Building an Interframe Folder

Build a Knife Method

As a break from building liner-locks and because I bought some nice gear at this Blade Show in Atlanta, I’ve decided to build an interframe. Also as a result of popular demand (Haha), I am going to post it on this forum for those who are interested. I don’t propose to go thru the process of building the basic folder on this forum but this process I use to mill the cavities and fit the inlays.
I don’t own a pantography so I’ve had to resort to using my mill-drill and the result I get is amazing. I will show you my setup and the jig etc. I use, and the rest is up to you. If you have any questions, you will have to post them on the thread I have opened up, and I will endeavor to do my best.

You will have to bear with me as I build this piece as the process is slow anyway and as I have to stop and photograph each step that will slow the process down even more.

The drawing of the basic folder and my hardened steel (O1) template that I use as a drilling and profiling guide.

The two halves of the frame profiled and all holes drilled and reamed. Note that the bar pivot pin hole is not drilled all the way thru., I have drilled in about .050″.

All the parts of the folder laid out and I will now proceed the build the basic folder.

Ok, I have built the basic folder with the blade profiled, bar fitted to its almost finished state, and it opens and closes OK.

It shows it in its open position and figure 103 in the closed position. Note that I have yet to grind the blade, I can do this as a break during the next stage.

To build an interframe by whatever means you need a master to work from and designing the master is not difficult.
You need a piece of graph paper (I use metric as the squares are of smaller size than imperial) on which you place your template and trace the outline on the graph paper trying to keep the horizontal axis of the knife parallel to one of the axes of the graph paper.

Take several photocopies of this to work from (this preserves your original), and draw the cavity or cavities that you wish to have, place a nice square around the drawing. You now take a photocopy of this or stick the drawing on a piece of ground steel ( mild steel will do), now place your template over this aligning it with the traced outline, clamp, drill and ream the blade pivot pin hole and the two spacer pin holes. Remove the template and drill, saw and file to the line that you have drawn to mark the cavity/cavities.

Try and keep your edges square as much as possible, but if you’re like me and not the best filer on earth not to worry I’ll show you how to square them up later.

Two masters that I use, the one with two cavities has been hand cut and the master with the oval has been wire cut to give a perfect oval. I will be using this one for this knife.

Next step is to mark the cavity on the frame that is going to be cut. The reason for this will become apparent in the next stage.

The oval scribed on each frame half.

OK, I measure the thickness on the frame halves (in this case 3.45mm) then mount the two halves on my milling plate ( as shown in my previous tutorial on how to make a lock-back folder) then clamp the plate to the table of my mill/drill. Firstly with a 1/4″ drill and secondly with a 1/4″ endmill I drill/mill a hole to the depth I want my cavity to be. I like to leave “a wall” of about 1mm (.040″) at the bottom of the cavity so in this case I drill/mill to a depth of 2.45mm (.096″). The reason for doing this will become obvious as I progress.

NOTE: All my measurements are in mm. As my mill dials are metric.

The halves mounted on the plate on the table, the holes have been drilled and milled out.

I now proceed to set up my milling arrangement.

My milling “base,” a piece of 800mm (8″)x 300mm (12″) x 12.5mm (1/2″) surface ground mild steel plate into which I have inserted a steel collet with a 3/16′ hole drilled in it. The piece of rod you can see in the picture is the follower, a length of 3/16″ O1 drill rod that I have heat treated.

After clamping the “base” to my mill, I put the follower in the chuck and with the hand wheels center the follower over the hole in the collet. I then clamp both axes of the mill, zero the counters and remove the hand wheels. This now ensures that the milling cutter is centered over the follower.

The topside and underneath side of my milling “table.” The table is made from surface ground mild steel measuring 6”x4″x1 1/4″ with the legs being 4″x1″x1″ and weighing 10.5 lb (approx. 5kg), the weight been the most important factor (the heavier, the better). On the table are the locating holes for the frame and the master, these have been precision drilled all the way thru the table.

I now place and clamp one of the frame halves on top of the “table,” locating its position with the pin holes and on the underneath side I locate the master making sure that I have it the correct side “up.”

I then place the “table” on the base ensuring that the follower is inside the cavity and with the milling cutter in the chuck, I check that I have the master positioned correctly.

I then zero the downfeed and lower the cutter .1mm (.004″) into the hole I’ve milled in the center of the cavity. This is a solid carbide end cutting burr, and I run it flat out (2200 rpm) and use plenty of cutting oil.

IMPORTANT NOTE: When milling using this technique ALWAYS remove metal in a clockwise rotation and don’t ever let go the table. The reason for the weight of the table now becomes obvious, because the “table” is not clamped but free standing it will want to “take off.” This is the reason why I take very light cuts and always move clockwise to the hole milled in the cavity.
I now proceed to mill out the cavity.

the first frame half completed.

Once the first frame half has been milled, replace it with the second half using the appropriate locating holes and on the underside of the table turn the master over, reclamp and mill out the second half.When milling has been completed drill two small holes (1/16″) in the floor of each cavity. This will enable the inlays to be removed and allow trapped air to escape.


Figure shows both frame halves milled out. Occasionally I like to keep track on how long I spend on a task, helps me get a feel for the overall difficulty in making a particular knife, and on this occasion, it took me 2 1/2 hours to mill out both cavities. When I first started making interframes, it took me considerably longer.

