Another Rupnow 1 by 1

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Brian Rupnow

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Very glad that I see you continuing with the build.---This build isn't for sissies. You will learn to figure out a few things before you are done here.---Brian
 

Eccentric

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Looking great. I think making the crankshaft is one of the most challenging, most rewarding and most nerve wracking parts of the build. I hate to admit it, but I rarely get my crank right on the first try, hopefully you will best me in this regard. But I learn something everytime and I am getting better and learning little tricks. Patience is the key.

I agree with you and don't think the homemade aluminum lathe dog is going to hold up, you have a lot of turning ahead of you. I recommend this set: Lathe Dog Set | Lathe Dogs for Sale | LittleMachineShop

They are only 35 bucks and have a whole progression of sizes that you will use as you turn down the crankshaft. They are steel and will allow you to really crank down on the hold down bolt. You can see an example in the last picture of this series.


1631043350859.png


I use this type of small carbide cutter to turn down the sides of the crank web. Like you I use the mill to remove the material and cut the slot to size, but there is one last cut the mill cannot do. And I use

1631043375428.png


this type of homemade HSS cutter for the crankpin. It is relieved on the sides and has the forked snake tongue shape on the end to reduce the amount of the cutter actually in contact with the work piece. I crank it in a couple of thou and then move the cutter back and forth. As I approach the target dimension, I run my lathe slow, like 250 RPM to eliminate the chatter. This is the most nerve wracking part for me, as I approach the actual dimension, you over shoot and the part is ruined. I turn to about .0015" over then use files, stones and emery paper to finish to size.

1631043404523.png


Here is a collection of tools used to bring the crankpin to final dimension and polish. It is important to be cognizant of the pressure used across the pin, you don't want to make one side of the pin smaller than the other. That is a problem with files for example, if you press evenly then move it back and forth, the middle of the pin is in contact with the file more than the edges and you get a low spot in the middle. I use the calipers and micrometer constantly throughout the process. I use strips of emery paper for the final finish.

1631043421764.png


If it is available, I use the connecting rod to test fit. I am careful not to over tighten the cap before the pin is to dimension, but this proves that the web dimension is good and the final fit is good.

You can see the lathe dog in this picture. Also the reason my steel is black is that I stress relieve the blank in the heat treat oven and let it oven cool overnight. Don't know how much this helps.

Keep up the great work.
 

CFLBob

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Thanks for that excellent discussion. Lots of good points to come back to again.

This one really resonated
That is a problem with files for example, if you press evenly then move it back and forth, the middle of the pin is in contact with the file more than the edges and you get a low spot in the middle.
I think I've been there on different tasks.

My immediate problem is that I have two sets of cutters, one 1/4" shank set for the Sherline lathes and one 3/8" shank set for this big lathe, the Little Machine Shop 3540 (a SIEG SC4). The L & R cutters are wider than the opening in the bar that I roughed out on the mill. I used a flat ended cutter similar to the one you show except with no cutout that happened to fit. I need to open the slot close to final width with either the square tip or something. I'm thinking of using one of the 1/4" cutters.
ChatterMarks.jpg

I hadn't noticed the chatter until this picture.

Your lathe looks so much like my LMS lathe that it's spooky.
 

CFLBob

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Well, it has been almost two weeks since the last update and not much to say. I concluded my shop-made dog wasn't going to work and after exchanging emails with Little Machine Shop about using the chuck mounting plate instead, I ordered a face plate for my lathe and their two biggest lathe dogs. For smaller pieces, I have the equivalent tools for my Sherline, but I've never used them in the 15+ years I've had them.

Let me note first that the people who make these accessories never include instruction sheets. I think their view is that if you're using a lathe you should be professionally trained and you should know how to maintain or upgrade it. I also wouldn't be surprised if not including instructions might have some aspect of trying to protect themselves from spurious lawsuits.

Now, I'm fully self-trained, I take responsibility for myself, and there really didn't seem like many ways to put it on incorrectly. It has three bolt holes on the back which match with three through holes on the mounting plate that's standard on the lathe. I put the first bolt in, went to rotate the two plates to put in the next bolt and quickly found the combination wouldn't turn. There was interference between a different bolt on the lathe and the faceplate.

