Frame Captivated External Stop Pin Guidance

Whats up everyone! New to the forum, and new to knife making. I am currently on my journey with my first knife. Shop is still being finished up, but I am in the process of ordering tools and materials. One of many issues that I am having the most trouble finding an answer to is in regards to the stop pin. My design has an external stop pin that will be pressed into the blade. I am using CPM-3V steel at .190 thick. My stop pin is .1873 diameter made out of Hardened 440C.

The question I have is how much smaller should I ream the hole for a good press fit?

I understand there are many variables in this question that will affect the outcome. Runout of my setup, post HT changes, etc..

I am really looking for a good starting point. I am sure I will still have to undergo some trial and error, just want to minimize it. You can always remove more metal, can't put it back.

Reamer options I have are:

.1862 (.0011 undersize)
.1866 (.0007 undersize)
.1870 (.0003 undersize)

Which drill size should I use? #14, #15, 4.5mm, #16, #17? I understand that drill hole size can impact final reamed hole size.

Lastly, any use of some type of loctite or epoxy to ensure it stays put?

Thanks in advance!!! Looking forward to learning from everyone!!

I like to be able to remove the stop pin for cleaning and such, so I don't use a super tight press fit. Making sure you have precision tooling and parts is a good place to start. You want to know that your reamers and pins are exactly what they are supposed to be.

Also, I like to have the track cut in the blade not the liners. The liners are titanium and are a little 'gummy' so they kind of grab the pin anyway.

All that said, if I'm using an 1/8" pin, I know it's exactly .125", I'll drill an 1/8" hole in the titanium liners. It's a real tight fit and it will go in there, but you can also get it out. I don't use any loctite or epoxy or anything.

I know the whole thing about an 1/8" pin won't go into an 1/8" hole and I agree with that completely. For whatever reason, with the titanium liners, ***FOR ME IN MY SHOP, WITH MY TOOLS*** it works. The pin is real tight but I can still get it out.

In your situation, and your stop pin, I'd recommend the .187" reamer. Trying to press fit that pin in any tighter of a hole could cause you other issues.

Doyle,

Thanks for the reply. I appreciate your insight. Hopefully someone else that utilizes an external stop pin will chime in.

I have never installed a stop pin but I ream holes almost every day....
If it were me I would drill ~.03 smaller than your reamer and ream .0003 to .0005 smaller than your pin for this application . Also stopping your spindle once you get through your material and not having it spin when you bring it back out will help keep a truer size.....also....lube....alot.

I hope this helps.

Thanks Ian,

So you would recommend using the .1870 reamer (.0003 undersize) and drill with a #22 drill (.03 undersize of reamer). That much smaller of a drill? Haven't seen anyone recommend that much smaller of an initial drill. Could you provide your reasons? Lube will absolutely be utilized.

.02 to.03 (.01/.015 per "side"...if holes has sides) is enough to keep your reamer making an aggressive cut. So if you drill too big the cutter won't have enough to "bite" and this will allow any runout in your chuck to affect the reamer thus causing an oversized hole. On the other hand too small of a hole (depending on how small) can cause your flukes to clog and leave a terrible finish and also make it oversize, dull or even break the reamer. .02 to .03 is the "sweet spot". Pretty much: one extreme ruins the tool, the other ruins the hole.

If you have a mill (and a 1/8 endmill) you can "proof" the hole by plunging the end mill the depth of the chamfer on the end of your reamer too...this helps keep your reamer straight....if your blade is thick enough.

Sent from my SAMSUNG-SM-G890A using Tapatalk

Got it. Thanks for the info Ian!!

I'm glad I could help.