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[4]

Bull Nose Live Center

January Project of the Month [3]
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Ray C

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#31
I'm told there are three kinds of lathe operators, those that use toolpost grinders, those that do it begrudgingly and those that simply won't allow it. Right now, I'm somewhere between "begrudgingly and won't allow it". That said, I'm pulling the tool grinder out of storage. I've been meaning to build a table for this device for a while now and it will be placed next to the other grinders, belt sanders, sandblasting boxes etc.

So, here's the old beast that still runs very tight. From the picture, you can probably see how this will pan-out. It might take me a day or two to get to this so hang in there.

IMG_20180102_193146.jpg
IMG_20180102_195928.jpg

Later...

Ray C.
 

Silverbullet

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#32
Nice grinder, really I'd have some jigs to do some sharpening on specialty cutters.
 

Ray C

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#33
Nice grinder, really I'd have some jigs to do some sharpening on specialty cutters.
Yes, this is a more "general purpose" cutter/grinder made by KO Lee and I've made various taper reamers for sizes that you just can't get anymore. These days, when you buy a cutter/grinder they are really designed for sharpening carbide endmills and cannot do odd-ball pieces like this one. Anyhow, yes, I've made some custom fixtures to hold pieces and make strategic grinds. It's pretty good for that.

Because of limited space, it's been in the storage room but, I recently parted ways with an old B&S surface grinder which freed-up some space for now. I am however, in the market for a new grinder but this time around, it will be a smaller one. When it comes to surface grinders, I only do small pieces and have no need to hold better than half thou. If the right SG comes along, I might part ways with the KO Lee.

BTW: That KO Lee looks small but, it is darn-toot'n heavy! It is very thick cast iron.


Regards

Ray C.
 

Ray C

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#34
Sorry, but there aren't too many action shots of grinding the nose. It was a matter of setting-up indicators to set the angle then, hand turn it in the spin-indexer while slowly cranking the table. It was a slow process and took about an hour and was a two-handed operation which took a while to get the rhythm down. Could only take off roughly 1/3 thou per pass and about 20 minutes in, my arms were screaming at me. Stopping to take pictures was not in the cards.

Anyhow, as you can see, little Leila was impressed by it. I think it looks better in person than in the picture. My cheapo camera flares-out when it gets a strong reflection.

IMG_20180105_210626.jpg

I have not put it on the granite table of truth but, the angle is looking pretty nice. That measuring scale (LOL: I call it the Angle-ometer) measures angles with surprising accuracy. It's made by GemRed (some off brand) and it reads dead-on with all the precision squares and angle blocks in the shop. It also re-zeros with surprising predictability. So, just holding by hand with a light behind it, I'm consistently getting an angle of 30 to 30.1 degrees. So far, so good... The real truth will be told when the mating part is finished and we find-out if the whole darn thing wobbles or runs true. -Keeping the fingers crossed...

IMG_20180105_210757.jpg

Ok, next we're going to start on the MT3 holder part. Can't promise how quickly we'll get that done because (I'm sure you noticed) it's darn cold and it's costing real money to heat the shop. Hopefully, we'll make a little progress this weekend.

Regards

Ray C.
 

Ray C

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#35
Now we're working on the non-spinny piece by cleaning it up and cutting it straight. It bowed a little bit during the heat treating. In this first picture here, I've already flipped it once to catch the other side. It would be best to spin between centers but, with enough care the part can be setup in a chuck and held with a tailstock without making barrel (convex) contours in it. (NOTE: Last sentence edited to correct descriptions about concave/convex).

IMG_20180106_104533.jpg

This piece is hard (RC 53) so I use a little cutoff-blade to dig a starting point for the tooling. Notice the paper towels to catch (most of) the grinding dust. I sprayed the paper towels with kool mist to grab the dust better. There's plenty of meat to work with and once I get down another 40-50 thou, the hardness will ease-up. There are reference materials which show hardness vs distance from the surface. It drops off rather quickly.