FacePlateCollision.jpg


That bolt (M8?) has two nuts on it, putting that spring under tension. It sticks maybe 1/8" inch into that cavity in the casting. The bent, black sheet metal you see on the left and top edges is holding a clear plastic "lathe chuck guard" that is supposed to keep your fingers away from the chuck but primarily seems to catch oil the chuck may sling. A closer look showed that when the guard is down, the faceplate will rub on the plastic and I'm sure eventually (a few minutes) will wear through it. A note on the faceplate's product page says, “This faceplate will not fit with the plastic chuck guard in place.”

I'm going to gloss over me looking at the lathe and trying to figure out how to remove that for several hours when the answer is visible right there in that picture. All I had to do was unscrew the two nuts on the right end of the interfering bolt and then the cover just slides off the bolt, Once that's done, just unscrew that bolt. That's when I set things up to hurt myself.

FacePlate_w_Dog_bar.jpg


This is the faceplate, lathe dog, crankcase blank and all.

You can see above that I'm using a parting tool to shave that side of the cutout, and to minimize how much tool was exposed, cranked the cross slide and QCTP forward. It's like this.

Along_Bar.jpg


I'm not completely sure how it happened, but I think I put my right hand on top of the tool holder and let my finger stick out forward a little too far while getting started. The bar was spinning and it whacked my finger. It tore the end of my finger off breaking almost all of the fingernail, but it stayed attached by a lot of skin. We figured it was time to go to an urgent care place. The doctor there said the end segment of bone in that finger was broken and they don't treat "open fractures." They told me to go to an ER. Where I sat for 3-1/2 hours, never talked to or saw a doctor, never really had anyone look at it closely, then had a nurse leave the blood soaked and hardened gauze pad from the Urgent Care place on the finger, wrap some self-adhesive gauze around it, and refer me to a hand surgeon. This was last Monday the 13th.

Long story shortened, the surgeon got me into the office Wednesday and did the surgery the day after that. This is called a degloving injury but do yourself a favor and don't look for example images. I will still have 10 full-length fingers, and might even have 10 fingernails. I mean, I do now, but part of the fix was to sew the half or 2/3 of nail that broke off back onto the nail bed and it's going to take months to see how that grows.

I just took off the oversized bandage I've been wearing since Thursday and switched to something smaller. It's likely to be another week before I can get any more work done.

I need to order some more metal, so this is a good time to pay attention to those things.
 

Brian Rupnow

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Bob---Sorry you hurt yourself. I've had a few whacks from the chuck, but nothing hospital worthy. I'm not exactly afraid of my machines, but I treat them with a great deal of respect.
 

CFLBob

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Bob---Sorry you hurt yourself. I've had a few whacks from the chuck, but nothing hospital worthy. I'm not exactly afraid of my machines, but I treat them with a great deal of respect.
This is the first time I've ever needed anything beyond a plain old band-aid from anything in 40+ years of wood and metal working It obviously could have been much worse, but it was just from a moment of inattention.

The previous week, I was telling someone to watch out because anything that cuts metal isn't going to get slowed down by skin and bone. Anytime we're using any machine, something bad could happen.
 

Eccentric

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Bob,

I am also sorry you got hurt, I hope everything heals OK. The name of the injury , degloving, gives me the creeps and shivers. Sorry it had to be you, but a little reminder now and then of how dangerous our machines can be is not a bad thing. I'll continue to be extra vigilant in your name.

I've always had mixed feeling about those "chuck guards" on the smaller hobby lathes. Do they give a false sense of security? Do they enable people to be lax respecting the moving chuck? Are they a neccessity for the beginning hobbiest? We all are aware of the chuck and work close to it, especially with files (which always have a nice fat handle so it won't be driven through the palm of our hand by accident, right?).

Take care of yourself and I hope to see you back in the workshop soon. Your crank is coming along nicely.

Greg
 

CFLBob

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Thanks, Greg. I've found over the last two days that I forget to use the pain meds, which clearly means I don't need them. That's a good sign. The finger is still a bit swollen and the range of motion isn't back but it's coming back.

My followup visit with the surgeon is Friday morning and I'm hoping to be back to more or less normal. I don't know if that's even possible, if I'll get another 10 day followup or what, but 10 days to two weeks is about when they take out regular stitches. That's ignoring the 6 months for the nail to grow back out.

