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View Full Version : Po' man's TP grinder, as it sits now...



DICKEYBIRD
01-30-2016, 06:34 PM
It’s a long way from being finished but I decided to start a thread anyway as it might motivate me to keep at it ‘til it’s done.

The Sherline spindle was picked up cheap on ebay a couple years back to make a 3rd axis CNC milling spindle for the ORAC but it just sat there in the box & the project never got any traction. I decided a lightweight, compact QCTP grinder would be easier to build and more useful.

I sawed the excess aluminum bracket off of it & then milled a dovetail to fit my AXA toolpost. That process was made so much easier by the new DRO on the X-3! It fit onto the toolpost perfectly and the original motor bracket boltholes faced upwards in perfect position to mount the new homemade motor bracket.


http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Dovetail_zpsf4x6zmyz.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Dovetail_zpsf4x6zmyz.jpg.html)


The motor choice slowed me down for a while but I finally decided to pick one via my usual calculating method called “SWACAG”. Scientific wild-a$$ cheap- a$$ guess. The LMS cheapo TPG lists a 150W motor so I figured around 200W would be about right for me. Originally I was enamored with the big brushless model motors but they’re a bit pricey when you figure in a controller. I ended up with a 150W (advertised) 24VDC scooter motor off ebay for $32.50 shipped. I took it apart & milled in some cooling holes in the endbells & mount bracket & machined up some pulleys

http://i57.photobucket.com/albums/g227/DBAviation/TPG_zpsi61kua60.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG_zpsi61kua60.jpg.html).

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Driven%20End_zpsqnzgwoqx.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Driven%20End_zpsqnzgwoqx.jpg.html)

The first powered tests were very disappointing; it didn’t put out enough power to even start itself up in the higher speed pulley mode even wide open at 33.5V out of my homemade power supply. Hooked up an ammeter in series last night & quickly found it was only seeing 2.2 amps from the power supply. Bummer!

Woke up this morning thinking about the oddball 36V KB speed controller’s plug-in horsepower resistor & when I took a look it was a only .1 ohm (1/8 hp) value. I have no idea what the correct value should be with this one since it came with a Peco add-on board that was designed to run on 36V. I changed it to a .025 ohm (1/2 hp) resistor and it immediately woke things up. The motor started up with authority and I could load it down with a rag to 6.5 amps. About 200W if my cipherin’ is right.

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20High%20Speed_zpso0da1xiv.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20High%20Speed_zpso0da1xiv.jpg.html)

DICKEYBIRD
01-30-2016, 06:34 PM
The Sherline bearings must be pretty funky because it would start to wind up to full chat in the high speed pulley mode & suddenly bind up at around 7000 rpm, slow back down to 4000 and still show max amp draw. I’ll have to replace the bearings with better quality ones & re-set the preload a little looser before spinning it up to the planned >10K for my little 3/8” round stones to straighten up the taper on the cheapo ER16/R-8 collet chucks I bought. The lower speed setup runs fine & looks like it will manage the light cuts I have planned for the 4” dia’ 1/8” wide CBN wheel. Gotta make a 1 ¼” flanged arbor for it yet though.

I also plan to make a guard/splash shield with a big coolant return pipe on the bottom to allow a stream of coolant to run on wheel & make its way out of the shield & back to a big reservoir. Hopefully it will reduce the spread of abrasive debris onto the lathe.

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20CBN%20Wheel_zpsuldxu1qn.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20CBN%20Wheel_zpsuldxu1qn.jpg.html)

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Low%20Speed_zpsurnaifpr.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Low%20Speed_zpsurnaifpr.jpg.html)

I ran it wide open for about 20 min on the low speed pulley setup & took a few rpm/temp notes. Unloaded at 33.5V the motor ran 5250 rpm; with the belt on it ran 5050 rpm, spindle speed was 3860 rpm, safely below the CBN wheel's stated max speed of 4700. At the end of 20 minutes, the motor read 120 degrees, the spindle got up to 135 degrees, too hot for my taste.

sasquatch
01-30-2016, 07:17 PM
Good post, ill be watching for the updated progress on this.

Doozer
01-30-2016, 07:35 PM
Milton-
I am very impressed with that you have so far.
Super idea.

--Doozer

DICKEYBIRD
01-30-2016, 08:21 PM
Thank you sirs; makes my chest swell with pride!:)

Let's hope the rest goes reasonably well. I just ordered some Nachi C3 rated bearings to replace the funky original ones. Actually it should work out pretty well since I need to turn an accurate arbor to mount the wheel. With the spindle out of its housing, I can dial it in the lathe & turn the arbor "in situ."

