Once the magic smoke comes out, it won't work any more.
John Kasunich
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Mon, 01 Sep 2008
Spindle Project - Part 1 - The Spindles
The "Spindle Project" is my attempt to make something usefull (and perhaps somewhat profitable) out of some surplus machine tool spindles that I bought in late 2007. In the process I hope explore some areas of machining that I haven't done before, including hard turning, grinding, and extreme precision work.
I have sixteen spindles, all more-or-less identical (details later). I initially bought two, just for the bearings. When I figured out what they were I went back and bought the rest. A picture is worth a thousand words, so here are side and end views of an assembled spindle (click to enlarge):
After examining the business end for a while, and doing a lot of googling, I figured out that the spindle taper is HSK32. HSK tapers are relatively new and at least for the home-shop world, very exotic. Toolholders start at $200 and go up - way up. The premise behind HSK tooling is that it doesn't just make contact on the taper. It is designed to contact on both the taper and the flange at the same time, for increased repeatability and rigidity. The HSK design is also suitable for very high speeds.
The somewhat exotic and high-speed nature of HSK was my main clue that these were probaby some very high-class spindles, with correspondingly high-class bearings. Although most of the spindles had tags on them indicating that they needed repair, none were tagged for bearing problems. Most were things like damaged retention mechanisms, drawbar sticking, etc. So I decided to take a chance, and bought the whole batch.
The first step after I got them home was to remove the retention mechanism. That consists of a tapered piece that is screwed onto the drawbar, six fingers that expand inside the toolholder, and a crown-shaped piece that sits in the back of the taper and hold the backs of the fingers. Several spindles were missing one or more of these pieces, and some had broken or bent fingers, etc. The tapered center part unscrews, and the fingers and "crown" come out with a pair of needlenose pliers, leaving this:
Some more carefull fiddling around and I figured out how to get the rest of the spindle apart. Since HSK spindles are pretty much always used with automatic toolchangers, the drawbar is spring loaded. Some have a long stack of Bellville spring washers, others have helical springs that are sort of like a stack of Bellvilles where each layer is twisted and connects to the next. The helical versionis a lot nicer to handle - two spring sections instead of 132 individual washers stacked in a precise series-parallel pattern. I had to make a simple tool to allow me to compress the drawbar and retain it in that position while I loosened a setscrew and removed a cross pin - then I could release the spring pressure and the drawbar came out the back. The two photos below show the results of the second stage of disassembly:
In the first photo, the retention "stuff" is assembled as it goes into the spindle - in the second, the fingers, crown, and tapered part are separated. The drawbar in the photo has the helical springs (of my 16 spindles, 10 have helical springs, and 6 have Bellville washers).
Across the bottom row in the first photo are parts related to a spring loaded key, which engages a slot in the back of the toolholder. In the front view photos above, you can see the key on the bottom inside of the taper, and the end of the pin that holds and drive it is visible on the spindle face. The long skinny rod runs thru an off-center hole in the spindle, and is spring loaded by the largish assembly at the back end of the spindle.I'm about 99% sure I'm not going to be using the retention stuff or the keys, so those pieces are bagged and tucked away. The drawbars, drawbar springs and various other bits and pieces will probably be reused, so they've been carefully cleaned, sorted, and stored.
The only thing left is to remove the bearings themselves from the spindle. So far I've only done that to two spindles. I figure if I don't mess with them, I won't mess them up. I might be able to do whatever work I need without removing them. If not, I'll remove them when it becomes neccessary, not before. The picture below shows one of the two that I did carefully take apart:
From the left, the pieces are: front ring (part of a non-contact labyrinth seal), front bearings, outer race support ring, inner race spacer (long tube), back bearings, and inner race nut. The bearings are two pairs of matched 25 degree angular contact ball bearings, each pair arrainged in "back-to-back" configuration. The clamping nut loads up the entire stack, with the clamp force going through the first back inner race, both back outer races, second back inner, the long spacer tube, first front inner, both front outers, second front inner, and into a shoulder on the spindle shaft.
