Lyman 450 O Ring sizes


March 25, 2010, 10:59 AM
Hello everyone,

After an extensive search, I found some O rings that fit my Lyman 450 lubrisizer and I thought I would share the info with everyone. These should work with the 4500 and maybe the 45.

These seem to work great and I have lubed several hundred 9mm bullets so far:

Pressure Nut:
OD: 1 1/16" ID: 13/16" Thickness: 1/8"
Lyman part #: 2990689

Seal Plug:
OD: 1 1/16" ID: 15/16" Thickness: 1/16
Lyman part #: 2990623

I have not tried these, but read elsewhere they work:

Sizer die:
9/16 x 11/16 x 1/16
O ring size #35

I contacted Lyman support from their site and they said I would never find the correct size O rings. I took that as a challenge. Lowe's and Home Depot did not have anything of use. Their inventory is for standard faucet sizes only. I found a little hardware store that was stuffed to the gills with almost everything they have at the big retail places. They had several drawers full of different size O rings. I tried out a few and selected the ones that fit most like the originals. I paid much less for them than what Lyman wants, too. I hope this helps people because I spent a few days searching for the sizes and could not find them anywhere.

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March 25, 2010, 11:44 AM
Any good Auto parts or tractor shop would have a good selection of rings. NAPA has a big pull out drawer at most of their stores, that is loaded with o-rings, check there. There are two good hardware stores near me that have almost the same drawers as NAPA.

Jimmy K

March 25, 2010, 12:01 PM
Horrible Freight sells 300 piece o-ring kits for $6 or's saved me many a trip.

March 25, 2010, 12:09 PM
Thanks for your work, I appreciate it alot (Just Kidding on the alot thing) I have a 450 and hope it works for that one too. If you have additional tips on the 450 for replacement parts and such there are those of us waiting with baited breath.



March 25, 2010, 12:21 PM
...waiting with baited breath.I think it's 'bated' breath, meaning to restrain. As in, "We're holding our breath."

Unless you've been eating nightcrawlers, anchovies and powerbait. Then you might have baited breath for sure. :neener:

Good job, eatont9999. I like when a guy takes a challenge like that.

March 25, 2010, 02:52 PM

You confused the heck out of me. I had to Google search "Horrible Freight" and eventually found that it is slang for "Harbor Freight." In case anyone else was confused, I figured I would mention it. $6 for 300 O rings is not bad. Handy to have around the house for sure. Make sure you pick up some silicon plumber's grease to prolong the life of the rings.

Unfortunately, those are the only tricks in my bag. I wish I had something else for you guys, but luckily noting else has broken on my Lyman. I guess the only other thing worth mentioning is that I use a blow torch to heat the cast iron frame until it is warm to the touch. I use the torch in lieu of owning an electric heater. I back off the pressure nut a few turns so the lube does not force itself out of the sizing die and make a mess.

I also applied some silicon plumber's grease to the grooves in the pressure nut and seal plug before installing the O rings; they should last longer and not dry out that way. You can get the silicone grease at any hardware store; usually in the plumbing section.

March 25, 2010, 03:20 PM
For heating the lube... I use a Electrical heat lamp that is used for pigs, dogs..whatever.
No open flames...

Jimmy K

March 25, 2010, 07:52 PM
I took a peice of 1/2" pvc & cut a peice 3/4" & put it over the pressure stud so the pressure nut won`t run off the bottom threads.

March 26, 2010, 12:52 AM
OD: 1 1/16" ID: 15/16" Thickness: 1/16

That would mean a thickness of 1/8". 1-1/16" minus 15/16" equals 1/8".

Most O-rings are measured by I.D. + thickness of ring.

I used to have a RCBS Lub-a-matic II a few years ago. They used the same sizer dies as Lyman. So the O-rings should also fit RCBS.

March 26, 2010, 09:21 AM
I figured I would make it simple and provide all the dimensions. Can't hurt to have too much info.


I read about people installing nylon or other kinds of bushings at the bottom of the reservoir so the pressure nut does not get jammed when you are empty. I had a jam before and it is a PITA because I had to unmount the 450 and take it apart. Not to mention the bullet lube was hard to work around and everything was covered in it.

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