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

[WobblyHand]

Finally, the confluence of time and material. Got sidetracked putting up a rabbit fence the other day. Felt like Elmer Fudd chasing them away all the time. Unfortunately I chose one of the hotter days to do this fence 97F. But it is done. Or at least until they learn to burrow under the fence. It was too darned hot to dig a trench by hand to bury part of the fence. I'll wait for a cooler day to do that. So my garden has a reprieve for a while.

Back to machining. Pins are cut off. Put them in the lathe to face them off and to slightly bevel the ends, so they will be easier to insert. Need to cut the notch in the pins for the retainer.

The 1.25" LOC 1/4" diameter carbide end mill came in the other day. Mounted it up and finished off the slot in the arms without any trouble. Pulled the arms out of the vise and inspected the pieces. Could see where the mill grabbed the bottom piece and dragged it. (Third photo, bottom arm is on the right.) Hope I can make that arm the bottom arm. If not, maybe the nut will hide the scar. Doesn't prevent it from being useful, so I'll keep it. Still have some more deburring to do on these pieces.

Next operation on the arms are to make a 5 degree cut in it. I'm still waiting for some angle blocks to do this.

While I wait, I will take a look at the body plates. They never were squared to my satisfaction (before mill) so now is the time to tackle this. (After notching the pins.)

 

[mikey]

Looks good!

 

[Papa Charlie]

Looks real good.

Question, was there a reason you didn't part the pins in the lathe?

 

[WobblyHand]

Looks real good.

Question, was there a reason you didn't part the pins in the lathe?

The pins are hardened M2 steel for longer life. Don't have a carbide parting tool, just HSS. I could face them and bevel them with carbide, however.

Oh and thanks!

 

[WobblyHand]

Managed to notch the pins. For some reason I was hesitating to do this. The spindle bearings of the drill press are failing and making noise.

Also, had some distractions in the interim, namely a 3 alarm house fire just 2 houses away from me on Wednesday. Thankfully, no one was hurt. The fire spread fast. For a while, that tree on the left was on fire. Fortunately the fire was subdued in 30 minutes. But two families are homeless now.

Got the notching over and done with today. Then I tried to fit the knurling wheels to the pins and arms. One fit fine, very snug fit, and rotated freely, but the other wheel would not go in the slot very well. There was a burr at the bottom of the screw hole in the slot. So a little filing happened, and some honing with a 400 grit diamond hone. Finally the wheel dropped into place, but still it wouldn't turn. So took it apart and honed the inside of the arm to take off the final vestiges of the burr. Placed the pin and was rewarded with a knurling wheel with practically no play, but freely rotating.

Finally, had to grind off the 6-32 1/4" long SHCS a few threads so the screw would not penetrate into the cavity, fouling the wheels. It's beginning to look like this could turn into a knurler!

Still more work to do, on this, but I am encouraged!

 

[WobblyHand]

I found the screw that I single point threaded a looong time ago. It doesn't fit in the slot. More correctly, it fits in the ends of the slots, but not in the middle. It's not the end of the world, because I can machine or file it away. Or as they say, "some hand fitting is required". It's only a thousandth or so, it's real close.

I think I know how it happened. I drilled the ends of the slots with a quality 0.250" stub drill in the mill. I used a 0.250 end mill at the "end" of the process to mill the slot. The body of the screw is 0.25000" as measured by my QuantuMike. It's clear that the 1/4" end mill is undersized. Actually 2 of my 0.250" end mills are slightly undersized. (I used 2 1/4" end mills, because the first one was too short!)

The half moons need some deburring and smoothing. They won't move in the reamed sections due to the raised edges of threading. Some filing and honing cleaned it up enough to fit it. Now that the arms are fitted with the half moons I can see the need for a little more angle relief on the arms. That will require a few more days for the angle blocks to arrive. The screw is a very tight fit still. I'll fix that when I do the angle relief.

 

[Papa Charlie]

Real nice work there. I am generally impressed with your thought process and execution.

One question, Was there a reason that you chose a socket head screw over two C clips to hold the pins in place. Not that is should make a difference in performance and function. But was just curious.

 

[WobblyHand]

Real nice work there. I am generally impressed with your thought process and execution.

One question, Was there a reason that you chose a socket head screw over two C clips to hold the pins in place. Not that is should make a difference in performance and function. But was just curious.

Oh, how flattering If anything, I overthink this stuff.