The BearingsThe two spindles I've taken apart so far have bearings from two different makers, but they are basically the same thing. The front pair are trade size 7008, 40mm ID, 68mm OD, and 15mm thick. One vendor's datasheet for the front bearings is here. The back bearings are size 71908, 40mm ID, 62mm OD, and 12mm thick. Vendor data is here. A general page for that vendor's spindle bearings is here, and from there I was able to download their 11-megabyte spindle bearing catalog with lots of good engineering info about the care and feeding of high-end bearings. The other vendor doesn't have the same detailed data, but a magic decoder ring for their part numbers is here - the number on the front bearings is VEX40/NS 7CE3 DD/3. Both sets of bearings have ceramic balls in steel races, and are ABEC-7 grade, or the European equivalent. While googling for data on these bearings, I found a 2006 price sheet that listed the back bearings at 276 Euros each. At today's conversion rates, that is about $400 per bearing!
After much measuring and investigating, I made a to-scale EasyCad drawing that shows all the important spindle parts, along with several partial sections to show all the various holes and details near the front of the spindle. Click on the thumbnail image below to get a scalable PDF version.
The drawing does not show the retention pieces, or the key. Section B-B does show the slot that the key fits into, and the long hole for the spring loaded push-rod. The holes in section A-A are for coolant - apparently HSK tooling can accept high pressure coolant either through the center of the drawbar, or through the toolholder flange.
In my next posting, I'll describe my plans for these spindles.
(posted: 01 Sep 2008 00:45) (permalink)
Sat, 02 Aug 2008
I took a break from my grinder reconditioning project and went to the North Chagrin MetroPark this evening. I spotted some thistles blooming along the path to the pond:
In the sunny area next to the pond, milkweed pods are getting ripe - soon they'll break open and the seeds will float away.
The pond itself is just about covered with lily pads, and their flowers are starting to bloom.
There is a "resident" blue heron who usually hangs out on the side of the pond that is least accessible from land. It is far enough from the walkway across the pond that you can't realy get a good look at him. When I arrived he was in his usual spot, but just as it was starting to get dark, he went flying across the pond. I shot several pics as he went by, but light, focus, and all the other factors were against me. The best one is this blurry shot of him skimming over the lilypads.
Once he got to the other side of the pond he started hunting. That area is much more accessible, and I slowly and quietly got as close as I could, before shooting these photos.
He caught something at least three times while I watched, including what I think is a frog in the following picture. The photo is blurry because he was tossing his head back to swallow it. By this time it was quite dim, and my shutter speed was down to about 1/8 second. The only reason the three pics above aren't blurry is because a hunting heron stands very still.
As the heron walked through the water I moved to a better vantage point. That's when I noticed another pond resident I've never seen there before. A beaver was a few feet in front of the heron, munching on lilypads.
(posted: 02 Aug 2008 23:37) (permalink)
Sat, 26 Jul 2008
Last Saturday I confidently wrote "Tomorrow I'll bring in the rest of the pieces, clean everything, and put it back together". I should have known better.
The table ways are ball-bearing, and seem to be in good shape. Not so the cross-slide ways. They are dovetails, and have significant wear on the flat surfaces. Last Sunday I started scraping them flat. A business trip in mid-week cut into my time, but I finished today. It took 37 rounds of scraping. They are still far from perfect - I am not an experienced scraper hand - but they are much better than they were.
I took pictures before I started, and after every 5 rounds. I used GIMP to color enhance the photos, turning almost everything except the blue spotting dye to grey-scale. The image below is what I got when I first spotted the cross-slide on my surface plate. It made contact only on the front left corner, and on the two back corners. Sorry about the bad lighting, you have to look closely to see the nearly square patch in the back right. (Click on images to enlarge.)
The next six photos are after 5, 10, 15, 20, 25, and 30 rounds of scraping. In round 5, the initial patches grew a bit, but it wasn't until round 10 that I got contact on all four corners. From then on to round 30 I was mostly trying to bring the badly worn left center portion of the left way into contact. The last 1/4" or so is simply too badly worn, and I decided not to try to work the entire rest of the surface down to the level of the worn spot. Somewhere between rounds 20 and 30 I started to develop a low area on the near end of the right way. The last 7 rounds were mostly focused on fixing that, as well as improving the overall surface and breaking up any large areas.
After round 30, I stopped replenishing the spotting compound on the surface plate. That means the film on the plate got thinner after each round, and the readings became more sensitive. Large uniform areas in round 30 became collections of smaller spots in subsequent rounds, and I made smaller and smaller scrapes.
