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Bull Nose Live Center

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Ray C

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I've been meaning to make this live center for a while now. The bull-nose is a special size and length that would make a particular task a little easier. Here's an outline image. This is a background shop project that's going to take a while. The nose is 4140 that I plan to bring up to the RC 55 range. The rest will just be 1045 raised to a low/moderate hardness. And before the spiders come dashing out of their webs, I'm well aware of the torque issue in the design. This is special-purpose and does not need to support heavy loads at all.

There's a 3D .pdf enclosed n this post too but I'm not sure if it's attached properly...

OleBully.JPG

Ray
 

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Ray C

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Great job Joe. That's very nice!

Thanks for showing your design. I'll probably stay on course with my current plans though, because this will consist entirely of shop drops and available parts. The main ingredient is a very small taper bearing with an ID of 0.6875" and OD of 1.5700". Been saving that bearing for this purpose for about 2, maybe 3 years now. There's also a little radial bearing at the back and somewhere along the line, I acquired about 20 brand new of the little devils.

Anyhow, here's a few pictures of getting the raw stock trued up. Normally, I sandblast mill scale first but, I didn't want to wake-up the neighbors with the air compressor (it's outside in a shed in the backyard about 20 feet from the neighbor's house). I really don't like busting-up my inserts on mill scale.

Along the way... I suspected the tailstock was out a little so, several light passes at .030 (.060 dia reduction) were taken to adjust the tailstock. -And of course, I had to chase that chicken around the coop for much longer than I wanted. The good news... it's about dead on now.

IMG_20171224_083808.jpg

These are fairly fast passes digging in 30 thou with 12 thou IPR. There's my favorite insert for this machine. Makes nice chips and is a perfect size for 2-3 HP lathes. I wish I could find some 1/2" holders that take these inserts but in all honesty, I can't find a reason to complain about the 3/8 holders.

IMG_20171224_101854.jpg

This piece was flipped around to catch the other side and you can barely see the cutting junction.

IMG_20171224_083303.jpg

More eye-candy later...

Merry Christmas

Ray C.
 
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tweinke

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Opened the PDF, works fine! nice idea, might have to try that idea.
 

Ray C

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Opened the PDF, works fine! nice idea, might have to try that idea.
Thanks for letting me know. I remember many years ago, I had troubles posting 3D PDF files. With that PDF, you should be able to click and rotate the part in all directions. Some websites block PDF with active content.

FYI: The second "silhouette" (looking from left to right) in the holder part, holds the taper bearing cup. Way at the back, a small radial bearing stabilizes the shaft. I can't find those bearings in the library, don't feel like modeling them, so they're not shown... :rolleyes:

Ray C.
 

dlane

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Was wondering where the bearings were, and on that note where are you located
 

Ray C

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Was wondering where the bearings were, and on that note where are you located
Does the location information not show below my avatar? If not, let me know but otherwise, the location information is correct.

Ray C.
 

zmotorsports

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Nice looking finish on that piece of 1045 Ray.

Mike
 

dlane

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I’m not seeing a location below your avatar , don’t worry if your my neighbor I won’t bug you. :big grin:
 

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I guess with taper bearings you won't need a thrust bearing? I've wanted to build an interchangeable tip center for years but I'm watching to get my build right in my mind. I've picked up some bearings through the years also , my current lathe will likely be my only one ever. 11" Logan it's been used by me quite alot over the forty plus years I've owned it. Always wanted a more stout lathe in a 14-16" range ,,,, Monarch ,,, being my favorite ,, but beggars can't be choosers . Nice build I'm watching to see the completion .
 

Ray C

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@dlane: I'm in the people's federation of Maryland a few miles west of Annapolis.

@mike: Yeah, 1045 always looks like that. Carbon-wise, anything north of, and including 1030 cuts nice and clean. Most of the alloy steels are nice like that too.

@ed: That particular insert is a ccmt 2151 in a SCLCR, 3/8" holder. I use many different inserts (probably too many) but for that 12" lathe with a VFD driven motor that probably varies between 2-3 HP, only a handful of inserts are practical for machines that small. If you want to talk about inserts, go right ahead. BTW: Today is my lucky day, I just found a 1/2" holder for that size insert. AXA toolposts with 3/8 or 1/2" tool holders is the sweet-spot for little machines like that.


