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Elninio
04-30-2012, 09:55 PM
I'm back in the machining hobby, at least for a short while, and have started a TPG. Was wondering, why don't people put the pulley belt in between the spindle bearings, and flip the motor to face the other way? It gives more space for working close to the lathe spindle, at least on these small lathe grinders. In this first picture, he could have flipped the motor and made the grinder spindle shorter
http://i431.photobucket.com/albums/qq32/sbwhart/Tool%20Post%20Grinder/100_2593.jpg
http://i.imgur.com/aUYLb.jpg

in larger tpg's, it won't make a difference:
http://www.powermaster-india.com/images/img57.jpg

http://i.imgur.com/mJVpx.png

lazlo
04-30-2012, 09:58 PM
Wow, that toolpost grinder is gorgeous!

I had to look it up on Google Image Search: Joachim Steinke, no surprise :)

http://madmodder.net/index.php?topic=1903.25

Elninio
04-30-2012, 10:16 PM
how much faster can bearings run if they are submersed in oil? how to make seals ? - spring or felt - i have some ideas ...
http://i.imgur.com/wuxFw.jpg
http://www.bearingkinetics.com/seals.13.gif
my router is long, in fact longer, because the power switch and eletronics are mounted behind the axis or rotation;
http://www.toolmarts.com/media/Bosch/Bosch-16186-th.jpg

darryl
04-30-2012, 10:43 PM
Oil filled bearings, as in the spindle shaft inside a case, which is partially oil filled? I like that idea as you can have some cooling from the oil, along with it lubing the bearings. It would rely on the outer seals to keep the oil in, and you could dispense with the inner seals or shields entirely. You might have to vent the case to allow pressure to equalize- you don't want temperature build-up forcing oil out through the seals.

Your other question, relating to the mounting of the motors- on mine I have the spindle pulley just behind the business end of the spindle. My motor is fairly short, so it wouldn't have mattered in my case, but I figured the belt tension might as well take out any bearing play in the same direction that the workpiece would force it anyway. That way there is no looseness that the workpiece is forced to control. Gives better results I think, though I can't confirm that since I didn't try it the other way. It wouldn't matter if the motor is toward the operator, or toward the rear of the tpg spindle- it would still leave the motor clear of the chuck, etc. I prefer to have my tpg come in from the rear of the lathe, and the spindle turning clockwise- both spindles actually. If the lathe spindle is turning in the normal direction while the tpg spindle is turning clockwise as seen from the front, then the grindings are still forced downwards and you have room to see what you're doing.

cameron
04-30-2012, 11:33 PM
My understanding is that the amount of oil present in a high speed bearing should be restricted, as too much oil can cause overheating due to oil churning.

I hope to be corrected if this is wrong.


Dave Cameron

Elninio
04-30-2012, 11:38 PM
My understanding is that the amount of oil present in a high speed bearing should be restricted, as too much oil can cause overheating due to oil churning.

I hope to be corrected if this is wrong.


Dave Cameron
That is correct, but there are light oils that don't have this problem --- depends on the speed of course ...
I found a paper on oil churning for planetary gears http://ojs.sv-jme.eu/index.php/sv-jme/article/view/100
46 page on spindles, little bit on seals http://www.scribd.com/doc/82924226/18/Oil-Lubrication-Techniques
How to calculate the % oil to air mixture for the highest bearing speed, assuming a homogenous mixture?
http://i.imgur.com/aVyss.png
just a bit more reading ...

cameron
04-30-2012, 11:48 PM
Elninio,

Why make bearing seals when most bearings can be bought with seals or shields ? The bearings that can't be obtained with seals usually have a configuration that makes integral seals impractical.

Not meant as criticism, just curious.

Dave Cameron

PS: Please notice my striving towards a kinder and gentler phrasing in my postings.

Elninio
04-30-2012, 11:58 PM
Elninio,

Why make bearing seals when most bearings can be bought with seals or shields ? The bearings that can't be obtained with seals usually have a configuration that makes integral seals impractical.

Not meant as criticism, just curious.

Dave Cameron

PS: Please notice my striving towards a kinder and gentler phrasing in my postings.
I have some good bearings that didn't come with seals, they came off a high speed linear motion positioning clutch. Poverty, to be brief. I don't know if I'll be able to machine my grinding extensions to cover the exit passage on the bearing nicely. I have problems grinding toolbits to produce very nice finishes, and don't have any fine hones. Maybe once the TPG is done, I can use it to grind a nice flush cup that will fit in between the races, on the end of the extension shafts .. though, it will be mildy annoying to change the extensions. I will have to take the TPG off the compound if I don't want to have to refill it. But, since it contains so little oil (even the space between the shaft and the body, between the bearings, is extremely small), that may not be bad at all. Silly question; are the oil holes in the green picture above spring loaded?

cameron
05-01-2012, 12:50 AM
Sounds like a good enough reason to me (even if wasn't poor, I'd still be chea.. I mean frugal).

