Straddle knurler build, no mill required (we hope!)

[WobblyHand]

Mounted the knurler to the plinth. Still need to make the spacers. I also need to thin the head on one of the shoulder washers to make the length a few more thousandths. The arm binds a little, and I can see the washer is a little short. It's a bunch of clean up, and minor redo's. Finally I need to make the arc in the plates. I can see the knurler coming to fruition before my eyes. It's quite gratifying for me.

Never used a forming tap before, it wasn't difficult. Pretty strange to have no chips at all, and no need to backup and break chips. Just straight in. This was a blind hole and still it wasn't a problem. Material is 7075.

Another good day. I'm liking this.

 

[ttabbal]

It's always nice to see parts come together and work well. Very gratifying.

 

[Papa Charlie]

It's always nice to see parts come together and work well. Very gratifying.

Work in progress, I have never built anything that I was completely happy with. Maybe some day.

 

[WobblyHand]

Made some spacers out of 1144 rod. Right now they are 0.505" long and the arms are 0.4995" wide. I can trim them down some, but first I need to fix one of the shoulder washers. That shoulder washer is slightly too short. This causes one arm to bind. I can try making another one, or fixing the one I have. I have plenty of overall length, so if the head is thinned (making the spacer part a little longer,) it should be ok. In order to do this, I need to make a left hand knife edge tool. I've made a right hand knife tool, but never made a LH tool. So this afternoon I will grind one.

I only need to take off a thousandth or two. Lot of work for that last thousandth! But that's what you have to do to make everything work.

 

[WobblyHand]

So I ground a LH knife tool. It's not pretty. Was hard to grind with the limitations of my belt sander. But there was enough of an edge in the place that mattered and I removed 0.004" from the underside of the shoulder washer head. This made the body 0.004" longer. I figured it was easier to sand or hone off a few thousandths on the body length if I needed to. As it stands, everything is pretty snug. No play in the arms. As I was reassembling the unit the 10-32 screw got stuck in the bushing. It wouldn't allow the screw to get to the screw threads in the bottom plate. Finally got it free, but the sharp edge under the head of the washer sliced my thumb. Guess it's my sacrifice to the machining deities. Umm, next time I'll make a point of chamfering that edge! Then I used a drill in a hand chuck to act as a reamer for the hole. It cleaned out the bur or deformation and the screw passed through.

Put it all together again and mounted it on the lathe to check the height. It's so close to the scribe line (within the fine vee) that there's no point to move it. Looking at it there, it was clear I needed to remove the compound to use it. So I did and thought, "you know, you need to try this now!"

Yes the photo is staged. I had cleaned the rod and put it back. I confess, the collet isn't even tightened!

The knurls are very distinct. I probably could have used more pressure, but didn't want to without a live center. Here is a better picture of the first knurl with this tool. It's ok for a first try. Not like some of the masters here on HM, but it's a start.

There's more to do. Have to make the angle cuts in the arms, and an arc in the body plates. I also need replace the spring with a stainless spring, and make a new nut with longer threads. (I have found Tap Magic cutting oil (the one for ferrous) is a bit corrosive to plating. It does not bother steel, but it does seem to attack stuff like zinc. My Huot index has shown some signs of corrosion, only around drill bits that were used with ferrous Tap Magic. I have to be fastidious about cleaning the bits of cutting oil. There is also corrosion on galvanized washers that I am using for my vise hold downs.)

I'm pretty pleased that this project is nearing completion. There were so many setbacks. Happy to have picked this project up again and see it through. Learned a lot along the way!

 

[jwmelvin]

Congrats on a useful tool. Thanks for sharing your process.

 

[WobblyHand]

Made the knob for the knurler out of 1.25" OD 1144. Of course I had to knurl it! This time I tapped it from the bottom(the narrow side). That way it is always engaging the threads. For some reason I had made the first nut incorrectly, and did it the opposite way. (What was I thinking?) Can't say I did much planning on this knob, sort of just did it, kind of on autopilot. Was fun to do.

