As some of you may have seen, I built a prototype of a small infill smoother (blog starts here). This went well enough that I decided to make one for myself from precision ground steel. Well, as it turns out, with the way lengths work for precision ground O1, I ended up buying enough for 3 small smoothers and 4 blades, which is perfect, since the prototype needs a blade.
So off went my money and a few days later, a package arrived with the steel, some new drill bits, and a scriber. A good scriber makes life so much easier when working with metal, and they are cheap enough that replacing them regularly is a good idea. The one I got was a whopping $1.50 or so. Anyway, here are the raw materials: 13/32”x1.5” O1 for the sole and 5/32”x2” O1 for the sides and blades (only one of the three lengths of O1 is shown). The infill will be from a Burmese blackwood turning blank I have had for a couple of years. I’ve never worked with it.
So the first thing to do was rough cut the sole pieces on the band saw. After that, I marked one side of each with Dykem so that I could scribe a center line. Then, using my calipers, I marked the location for each of the holes. The construction of these will differ slightly from the prototype in that I will be doing through pins. I decided to go this route because I found that using screws and peening them (if you find the right type) is still not as nice as peening plain rod. Also, plain rod is cheaper, and through holes made sense since I was drilling 1/2” from either side anyway, so I didn’t have to worry about threading. Anway, after 20 or so minutes with the band saw, we have this:
So one thing I learned here is that you need to try to get your cuts as square as possible to start. I didn’t, and it made me miserable later. Read on.
After getting stuff marked, it was time to drill. I ordered 3 new, high quality USA HSS drills for this project. I highly recommend you do the same. A new drill is like new socks: cheap, easy to not think about, but when you have it, you just smile and it makes you happier. So just do it. These were maybe a buck a piece. Anyway, for drilling, make sure to use plenty of cutting fluid, but not too much. Here is what I settled on and worked really well:
- Drill without any fluid just past the lip of the flute
- Fill the divot with cutting fluid, should only be about a drop
- Drill between 1/8”-3/16”
- Retract to clear the chips from both bit and workpiece
- Put in another drop of fluid
- Lather, rinse, repeat
Don’t lay into the lever too hard. It will cause the drill to flex and not drill straight, ask me how I know. Luckily, over 1.5” I only had about 1/32-1/16” drift, so no big deal here. Here are the resulting pieces:
Next up was rough cutting the infills. This resulted in another
Make sure your infill stock is all square (yes, all four sides) and just slightly oversized (I shot for about 1/16” in width and about 5/16” in height so as to round it over nicely). I did not, and it came back to bite me later. This, in conjunction with the not square bandsaw cuts made life hard. Read on, good reader.
So I originally anticipated having the sapwood run the same on all the pieces. Well, then I got the idea that it would be more efficient to use common angled cuts, meaning one cut at 60 degrees and one at 90 would get me two 60 degree pieces. Well, this also makes it so that the sapwood is in different locations. It will be fine, but I could have thought it through better. Here it is after rough cuts:
Then it was time to lap everything in nice and square. I did the same as on the prototype: two F clamps with a little bit of wood overhanging each side and the slightest bit protruding over the ramp, like so:
Now here is where stuff came back to bite me. I realized that because stuff wasn’t level and square, I would have to lap it in. I blew through 4 sheets of 80 grit and half a sheet of 100 grit, totaling about 2 hours of solid lapping. I bruised some fingers just from all the pressure. In fact, after 1 hour 45 minutes, I was still way far off. Then I thought “I’ve already lapped one side square to the bottom, so I could just put it on that side and use my oscillating belt sander (ROSS) to do the bulk of the work”. The ROSS doesn’t sand perfectly flat or square, but a whole lot closer than trying to lap by hand, especially after all the arm and ab muscles were totally exhausted. 15 minutes with the 100 and 180 grit belts, and I was in good shape, though I continued to check with a small machinists square just to make sure. I finished out by lapping with some 220 grit to remove any burrs and other scratches. No picture, as it doesn’t look any different in a photo.
I also cut one 18” length of the side material down to width on the bandsaw. I will need to clean it up, but O1 actually cuts pretty nicely in its annealed state.
So, that is where we end for today. But remember MAKE SURE EVERYTHING IS CUT AS SQUARE AS POSSIBLE PRIOR TO LAPPING OR ANYTHING ELSE, OR ELSE!
Time to this point: ~4 hours
-- Brian T. - Exact science is not an exact science