IMG_20180106_104813.jpg

Cleaning up the angles and back-side. The sharp angle is purely aesthetic.
IMG_20180106_113234.jpg

Here's the overall setup.
IMG_20180106_113252.jpg

Next steps are to get the OD of the big part to size then, turn the entire thin part of the shaft to the largest diameter that it needs to be. That will allow me to hold it in a 5C collet so I can start boring-out the body. Once that is done, I'll flip it around, indicate it very carefully and cut the MT3 taper.

We're getting there...

Regards

Ray C.
 
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Ray C

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#36
Didn't have much time to mess with this because I'm doing other things in the shop (like weekly cleaning and maint).

Here's how far we got. The body OD is turned to size and the front was faced off. A very straight 1/2" hole was bored to the necessary depth and the first step for the oil seal was taken to depth but stopped 75 thou short of the final ID. If folks are interested, I can describe how I sneak up on the final cut and usually nail it on (or within) the forgiving side of 1 thou. Also, when drilling hardened metal, I do a series of chasing bigger holes after smaller ones going about 1/2" depth each time. Typically I use a 1/4" dia pilot drill for 1/2" depth then chase it with a 1/2" bit.

Anyhow, the metal here is wonderfully hard. At this depth in, I'll guess about RC 35. To me, that's ideal. I much prefer working on moderately hardened metal.
IMG_20180106_204558.jpg

Here's what we're making BTW.
Body.JPG

OK, that's it for today. Probably a little more coming tomorrow.

Regards

Ray C.
 

tertiaryjim

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#38
Nice work! You must have a very solid lathe to get such fine finishes even machining hard steel.
I wanted to chime in about heating bearings for fits just because so many people unfamiliar with it will be following
your post.
Most small bearings, like your using for this project, have interference of only 2 tenths and those bearings designed for it
may have more but thats unusual for small bore bearings.
If the bearing has dust covers or seals it can stand much less heat and if the cage is brass or plastic that will also limit
how hot it can be.
My calculations show that heating the bearing to 300deg F. would give 0.002" expansion of a 1" ID race.
0.0000067 X 300deg F. X 1"
I would think that 200deg F. would be plenty hot and allow plenty of time to transfer the bearing to the shaft with
a 0.0007" interference.
 

Ray C

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#39
OK then... I toss those questions out because I have no idea if anybody is watching this or not. I'm not doing this cause I need the practice... LOL...

I'll write it up and post either later tonight or tomorrow AM.


Ray
 

Ray C

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#40
Nice work! You must have a very solid lathe to get such fine finishes even machining hard steel.
I wanted to chime in about heating bearings for fits just because so many people unfamiliar with it will be following
your post.
Most small bearings, like your using for this project, have interference of only 2 tenths and those bearings designed for it
may have more but thats unusual for small bore bearings.
If the bearing has dust covers or seals it can stand much less heat and if the cage is brass or plastic that will also limit
how hot it can be.
My calculations show that heating the bearing to 300deg F. would give 0.002" expansion of a 1" ID race.
0.0000067 X 300deg F. X 1"
I would think that 200deg F. would be plenty hot and allow plenty of time to transfer the bearing to the shaft with
a 0.0007" interference.
The lathe is just a Precision Matthews 1236 -about 8 years old now. It's fine for stuff like this. Just need to use the right inserts, nail the F&S on the money and get the approach angles just right.

Yep... you gotta watch the temps with bearings. Good bearings will have spec info available from the manufacturer. The low-end bearings are more of a concern but, in the absence of synthetic seals, 325 (even 350) is safe territory. Tempering really won't start happening until 375-400 and it would need to be sustained for over 30 minutes. At those lower temperatures, maritinizing is more of a time-game.