Rummaged around & found foot-long piece of 1/4" wall 4 1/2" ID alum tubing. Should be able to slice off an inch or two to get a good start on the shield. I'm trying to make everything out of hefty aluminum stock to get as much heat-sinking as possible.

CarlByrns
01-30-2016, 08:21 PM
That's better than my wooden clamp and Dremel tool. I did use really good plywood.

DICKEYBIRD
01-30-2016, 08:30 PM
That's better than my wooden clamp and Dremel tool. I did use really good plywood....and a heckuva lot less work!:) I've done something like that as well but was looking to make something more powerful and rigid. We'll see how it actually works out.

Mike Amick
01-30-2016, 10:50 PM
Really nice compact design .. I like it.

Are you afraid that crap will get into the motor through the cooling holes you made ? Its a pretty messy
operation.

DICKEYBIRD
01-31-2016, 03:04 AM
Really nice compact design .. I like it.

Are you afraid that crap will get into the motor through the cooling holes you made ? Its a pretty messy
operation.Thanks Mike, I don't think it'll be a problem especially if my guard system comes out like I want. I envision it covering the entire wheel except for a small opening barely large enough for the wheel to contact the work. Hopefully it will contain all the grinding residue. I chose a CBN wheel to prevent having to deal with the aluminum oxide wheel dressing mess.

Mike Amick
01-31-2016, 01:50 PM
Oh yea .. I forgot, you did mention a guard ... please post pics when you add that ..
And thanks for the heads up on the CBN wheel .. didn't know that.

DICKEYBIRD
01-31-2016, 05:22 PM
Oh yea .. I forgot, you did mention a guard ... please post pics when you add that ..
And thanks for the heads up on the CBN wheel .. didn't know that.Will do Mike. Tied up right now whittling an arbor for said CBN wheel out of a big rectangular chunk of 2024. Lots of slitting saw work & interrupted cuts but I've just about finished it other than the OD of the actual boss that the wheel ID fits on. Gonna wait 'til the new bearings get here to tear down the spindle & try to turn that to final size while fitted to the spindle shaft itself.

I'm real nervous about the runout of the Cheapo Chinese wheel because it's a major ordeal trying to dress CBN. I may regret making a perfectly true (well as close as I can make it) arbor. May need a little runout to mix n' match the wheel to.:eek:

Now that I think about it, maybe I should make a quick "mule" arbor to test the wheel before finishing up the real one. It never ends!:rolleyes:

darryl
01-31-2016, 06:35 PM
You can chuck a piece of rod with about 6 inches or so sticking out from the jaws, then turn a snug-fitting portion on the outboard end for the wheel to slip over. When you run the spindle again there should be no vibration of the rod. If there is, you could turn down the portion slightly to fit a shim and thus experiment with wedging the wheel in place. You'd be running the wheel offset, and you would then find out where the shim should be to offset the wheel in the right direction to reduce vibration.

But now, looking at the wheel again- I'd be surprised if you had any vibration worth trying to reduce or eliminate. It would be nice if we as HSMers could have a simple but effective device that would at a minimum show a light or heavy side to within some degrees. Then you could drill divots on the heavy side or add weight to the light side. Years ago I did some crude balancing using a device I made up using a strobe tube. It relied on the mounting shaft vibrating in response to an off-balance, and an adjustable contact point to trigger the strobe. Pretty crude, but it did work- the heavy point was where the shaft vibrated in a direction to touch the contact.

You do have another option. Because that disc is thin you don't have to worry about a different offset from side to side, so it's only a simple balance problem. Take an ordinary washer and bore it to closely fit the same shaft that you mount the wheel on. Then drill a hole on one side to off-balance the washer. Assemble it to the arbor along with the wheel. Mark a series of numbers around the wheel so you can reference the position of the washer. Now it's trial and error- keep testing and rotating the washer one mark at a time until you find either a worst peak or a close null. If the minimum vibration is greater than it was before adding the washer, then you drilled the washer too far offset. I know this is crude and time-consuming, but it does work and will allow you to keep the arbor diameter a close fit for the wheel.

As far as the motor you're using, 150 watts isn't much power but it could be enough. For one of my TPGs I salvaged two satelite actuator motors to make one motor, then wound the lengthened armature myself. I epoxied it while having it slowly spinning in the lathe to distribute the epoxy into all the windings and around the core. Balancing was crudely done on knife edges to show the heavy side, and epoxy was added at the top (light side) until there didn't seem to be any preferred stopping place as I rolled the armature.

