I would opt for your offer, I sent you a pm.

Thanks again, András.

Something like this might be a good option.  Not sure if the size you want is available.  Looks like these are mainly metric



Personally, I wouldn't prefer the standard cap screw for a prop with a spinner as it spoils the appearance of the spinner's rounded profile.  The point of having a spinner is to give a sleek appearance.
The screw that I pictured, if available, would overcome my concerns and I may use them in preference to the slot-head screws

Thanks, Rod, I agree with your  note on  aesthetics, the cap type screw head follows the aluminum spinner contour better than the socket head. But the slit head of cap type screws  is anything but lasting with the normal screwdriver tip, at least in my experience.

Unfortunately Whitworth thread screws are not easy to find in my area.

balogh wrote:

Unfortunately Whitworth thread screws are not easy to find in my area.

Just one correction, Cox engines do not use Whitworth threads, rather, S.A.E. or Imperial.
https://en.wikipedia.org/wiki/British_Standard_Whitworth

I think the screw chart is a good idea , and with a little more research could be completed Medallions ,TDs all ! , space Bugs ,.09 , 15 s lets see there has got to bee more But a good start to the most used !!

Our screw listings generally show application / size / thread, etc and the info can be copied from there: https://coxengines.ca/fasteners/

All the screws used by COX engines are classified as SAE Course Thread.
There are many US companies that will sell in 100 or 50 unit lots and several that will sell standard thread socket or button head screws by the unit.

Bolt Depot is one.  A 100 pack of 5-40's is $4.96; by the unit, the screws are $.08 each.  An example order would be 100 each of 5-40 x 3/4", 4-40 x 3/4" and 2-56 x 3/4".  Shipping is $4.95 for a total of 18.51.  Easy peasy -- and never buy another screw.

A 3/4" 5-40 will bottom out in the crankshaft of every 1/2A engine I own.  Actually, they have to be ground down a bit, so I bought a 100 pack of 3/4" screws with the intent of cutting them to whatever custom length I needed.  Screws can always be cut to an appropriate length and bulk packs are the most economical in the long run. OTOH, should you need only a few of each thread and length, per unit cost may be the better option.

But, the above is just an example of mix and match --- the base shipping stays the same for a pot full of screws.  When buying, be sure to add in whatever you may need since shipping is usually the big cost for small orders.

Thanks Andrew. I think tthe 1 inch long is for aluminum spinner that takes up some of the screw length so it will not bottom out.

Admin may want to move (or just delete it) this table into the Info section for future reference.  Since there had been some discussion concerning screw threads, type and sizes, I've attached a table that lays out typical sizes and thread pitch.  This is likely old hat for most of you, but it does list it in one place.

You can also find a Cox screw chart on a site that we host. Just click on "Technical Info" once on the site:  https://coxengines.ca/cox/www.mh-aerotools.de/airfoils/cox_frameset.htm