Folder progress, + running into a problem

Chiro75

Chiro75

Joined
Feb 4, 1999
Messages
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Well, I couldn't wait for this bandsaw that it supposedly coming from Harbor Freight (going on two weeks now), so I took out my trusty hacksaw and started in on my titanium slabs last night. I drilled, reamed, etc my pivot pin location for the 7/32" pivot pin, and for the 3/16" stop pin. My progress is good in that the lock side of the knife has a nice press fit for both the pivot and stop pin, and I have a nice "slip fit" for the show side of the knife. Everything lines up perfectly, and so far so good.

The problem: the only stock I had in the right width was 1084. Drilled it, reamed it, etc and there is a lot of play with the pivot. Used the same bits, procedure, reamers, etc. There is a bit of a warp in the steel, so is that enough to create play? It has a nice slip fit, but it wobbles all around on the pivot. I bit the bullet and ordered some precision ground O1, so I'm hopinh that fixes it, but other than not having flat stock to start with, is there a reason the steel wouldn't ream out to the right size using the same tools (heat expansion something like that?).
 
what i have found is that no matter how precise the holes are its going to have play until you tighten the liners. tighten the pivot pin. if there is alot of play left you might have to use some washers
 
The best step I took in getting my folders to work better was to start measuring in ten-thousandths. I still work to thousandths in dimension but the extra precision high-lights error. When Benchmade started out there knives left a lot to be desired especially in fit and function. After Les spent about $100K in optical comparison equipment there was a radical change in the mechanical preformance of thier knives.
All 1/8 pivots are not .125, some are bigger some are smaller. I keep carbide reamers .001 over and .001 under for 1/8 and 3/16. I have 1/8 and 3/16 rubberized abrasive rod in a very fine grit for polishing the pivot hole; this can give you a quarter of a thou or so. I go through 5-10 pivots to find the one that fits best. As my friend Matt Diskin teaching at a hammer-in said as he held up a micrometer; "This is not a "C" clamp."
If you want your folders to work well follow Chris Reeve's advice; "Measure twice, cut once."
I recommend a Mitutoyo Digimatic that reads to tenths of thousandths. The readout is big and easy and quick to read. This caliper also goes to hundreds of mm, and wil be a great meteric conversion tool. This machines LED is energy efficient and battery life has been about 3 years, left on most of the time. They cost about $100 or less. Do you want to make $200 or $500 folders? A good measuring tool is your quality control. As you work in folder tolerances your eye will become trained and you will begin to "see' in thousandths. Dan Nedved makes slip joint folders without a surface grinder or precision stock, he is the only folder maker I know with the natural ability to parallel grind his stock by eye.
I recommend thermal cycling all high Carbon bar stock before using, this will help with warping and performance.
Folders are really simple machines, but tolerances are close and small. A good measuring tool will help you "see" the problems...Take Care...Ed
 
Thanks for the advice, Ed, but what confuses me is that the fit is perfect on the titanium liner, but using the exact same tools and method I got slop on the steel, and so that doesn't seem to make much sense to me.
 
I see the same thing Dr. Steve. I think it has to do with the Titanium sort of springing back after being reamed. What Ed said is good advice also. The variation in pivot size is annoying especially when they charge $1.50+ for a 1/8 pivot pin. All of the pivots I have measured are less than 0.125.
 
Did you chamfer the edges of your pivot hole in the blade? You don't want to do that. What's the difference in diameter between your drill and reamer? 10 thousandths? You might need more. How many times have you put the knife together and pulled it apart? An annealed knife blade will wear on the pivot after taking it apart a few times and give you blade slop. It als can wear your pivot hole enough to make it no longer round.

Try putting the whole knife together, as if you were doing the final assembly, and then grab the blade and push and pull it to see if there is any slop in the pivot area. Sometimes you need everything to be tight to not get any movement.

While I am working on a folder I use a dummy pivot the same diameter as my undersize drill, the last thing I do after heat treat is to ream my pivot hole to a precision size.
 
Did you drill a pilot hole before drilling your final hole for the pivot? If not this will definitely cause slop in the pivot hole.
 
Welcome to the wonderful world of folder making Steve! :D Just finish this one regardless of your high standards when making fixed blades. Keep making them and all these little details will really start to make sense. And it gets easier....sorta.

A lot of this comes down to investment. When I got a Digital caliper it made a big difference, same thing with an angle gauge, over and under sized reamers and countless other spacers and screws of various diameters and lengths. Making folding knives is the most expensive endeavor I've ever embarked upon but some of these things are absolutely essential. It's a journey and a darned fun one at that! :)
 
Ed---No Email or pMs have a question?
Where did you get the rubberized abrasive 1/8" + 3/16" for polishing the insides of the pivot holes?
Would be a great help to know!~
 
I found these at the SHOT show. The SHOT show has a web site and I believe they list thier exhibitors. At the end of the show a lot of small items and display items are sold for very reasonable prices. Sorry I don't know the brand off hand...Take Care...Ed
 
Hi Blinker,
Yes, I checked the link and you are correct. Prices are much better with numbers. I use them and inch at a time in my flex shaft tool...Take Care...Ed
 
gotta agree with ed


along with careful measuring, you need to make sure you have the right tools

How accurate is your drill press???

As said above, ti is springy, it wont stay open like carbon steel does


The two most important things, three actually, accurately sized holes, perfectly sqaure to the part, and making sure everything is FLAT!@@
 
I have some precision ground O1 on the way, so I'll try again and see what happens. As far as the method I'm using, I'm going right off Peter's framelock video, so I think I start the hole with a #2 combo bit, open it up with 1/8", drill with 13/64", then ream 5.5mm and ream 7/32" for the final fit. I guess I'll have to invest in some more reamers and just try, try, try (and invest in calipers to measure, measure, measure). I think I can make something as good as maybe a decent production folder, so we'll see. I'll keep at this one and see what happens! Gotta hit the grinder and sell some FB's so I can buy some more folder crap! :rolleyes:
 
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