Meanwhile, I've been rounding up the metal stock I need but didn't pick up when I was starting because it seemed like the sizes I could buy were absurd compared to what I need. Like I need about 1" length of a O-1 tool steel to make the cam, and the smallest bars I could find were 36" (that 1" I quote is over twice the finished length of the cam).

I think I'm about to order a flywheel casting from Martin Models instead of doing the built up flywheel Brian did in the original.
 

Brian Rupnow

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Bob--In my opinion, no one should feel bad about buying a flywheel , a sparkplug, or a carburetor. I think everyone should build one of the above mentioned things once, just to prove to themselves that they can. Then, having proved to yourself and the world that you have actually made these things and that they are in the range of your capabilities, go ahead and buy them.---Brian
 

Steamchick

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Bob, Sorry to hear of your injury. And thanks for NOT posting pictures. I don't enjoy hearing of painful experiences... call me squeamish! I can't rememeber having any bad cuts and bruises, except from crashing motorbikes. But I have experienced (months of!) severe back-pain and sciatica, on and off for 40 years... so hope it wasn't as bad as that.
A salutary lesson in there.
Take care...
K2
 

jlchapman

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Bob, Sorry to hear about your injury. It happens, just be glad it wasnt more serious then it was.

Thanks for posting your CNC adventures. I love seeing the fixtures and how the machining is done. I'm self taught also and use these post for learning. I'm also applying my new CNC skills to model building.

Jerry
 

CFLBob

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Bob, Sorry to hear about your injury. It happens, just be glad it wasnt more serious then it was.

Thanks for posting your CNC adventures. I love seeing the fixtures and how the machining is done. I'm self taught also and use these post for learning. I'm also applying my new CNC skills to model building.

Jerry
Thanks, Jerry.

Re: the CNC adventures, I've been working on the G-code for the CAM, which combines arcs from three different circles. I did a similar approach on the Webster's cam, but the Webster's cam was a simpler design that had a couple of straight lines in it while Brian's cam has no straight lines.

The simple way to do that is to dump the cam into my CAM program. The drawback is the motion is done as straight line segments, so the curves are approximated as stair steps. First off, it's ugly, but more importantly is that I'm not sure it doesn't harm the function.
 

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Hi Jerry, I too am learning from all these posts. So when you see "advice" from me, take care, I'm not expert like these other guys! (I never got into CAD and CNC.... pencil drawings, chalk on the kids toy blackboard, and total hand and brain power to manage where the tools cut has been my life!).
Cheers!
K2
 

L98fiero

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Thanks, Jerry.

Re: the CNC adventures, I've been working on the G-code for the CAM, which combines arcs from three different circles. I did a similar approach on the Webster's cam, but the Webster's cam was a simpler design that had a couple of straight lines in it while Brian's cam has no straight lines.

The simple way to do that is to dump the cam into my CAM program. The drawback is the motion is done as straight line segments, so the curves are approximated as stair steps. First off, it's ugly, but more importantly is that I'm not sure it doesn't harm the function.
Brian says he uses the same cam on all his engines, here's the cutter path for the T-head engine using a 1/4" endmill, with the XY0 at Y-.04 so you can cut it from a piece of 3/4 stock. It's for a Yasnac control with a tool changer and was originally for a 1/2" mill going full depth so feeds and speeds aren't correct and it uses adaptive cutter paths so you'll probably need/want to do some editing, at least the finish pass should be good. Hope it works for you.

%
O100 (BRIANS CAM.TXT)
N01 G17 G20 G40 G49 G80 G90 (G17= XY PLANE, G40= CANCEL CUTTER COMP, G49= CANCEL TOOL LENGTH OFFSET, G80=CANCEL CANNED CYCLES, G90=ABSOLUTE COORDINATES)
N02 G00(RAPID TRAVERSE)
N03 G91 G28 Z0(G91=INCREMENTAL MOVES, G28=GO TO HOME THROUGH SECOND POSITION)
N04 G91 G28 X0 Y0
N05 T6 M06 (1/4 FLAT ENDMILL - ROUGH)(M06=TOOL CHANGE)
N06 G90 G54 X-.5786 Y-.0622 T16 S2450 M03(T16 CALLS NEXT TOOL TO TOOL CHANGER)
N07 G43 H6 Z.1(G43=ADD TO Z FOR TOOL LENGTH COMP)
N08 Z-.7
N09 G01 Z-.8 F31.
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Last edited:

CFLBob

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Brian says he uses the same cam on all his engines, here's the cutter path for the T-head engine using a 1/4" endmill, with the XY0 at Y-.04 so you can cut it from a piece of 3/4 stock. It's for a Yasnac control with a tool changer and was originally for a 1/2" mill going full depth so feeds and speeds aren't correct and it uses adaptive cutter paths so you'll probably need/want to do some editing, at least the finish pass should be good. Hope it works for you.

