Lee auto-prime failure analysis and design flaw identification

[joeb33050]

LEE AUTO-PRIME FAILURE ANALYSIS AND DESIGN FLAW IDENTIFICATION

The Lee Auto Prime comes with a brochure showing the parts and names of the unit along with the shellholder/cartridge case list. That’s where the following names came from.

The CONNECTING ROD has cylindrical sections at both ends, the small one going into the BODY and the large one pushing against the PRIMER PIN in the PRIMER TRAY. The PRIMER PIN surface, where the CONNECTING ROD meets it is a section of a sphere, spherical. Thus, there is a cylindrical surface rubbing on a part-spherical section. Hence, since the PRIMER PIN is steel and the CONNECTING ROD is a ?Zamak? casting, the edges ONLY of the CONNECTING ROD large cylindrical surface are what wears, causing slow failure. Check your edges!!!

If the friction surface of the PRIMER PIN were cylindrical or even flat, there would not be any wear on the CONNECTING ROD in a lifetime.
joe b.

[Rocky Raab]

Or, put a dab of grease the size of a #8 shot or so on the pin and it will last only three quarters of a lifetime.

[Sprue]

I used to have pictures showing this wear. My first Primer is still working and has seen a lot of use over the past five years. Once I first noticed that wear, I ordered another one to have on standby. So far I've not had to get the new one out of the box.....

Good tool ! Easy on the pocket book too.

A+ Tool IMO

[Gee_Wizz01]

I keep a dab of Moly grease on mine and it really helps. I bought mine '93 and it has installed at least 8000 primers and it appears that it will work for at least 20K more. I still have one of the orginal Lee primer tools with the screw in shell holders, and it still works too. This tool is a great value and I believe it will last MOST reloaders a lifetime.

G

[Leftoverdj]

Like most things Lee, it's made just good enough. I've worn 3-4 out, but got my money's worth out of them, so no complaints. One failed when the top holding the shellholder cracked and the others were connecting rod problems. After the first one died, I kept two around, one each for large and small primers, so I always had a spare. At the time, I was shooting competition and loading c. 10,000 rounds a year, so I can't fault them.

I have since switched to the AutoPrime II and ain't gonna live long enough to wear it out. It's press mounted and all steel. I do wear out some of the disks and covers. Best feature is that it uses regular shellholders, so that if I can load, I can prime. It's not quite as portable as the regular auto prime, but I have it installed in the little Lee Reloader press I got for free, and mounted on a board that I can C clamp to any available flat surface. I recommend it highly, even if you only keep it as a spare.

[MT Gianni]

The concept of lubing metal parts gets beat into us for high revolution things like engines and ignored on low repitition ones. If I count cost to prime each rep it is still cheaper with the Lee, without maintaince, than any other option I have seen.

[jlchucker]

The concept of lubing metal parts gets beat into us for high revolution things like engines and ignored on low repitition ones. If I count cost to prime each rep it is still cheaper with the Lee, without maintaince, than any other option I have seen.

Amen to that! You get what you pay for--and in my experience my Lee has paid for itself many, many times over.