Thread: Building a small surface grinder
21st Jul 2011, 11:10 PM #1
Building a small surface grinder
Well, I'm excited!
This forum is unbelievable!
One of the members of this forum found a small horizontal Whitney No6 mill beyond repair as a mill (and not really convenien or flexible enough).
Since he only had a project in mind for the spindle and head, he let me have the rest: delivered from Sydney to my shed near Bendigo - as a present! Where do you find strangers like that - except on this forum?
Anyway, this mill in my eyes is a perfect basis for a small surface grinder! Nice and rigid, 300mm x-axis table travel, 110mm y-axis travel and 450mm vertical range. The table supprt (knee) travels 350mm for work positioning and the slide for the head another about 100mm.
The table is rack driven - with just under 2 turns for full travel.
My plan is to make a new head slide with a 3/4 or 1 HP 1440rpm 3-pahse motor bolted directly to the slide. I'll change the motor spindle bearings for precision bearings (maybe angular contact or 4-point bearing at the wheel end and good quality and tolerance single row deep-groove at the far end). The motor will have to be a modern slim frame and the grinding wheels will have to be larger in diameter that the motor. I'll drive it with a small VFD to set the speed to suit the wheel.
When I get to starting this project, I'll post photos of the progress.
For now I'll be searching and collecting bits and pieces: motor, grinding wheel(s), VFD, materials for the slide and the arbours, magnetic chuck (4"x8" or so) etc.
Does anyone have a lump of cast iron to machine the dovetail slide from for me? I need 8"x8"x1 3/4" - 2" approx.
This is what it looks like today:
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21st Jul 2011, 11:28 PM #2
Now there's a project to get your teeth into. Is there any easy way to motorize the X axis?
I would seperate the wheel spindle from the motor bearings, maybe you could make an spindle with AC bearings and have a flexible coupling direct to the motor shaft. Wheel size depends on how much horsepower you can muster.
21st Jul 2011, 11:54 PM #3Dave J Guest
I have an old horizontal mill here a little bigger than that one and have thought about this myself.
Will be interesting to see how it works out.
22nd Jul 2011, 08:29 AM #4
Joe, I strongly agree with Ray, make a separate spindle for the wheel and drive it with some form of belt arrangement. There are several reasons for this, the main one is balance, having the wheel/spindle assembly running so there is no vibration at the wheel face is critical if you expect to get decent results. It's unlikely you will be able to balance motor to that extent. It's not just a question of bearings. Besides which, there are no facilities within the motor to pre-load the bearings.
Another reason is that a spindle assembly is physically much smaller than a motor, so can likely be placed closed to the axis centrelines for greater rigidity.
Finally, if you make your own spindle you are free to choose and size the bearings to whatever size you like. It will give you far more flexibility than being stuck having to find some unobtainable precision motor bearings. Precision bearings are never cheap, but if you choose a common bearing you can at least minimise the cost.
Making a spindle is not especially difficult, at it's most basic just a simple boring project. However you do need to incorporate a pre-load arrangement. There have been many designs published on the net, however I would recommend a book called, "Spindles", number 27 of the Worksop Practice Series. It's available online and like the rest of the series is a "how to" style book with quite a number of spindle designs you will be able to replicate.
22nd Jul 2011, 09:20 AM #5
There are photos and a cross sectional drawing of the simple spindle Hercus used on the No.3 tool and cutter grinder is this old thread. They show the preload arrangement. http://www.woodworkforums.com/f65/mo...30/index2.html
If Pete has a manual for his surface grinder, it may also include a drawing of the spindle. I have some drawings of Brown and Sharpe grinding spindles along with those made by Dumore if you think they may be of use.
You could always buy a slice of cast iron round bar from Interlloy or Bohler. A lot of the bits and pieces I've made have started life as chunks of round bar.
22nd Jul 2011, 09:35 AM #6
Having said making the spindle is not especially difficult, I guess I should quantify that a little, as it really depends on precisely how good you need the spindle to be. Compared to simply bolting a wheel on to the end of a motor, then it's not difficult. However if you're talking about building an extremely precise spindle to rival a good commercially built grinder then that's a whole different ball game. So I guess in reality, building a spindle could range from quite straightforward to almost impossible to do in a home shop just depending on the precision you require. Sorry I just didn't want to lead you up the garden path by dismissing it as "pfft, just build a spindle", then you being disappointed you weren't getting results like Ray's when you're finished.
22nd Jul 2011, 09:49 AM #7
I had thought about mounting the Dumore onto the overam of the little Hercus O mill and trying to use it as a Mickey Mouse surface grinder. The table rack and pinion assembly was given to me a number of years ago and thought that it might be a way of putting it to use. I will be watching to see how Joe progresses with this project.
22nd Jul 2011, 10:11 AM #8
Yes the rack and pinion is an absolute must have, it's bad enough cranking the handle back and forth on a manual grinder as it is, never mind if it was a conventional mill feed!
