Star washers

shanecfi · #1 01-17-2020, 11:01 AM

Hey all,

Finishing up firewall forward. I have come across both types of star washers. Internal and external teeth. Are these interchangeable? I am attaching Adel Clamps to the bolts on the valve covers. These are of the external variety. Different from the rest of the engine bolts/nuts.....

JonJay · #2 01-17-2020, 11:24 AM

Valve Cover screws typically use external washers. Both types are locking. Smaller head screws are better suited for internal type, larger head with more surface contact area external are better.

plehrke · #3 01-17-2020, 11:28 AM

Do people re-use star washers?
I tend not to as I feel once used they become fairly flat and loose some of there locking potential.

shanecfi · #4 01-17-2020, 11:33 AM

We don?t re-use the washers. They are literally pennies and the plans say to use new ones. That?s actually the reason for my question. I have bought a supply of the external ones. I?ll just add the internal ones to one of our myriad ACS orders.

bjdecker · #5 01-17-2020, 11:35 AM

https://www.seastrom-mfg.com/washers_lock.aspx

I believe (I'm sure there is data available, but I don't have it...) that it's probably "ok" to re-use lock washers once, maybe twice.. However, they're cheap and why take the risk. I consider them to be disposable, one-time-use only.

On the engine, they're mostly internal teeth, except for valve covers, and maybe some others. I think the external ones provide more resistance for a given torque value - probably why they are used on valve covers; don't want to over tighten these but still keep them from backing out.

Cheers!

B

JonJay · #6 01-17-2020, 11:55 AM

Quote:

Originally Posted by bjdecker

https://www.seastrom-mfg.com/washers_lock.aspx

I believe (I'm sure there is data available, but I don't have it...) that it's probably "ok" to re-use lock washers once, maybe twice.. However, they're cheap and why take the risk. I consider them to be disposable, one-time-use only.

On the engine, they're mostly internal teeth, except for valve covers, and maybe some others. I think the external ones provide more resistance for a given torque value - probably why they are used on valve covers; don't want to over tighten these but still keep them from backing out.

Cheers!

B

It?s all about surface area making contact with the underside of the bolt head. I wouldn?t say one works better than another as it is hardware and application specific. I believe there is a lot of cross over where both would work fine.
To your point, valve cover screws have large heads, external works better. However, for small head screws and many bolts, you can get more of the ?teeth? under the head with an internal.
I don?t think torque values, low or high, have anything to do with it, but I could be wrong.