Not sure I understand the machining problem, because I don't know the details of your design. But, at the cost of some space, wouldn't it be easier to use separate seals on both sides of the bearings, rather than integral with them ?

They could be comercial lip type seals with the same OD as the bearings, sealing on the shaft, if you can find a suitable size. Or they could be simple shop-made retainers for felt seals.

Dave Cameron

Elninio
05-01-2012, 01:00 AM
Sounds like a good enough reason to me (even if wasn't poor, I'd still be chea.. I mean frugal).

Dave Cameron
http://i.imgur.com/uwEXO.png
The bottom zoomed-in corner will be tight on the bottom race, the top one must be as close to the race as possible whilst leaking as little oil as possible. the end of the shaft on the other end of the housing will be taut by a spring to preload the bearings, this tension must not allow the top corner to touch the top race.

EVguru
05-01-2012, 05:14 AM
I'm back in the machining hobby, at least for a short while, and have started a TPG. Was wondering, why don't people put the pulley belt in between the spindle bearings, and flip the motor to face the other way?

Because it would be much more difficult to align the bearings compared to boring a seat both ends of a tube.

I've seen designs with a pulley just behind the collet and the old school way of doing things was an over head 'drum' shaft.

lazlo
05-01-2012, 10:08 AM
how much faster can bearings run if they are submersed in oil?

You want a lubrication film, whether oil or grease. Submersion is not what you want.

But in general, oil lube will give you 50 - 100% higher max RPM rating, depending on the ball size, bearing type, etc. Each manufacturer will have tables like this in their datasheet:

Bearing Oil Grease
Cylindrical Bearing 500000 300000
Spherical bearing 290000 145000
Thrust ball & roller 280000 140000


My understanding is that the amount of oil present in a high speed bearing should be restricted, as too much oil can cause overheating due to oil churning.

I've rebuilt a couple of Dumore TPG spindles (I've posted pictures here), and they have a simple, very clever, oil mist system: there's an oil reservoir in the center of the spindle, with felt pads that keep it from leaking into the bearing modules on each end. When the spindle spins, the felt sprays a mist of oil, proportional to the spindle RPM.

Elninio
05-01-2012, 12:36 PM
Because it would be much more difficult to align the bearings compared to boring a seat both ends of a tube.

I've seen designs with a pulley just behind the collet and the old school way of doing things was an over head 'drum' shaft.
Why would it be harder? It's the same setup to machine, with an extra slotting.

SilveradoHauler
05-01-2012, 10:46 PM
Check your bearing specifications, likely the sealed grease lubricated bearings have a higher RPM limit than your grinding wheels. TPG duty is really very light. Oil lubricated would be a waste of time and design talent.

I was grinding centers for about two hours today, could not feel any temp rise at all in the spindle housing. Bearings are grease lubricated.

Motor does not get in the way in my configuration below.

http://im1.shutterfly.com/media/47a2db20b3127ccef056d8ef265a00000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/

darryl
05-01-2012, 11:54 PM
Something I thought of after reading through this thread and seeing the pictures- what would be the pros and cons to putting the motor directly above the tpg spindle? One of the pictures shows that, or very nearly that anyway.

It would seem that it would put less stress on the carriage, as it would be more or less just weight straight down on it, plus you could more easily use it in front or behind the workpiece.

oldtiffie
05-02-2012, 12:34 AM
I thought about the "motor getting in the way" some time ago.

There is no good reason why the motor should not be behind, in line with and close-coupled/integral with the TPG wheel shaft.

A typical small surface grinder grinding head or a good die grinder come to mind.

http://www.littlemachineshop.com/Products/Images/480/480.2891.jpg

http://www.littlemachineshop.com/products/product_view.php?ProductID=2891&category=

and its mounting attachment (1/2" max grinding (wheel):
http://www.littlemachineshop.com/Products/Images/480/480.2935.jpg

Or a bigger better (very good) die-grinder (will drive 2" wheels):

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Bosch_HS_Grinder15.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Bosch_HS_Grinder7.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Bosch_HS_Grinder2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Bosch_HS_Grinder3.jpg

All of these were bought "off the shelf".