%
O100 (BRIANS CAM.TXT)
N01 G17 G20 G40 G49 G80 G90
N02 G00
N03 G91 G28 Z0
N04 G91 G28 X0 Y0
N05 T6 M06 (1/4 FLAT ENDMILL - ROUGH)
N06 G90 G54 X-.5786 Y-.0622 T16 S2450 M03
N07 G43 H6 Z.1
N08 Z-.7
N09 G01 Z-.8 F31.
N10 X-.5419 Y-.0665
N11 G17 G03 X-.5002 Y-.0413 I.0046 J.0395
N12 X-.4911 Y-.0116 I-.1569 J.0643
N13 X-.4871 Y.008 I-1.095 J.2373
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N83 X.1934 Y-.5131 I-.3535 J.5997
N84 X.1056 Y-.5451 I-.371 J.8823
N85 G01 X-.0188 Y-.5836
N86 G02 X-.0624 Y-.5688 I-.0116 J.0376
N87 G01 X-.0891 Y-.5315
N88 X-.1182 Y-.4908 Z-.8 F31.
N89 X-.1298 Y-.4745
N90 G02 X-.1329 Y-.4694 I.0334 J.0237
N91 G03 X-.1548 Y-.4487 I-.0362 J-.0162
N92 G02 X-.4265 Y.055 I.1548 J.4087
N93 X-.3789 Y.1888 I.4816 J-.0963
N94 X-.2839 Y.3107 I.3924 J-.2077
N95 X-.1807 Y.4102 I.6304 J-.5507
N96 G03 X-.2433 Y.4542 I-.0251 J.0308
N97 G01 X-.2491 Y.4379
N98 G02 X-.252 Y.4316 I-.0388 J.0138
N99 G01 Z-.7
N100 G00 Z.1
N101 X-.4982 Y-.0041
N102 Z-.7
N103 G01 Z-.8 F31.
N104 G02 X-.5085 Y.0469 I-.0346 J.0196
N105 G01 X-.4897 Y.0324
N106 G03 X-.4265 Y.055 I.0243 J.0315
N107 G02 X-.3727 Y.1884 I.4322 J-.0971
N108 X-.283 Y.3118 I.7195 J-.4287
N109 G03 X-.281 Y.3616 I-.03 J.0261
N110 G01 X-.2993 Y.3862
N111 Z-.7
N112 G00 Z.1
N113 G91 G28 Z0
N114 T6 M06 (1/4 FLAT ENDMILL - FINISHING)
N115 G90 G54 X-.0313 Y.5644 T16 S2500 M03
N116 G43 H6 Z.1
N117 G01 Z-.8 F20.
N118 G41 D46 X.1652 Y.4098 F15.
N119 G17 G02 X.3698 Y.1735 I-.5116 J-.6498
N120 X-.3698 Y.1735 I-.3698 J-.2135
N121 X-.1652 Y.4098 I.7162 J-.4135
N122 X.1652 Y.4098 I.1652 J-.2098
N123 G03 X.5162 Y.4516 I.1546 J.1964
N124 G40 G01 X.3198 Y.6062
N125 G00 Z.1
N126 G91 G28 Z0
Thanks! I'll have to look at that in my G-code simulator and see what it looks like. There are codes in there I've never seen before.
 

Eccentric

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Meanwhile, I've been rounding up the metal stock I need but didn't pick up when I was starting because it seemed like the sizes I could buy were absurd compared to what I need. Like I need about 1" length of a O-1 tool steel to make the cam, and the smallest bars I could find were 36" (that 1" I quote is over twice the finished length of the cam).
Bob,

One thing you might want to research is case hardening. This is where you use a low carbon mild steel and only hardend the surfaces that need it. I have not made my camshaft yet and I am going to try this. I will be using this: BROWNELLS SURFACE HARDENING COMPOUND | Brownells

I have not case hardended mild steel before, but I am going to give it a try.