Ray C.
 

outsider347

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#41
Ray
I one of your many posts you mentioned the inset that you use to achieve the fine finishes.
I know that I saved it somewhere , but can't find it in my smarter than me filing system
Tks for your patience
ed
 

Ray C

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#42
Ray
I one of your many posts you mentioned the inset that you use to achieve the fine finishes.
I know that I saved it somewhere , but can't find it in my smarter than me filing system
Tks for your patience
ed
My pleasure...

Meet the immediate family... They're color coded to designate which ones are for the left side of the wedge post vs. right side.
IMG_20180107_113717.jpg

I try to keep the alignment of the wedge post pretty-much in the squared-up position as shown.
IMG_20180107_133515.jpg

The 5 or so holders on the far left are less frequently used but, invaluable when needed.
IMG_20180107_113731.jpg

All the others are Left, Right and Center tools with CCMT 21.51 and TCMT 32.51 inserts. On another shelf nearby is the store of inserts. I also keep 21.52 and 32.52 variants of those inserts and have them all in both TiN coated and naked carbide. I always get C5 or C6 base carbide. By far, the xx.x1 versions are used more than the xx.x2 versions. In the TCMT inserts, I also have the CERMET versions in the 32.51 format. CERMET is for very hard materials and I used it for the first skim passes on this project. Once the hardeness drops below 50 RC, they are useless and will dull fast. They need extreme heat to run properly... they're ceramic.

The tools are a hodge podge of 3/8, 1/2 and 5/8" shanks. The color coded ones are BXA and a smaller set of AXA holders are nearby.

So, there you have it... These are about all I need and in my opinion, are fine for 12 and 14" lathes with motors in the 1-3HP range. All those inserts have positive relief of 5 or 7% (or somewhere around there). With higher HP machines and heavier removal rates, these inserts would get eaten alive. The 21.5x and 32.5x inserts are appropriately sized for medium-duty work on 12 and 14" machines.

Regards

Ray C.
 

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Ray C

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#43
I'd like to know Ray. I'm sure others would too.
First things first, lets talk about turning a shaft. Boring a hole is pretty much the same thing (but in reverse).

Metals: With carbon steels (including/especially stainless steel), you need to know it's condition: Is it hot or cold rolled, hardened, normalized, annealed... etc. If it's unknown or known to be either hot or cold rolled, the outer portion to about 1/8" deep from the surface, is unpredictable and will not behave "linearly". It may have hard spots in unpredictable places. You need to chew-off that outer layer for this technique to yield results. Normalized, fully annealed and known hardness metals are OK. The exception being really hard metal near the RC 50 or above range.

Having said the above, you probably know why I like working on conditioned metals.

BTW: Brass, bronze, aluminum etc don't have these problems and are pretty homogeneous so, the technique should work.

Tooling: I use this technique with carbide only but I see no reason why it won’t work with HSS. Often times, older (aka, slightly dull or chipped) inserts are used for hogging-off scale and to reach the final diameter. When making final passes, it’s best to use fairly fresh or new inserts for this to work properly.

Cutting angle: Every insert style has a preferred “angle of attack” to work properly. For now, it’s assumed the tool is positioned appropriately for the insert and is setup for finish passes. (BTW: This is a whole different topic).


So…. Let's say you have a known clean shaft that's 1.310" dia and it needs to be 1.1250" -0, +0.0010.

You need to know your machine, your tooling and what DoCs you can take with confidence. In the case of my PM 1236, when I'm approaching the final passes, I aim to dial-in 0.030".

1.310 - 1.1250 = 0.1850 (EDIT: I had a typo here and changed 1.1255 to 1.1250).

On my machine, when I dial-in 30 thou, it reduces the diameter by 60 thou (some lathes are calibrated for diameter reduction and not tool position). Since .1850 / 0.60 is 3.0833 we know I must take 3 passes at 30 thou and an oddball pass at 2.5 thou (.0833 x .06 / 2 is 0.0025).