The original motors were rated at 1/6 hp, so with double the armature lamination stack and double the magnets, that would translate to 1/3 hp. The rewinding was done to raise the operating voltage by about 30% and thus allow the current draw to remain within reason. Because of the higher motor rpm, the output power would now be more like 1/2 hp, or 375 watts. In use I don't think I'm using any more than about 150 watts, but the excess capability allows the motor to remain fairly cool even if running for tens of minutes at a time. This is where I think you'll get bit- your motor is going to heat quite a bit if you're taking it near its power rating for any real length of time.

I'm not advocating that anyone should turn two motors into one- that's a lot of work and time spent. What I would suggest to anyone going the same route is to try to find a motor with a higher voltage rating. Minimizing the current draw does help to reduce motor heating, and the higher voltage motor would probably have a higher rated output as well- plus the fact that controllers will run them well.

For my machines with treadmill motors and converted motors, I have built power supplies that range from variac with bridge rectifiers to transformer based multi-tap secondaries with rectifiers and filters. This all becomes expensive unless you have access to surplus parts- plus with the exception of the variac they don't give smooth speed control, just several steps, and none are regulated. It all works well, but most people would be best advised to find a higher voltage motor like a treadmill motor, and use an available controller.

jhe.1973
01-31-2016, 06:57 PM
........ but I decided to start a thread anyway as it might motivate me to keep at it ‘til it’s done...................my usual calculating method called “SWACAG”. Scientific wild-a$$ cheap- a$$ guess.......... It never ends!:rolleyes:



So, I guess I'm not the only one who works like this?

Great project and I'm glad you posted it.

Thanks!!!

ahidley
01-31-2016, 07:11 PM
I made one awhile ago and posted it here. The motor I chose was a harbor freight 4-1/2 grinder for$9.99. Worked out great

DICKEYBIRD
01-31-2016, 07:27 PM
You can chuck a piece of rod with about 6 inches or so sticking out from the jaws, then turn a snug-fitting portion on the outboard end for the wheel to slip over. When you run the spindle again there should be no vibration of the rod. If there is, you could turn down the portion slightly to fit a shim and thus experiment with wedging the wheel in place. You'd be running the wheel offset, and you would then find out where the shim should be to offset the wheel in the right direction to reduce vibration.Thanks Darryl, that might just work. I'm not worried so much about vibration, mostly about runout which would cause chattering & lousy finish. I ran out of energy for the day so a test arbor will have to wait. I'm still not 100% recovered from the stroke but I'm not complaining under the circumstances.:)

metalmagpie
01-31-2016, 10:03 PM
Years ago I did some crude balancing using a device I made up using a strobe tube. It relied on the mounting shaft vibrating in response to an off-balance, and an adjustable contact point to trigger the strobe. Pretty crude, but it did work- the heavy point was where the shaft vibrated in a direction to touch the contact.

Don't want to hijack this thread but I'm very interested in balancing in the home shop. Your post reminded me of this one:
http://www.antiqueautoranch.com/montana500/septnewsletter/page4.html. Did you ever write up your balancing project?

metalmagpie

jhe.1973
01-31-2016, 11:58 PM
Don't want to hijack this thread but I'm very interested in balancing in the home shop. Your post reminded me of this one:
http://www.antiqueautoranch.com/montana500/septnewsletter/page4.html. Did you ever write up your balancing project?

metalmagpie

metalmagpie:

Thanks for posting this link. I saved it 'just in case'. I have a static balancing wheel setup now, but in case I need something to locate a rocking motion in the future it will come in handy.

I don't wish to hijack this thread either, so if you wish to start one on balancing in the shop I might have a useful contribution.

;)

darryl
02-01-2016, 01:30 AM
I have one of those bearing block balancers- well, just the blocks with bearings on them. I clamp them to a table or whatever for use. Works pretty well. I used skateboard bearings since they have shields and not seals- very easy rolling and smooth enough. I like the knife edge design for fairly light stuff though.

Yes I'd like to have a home shop balancing machine for more critical applications- armatures, etc. Something fairly simple and easy to use- I'll have to think on this.

Norman Bain
02-01-2016, 02:28 PM
Can I suggest changing the "covering rag" for "3 or 4 layers of newspaper". Safer that way should the swarf pickup in the spinning elements.

I use newspaper over the bed of my lathe most of the time. Somehow I feel bad about the "little bits" getting under the sliding elements if I don't.