I am sure that there are other similar options.

SilveradoHauler
05-02-2012, 11:00 AM
Don't forget RPM limitations for the larger diameter wheels.

Usually painted on the wheel or printed on the paper side panels.

Most die grinders will exceed the RPM limits of 2 inch or so wheels and the larger mounted stones.

When a wheel or stone lets go it is no time to be in the shop!

And be sure to have a diamond dresser to true the wheel.

I do not like a die grinder as a TPG as it is noisy, not as rigid a setup, cannot use larger wheels, and the chucking arrangement is not as accurate. Every time you change a stone you have to use the diamond dresser and true it.

Back to motors, a top mounted motor obstructs visibility.

Elninio
05-02-2012, 11:37 AM
Check your bearing specifications, likely the sealed grease lubricated bearings have a higher RPM limit than your grinding wheels. TPG duty is really very light. Oil lubricated would be a waste of time and design talent.

I was grinding centers for about two hours today, could not feel any temp rise at all in the spindle housing. Bearings are grease lubricated.


For those really small grinding stones, the RPM limit is higher on the stones than on the bearings.

Small grinders like the bosch and dremel don't produce nice surface finish - a guy on youtube went to parallel bronze bush design, after trying tapered, needle, angular contact, ball. If I'm not mistaken, even high tolerance ball isn't good for this job (but it will work in a hobby application, sure).

All of the grinders on this page overhand the compound by a few inches - either the shaft or the entire housing. Maybe I'll use orthogonal pulleys (though, where to get that large diameter O-ring to use as a belt?), and place the motor on the other side of the carriage? I will be screw-cutting the mounting thread tonight on the grinder spindle, then grind against the lathe chuck to true the spindle. I still don't know what the hell I'm going to do with the die grinder, It is just a bit too tall to attach in-line to the grinder spindle, though this seems the most convenient ..

cameron
05-02-2012, 02:58 PM
Round polyurethane that can be spliced to the size required is available. I wanted to use it on a Quorn, but the distributor wouldn't order less than a box, more than I needed or wanted to pay for. Somebody must sell it in smaller quantity.

Dave Cameron

The Artful Bodger
05-02-2012, 04:31 PM
I do not have any luck with urethane or even big 'O' rings as drive belts on my TPG. The high speed makes the belts balloon and fly off to some hidden corner of the shop. My best belt is several loops of hemp string soaked in contact adhesive.

SilveradoHauler
05-02-2012, 04:58 PM
Flat vacuum cleaner belts are just the ticket for the TPG.

I will pull the guard later and take a photo. Motor pulley and spindle pulley are flanged and crowned. Belt is about 3/32" thick and 5/8" wide.

Yea I know about the small grinding points but the large diameter grinding stones can get one in trouble. I have a dozen or so air and electric die grinders and hundreds of stones, points and carbide burrs scattered around the benches. Even have a tool post bracket for one of the larger electric grinders, but never use it, the TPG and the belt grinder in the below photos get most of the work. The wheel on the TPG may be replaced with a standard die grinder 1/4" chuck if I need to use a grinding point, spindle is threaded 3/8"-24, same as the spindle on the larger air die grinders.

http://im1.shutterfly.com/media/47a2da24b3127cceff9eb3d6f9b500000040O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/


http://im1.shutterfly.com/media/47a2da26b3127cceff9a05b0c8e100000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/



The central slotted bar is a sliding tensioner. Spring on the back side. The two small wheels have internal ball bearings and are hard rubber contact wheels. Motor pulley is flanged.

http://im1.shutterfly.com/media/47a2da26b3127cceff9b1501692400000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/



http://home.earthlink.net/~old-iron/sitebuildercontent/sitebuilderpictures/muzzlegrinding2.jpg

SilveradoHauler
05-02-2012, 05:10 PM
Belt grinder can also be used in the "slack belt" position:

http://home.earthlink.net/~old-iron/sitebuildercontent/sitebuilderpictures/slackbeltgrinder.jpg

SilveradoHauler
05-02-2012, 08:57 PM
Tool Post Grinder Belt Drive

I need to machine another set of pulleys, with the present configuration and a 3-1/4" grinding wheel I am too fast at max motor speed and I am running the motor at about 1/3 speed. So I will just reverse the ratio, smaller pulley on the motor. The present pulleys are just fine for 2 inch or under wheels. Pulleys are crowned and flanged.