Here’s the rub… What you dial in and how much comes off are two different things most of the time. Unless there is a gross F&S error or tool alignment issue, it will almost always take off less than what you desire. First, just go ahead, dial in the 2.5 and remove it. An amount that small should come off with no problem.

So, take the first cut at 30 thou then measure your diameter. Lets say the diameter was reduced by 56 thou instead of the desired 60 thou. This means you are getting 56/60 of what you ask for. Take the next cut at 30 thou. This time, lets say you get 57 thou reduction. Now, your part needs the remaining 30 thou cut plus one at 1.5 and another at 2 thou (to account for shortage of the other two passes).

You now aspire to have an effective dial in of 33.5 but you know that if you dial that amount in, you will come up short and be left with a skim pass that will ruin the finish. What to do: Linear projection:

In the first two cuts, you got on average 56.5 out of 60 which is 0.9417. Take 33.5 and divide by .9417 and get 35.58 which we’ll round to 35.6. So, if the past history predicts the future, dialing in 35.6 thou should get you the 33.5 you hope for. If you’re afraid of blowing the mark, pull your dial in by about a quarter thou. I do all this with dials (not DRO) and it gives me very successful results.

When doing this, you want to remove stock until you get within 2 or 3 passes of your final size at your desired DoC. 4 final passes is too many. If use too many averaged results, things become non-linear as removal rates are influenced by part diameter.

The remaining questions are how you ready the tool for the cut. Do you scratch-off and reset or, do you keep track of where your last cut and increase your numbers from there… That’s up to you and your particular style. Whatever you use, be consistent the entire time.

Give it a whirl…

If this works for you, I'd suggest creating a spreadsheet that automatically does the calculations. I've created this and other spreadsheets that work in-conjunction with each other. It tells me ongoing effective dialed-in amounts and determines the final dial-in amount for a finish pass within a range of acceptable DoCs. Also, they tell me if I should take those odd-ball passes right up-front or, if they should be averaged in with the final passes etc... That's the magic that works for me and my lathe -and probably won't work well for someone else and their equipment...

Ray C.
 
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Ray C

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#44
Quick additional thought... In the last step, when you are calculating your final pass, if the suggested final number is more than 15% of what your control dial-in values were, you need to take a light skim pass to get that final dial-in value closer to your control values.

EX:

Above, we had 33.5 / 0.9417 which gave us 35.58. The control dial-in values were set at 30 thou. 30/35.58 = 85.71 The percentage is then 100 - 85.71 = 14.29%

Technically speaking, in this example, I should have taken a skim pass of about 2-3 thou to reduce the OD just a little. That would have brought the final value down enough to bring it further inside 15%. The closer you setup your final cut so that the final value has a very small percentage difference from the control value, the more your chances of nailing it dead on, increase.

The spreadsheets I have do all these calculations automatically. I just enter my target diameter, dialed-in control value and the amount actually reduced. When it gets to the last cut, it tells me what to dial in.

Hope that made sense...

Ray C.
 
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Ray C

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#45
Just a tiny bit of progress today. Here's the step for the bearing cone which measures 1.5710" dia and 0.6356" deep. The target dia was 1.5708" and using the technique described earlier, I hit 1.5701 so I'll need to go in there with emery cloth and a popsicle stick and take a little off.

I must admit that even though the technique works pretty well, I always check, double-check then triple-check the measurements, calculations and setup for that last pass.

Next, the slightly more challenging parts happen. Boring deeper inside then, creating a precision bore about 2.75" deep inside the part.
IMG_20180108_183137.jpg

Next steps: Bore a passageway then a precision radius for the rear bearing. After that, flip the part, indicate it and cut the MT3 taper.

Until next time...

Ray C.
 