Merry Christmas...

Ray C.
 

Ray C

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I guess with taper bearings you won't need a thrust bearing? I've wanted to build an interchangeable tip center for years but I'm watching to get my build right in my mind. I've picked up some bearings through the years also , my current lathe will likely be my only one ever. 11" Logan it's been used by me quite alot over the forty plus years I've owned it. Always wanted a more stout lathe in a 14-16" range ,,,, Monarch ,,, being my favorite ,, but beggars can't be choosers . Nice build I'm watching to see the completion .
Taper bearings handle both radial and axial forces fairly well and this should do fine because of the rear radial bearing that's stabilizing the shaft. The taper bearing I'm using has a dynamic radial load rating of 24,000lbs. Taper bearings typically have an axial rating of about 40-50% the radial value which would be roughly 10,000lbs. Cutting forces are only a few hundred pound (at best) and a 10,000lb part on my 12" lathe would flatten it -so I should be OK.

BTW: The torque issue mentioned in the intro is basically a non-problem in this design until load rating gets near the searing limit of the diameter of the shaft in the rear radial bearing. You know how it goes in website forums though...

Ray C.
 

Ray C

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Nothing better than hanging-around the house with family, taking the dog for walks and screwing-around in the shop, on Christmas day. So, here's a few more action shots hot off the press...

I'm making the nose part out of 2 pieces; why you ask? Because I feel like screwing-around in the shop -and because I can. The big piece is bored undersize, the shaft was cut oversize -and when the two come together they'll never come apart again. Once the two are sweated, I'll toss it back in the lathe and cut a 1/4" deep groove at the junction then, I'll TIG a bead of weld to seal the deal forever.

I settled on base dimensions for the sweat fit of 1.3100".
The boring came-out fine with final ID of 1.3095. Shaft OD was 1.3110 so we have 1.5 thou interference fit. The temps were measured in the shop at 60 F. The shaft is now in the freezer. The nose piece is now in grill warming-up with a rack of ribs. I'll re-measure after a couple hours of temperature soaking then, press the pieces together in the press.

Hope everyone is enjoying the Christmas holiday....

Ray C.


IMG_20171225_125303.jpg
IMG_20171225_134738.jpg
IMG_20171225_134752.jpg
IMG_20171225_135922.jpg
 

Silverbullet

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Looks good, were watching. Had a thought you could pin it through and only plug one hole for weld over. Less chance of any warping or hard spots ... maybe ???
 

Ray C

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So, here's how it all panned-out...

The nose part spent an hour in the grill and another 1/2 hour in a toaster oven at 450 F. It got slightly discolored. The hole expanded 1.8 thou to 1.3113".
The shaft spent the same time in the freezer at 0 degrees F. The shaft contracted 0.0003" to 1.3107.
The positive clearance was 0.0006" I didn't need the press, just needed to protect the end and thump it in with a few hammer strikes. It went in very easily. It went in very straight. I spun it in the lathe just for grins and the wobble, is almost imperceptible and compensating for the fact that my 3-jaw has a tiny bit of runout at/around that range of diameter.

They are both 1045 (same material) so as temps stabilize the two are joined with a 1.5 thou interference fit. That probably equates to a very significant crushing force.

And now for coefficients of linear expansion:

1045 steel has a coefficient of expansion of 6.3x10 EXP-6 (adjusted to Fahrenheit scale).

Here's what the expansion theoretically should have been:
Shaft was reduced 60 degrees F so, starting OD x 60 x 6.3 EXP-6 + original OD is: 0.0005". The shaft should have shrunk 0.0005".
Nose was raised about 400 degrees F so, bore ID x 400 x 6.3 EXP-6 + original ID is: 0.0027". The bore should have increased by 0.0027".

For whatever reason, the actual measured expansion/contraction fell short (just a little bit) in each direction. I suspect heat and cold soaking for 8 or more hours would do the trick.

Still though, these two pieces are stuck together and soon, I'll dig a groove at the junction and TIG them together.

Merry Christmas

Ray C.

IMG_20171225_160413.jpg
 

Ray C

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Looks good, were watching. Had a thought you could pin it through and only plug one hole for weld over. Less chance of any warping or hard spots ... maybe ???
Hey there Silverbullet. Happy Holidays. Hope you're having a good day.