I used the 25 pitch FORM ROL EQL 225 wheels and sulfur cutting oil. Never knurled steel before, but using this knurler it was pretty easy. Cranked down the nut until a decent pattern showed up, then cranked it a little more. Came out ok, or at least ok for a beginner. Here is the new nut on the knurler.

Trying to locate my hole saw set (in the abyss called my garage) to make an attempt at the arc between the arms. Thought I'd hog out most of the arc with a hole saw, then use a boring head to finish it. Never used a boring head before so that will be a learning experience.

 

[brino]

Can't say I did much planning on this knob, sort of just did it, kind of on autopilot. Was fun to do.

I LOVE those projects!

Trying to locate my hole saw set (in the abyss called my garage) to make an attempt at the arc between the arms. Thought I'd hog out most of the arc with a hole saw, then use a boring head to finish it. Never used a boring head before so that will be a learning experience.

From what I have seen you will figure it all out and enjoy it in the end!
New skills = better machinist = more projects done well.

-brino

 

[WobblyHand]

Eking along trying to get this closer to being finished. Found the hole saw and cut a ~2" diameter partial arc out of the plates. The hole saw or arbor was out of round by 0.1". Was kind of awful, but taking it slow, it cut through. Then more or less figured out the boring head and finished the cut. I have no idea what the actual diameter is, but I did it enough so it is just proud of the spring when it is assembled. As it turned out I used too high of a cutting speed (220 sfm) on the boring head so the finish isn't the best. 400 RPM. Yeah, so next time, I will know better. Hope I can just use some sandpaper on a dowel to clean it up. It's still better than I could do by hand, so it's still good.

It's time to bring the shoulder washers and spacers down to size. One shoulder washer is fine - there's no play. The second one was about 0.005" too long. I don't have a way to hold the washer in the lathe any more (that I know of). The shoulder height is 0.036 high, so there's nothing to grab with an ER32 collet. So I have been taking down the length on a 800 grit diamond hone, about 0.0005" at a time. I find the removal rate is about the same as using 400 grit, but it is easier to keep the piece from catching using the 800 grit. I rotate the piece a bit on every stroke of the stone, attempting to avoid inadvertently making it non flat. When I can't stand it any longer I measure it with a mic and find I've removed about 0.0005". I've removed about 2.4 thousandths so far. It's better, but still too much play. Took off another 0.001" and it's much tighter. Fortunately I'm inside, (beastly hot outside) so it's an ok activity to be doing right now. My spacers are at 0.5030 right now, they need a few thousandths of shortening as well, think I will just hone them closer, since it's hard to take off too much this way. The mechanism is pretty tight at this point, but I might as well stone the inside of the plates now, if for nothing else to take off any small burrs.

Might as well show this here. Knurled a tommy bar I had made for my ER32 collet. 6" long knurl on 12L14. Knurls were deeper at the tailstock forming full points, and much less so closer to the collet at the headstock. But it's a nice addition to my tooling. Previously the tommy bar would get slippery - not any more! Used a live center in the tailstock and sulphur based cutting oil. Got to say, I like it!

Have some stainless coming in that I'd like to knurl. Going to try making a nicer and slightly longer handle for my Mercur razor.

 

[WobblyHand]

Replaced the SHCS with button heads on the knurler. Makes it look a little less clunky, especially on the arms. Gives me the feeling (but probably not the reality) that I could approach the chuck a little closer. Also replaced the galvanized spring with a stainless one, that has a slightly longer length of two (2) inches and a wire diameter of 0.047". The compressed length is shorter than my 1.5" spring. This allows the wheels to close to 0.218" between the wheels (at coil bind). Hope that will allow knurling of 0.25" stock.

Needs one more major teardown. Haven't machined the arms to allow slightly larger opening. Need to mill the slot using a 5 degree block. My angle blocks came in a while ago, so I get to use them for this operation.

I just measured the opening. The arms can open to 2.125" with no problem. (Actually can go until 2.3".) Not going to machine the arm slots. They are good enough. The limit is not the arms, but the cut out and the spring. The spring just peaks out from the bottom of the arc. No need to risk ruining the part for zero improvement. Have to use the angle blocks for something else...