You must be mistaking me for someone who knows what they are doing! I'm just a beginner in this machining journey. I have a lot of trouble with the setup stuff that I think more experienced folks take for granted. So far I have been (mostly) following @mikey's fantastic writeup. It never entered my mind to use C clips. My previous experiences with c-clips haven't been that good. They have a habit of flying everywhere on insertion or removal! Have gotten better at them, but I make sure I have a bag of clips around before doing anything with them.

For the future I could keep c-clips in mind. A carbide grooving tool could be used on the hardened pins. So far, cutting off the pins and grooving them has been the least pleasant part of this job. It would be much nicer to do it on a lathe, rather than that failing drill press. Noisy bearings make me cringe, it's like a machine is crying out in pain.

Have to say, the SHCS are a little "tall" looking on the arms. Might replace them with something lower profile, like maybe a button head? Seems that the button head screws head height is about half that of the SHCS. I'll see how I feel about them after it is all put together.

Think it's time to do some more work. It's cloudy and cool today, so I don't feel bad about spending the day in my below grade shop.

 

[Papa Charlie]

Oh, how flattering If anything, I overthink this stuff.

You must be mistaking me for someone who knows what they are doing! I'm just a beginner in this machining journey. I have a lot of trouble with the setup stuff that I think more experienced folks take for granted. So far I have been (mostly) following @mikey's fantastic writeup. It never entered my mind to use C clips. My previous experiences with c-clips haven't been that good. They have a habit of flying everywhere on insertion or removal! Have gotten better at them, but I make sure I have a bag of clips around before doing anything with them.

For the future I could keep c-clips in mind. A carbide grooving tool could be used on the hardened pins. So far, cutting off the pins and grooving them has been the least pleasant part of this job. It would be much nicer to do it on a lathe, rather than that failing drill press. Noisy bearings make me cringe, it's like a machine is crying out in pain.

Have to say, the SHCS are a little "tall" looking on the arms. Might replace them with something lower profile, like maybe a button head? Seems that the button head screws head height is about half that of the SHCS. I'll see how I feel about them after it is all put together.

Think it's time to do some more work. It's cloudy and cool today, so I don't feel bad about spending the day in my below grade shop.

I forgot that the pins are already hardened. Something I would like to add to my tool list is a small heat treat oven. Would be very nice to fabricate the part and then harden afterwards.

Button heads would be a good idea. Since there is no force on the fastener, you could even countersink the washer and into the body and use a countersunk screw. Just a thought.

 

[WobblyHand]

Have to stop on the plates. Gone as far as I can go with the tooling I have. Same with the arms.

With the plates clamped together using some cereal box cardboard, in the movable jaw, they were squared off and two holes were drilled using a #18. The holes were 0.250" and 0.250" from the long edge corners. Eventually that is where the pivot pins will go. Have to say the thin cardboard trick is really good. Had no problems with pieces lifting.

Then removed one of the plates and drilled out the holes with a C drill, and then a D drill. Finally reamed the hole to 0.2500" at 200 RPM. The reamer cut just the slightest amount of material, leaving a nice hole. Deburred the edges. Was all excited that I didn't need to make shoulder pins, since I had some O1 rod that measured out at 0.24995", but quickly realized that, duh, I need a larger diameter to make the shoulders! No worries, I have some additional O-1 that I can turn down. Was going to tap the other plate to 10-32 but realized that the only 10-32 tap I have is from my "questionable set". That set, bought from HF 20 years ago, is ok to get it done, but is not true to size. (Most of the pieces are oversized resulting in a sloppy fit.) Decided to order a decent tap from McMaster, and a few more short drills to add to my mostly empty short drill index box. If I place the order today I'll have it on Monday, so that is pretty good.

Next thing to work on is the shoulder pins. These are supposed to precisely space the plates around the arms. Initially aiming for an exact fit, (for maximum rigidity) so will need to use the micrometer to help me calculate the length. The critical length is equal to the sum of the reamed plate thickness plus the arm width. This length is to be 0.2495" in diameter to fit snugly in the reamed hole. Then there should be a 0.050" thick shoulder that is slightly wider than a 10-32 SHCS. Measuring the plate and arms, I get 0.7492". Found some 11/32" (0.3438") diameter O-1 in my stock collection. That ought to work. It is just a hair wider than the 10-32 SHCS head.

Running out of concentration for some reason. That's a sign to stop machining, so I will give it a break for the day.