No, not worried about warping or hard spots in the least bit. The whole thing is somewhat oversized by nearly 1/2" in some dimensions. After it's welded, I'll next cut the nose taper to rough size but it will still be over-sized by a good amount. I'll also cut the weld caps off and put some rough steps in the shaft. After that, it will get heat treated. When I do 1045, I hold the austentizing temp for 45m/1in thickness so, this part will stay in the oven for about 2.5 hours. That will completely normalize and stress relieve it. When it's quenched, it will go in the oil, suspended from a chain, nose down, linearly (not sideways). That minimizes bending of long parts.

Finally, the part will be annealed (I always do 2-part annealing) to RC 55 which is about as hard as I can cut with CERMET inserts on my lathe. The final step is to turn it down to exact/final dimensions. I'll use a tool post grinder on the shaft part. I estimate that about 0.050 to 0.100 inches of material will be needed to reduce it final size. At that depth, the hardness will only be about RC 50.

I'll do the same thing with Morse taper part but, but will temper it down to about RC 45 because A) MT shafts should not be super-hard, B) the part does not need to be that hard and C) it's really a pain to lathe cut precision bores in really hard metal. RC 45 is very easy to cut. It's 55 and above that get tricky. I'll explain how that is handled when we get there.

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Ray C.
 

Ray C

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Ok, here we are...

Grooved-out a little notch about 1/4" deep at the junction. Kinda boxed myself in a corner and had to grind a piece of HSS to reach in there.

IMG_20171225_181808.jpg

The piece was pre-heated to a light straw color (about 400-500 F) before the 1st pass bead. I hit it with 150A, pedal to the metal using 70s6.

Here's the first pass.

IMG_20171225_183712.jpg


And here's the second pass. Now it needs to cool slowly and naturally. Pre-heating the metal prevents the large piece from "auto-quenching" and this does help keep the weld caps from turning into diamonds.

.... Yes, that looks like undercut but its really due to a shadow and even if it were undercut, the part is going to be trimmed-down in the lathe. The weld-fill was adequate all the way around.


IMG_20171225_184102.jpg


Regards

Ray C.
 

Ray C

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... A few more baby steps on the bullnose center in-between enjoying this beautiful day ...

Admittedly, I scratched my head for a couple moments thinking how I wanted to hold this piece for the roughing cuts. Here's what I did and I'd love to hear how others might have tackled it.

I chucked it up in the 3 jaw using a technique that seems to work for me. First, my 3 jaw is pretty well behaved. Through most of it's useful range, it only loses center by a few thou at most. On my lathe, I recently re-tuned the tailstock and with past history, I trust the TS pretty-much all the way down to the end of the bed.

So... a technique I often use, is to bring the TS into position and lock it down. While the jaws are very lightly grabbing the piece, I put the end of the piece in the tailstock then, use a small, hand-held leverage bar to push it lightly (but firmly) against the live center in the TS. While holding that light pressure, snug-up the chuck jaws. The jaws will grab the part and hold so the piece will naturally spin on the axis of the tip of the live center.

Here's a picture. Mind you, I'm only using medium, 3-finger pressure to push that piece into the TS. NOTE: Normally, I like to hold the piece further into the jaws but, I only gave myself about 1.75" of wiggle room on the stock.

With the piece tightened securely, I was pleased to see that the piece only had 8 thou total runout. Not only was I pleased, I was a little surprised.

IMG_20171226_104248.jpg

The weld cap came off without a struggle! Indeed, it's a little harder than the base material but, the carbide didn't even wince or groan.

IMG_20171226_105123.jpg


You're probably wondering why I put the big piece in the chuck given that the next step is to carve a rough taper in it. Here's why... I'm going to use a parting blade to dig down to about where the taper will come to a point. Trying to dig-away at the taper using normal inserts would not be a fruitful way of doing things. Anyhow, I wanted the business end of that piece next to the chuck for the parting operation. Another note: I'm parting a fairly large piece with a 3 jaw chuck. This is dangerous territory but, since the linear distance from one jaw to the next is less than the diameter of the part, I will be OK. Need to keep these things in mind when putting a lot of pressure on a piece. (ask me how I know).