Ray C

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#46
Here's the setup to reach the last pocket to hold the rear bearing. I've turned up the air pressure just a little on the Koolmist to blow the crud out. It works very well. It's not an excessive amount of air pressure by any means. Notice I'm using an insert that does not have a chip breaker. This is by design. When zillions of chips end-up in the bore, it's a real pain to flush them out to take measurements. With no breaker, material comes off in long strings. It's sharp stuff but not really dangerous because the cuts are slow, not very deep and cuts like this don't send metal in the direction of your face or hands. Actually, most of it wrapped in a nice 1.5" coil around the boring bar. -How convenient...
IMG_20180109_204539.jpg

It's a long reach back in there but all that's left now is to make the pocket for the bearing. The work done tonight had only one critical dimension which was the depth (2.052" deep). I specified a diameter just enough so the front bearing cup had a lip to rest against. I don't recall the diameter but, I made a half hearted attempt to hit it. The pass fell 2 thou short and we can call it a day! Close enough.
IMG_20180109_204113.jpg IMG_20180109_204243.jpg

I've been very busy with my real job these days so, I can only do these little bits & pieces when I have an hour before turning in for the day...

Hang in there, we're almost done.

Ray C.
 

Ray C

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#47
The last feature (way back there) is now done. The bearing OD is 0.875 and I aimed for 0.8745 with the intention of touching it with emery cloth and sand paper. The final pass came out at 0.8741 as near as I could measure in there with telescoping gages. After touching it with emery cloth it opened-up a few more tenths and I'm call it quits before I monkey it up. It will get sweated and pressed in with no trouble.
IMG_20180110_184135.jpg

Now, I'm in a quandary... I'm wondering if I should drill oil or grease passageways to reach the bearings. Thoughts? I'm only planning to have an oil seal in the front but, this whole thing is not really serviceable because the bearings and shafts are very slight interference fits. I don't plan to do heavy work with this. Occasionally, I get a job with aluminum tubes that need to be turned down and that's all I have plans to use this for.

The rear bearing is an R6ZZ from VXB. It says it's "self-lubricated" with grease. The front bearing is an open cage taper bearing.

What do you think?
IMG_20180110_184307.jpg

Anyhow, we'll be putting this thing together soon and we'll know then if it spins true or, if it becomes a desk ornament.

Ray
 

mattthemuppet2

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#48
beautiful work Ray. I wouldn't bother with an oil port, those bearings are greased "for life". If they're going to be behind a seal then open cage will be better, less worry about high speeds. One question though - how will you get it apart if you need to replace the bearings?
 

Ray C

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#49
beautiful work Ray. I wouldn't bother with an oil port, those bearings are greased "for life". If they're going to be behind a seal then open cage will be better, less worry about high speeds. One question though - how will you get it apart if you need to replace the bearings?
I see you're Mattthemuppet 2 now... How you been?

If the bearings wear out, it will become a paperweight or food for the recycle bin.

Ray C.
 

Ray C

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#50
We're at home stretch now. All set up for the MT3 taper. An oddball piece of stock about 1.25" dia was chucked-up in the lathe and live center and a straight pass was made along the length. It was verified for even diameter at both ends and after that, the angle was adjusted using the technique mentioned early on in this thread. After finishing that, a store-bought MT3 live center was chucked-up and I verified with a TDI that it showed no movement running a parallel path.

And speaking of setup, there is no room for error when making something like this. If the bearing race-ways inside the housing are not perfectly concentric and in-line with the external MT3 taper on the other end of the shaft, this thing will be a paperweight. At every step, when this part was flipped around, a tenths dial indicator was used and I did not walk away from the part until it spun dead-on true. Keep in mind that tiny little variances at one end of the part, "magnify" over longer distances.

So here's some eye-candy for now.