The round 37 photo below was taken with the slide rotated 90 degrees for more uniform lighting. The lighting was still a bit uneven - the photo shows much more blue on the right way, but in reality they are better balanced. There is still some uneveness on both ways, but when I go back and look at the starting photo, I don't feel too bad about saying "that is good enough". Especially since I still have to do the mating ways. I'm hoping they will be easier and faster.
One of the guys on IRC was wondering what a scraper looks like, so here is a photo of my scraper (given to me by my machinist father). It is carbide tipped, which saves a lot of honing. Behind it is my 12x18 surface plate.
(posted: 26 Jul 2008 23:03) (permalink)
Sat, 19 Jul 2008
Surface grinder into the basement
One unfortunate fact about where I live is that my shop isn't limited by what machinery I can afford - it is limited by what machinery I can find room for. My garage is detached and unheated, and in Cleveland's climate, that means I have to fight rust, especially in the spring. My Van Norman #12 mill is out there, but I'm not willing to put any other machines in the garage. So any new tools not only have to be small enough to fit in my rather cramped basement, but they also have to be light enough to move down the steps.
Today was the "Saturday Sidewalk Sale" at HGR Surplus (they're only open one Saturday a month). After spending a few minutes looking at a reasonably affordable and very nice Mitsui surface grinder, sanity kicked in and I walked away - it probably weighed over a ton. But a little later I found a nice benchtop 6x12 grinder. "Targa" brand, made in Tiawan (a bit better than made in China), it seems to be identical to this Enco one - 3/4HP, single phase 120V motor, 451 lbs. But it was a LOT cheaper at HGR - I paid about one-tenth the Enco price.
HGR's forklift easily loaded it into my truck, but the hard work started when I got home. Before I even unloaded it I started taking it apart to reduce weight. The table lifts right off - 65 pounds. The "saddle" (dunno what the proper term is) slid off after I unscrewed it all the way to the front and loosened the gibs - 74 lbs. Four socket head capscrews and some disconnected wires let me remove the motor/spindle assembly - 48 pounds. And finally, screwing the vertical slide all the way up and loosening the gib allowed it to be removed - 33 lbs. The remaining base casting is about 225 lbs - still too much to move by brute force.
Step 1 was sliding it from the truck tailgate onto a rolling cart. That wasn't too hard - the cart is only a few inches higher than the tailgate, and the machine was on a small pallet.
Step 2 was getting it onto the back porch. The cart is about level with the porch, so I moved it to the foot of the porch steps and spanned the gap between cart and top porch step with a seven foot piece of 2x8. I carefully slid the machine along the 2x8 until it was setting safely on the porch.
Step 3 was getting it into the kitchen. I left it on the 2x8 - it made a handy lever. By pushing the casting to one end of the board, I could lift the other end, and stick a moving dolly under the middle. Then I slid the casting back to the middle over the dolly. The 2x8 very nicely bridged the threshold of the sliding glass door, and a bit of sliding and levering was all it took to get the casting in the house with the dolly once again under it. (See first picture below.)
Step 4 is the biggie - getting it down the steps. There is a bathroom directly across from the top of the steps, and I braced a piece of 2x6 across the inside of the bathroom doorway. That served as an anchor for a block-and-tackle that allowed me to ease the casting down the steps, still sitting on the long 2x8. The rigging allowed me to have total control of the casting during what would otherwise have been some very hairy moments. The second picture below shows it just about to go "over the edge", as the 2x8 tilts from level on the floor, to sliding on the steps. The third photo shows it about half way down - note the superviser at the top of the stairs, making sure I'm doing it right.
Step 5 was getting it from the basement floor up onto the bench. I used a few deck screws to fasten a short piece of 2x8 across three joists. Then I wedged uprights on both ends, so the screws and joists wouldn't need to carry the weight. Rigged the block and tackle again, this time to lift the casting straight up. The next-to-last photo below shows it half-way up, and the last photo shows it sitting on the bench.
Tomorrow I'll bring in the rest of the pieces, clean everything, and put it back together. It still needs a magnetic chuck, but Small Tools Inc. has some used ones in the $100-125 price range that look promising.
(posted: 19 Jul 2008 23:21) (permalink)
Sat, 31 May 2008
I've spent much of the last month remodeling one corner of the basement. It's funny how projects happen...