And BTW, I really like that parting tool. It's a Shars brand that does very well with these small lathes. I've tried 3-4 different parting tools on this lathe and this one works the best for me. Let me know if anyone wants a part number and I'll look it up.

BTW: Kool mist works just fine for parting.

IMG_20171226_120921.jpg

OK, going to take another dog walk now...

Happy upcoming New Year.

Ray C.

PS: Feel free to share ideas and start-up a conversation about different ways of doing this.
 

Ray C

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Now we're cutting the taper in multiple passes. The carriage position is adjusted once and then it's locked down. Multiple passes are made with the compound doing all the work after being set to 30 degrees. Whenever I do something like this, I clean and oil the compound ways and adjust the gibs. Doing this will likely prevent the acme screw from imprinting in the cut.

IMG_20171226_151229.jpg

Once in a while though... nasty swarf is unavoidable for a while. Here is your worst nightmare that can take you out of commission. When this kind of swarf is happening, I clean it up after every pass using a pair of long-nose grabbers. This kind of swarf will slice tendons instantly.

IMG_20171226_152741.jpg

BTW, I use a simple drill attachment in the compound to feed it smoothly. It's just a piece of T-shaped rod. Carbide does not like to be toyed with. It wants a decent DoC and feedrate. Using a drill helps keep the carbide buried in the cut. Uneven hand motions from manual turning is the enemy of carbide.

IMG_20171226_153329.jpg

And here's what it's looking like right now. It's just about ready to come out and get ready for heat treating. It's still oversized by a good bit because it will brought to final size in the hardened condition. I'm allowing about 0.050 for warping (but I know it won't warp anywhere near that much). Before it's heat treated, I'll cut the scrap plate off the front and will drill a center hole in the tip that will be needed to mount it after it's heat treated.

IMG_20171226_163848.jpg

FYI: Once I got rolling on that taper cut, I was able to make some 0.135" DoC with a slow feedrate. This is not advisable because of the injury potential with such razor sharp swarf. Ultimately, I reduced DoC to about 0.035 (eye-balled) and increased feed with the drill. That ended-up producing ideal (and very safe) blue chips.

IMG_20171226_164343.jpg


If anyone wants to hear/see my shortcut for setting the compound to 30 degress w/o using an indicator of any sort, let me know. It's quick and dirt but has always produced great results. When this project is over, I'll take it to the granite bed of truth to see how close I get to 60 degrees...
In the upcoming days, we'll start working on the mating part.

BTW: Things are going to slow-down now. I have to spend some time in the "other office" to keep the rails greased.

Happy upcoming New Year...

Ray C.
 

Ray C

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I'd like to hear it.
OK then. Keep in-mind, this is a shortcut but, when done properly, has produced results just as good as when I do the setup with indicators and verify with angle blocks. To do this properly, you must understand how backlash works and backlash has to be adjusted for given the directions you're traveling when doing the setup moves.

First, assume you have a triangle that has a hypotenuse (diagonal leg) of exactly 1 inch. I'm using 30 degrees as an example but any angle can be used here. Just use and assume a hypotenuse of 1 inch.

Everything is done with the lathe off (not running). Also, you should have a piece of stock that was just cut in the lathe without it being removed from the chuck.

See the diagram. Assume the black horizontal line is the workpiece. At point "A", touch the bit to the workpiece. Next, zero your compound dial and back it out exactly 1 inch to put you at point "B". Next, zero your crossfeed then, turn it to move the bit to touch the piece again at point "C". When you touch, read the crossfeed dial. If the compound was at exactly at 30 degrees, the crossfeed will read 0.500.

Repeat the process until and adjust the compound angle until the crossfeed dial reads 0.500 when it touches at point "C".

Diagram 1

Triangle.JPG

Actual examples:

First make sure you'll have 1" of travel in the compound and preset to about the angle you want.
IMG_20171226_184513.jpg

Zero the compound dial:

IMG_20171226_184529.jpg

Move the bit forward to just touch the piece. Use a consistent touch for every step. In this picture I have not touched yet.

IMG_20171226_184600.jpg

Now it's touching.
IMG_20171226_184638.jpg

Zero the cross-feed dial as soon as you touch the piece.

IMG_20171226_184632.jpg

Crank the compound backward 1 inch (in my case, 10 turns).

