POTD- PROJECT OF THE DAY: What Did You Make In Your Shop Today?

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JRaut said:
I would have preferred if the square slot was rotated 45* with respect to each half, but that would have gotten even more complicated to grab onto. I'm sure this will work just fine.
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yea lining up the 2 cuts would have been tough as well. you could have marked it while together.. but it sounds like you grabbed it on the ends in the vise to mill, and if you did your mark would disappear also.

I wonder if you made a holder, turned it on the 45, then glued it with C/A would have worked, still alignment being key.
The holder would be a block drilled out, then a quarter cut out.
All still more work, and probably not needed.. just thinking (dangerous) out loud.
 
Made another mess as usual , but I also organized a bit . :encourage: Cemented carbide , HSS bits , countersinks and taps separated . Only a few more boxes to go .
 

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ShawnR said:
Very nice. Being kind of new at this, may I ask for a brief description of your order of operations or how you did that? I am guessing turning the outside diameter first, then splitting it somehow? Slitting saw? How would you hold it? But then to mill the tool slot, again, how would you hold it? Or did you start with a longer piece, thereby having an area to clamp, and only cut to length when all other operations were complete? Or, typing as I am thinking, cutting the square hole into the round stock with a rotary broach, then splitting it after? Or a variation of those?

Thanks
Shawn
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Harold Hall has a page or 2 on his website on the subject of making square collet adapters.

His website is WELL worth a look. There is a boat load of useful info for the home machinist.
 
JRaut said:
I made up a little 3/8" square lathe tool bit holder for my Kuhlmann (Deckel-type) single-lip cutter grinder.

For my current project, I'm needing to put a nice radius on the back side of some SS valves. The cutter grinder is much more capable of grinding a smooth curve than I am over at the bench grinder.

I had some nice pre-hard material (4140 maybe?) on hand in the right size, so that's what I used.

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Well, I had a partial success.

I ground out a tool with dead-accurate cutting angles.

Only problem is that the nose radius didn't come out right.

The baseline formulas provided by all the D-bit manuals are based on the assumption that you're cutting the nose radius at the edge of a D-bit, and (because the D-bit is split half-wise down the middle) located exactly at the centerline of the grinding head.

The nose radius I was trying to cut was (1) not right at the edge of my 3/8" tool blank, and (2) all the way at the top of the tool blank, i.e., 3/16" above the centerline of the grinding head.

So I've got some more geometry to work out before I'll be able to get the nose radius correct.

Either way, this'll make a damn good cutting tool. It's so sharp that I sliced my thumb when checking the edge...

I might make up a separate thread on the topic, as I'm sure I'll have to break out Soh Cah Toa to get things sorted out.


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JRaut said:
I ground out a tool with dead-accurate cutting angles.
...
I might make up a separate thread on the topic, as I'm sure I'll have to break out Soh Cah Toa to get things sorted out.
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Maybe a CAD drawing will get you there without Trig? A lot of times doing a to scale cad drawing can get you numbers without math. (I don't mind doing the math, I'm just lazy! )

Second. That's a darn small valve drawing! Model engine?

Also, not even the 'professional' tool grinders always get the radius correct. Had a bunch of work on 1/2" delrin bars a while back. Made soft jaws with a groove milled by a 1/2" ball end mill. The 1/2 end mill end radius was quite a bit oversize. Ended up CNC milling some tool steel to the 1/4" radius, heat treating it, and making a fly cutter to hold it. Then milled the soft jaws, and it held the delrin perfectly. Not sure if CNC and heat treat are an option for you, but if so it may be another way to skin that cat.
 
dkemppai said:
Maybe a CAD drawing will get you there without Trig? A lot of times doing a to scale cad drawing can get you numbers without math. (I don't mind doing the math, I'm just lazy! )
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Papa Bear on the left, Goldilocks in the middle, and Baby Bear on the right.

I drew it up in Fusion 360 and I derived a big long equation that matched the Fusion drawing.

But that didn't work in practice. The actual nose radius is extremely sensitive to small variations in any of the tool geometry angles.

So I just did a bit of guess/check and crept up on a reasonable looking nose radius compared to a gage pin. No measurements or anything, but it'll be plenty good enough.

Also good to know that it ain't worth trying to be too finicky about setting angles or offsets on the D-bit grinder; just get it close and then creep up on the radius you want.

dkemppai said:
Second. That's a darn small valve drawing! Model engine?
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Yup! I'm building a 5-cylinder radial motor. Check out my progress here, it's coming along nicely:
www.hobby-machinist.com

Edwards Radial 5 build thread --- PHOTOS!

Episode 1 || Introduction to My Build Thread Background After a brief search through the H-M.com archives, I was a bit surprised that nobody had documented their journey building an Edwards Radial 5-cylinder engine. These engines are reasonably complex and time consuming to construct, but as...
www.hobby-machinist.com www.hobby-machinist.com


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Today was garage cleaning day, but i failed badly. In Fact i bought another car. It all started with me filling about 10 big garbage bags and not having anything to transport them. The littel niva is not in operation and i don't want to put them inside any of my cars. So i searched for vans and mpvs close to me and this was the cheapest. It runs, has one week of registration but the engine is knocking and some one cut off the catalytic converter, so it sounds like crap. Call the guy, he was 10 min from me so i went there seen that is not rusted it has the engine that i thought so i bought it. He was tight on price would not budge so i negotiated a free tow (he has a tow truck) free fog lamp he had a parts car there and half of the notary fees. So 5 min to get the title transferred, and 15min to get it loaded in less than an hour i bought an POS to get the job done. I clean a patch on the windscreen so i can see when driving, loaded it i did lay down cardboard that i throw away at the dump and get rid of all the garbage. Driving it straight piped and all muddy and knocking was sight to be seen. At the end of the day i free almost the same space the vehicle that i bought takes so in that sense i failed. I have two spare K series engines for it so i'll be changing the engine and probably just sell it, now prices of cars are higher then ever.
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