Back in March I ran across a great deal on a stereo microscope at HGR Surplus. I've wanted one for quite a while, so I bought it. When I brought it home and took it downstairs, I realize that I didn't really have a place for doing precision work like electronic soldering and surface plate work. My surface plate has been living on the floor for several years now, and I either use it there, or temporarily clear off a spot for it somewhere. So I decided I need a new workbench...
I went back to HGR, and found some 95" x 30" blue formica workbenches with sturdy steel frames for $35 each. At that price, I figured I might as well get two. I figured out where I wanted to put the first bench, but I knew I would want storage space above the it. That meant yet another project - framing and wallboarding the wall, so I wouldn't have to anchor stuff directly to the concrete blocks.
After the wall was done, I painted the wall and the floor while there was nothing to get in the way. Then did a little welding on the workbench frame - I decided that the front crossmember at the bottom would interfere with legroom, so I ground off the welds and moved it back about 8", then welded it back on. That was my first real welding project.
Once the bench was inside it was time for storage above it. I spent at least two weeks building the shelves in the photo below.
I finished the shelves and got the area cleaned up last weekend, and since then I've been slowly moving items over there. Today I used some of the scrap wood from the shelves to make a box for my ER20 collets.
And that is how "buying a microscope" turns into about six or seven projects that take a couple of months...
(posted: 31 May 2008 23:24) (permalink)
Thu, 08 May 2008
I went to the park Sunday. Spring is finally here to stay I think. There were lots of small flowers (most less than 3/4" across) and I had fun with my 70-300mm macro lens.
One of the neatest sights was leaves just getting ready to explode out of their buds. This is one of my favorite photos - the fine silky fibers make the leaf seem almost like a butterfly trying to break out of its cocoon.
On another branch I got several leaves in various stages of blossoming.
A little way down the path I was surprised by a large dragonfly - I think of them summer insects. It settled on a plant just long enough for me to grab a quick shot, then went flying again. Another one joined it, a mating dance maybe? In any case they never stayed in one place long enough for me to get another shot.
After a couple hours I wound up beside a pond not far from where I parked. I noticed a turtle had climbed out of the pond onto a log to bake in the sun:
While I was taking its picture, another one climbed out:
And then a third (the first one is out of the picture to the left).
Turtle number three hadn't even made it out of the water when number four showed up:
And then there were five:
Still an empty spot on the log, so turtle number six made himself comfortable:
I like this shot - I'm not sure why they are sticking their necks out and up, but it looks funny.
(posted: 08 May 2008 23:19) (permalink)
Thu, 01 May 2008
All the real welders can start laughing now
I went to the NAMES (North American Model Engineering) show a couple weeks ago. I've been wanting to learn to weld for several years now. There was a salesman doing demos of the Cobra 2000 (aka Henrob 2000) Torch. Of course the salesman makes it look easy. I succumbed to the demo, and bought a torch. Today I finally got all the other bits and pieces, and started playing with it.
The "starter kit" comes with a few pieces of steel for you to practice welding on. My first attempt at welding two of them together resulted in one piece of steel, but it wasn't very pretty. For real practice I'd probably need about 50 pieces. But since I only had three, I spent the next hour or so abusing the piece that I welded together - just running beads every which way, melting holes in it and then trying to fix them, etc.
When that got old, I started looking around for things to weld. They say when the only tool you have is a hammer, everything looks like a nail. Well, when you have a brand new torch, everything wants to get welded. But I didn't really find much. I did find a pair of brackets, I think they once held reflectors on a bicycle. So I welded them together:
The brackets were fairly thin - 0.040 by my calipers. I looked around and found some thicker stuff. A couple of pieces of 1/8" x 3/4" flat steel. So I butt welded them together. The first pass didn't quite get complete penetration, but it stood up pretty well when I tried bending it. I flipped it over and did the back just to make sure.
I soon got tired of looking for pieces of metal to abuse, when I thought of nails. My stock of 2-1/2" finishing nails is a bit depleted now - it took three tries (at six nails each) before I got this:
More practice is clearly needed - this weekend I'm gonna go digging through the scrap metal pile and see what I can come up with.
(posted: 01 May 2008 21:08) (permalink)
Tue, 15 Apr 2008
More Production - Tecumsah Intake Manifolds
A friend of mine is very into minibikes. These bikes use a Tecumsah engine that is identical in most respects to a snowthrower engine. However. the engine is mounted on an angle, and needs a non-standard intake manifold to keep the carb level. My friend had patterns made and got 18 manifolds from an aluminum foundry, and then came to me for machining.