IMG_20171226_184728.jpg

Turn the crossfeed in till the bit touches the workpiece then read your crossfeed dial again. You'll notice now the bit touches to the right (point C) of where it first touched off.

IMG_20171226_184900.jpg

If your compound angle was set properly, the crossfeed will read 0.500 now. Keep repeating with adjustments to the compound angle until you end-up at 0.500 on the crossfeed.

If you want to make a 10 degree angle, the distance you are shooting for will be Sin(10) which equals 0.174.

I can't stress enough that you need to understand backlash and turn the dials accordingly to adjust for it. Also, keep the same touch in your fingers when you touch-off the bit to the metal. If you are consistent, you will nail this dead on.

Also, I want to mention, this is NO substitute for a massively solid lathe and a good setup with dial indicators. It's quick & dirty but, I have perfected it to work as good as this lathe can cut given it is a 12", 1000lb lathe.


Have Fun...

Ray C.
 
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ddickey

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Great trick. I'll have to try that. Thanks for sharing.
 

Ray C

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Great trick. I'll have to try that. Thanks for sharing.
You're welcome. Also, when you're getting close to reaching the angle you want, lightly loosen the compound bolts, put your fingers on the base of where the compound rotates/pivots so you can use your fine sense of touch -and gently tap/thump the compound with your knuckle or fingertip. Snub them moderately when you re-test. Moving that thing a baby's breath will change that final touch-off indication by several thou. When you're tapping/thumping that compound, if you see it move, it's gone too far. If you barely feel it in your fingertips, you did it right. When you hit your mark, check again till you get it right 2 times out of 3. It's all about knowing your machine... (Don't forget to give the compound bolts a good snugging when you're all done).

Ray C.
 

Ray C

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Work started on the MT3 shaft and housing. At the last minute, I decided to make it from two pieces just like the nose piece. No action shots of lathe work. It was stuck together just like last time -oversized shaft, undersized hole, heated/cooled and pressed together. After temps stabilize, it will be a negative tolerance fit of 0.005" (Translated, it ain't never coming apart in our lifetime).

Like last time, the seam was welded. Some eye-candy:

Fusion weld at 175Amps, straight argon at 30CFM due to the long electrode to do this. 3/32 Lanthanated sharpened to a long fine point because that gap is just a hair over 1/8" wide. Do you remember the game called "Operation"? LOL.

IMG_20171229_105444.jpg IMG_20171229_105409.jpg


Left a little bit of a fish-eye but no big deal, it will be taken down in the lathe. Once the pedal is mashed to the floor at high amps, I have a hard time dropping down to the 10-15 amp range to taper the pull-out -and thus, fish-eyes are born. Anyhow, I love those iridescent colors and wish the camera would do them justice.

IMG_20171229_111939.jpg

Here's the other side.

IMG_20171229_112026.jpg

Happy New Year...

Ray C.
 

Ray C

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Dinner is served... On the menu today is AISI 1045, cooked to perfection at 1550F for 75 minutes followed with a rapid brine soaking down to 180F. We let the entree rest for 90 minutes at 450F for a nice crispy texture (of around 51 Rc). We'll let this naturally air cool to room temperature before we start slicing it up. (Now I gotta hurry and get that out of the kitchen before the wife gets home).

IMG_20171230_102903.jpg

PS: I didn't feel like doing the heat in a killed environment nor did I want to go outside to dunk in the oil tank. Yes, I know, the top 10 thou is now dead metal... no worries, I left plenty of meat on the bones.

Happy New Year

Ray C.
 

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Look in good , your little dog is like ours likes to be clothed . My buddy is getting up there he's over 15 now. He had a snowsuit on today.
 

Ray C

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Look in good , your little dog is like ours likes to be clothed . My buddy is getting up there he's over 15 now. He had a snowsuit on today.
That's little Linus -he's a tough guy (LOL) that's part Chihuahua. He starts to shiver when the temps get below 85 for cry'n out loud. I also have little Leila (Rat Terrier) and Sash (big breed mutt that doesn't have a mean bone in her body).

Well... The metal tested-out at Rc 52. I'll test again in 24+ hours and I'll bet dollars to donuts it will be 53. It always goes up a point after 24 hours.

Here are some action shots...