The tailstock is a tight fit which is typical of setups like this. It's important to know your lathe and know how far you can extend the ram and still hold the part w/o flexing too much. With pressure against it, everything bends! With lighter lathes like this, it becomes very critical to nail the feeds and speeds and use fresh tooling/inserts. Dull inserts not only give bad surface finish but, they put much more pressure against the part.
IMG_20180111_203757.jpg

Aluminum tabs are protecting the part from the jaws. The back end of the shaft is being taking down a little less than the small diameter for MT3. This one will be cut the full 3.1" length. The camera does not do it justice but the finish on the last 1.5" is like a mirror. The metal there is pretty hard and it cuts like glass. Can only take 25 thou DoC. RPMs are about 500. Feed is around 4 thou/rev. Note the angle of the insert. It's about 95 degrees with a slight attack. Too much attack and it will dig-in and bury itself, break the insert and ruin the part. If it has too much retreat angle, it will not stabilize and push will push-away from the part. When you're cutting hard metal and the parts keep coming-out tapered, not only do you check your tailstock, you check the angle of your insert.
IMG_20180111_203745.jpg

... Will probably finish this off tomorrow. The lathe is needed for something else.

Ray C.
 

mattthemuppet2

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#51
I see you're Mattthemuppet 2 now... How you been?

If the bearings wear out, it will become a paperweight or food for the recycle bin.

Ray C.
yep, it's the new me. I've been roaming the wilderness and now I have returned :) Good to see you back too!

I guess with the precision that you're trying to hit, even if you could replace the bearings the likelihood of getting the same TIR on reassembly would be pretty low.

I just finished making a new tip for the live center that came with my Atlas 618. It's a 3 piece - thread in MT1 shank, body with bearing and the tip that is a tight fit in the bearing. Once i got the tip shank to size and roughed in the angle, I tapped a 10-32 thread in the body end of the tip and held it stationary in the body. then i could use the 4 jaw to hold the body and tip and do the final grind of the angle. Came out well as far as I can tell without doing a trial cut. Now I need to do a bull nose, it'll just be a lot smaller than yours :)
 

Ray C

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#52
Lots of pictures coming your way!

As expected, the Morse taper was a struggle. I've cut a bunch and each one kinda stinks in it's own special way. It all had a happy ending so here's a blow-by-blow pictogram...

Here's what it looked like after the raw cut. The same drill attachment was used to drive the compound. Two passes were required and as you can see, I started pretty far back (to give myself room to make corrections) in case something went south. The hard part is keeping even trigger pressure on the electric drill to keep the cut moving. I was not too pleased with the outcome but decided to take it and run. It's got some ridges. Yuk!
IMG_20180112_092008.jpg

Next steps were to take a flat file, grinding compound and Dykem to locate the high spots and remove them. From start to finish, it took about 20 minutes to complete the task. I can honestly say, I do not have this process down to a cookbook procedure. The last couple times I've done this, I used a flat file. This is the first time I tried grinding compound and it worked very well and made the work much quicker. Also, this was not a messy ordeal and I was not concerned about grit getting everywhere. It was all very localized and of-course, the ways were carefully (safely) covered.

NOTE: When you take a file near a spinning chuck, you must have a handle on the file point and you must be aware of how close your arm is getting to the chuck. No loose clothing. Keep a sharp and clear mind when you do these things.


IMG_20180112_101949.jpg

First, cover the part with dykem then, use the flattest edge you can find and press it to the rotating part. Upon doing that, the high spots are easily seen and addressed with the file and grinding compound. A 3 or 4" long HSS tool blank was used as a flat surface to scrape the dykem. It makes a pretty good edge. For filing, only use medium to light pressure and of course, a file is only worked one way. I opted to have the chuck spin forward and press down on the the top of the part. As a safety, sometimes when I need to touch a file to a part, I reverse the chuck and go from the bottom side. This is less likely to get you wrapped around your chuck.
IMG_20180112_101129.jpg IMG_20180112_100421.jpg

It did not take long to clean up. The valve grinding compound seemed to automatically hit the high spots and leave the low spots alone. I wrapped some emery around the tool blank and started to polish once I felt all the big ridges were gone. The edge of the tool blank is fairly sharp and it scraped all the dykem off leaving only tiny ridges that I can live with.
IMG_20180112_101406.jpg IMG_20180112_101848.jpg