Holding the raw casting was a bit tricky, but eventually I came up with a setup that located the part using some features at the carb end flange. The photo below shows the setup I used to machine the carb end. One program with one tool change, to mill the end flat, clean up the inside of the manifold to make the opening round and concentric, and drill the screw holes. The second pic shows 11 of the 18 parts after the first program. The final step at the carb end was to thread the holes. That went rather quickly with a tapping head on the drill press.
The block end had a lot of material to be removed. Instead of nibbling at it with the Shoptask, I screwed each manifold to a steel block, clamped the block in a tilt vise at the proper angle, and let my Van Norman make a single pass with my 5-1/2" face mill. A slow shutter blurred the cutter - it is only doing 140 RPM or about 200 SFPM.
The cores were pretty far away from the desired shape at the block end, so the ports needed a lot of work. I used the same steel block and angle vise to mount the parts with the port facing straight up on the Shoptask. Jeff Epler let me use some alpha-stage offsetting software that he has been working on. The resulting g-code matches the port in the manifold to the one in the engine block, and blends that profile down into the as-cast interior of the manifold. The program used a 5/16" end mill for roughing, a 1/8" mill for finishing, and a drill to make the mounting holes. Because of machining time, most of them were done with a 0.050 stepdown. But I did a few with a much smaller step size, and they came out very nice.
Both ends of the manifold needed tool changes during the program run. My machine has totally manual toolchanging. However, I'm using the "Tormach Tooling System". which works quite nicely. Each tool has a 3/4" straight shank that goes up into a collet in the spindle. As the collet draws tight, it pulls a 1-1/2" diameter shoulder up against the spindle nose for a very repeatable Z position. It is quite fast and easy to change tools - I was getting 30 to 40 seconds chip-to-chip, with very repeatable results.
Tormach sells a variety of tooling for the system, but it is really pretty simple to convert other tools. For example, I'm too cheap to buy the Tormach collet chucks at about $80 each. But I found some very nicely made 3/4" straight shank ER20 chucks from MariTool Inc. for about $45 each. I made 1-1/2" diameter rings with a 0.749 bore and shrunk them on to the 3/4" straight shanks, and they work perfectly. The photo below shows my current collection of spindle tooling - the collet chucks with the homemade rings are on the right.
(posted: 15 Apr 2008 22:15) (permalink)
Tue, 01 Apr 2008
Most of the CNC work I've done so far has been one or two pieces. But this job is different. I have a friend who works in a lab where they sometimes need the odd bit of metal. I've done jobs for her before, but this is the first one since I got the CNC working.
They needed 20 'pull blocks'. These blocks get glued to samples of tile, then they use a tensile tester to pull the blocks and tiles off of a substrate - it tests the strength of the tile cement.
The parts are made from 2" square steel bar, one inch long. Face one end, then face, drill, and thread the other end for a pull stud. I've been learning more about how to use EMC, and for this job I learned all about lathe tool offsets.
The above photo (blurry, sorry) shows the setup for the second operation. The facing tool is in the toolpost (on the left), the drill is in the tailstock, and the threading tool is clamped down with a couple step blocks on the right. I'm using tool offsets when I switch from one tool to the next.
The program first faces the block. Then it prompts me to drill the hole. It positions the table so a strap clamp bolted to the table lets me know where to position the tailstock, and I stop drilling when the nose of the chuck hits the clamp holding the threading tool. Then I retract the tailstock and hit 'Resume'. The program switches to the threading tool and makes a couple of boring passes first, to make sure the drilled hole is on center. Then it threads the hole M12-1.75. While it is threading, I debur the previous part.
The finished parts:
(posted: 01 Apr 2008 20:07) (permalink)
Mon, 31 Mar 2008
March in northern Ohio is still winter, but bird activity is starting to pick up. I took a couple walks in the woods over the weekend and got some nice pictures.
One tree was very popular with woodpeckers. Both male and female Hairy and Downy woodpeckers. I don't know which these are - I got photos of both but the others didn't come out so nice.
In addition to birds, I saw some ferns clinging to a steep hillside, and some kind of seeds left over from fall.
I think the last photo is my favorite
(posted: 31 Mar 2008 21:40) (permalink)