The pieces warped just as much as I expected; about +/- 10thou (20 total) from end to end. And of course, it's uneven warpage. Pieces like this are tricky to setup. I had to bite it a couple different ways and indicate in a couple places before settling on a setup that didn't need deep cuts in any one particular area to get down to clean metal.

IMG_20171230_123533.jpg

You can tell just by looking at it, that it's hard. Take notice that I do not have a solid bite with the chuck jaws. That's ill-advised but, it was done on purpose. I actually made a mistake when I first made the cone part. It had a 1/2" diameter stump sticking out at the tip that was intended to be a holding point. I blundered and parted it off close to the taper when I went to drill the center hole. Happens...
IMG_20171230_131300.jpg

The left-handed cutting tools got a workout today going from Left to right. The ways were covered with some damp paper towels and a hand-held dremel tool with a cutoff blade was used to make a starting point near the chuck jaws. With small lathes and really hard metal, you can't just bump in like with soft metal. The junky camera I have does not do the finish justice. The shaft looks chrome plated. The DoC was around 15-20 thou to get past the warpage.
IMG_20171230_132919.jpg

After every pass on each section, the chuck jaws were checked for tightness and the tailstock was checked too.
RPMs and DoC is low for hard machining. The thin part of the shaft is 1 to 1.5" diameter. I used an SFM of 65 so RPMs ended up being 450. DoC was very light at 0.015 from touch-off at the low parts of the warpage.
(Remember: 4xSFM/DIA is for HSS. Carbide needs 2-3 times more).
IMG_20171230_133338.jpgIMG_20171230_133546.jpg

And of course, I immediately destroyed an insert when I forgot to turn the R's down before cutting the 2.5" diameter part... There went $2 real fast. RPMs for that wide part was 250.
IMG_20171230_140235.jpg

So, now the part is all trued-up. Next, I need to mic it and take everything to size on the shaft. After that we'll recalculate the angle on the compound for the other direction and bring that down stopping a few thou shy of the print. The last bit will be taken down on the post grinder or, I might setup the tool grinder -we'll see.

More to come later...

Happy New Year...

Ray C.
 

Ray C

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Well, this was a PITB (Pain In The Butt)! Hard metal (and RC 52 qualifies as hard metal) has very little latitude on SFM. That cone goes from 2.5" down to 1/2". You got any idea how hard it is hold the cordless drill to power the compound and slowly turn-up the VFD at the same time? Take a close look and you'll know I'm not very good at it. Anyhow... No worries. I'll make it right with a tool post grinder or throw it in the tool grinder.

I still haven't turned the shaft down to size yet.
IMG_20171230_211751.jpg

And here's a little eye candy. Take a good look before we start carving it up. The next cuts on the shaft need to be pretty critical with a -0.0000 spec.
IMG_20171230_212758.jpg

And on a side note, look what showed-up today. I'm standardizing all the mics on one brand because I dislike having about 3-4 different brands and each one has different looking graduations, which has lead me to make errors in the past. Picked this up this 6-9 on eBay for a song. I estimate it's 70's vintage and it still came wrapped in the original packing oil and cellophane. Not a scratch on it. Normally, I don't like multi-size mics but I rarely do work over 6 inches. This was $150 and I couldn't pass it up.
IMG_20171230_174908.jpg
IMG_20171230_174945.jpg

More coming -probably tomorrow.

Happy New Year

Ray C.
 

Ray C

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Except for grinding the cone to final shape this piece is all done. The OD's where the bearings will fit are slightly oversized as per-plan by 0.0007 and 0.0005". I got them exactly 1 thou oversize on the lathe and pinched it with emery cloth to bring them within half-thou. When they are fitted, the shaft will be chilled in the freezer and the bearings will be heated with a hand-held air heater. I'm assuming these bearings are made of the typical 52100 (or equivalent) steel; therefore, their high-end temperature is 425F. Above 425F and that steel can (and will) anneal very slightly. Bearings are usually Rc 58-60 and a 1 hour anneal at 450 will bring the Rc down 1-2 points. Moral of the story, be careful warming-up bearings when a slight interference fit is needed.

Here's an action shot of the last few moments and a better view of how it goes together.

IMG_20171231_182646.jpg


IMG_20171231_183538.jpg

Hard to believe this year is over!

Happy New Year...

Ray C.
 
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