The cost of the hardening compound may be more than the 01 tool steel. Also I have read posts here where the camshaft gets distorted during case hardening. So take all of this with a grain of salt.

Greg
 

Steamchick

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Hi Greg,
Many will know more than I.... but here's my pennorth...
50 years ago, the machine shop where I worked part time made various tools and punches, usually from high-carbon or tool steel (often from annealed old files, re-forged as appropriate). Some softer tools were left in "my charge" for case-hardening. I was taught that any high carbon coating is adequate.... I even used sugar from the tea tray!. A red-hot tool end, dipped in a tin containing sugar, more heat, more sugar, and after "enough" the tool was quenched in oil (big flames, lots of smoke - outside!). Then I cleaned it with wire wool.....until shiny steel, and tempered the tool to the Boss's instruction for the colour temperature, then quenched in oil (again). The hard edge was then honed for sharpness. (Hand-dressed with a stone slip). Worked well for drills, scrapers, lathe tools, etc. I still do it when "needs must".

Otherwise, in industry, I know the cam-shafts for car engines were cast "grey" iron, then oven hardened, quenched or whatever for the cam lobes to be ground. But I don't know the process. I used the soft core grey iron to make odd (small) parts like pistons. (1/2" DIA).
Also in industry, I experienced nitriding: steel piston rings cooked in ammonia flames in an oven for over 4 hours to nitride the surface. At school I was taught that blacksmiths would keep a donkey, feed it on turnips, then collect the strong pee for quenching there plough shares after forging, to harden the edges. (Nitriding, but only just!). A modern way is too do the same multi-dip and cook process as case hardening, but using nitrogen fertiliser instead of carbon.

A proprietary tin of case-hardening compound in the UK would be Kasenite. But I have used ordinary sugar, coal, coke, carbon-arc, leather, etc. with success. The carbon-arc was when I brazed mild-steel brackets onto exhausts, then found the surface to be too hard for ordinary drill bits. After breaking through the surface, the steel beneath was "normal" mild-steel. The leather was old shoes, cut into strips, wrapped around the tools, wired in place, then burnt in a wood fire (red-hot bed of charcoal, not the yellow flames).
Hope there is something of use?
Have fun!
K2
 

CFLBob

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Bob,

One thing you might want to research is case hardening. This is where you use a low carbon mild steel and only hardend the surfaces that need it. I have not made my camshaft yet and I am going to try this. I will be using this: BROWNELLS SURFACE HARDENING COMPOUND | Brownells

I have not case hardended mild steel before, but I am going to give it a try.

The cost of the hardening compound may be more than the 01 tool steel. Also I have read posts here where the camshaft gets distorted during case hardening. So take all of this with a grain of salt.

Greg
I'm familiar with case hardening, and Brownells, but have never tried it. I bought a 3' bar of O-1 steel and I'm going to just try to make it like Brian suggests. Doing that was actually one of things I told myself I wanted to learn doing this engine.

I still don't have the stitches out of my finger, but I've been working toward resuming cutting the crankshaft. I really like the cutter you made with the gap in the middle, and have taken to calling it the Terry Thomas cutter, which may only be meaningful to those of us old enough to remember him as a comedian on '60s TV shows and movies. (I told my wife and she calls it the Lauren Hutton cutter - same reasoning).

I'm in the same spot there as the oil-hardening; I know some basics about making cutting tools, but have never done much of it. Right now, with still less than 10 fully functioning fingers, I'm reluctant to break out the bench grinder and try it. I have that square tipped cutter in a photo up in post #23, and I think I'm going to try to find a smaller one. Then I'll try to give it the Terry Thomas gap-osis with a diamond file.

Oh, and K2, thanks for the cool stories. I have neither donkeys or turnips, but it's fascinating stuff to read. Makes you wonder how in the heck they discovered these things.


Bob
 

Steamchick

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Blacksmiths would pee into the quenching tank, to save carrying water from the well... The "donkey pee" could be collected while they were shoeing donkeys and horses - saved it forming smelly puddles on the floor of the smithy! One of the jobs for the "bellows boy". The quenching water became nitrogen rich (Lye) and edges of blades became harder and blades became better able to hold an edge, hence they learned about nitrogen hardening (Nitriding) centuries before they knew of Nitrogen!
Simple if you look at history. (My Dad took us to a lot of museums as kids).
Cheers!
K2
 

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