The other consideration Bob is the Z axis. The Z axis feed on the mill is, if I recall correctly 2.0 mm per revolution (on a metric machine). My surface grinder has an imperial leadscrew and is 1.27 mm per revolution, or roughly half the mill's. I could imagine coming up on final size could be a little difficult with the coarser leadscrew, again if it's precision work you're after.
22nd Jul 2011, 09:32 PM #9
23rd Jul 2011, 11:30 PM #10
Thanks everyone for your input!
And thanks again to Peter for the machine and the delivery!
I've been gingn some thought to motorising the table travel - I think it may be reasonably easily done with a suitably sized and controlled stepper motor with toothed belt reduction. Alternatives might be a servo motor or simply a brushed DC motor with two micro switches to stop the motor a few revolutions before the intended end of travel and a timer delay to reverse it (so as not to reverse it at full speed). I'm able to do that with electronics.
I had intended to make provision for bearing preloading with shims or threaded options inside one end of the motor housings. However, I'm listening to the advice of separating the motor form the spindle - though the motor will need to be balanced propoerly in any case, as it will need to be mounted on the vertical slide somehow.
THere are several T&C grinders driving their grinding wheels on the motor shafts - that's what made me think of that option. Then there are all the CNC direct drive 3-phase soindles with minute run-outs and balance...
However, a dedicated precision bearing spindle and belt may well be easier - relatively - in any case.
If anyone has cross-section drawings or better, I'd be interested.
Another question: magnetic chucks range from affordable to quite unrealistic. What are the differences and how do they work? I mean the switching off of the permanent magnetic chucks. Is it possible to make a permanent magnetic chuck from a pile of rare earth magnets and brass strips?
24th Jul 2011, 12:11 AM #11
Here's something for you to think about while you wander around Darwin...
This is the setup on the Herless Surface Grinder, the cross shaped part #17 is the rubber coupling.
Might give you some ideas about how to approach yours.
PS Here's a 4"x8" mag chuck for a pretty fair price http://www.ebay.com.au/itm/4-X-8-MAG...item1e65624af7
24th Jul 2011, 11:45 PM #12
most of the direct drive spindles i have seen are very high rpm like 18,000 at full speed but to get them down to the speed you need even with a vfd they may lose too much power
id go for a dc motor option in the table feed
steppers are great things i have them on 4 cnc machines i converted or built but you have to have power supplies for the driver 50v and the logic 5v a driver something to control them ie a pc or microprocessor and if they mis a step or 50 things will start to get ugly you will need a pretty strong stepper to change direction as you have a largish amount of mass there
11th Sep 2011, 08:35 PM #13
Some progress - taking into account all the input and further reading thus far.
The damage to the T-slot is now quite visible.
Next I had a closer look at the mechanicals - and cleaned up and polished the knee and Y-axis scales:
This is that the head slide mount looks like on the top of the mill body:
Since the donor needed the original head casting for another purpose, I initially had the idea to have a spindle mount cast. This is what I had in mind to fit a tubular grinding spindle:
After some investigation and quotes, I decided against that and chose to mill it from solid. I soon realised it's not that easy to get scrap cast iron big enough - until I came across a tractor wrecker who had a lot of tractor (front) weights. An 'International' one suited me:
A friendly local firm had a large bandsaw to get me started:
The bottom right section is my target. I'm sure I'll find use for the off-cuts too
In the meantime, I took the table over to RayG's for a visit and Josh (Ray's son) gave the top and the bottom flat of the dovetails a good 'lick' with the surface grinder. It was surprisingly straight and showed very little wear - a good start to reconditioning the sliding surfaces.
Then I found a Massey Ferguson finger mower drive casting behind my shed - and the drive section looked suitable for a grinder spindle with a bit of imagination. So I cut everything off that didn't fit into that imaginary picture.
A bit of turning and milleing to go yet, but here is a strart:
Now I was inspired and made a start on the spindle slide. Here is today's effort of generating a mountain of chips, about half-way through the day:
I have purchased some angular contact bearings to suit my spindle casting and a nice little 4"x8" magnetic chuck. I also found a 1.1HP 2800rpm 3-phase flange mount motor at the local recycling yard and after cleaning it up and replacing the bearings, I now intend to mount that on the rear of the spindle, with a flexible coupling of course and driven by VFD. It runs very well at any speed and with pretty well no vibration at all in an intial test run.
Oh, I also found a couple of new old stock Norton surface grinder wheels there for $8 each.
More updates as I find time and energy to continue
14th Sep 2011, 08:26 AM #14
some of you guys never fail to amaze me with your skills....to be able to plan such a task and then carry it out from scratch is mind boggling...well to my noggin (and contents) it is
14th Sep 2011, 04:23 PM #15
I'm impressed that you saw a spindle bearing hiding inside the massey ferguson mower casting...
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