TIP: If you have hand filed the master the sides will be “off square” and need to be “trued” up. Figure shows a new cutter with the end teeth visible, the other cutter is a worn cutter with the bottom ground flat and smooth. Simply mount the hand filed master on top of the “table” over a piece of stiff card, lower the modified cutter into the cavity and go round the edges carefully until the edges are “true,” in other words use the burr as a motorized file. Be careful as carbide, although very hard, is very brittle.

The next step is to cast the master inlays from automotive body filler.

Because I can never align the cutter and the follower the same each time I set up and because all three jaw chucks have some runout (however minute) I cast my master inlays each time I make an interframe.

First off I apply a wax coating (either furniture wax or automotive wax) to the inside and outside of each frame and both sides of a flat piece of steel. Let it dry and rub off, the wax coating acts as a release agent for the body filler. Next, I mix up some 2 part automotive body filler and fill each cavity with it, then clamp each frame to the flat piece of steel. It now becomes obvious why the two holes are drilled in the floor of each cavity as the excess body filler oozes out, wipe off this excess..

Figure shows the frames clamped to the steel plate

When the filler has gone off unclamp the frames and mark each inlay (I use MO and PO with an arrow showing the front). Using the end of a 1/6″drill bit pop the cast inlays out of each frame, remove the slight “burr” at the corners and with a sharp knife cut off the two pimples on the bottom of each inlay. Check that the edges of the castings have no air bubbles if they have you will have to recast the inlay/s.
Next step is to mount the castings and cut a dummy inlay.

I now take each casting and mount them on a backing plate (with super glue) that has had locating holes drilled in it from the template (I use aluminum although steel or even micarta will suffice as long as it is flat and parallel sided). I also use a pice of 1/8″ micarta that has been drilled with locating holes, to mount my inlay material.

Figure shows the frames clamped to the steel plate.

Before I start to mill my inlays, I replace the 3/16″ carbide burr with a 1/8″ end cutting carbide burr and also remove the 3/16′ follower and replace it with a follower that I have turned down to 1/8″ on end. Because as I mentioned earlier all three jaw chuck have some runout the dummy inlay will by most accounts be smaller than the casting, and I need to cut a larger inlay than my master. How much larger I never know until I do it. To do this, I have turned some followers in .002″ increments, starting with the 1/8″ follower, up to around .135″.

When I have cut this dummy, I tap it off the mounting plate and try it for size in the appropriate frame. Figure 128 shows milling complete, and Figure 129 shows the inlay in the frame.


Nine times out of 10 it will be too small, so I replace the follower I’ve used with a larger one and repeat the process. I keep doing this until I reach the fit I want. It’s up to the individual to decide how close a fit they need, however, bear in mind that any gap will be magnified by any fixative you use to hold the final inlay in place. I like to have mine fitting as close as humanly possible, almost like a piston when you insert them in the frame.
I will now cut dummies until I get the fit I want.

IMPORTANT NOTE: The way I’ve mounted my master inlay will cut an inlay that is a mirror image of it. Therefore you must turn the cut inlay over. Always mark the inlay BEFORE you tap it off the backing plate. i.e., the top face of the cut inlay will be the INSIDE. Therefore you must mount your final material inside out. I hope this is clear, but if it isn’t, I will show you when I come to do my final inlay.

I am now ready to make my real inlay. I measure the depth of my cavity, 2.45mm (.100″ approx.) against my inlay material, 2.00mm (.080″), which makes the inlay material thinner the-the cavity depth, OK I now stick some white “knifemakers paper” on the back of the inlay material which brings it up to 2.60mm leaving me approximately 0.15mm (.007″) to grind off after fitting. I use Loctite 324 speedbonder, a 2 part adhesive which sets in about 5 minutes, I also use this adhesive to glue the inlays in.

I mount the inlay material on my micarta plate with superglue and carefully mill out the inlay; I take cuts of 0.5mm (.020″). After milling out the inlay, I mark the back for identification and alignment and then tap off the mounting plate. I then radius the bottom edge and polish the whole edge with 600 grit wet and dry.

Tthe inlay milled out and the back marked, remember previously I mentioned that the inlay was mounted inside out, this demonstrates what I mean. The arrows indicated front and top and MI stands for mark side inside.

I now carefully try my inlay in the frame, it should be tight, but I should be able to press it in with my fingers. Hot dog, it fits spot on.

I now remove inlay master from the bottom of the tap and replace it with the master of the other side, and on the top, I turn the micarta mounting plate over and reclamp.
Theoretically, the follower should be the same for both sides, but it’s better to be sure than sorry, so I cut a dummy inlay for this side and check. Ok, it’s fine, so I mount the inlay material and cut the second inlay, mark the back and remove from the mounting plate. Hooray, this one fits fine also.

OK, that’s the hard work done, now I will remove the inlays, file and polish the release cut-out, and relieve the inside of the frame.
I still have to grind the blade etc. so as I progress, I will post the pictures.

I have now ground the blade, ladder pattern stainless Damascus from Ed Van Hoy, heat treated, polished and etched it. I have also polished the bar, relieved, jeweled, shaped and polished the frame, and done the final fit up ready to assemble.
Figure 134 shows all the components ready for assembly.

I then assemble the piece, peen the pins, grind them off and re-polish the knife. Before closing it, I clean the internals with a degreaser, blow out the dust and add a drop of oil to the mechanism.
Now it’s off to the engraver for some deep relief engraving and to think about a name for it. When it comes back, I will post a picture.


Well, that’s it, ladies and gentlemen, I hope you are all inspired and can hardly wait to build one, remember if you have any questions post them on the forum, and I will do my best to answer them.

Well, it’s all finished, Figure 137 shows it all engraved. I think it’s come up looking great.

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