Motor is from an old style 1/2" drill with the gearbox removed and a new flange installed. It will hit around 5000 RPM. I run it with a variable speed DC drive.

http://im1.shutterfly.com/media/47a2db23b3127ccef0508d300f7200000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/


http://im1.shutterfly.com/media/47a2db23b3127ccef050d9bd8ee500000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/


http://im1.shutterfly.com/media/47a2db23b3127ccef05043cf0fea00000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/


http://im1.shutterfly.com/media/47a2db23b3127ccef051a9062f1a00000030O02QZsmjZw5aA9 vPgw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/

oldtiffie
05-02-2012, 09:07 PM
So far it seems that using a TPG for external work is required.

What about TPG internal grinding (that's what I intend using my really good die grinder/s for).

I have a pretty good universal grinder that does external grinding - and will do internal grinding as well:

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal-grinder28.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder3.jpg

oldtiffie
05-03-2012, 06:14 AM
If I wanted to, it would not be difficult at all to mount this grinding head on my lathe.

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder3.jpg

It takes standard 6" and below surface or tool and cutter grinding wheels with 1 1/4" bores.

I use "norton" wheels exclusively as they are very well balanced right out of the box.

oldtiffie
05-03-2012, 06:37 AM
Don't forget RPM limitations for the larger diameter wheels.

Usually painted on the wheel or printed on the paper side panels.

Most die grinders will exceed the RPM limits of 2 inch or so wheels and the larger mounted stones.

When a wheel or stone lets go it is no time to be in the shop!

And be sure to have a diamond dresser to true the wheel.

I do not like a die grinder as a TPG as it is noisy, not as rigid a setup, cannot use larger wheels, and the chucking arrangement is not as accurate. Every time you change a stone you have to use the diamond dresser and true it.

Back to motors, a top mounted motor obstructs visibility.

This die grinder is a real industrial machine. There is less than 0.0002" TIR on the 1/4" spindle of a standard "point". The collets - similar to an ER series collet - are really good too for accuracy and repeatabilty.

Speed can be an issue with all points but its up to the operator to look up the maximum speed, not exceed it and as always be careful.

http://www.google.com.au/#hl=en&gs_nf=1&cp=15&gs_id=1o&xhr=t&q=grinding+points&pf=p&output=search&sclient=psy-ab&rlz=1W1IRFC_enAU360&oq=grinding+points&aq=0&aqi=g1g-v3&aql=&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=bbce53977ebc5184&biw=1920&bih=785

Because of the accuracy of the collets only a minimum - if any - wheel dressing is needed. But I dress all my grinding wheels on all grinders (other than the pedestal grinder!!) as soon as the point is changed or at the start of the job for the day.

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Bosch_HS_Grinder2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Bosch_HS_Grinder3.jpg

My normal maximum point size is 1 1/2" (2" some times) and smaller points as necessary.

It, like most European drills and grinders etc. can use a standard ISO clamping set up for use in a vise too if required - as per this drill:

http://i200.photobucket.com/albums/aa294/oldtiffie/Med_Speed_Spindles/Metabo_drill3.jpg

dian
05-03-2012, 01:07 PM
silverado, what is the benefit of the belt grinder? as you cannot hold a size i would assume polishing?

SilveradoHauler
05-03-2012, 01:27 PM
silverado, what is the benefit of the belt grinder? as you cannot hold a size i would assume polishing?


Mainly barrel polishing, but I can hold a thou when using the contact wheel, mainly for fitting barrel band front ramps. On the band type ramp I want 0.003" or a little more clearance for silver solder. Note in one of the above photos with the barrel the slack portion of the belt is doing the polishing, the contact wheel is tilted down and away from the barrel.

Ramp installation below.

I am thinking about building a larger belt grinder for the lathe with about a 2 inch diameter contact wheel and a 1"x42" belt.

http://home.earthlink.net/~old-iron/sitebuildercontent/sitebuilderpictures/muzzlegrinding5.jpg

SilveradoHauler
05-03-2012, 01:29 PM
So far it seems that using a TPG for external work is required.

What about TPG internal grinding (that's what I intend using my really good die grinder/s for).

I have a pretty good universal grinder that does external grinding - and will do internal grinding as well:

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal-grinder28.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder3.jpg


Wow, just what I need for grinding chamber reamers! Nice machine.

oldtiffie
05-03-2012, 09:35 PM
Wow, just what I need for grinding chamber reamers! Nice machine.

It is "nice" - very nice.

Here are the details:

https://www.machineryhouse.com.au/G198