Anyways I hold the newsprint down with a few of those small magnets. When the swarf builds up just it all roll up, bin it and replace the newsprint.

Cheers,
Norman

DICKEYBIRD
02-01-2016, 05:10 PM
Can I suggest changing the "covering rag" for "3 or 4 layers of newspaper". Good advice Norman, thanks. One of those quickie things I did to catch most of the mess until I got 'round to a better solution....months ago!

DICKEYBIRD
02-02-2016, 09:01 AM
"You can't fix stupid."

Dunno who came up with that little nugget but I must be this month's poster boy for that club. I even looked on the edit menu in Photoshop & couldn't find "Undo Stupid" so I had to swallow my pride & order another one.

http://i57.photobucket.com/albums/g227/DBAviation/CBN%20Broke_zpswq4zkyh9.jpg (http://s57.photobucket.com/user/DBAviation/media/CBN%20Broke_zpswq4zkyh9.jpg.html)

So I turned up an arbor last night to see how much runout there was in the wheel. SWMBO called me in for supper so I slipped it onto the freshly turned stub & switched the lathe on for a quick look before stopping to eat even though it was still set for turning speed and I hadn't yet made a washer or tapped it for a retaining screw.

You guessed it. It wasn't tight enough on the stub to hold it in place but just tight enough to accelerate & spin off, bounce a couple of times and wedge itself between the motor pulley & backstop. "Stupid is as stupid does." (I think Forrest Gump said that.)

dian
02-02-2016, 09:43 AM
did you sneak up on top speed when you first started it? i usually do 3 or 4 steps until there is no temp. rise before going full rpm.

DICKEYBIRD
02-02-2016, 10:09 AM
did you sneak up on top speed when you first started it? i usually do 3 or 4 steps until there is no temp. rise before going full rpm.Actually I did. The power supply has a pot that varies the voltage between a few tenths up to 33.5. I ran it for a couple minutes @ 12V, then 20, then 24 or so. The higher it went, the more noise it made & when it approached 7000 rpm, the bearings suddenly started binding up & it slowed down to around 4000. I quit running in the higher speed config. and am waiting for new bearings before trying again. The Sherline spindle was bought used (cheap) on ebay and I think the bearings were already toast or at least the grease was dried up.

RichR
02-02-2016, 10:22 AM
"You can't fix stupid."

Dunno who came up with that little nugget ...

Ron White:

If I could offer one piece of advice to the planet, it would be this: Don't marry for looks alone, and I'll tell you why. In a few years, when Barbara's boobs start sagging, she can get plastic surgery, have them lifted, move the nipple wherever. You can actually go to a titty bar, pick out a set of titties and say, "I want those titties on that woman." If her belly gets too big, she can get a tummy tuck and have a belly like a cheerleader. If her vision goes bad, you can have LASIK surgery and have 20/20 vision. If her hearing goes bad, they can install a device in her ear that will give you hearing as clear as it was the day you were born. But let me tell you something, folks: You can't fix stupid. There's not a pill you can take; there's not a class you can go to. Stupid is forever.

DICKEYBIRD
02-02-2016, 11:07 AM
Thanks Rich, I needed that!

DICKEYBIRD
02-04-2016, 09:16 AM
So the new bearings came in yesterday & I stripped the spindle down last night. I pressed the spindle shaft out & man was it a tight fit in the bearings. Had to put considerable pressure on before it popped loudly & moved a bit. It popped at each movement thereafter leaving these marks...both bearings journals. Seems to me the bearing on the preload nut end should fit the shaft with a close sliding fit rather than a hard press fit.

This thing is dead simple, just 2 deep-groove shielded bearings in an aluminum housing, no precision spacers or anything. Just a locking nut to adjust the preload. I'm thinking it'd be real hard to get the right preload with the bearing fitting the shaft so tightly. I'm wanting to polish the shaft OD for a close, sliding fit before putting it back together. Anybody know a reason why that is a bad idea?

Only reason I could think of that Sherline made it so tight is for long term fretting wear considerations under milling loads. Since my use will be at higher speeds & lighter loads, I want to loosen it up a bit.

http://i57.photobucket.com/albums/g227/DBAviation/Spindle%20Shaft_zpsoojhi2n5.jpg (http://s57.photobucket.com/user/DBAviation/media/Spindle%20Shaft_zpsoojhi2n5.jpg.html)

DICKEYBIRD
02-06-2016, 07:37 PM
CBN wheel #2 came in the mail a couple days ago. So far this one doesn't seem to have a death wish.:rolleyes: Got up this morning & felt really good about getting out in the shop & finishing the arbor for it. Hah! My successful (for once) effort at making a precision arbor was just a lot of wasted time. The cheap-o Shars wheel is just that...a cheap P.O.S. It's lumpy & runs out about .004"!