Some close-ups as we got close to the end. Once again, this is the first time I tried grinding paste and it worked very well. Only 20, maybe 25 minutes of messing with it after the initial lathe cut. If anybody else has ways to improve this, I'm all ears.
IMG_20180112_101619.jpg IMG_20180112_102748.jpg

A final check with the TDI shows that it came out pretty good. The angle was preserved very well and the jiggling in the needle was very slight. Not as good as store-bought high production parts but, given what we're trying to pull-off with basic equipment, we can take this to the bank.
IMG_20180112_102409.jpg


Lunch time!

Ray C.
 

Ray C

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#53
Well, this had a very delightful ending... The bearings were pressed in after turning a couple scrap shafts suitable to press them in. They were entombed in the housing with a little extra grease. The nose cone was put in the freezer. Upon assembly, I almost forgot to put the grease seal on the shaft before tossing it in the hydraulic press. Woah baby, that would have been a bad way to start 2018!

Eureka! It works fine. I hope you can see the video but, with a tenths DI on there, you basically can't see the needle move. It runs perfectly true. If the video does not show up for some reason, I'll need to ask instructions on how to post it here.


IMG_20180112_160655.jpg IMG_20180112_160716.jpg IMG_20180112_162309.jpg

Hope you enjoyed the show. I had fun doing this...

Regards

Ray C.

EDIT: Let me know if the video shows as an attachment and you can see it. Since I'm the author of this thread, it shows-up but, I don't know if you folks can see it (or if anyone is even reading this at all).
 

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Ray C

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#55
And if you're so inspired to start a new project, here are the prints....

The front bearing is: http://www.vxb.com/LM11749-LM11710-Taper-0-6875-x1-57-x0-545-inch-p/kit7211.htm
The rear bearing is: http://www.vxb.com/R6ZZ-Shielded-3-8-x7-8-x9-32-inch-Miniature-p/r6zz-1.htm
The oil seal was a 1.156" X1.687" X0.312" which is not all that hard to track down.

I would recommend making the rear bearing a R8ZZ instead of an R6. If so, change the dimensions accordingly.
Nose Dimensions.JPG
Body Dimensions.JPG


Last but not least, I used it to turn a shaft and it worked just fine. For grins, I've always wanted to make one of these things and I can scratch that off my list now.

Enjoy...

Ray C.
 

ddickey

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#56
Any suggestions on alternative ways to get grind a precise center?
I have a surface grinder but with a 3x5 mag vise that isn't going to work.
 

Ray C

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#57
Any suggestions on alternative ways to get grind a precise center?
I have a surface grinder but with a 3x5 mag vise that isn't going to work.
Unless the metal is very hard, it can be cut on the lathe. The only reason the cone was ground in this project, was because the metal was about Rockwell 50 and it was too challenging to maintain the proper feed & speed as the diameter varied from 2+ inches down to about 3/8". With any kind of softer metal, you can fudge your way thru that.

Ray
 

john.oliver35

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#58
Great write up Ray! Impressive accuracy - I will use your shaft turning, boring and MT tuning methods from this thread in the future!
 

Ray C

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#59
Great write up Ray! Impressive accuracy - I will use your shaft turning, boring and MT tuning methods from this thread in the future!
Thanks! Practice the techniques on scrap as much as you can and if you have questions, just reach-out and ask.
When you practice on your own, there may be setbacks and you might miss the mark. It happens and is part of the learning curve.

Good luck...

Ray
 

ddickey

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#60
Ray,
A couple questions.
Why didn't you turn the MT first and do your boring with the piece held in the H.S. MT?
Also, would it be "better" to grind your 30° point after completion? I wouldn't know how you'd hold the MT though unless you did it in the H.S.
These questions are mute though as yours turned out perfect but curious to your answer.
 
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