I guess lumpy is normal for a cheap, new CBN wheel but I was really disappointed in the runout. That's a ton of very hard material to try to dress off unless one has one of the super-expensive commercial dressing tools. (I don't.)

So, I turned my precision fit arbor into a sloppy non-precision arbor by turning off .010" from the shoulder OD & made a hollow alignment dowel to keep the 2 halves aligned but still allowing the wheel to be bumped into the best possible position before final tightening of the bolt.

Anybody have a CBN dressing method better than worrying it down with a slow turning SC wheel & following up with grinding away at a piece of mild steel? Not looking forward to that!

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Arbor_zps0zigdqn9.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Arbor_zps0zigdqn9.jpg.html)

DICKEYBIRD
02-23-2016, 08:58 PM
Been working some more on the TPG project. This thing is sure eating up the clock. It’s turning in to a real blivet.

I decided to go ahead and polish off a few tenths off the spindle to allow an easier preload adjustment. I didn’t want to polish it freehand & tried to buy the next size up Sunnen hone to do it. Never could find one cheap enough so I used the small one I do have. I was able to just barely get it to work by making a very thin “shoe” from acetal & cutting down a stock stone holder to allow a strip of 400 wet-dry paper to slide in. With it I was able to hone off just enough for the bearing to slide on with a squeaky-push fit by hand. It worked great and the new bearings & looser preload allowed long periods of top speed running with no excessive heat buildup in the spindle. Looks like 9800 rpm is the maximum speed for this pulley setup. I’m hoping it will have enough power at that speed for a 3/8” stone to skim off a couple thou from the ER16 collet chucks this contraption was built for.

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Ext%20Hone_zpsp5dljkmm.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Ext%20Hone_zpsp5dljkmm.jpg.html)

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Ext%20Hone%202_zpsrdtg4g6m.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Ext%20Hone%202_zpsrdtg4g6m.jpg.html)

DICKEYBIRD
02-23-2016, 08:59 PM
Next up was the shield for the CBN wheel. Thanks to the new DRO, drilling & tapping the 16 holes in the main body & its end plates was a breeze. 4 equally spaced holes in the Sherline body & the shield plate for the standoffs was even easier. I can’t believe I waited so many years to get that thing!

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Shield%20Front_zpsrkz3hvqo.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Shield%20Front_zpsrkz3hvqo.jpg.html)

I had a taste of deep-hole while drilling through the end plate to allow a 5/32” rod to reach in to the arbor for tightening it to the spindle nose. Getting it centered & calculating the standoff length was a pain.

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Shield_zps7qfwtiyj.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Shield_zps7qfwtiyj.jpg.html)

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Shield%202_zpscqgklvop.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Shield%202_zpscqgklvop.jpg.html)

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Shield%203_zpsahjqa1cp.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Shield%203_zpsahjqa1cp.jpg.html)

DICKEYBIRD
02-23-2016, 09:01 PM
Lastly, I made a flanged hex nut for the 3/8-24 height adjuster along with a cut down nut to lock it. I got it adjusted dead on center now & locked down solidly. Next up will be the coolant drain fitting on the bottom and the cutout in the front to allow the wheel to get to the work.

It’s getting a mite heftier than I planned so I’m thinking about thinning the 2 end plates & the shield body to reduce the mass the steppers have to shove around. The pipe & plate I had on hand are much thicker than they have to be.

http://i57.photobucket.com/albums/g227/DBAviation/TPG%20Height%20Adjuster_zpsscvo1cqs.jpg (http://s57.photobucket.com/user/DBAviation/media/TPG%20Height%20Adjuster_zpsscvo1cqs.jpg.html)

I dread what comes after that….aligning & dressing that CBN wheel. I think that may require Kryptonite ®.

Mike Amick
02-25-2016, 04:57 PM
Boy .. is that thing lookin good.

Can't quite figure out how the guard works. The wheel is completely inclosed, I thought the guard would be
like a "C" ... not quite going all the way around.

DICKEYBIRD
02-25-2016, 05:30 PM
Thanks Mike, I hope it works!

You got it, like a "C" with a very small opening. The guard hasn't had the clearance hole added yet to allow the wheel to access the work. Gonna wait a bit on that as I'm working on coolant options.