Thread: I have the Power (Surface grinder)

Hey that guy has a TOS shaper like mine in the background. Must be a discerning chap.

Congrats on your new grinder Michael. No luck selling the T&C?
Wish I could have relieved you of it as it's tooled up and no doubt in better nick than mine.

No help at all am I?

I think the TOS in the background is at a dealer's place.
The T&C grinder did sell - perhaps not for as much as I could have got if I'd hung out but enough.

Additional question for SG users -
This unit is a bench mount one. I was thinking of positioning it so that the handle axis were around 100mm below elbow height. Good/ bad idea?

Michael

Originally Posted by Michael G

• I have not been able to find out a pulley groove specification for a M series belt (this is the 'classic' style, not the poly Vee type). It looks to be similar to the US 3L type but I'm not sure. Details would be good. I could copy the spindle pulley but wear may make this tricky

I'm going to pull my motor in the next few days in prep for a belt change so I can measure the pulleys at the same time. Pretty sure the one on the motor is cast iron so I doubt it's worn significantly.

Mine is so old that the belt has rotted apart.

PDW

Hi Michael.
Congratulations!
If you are going to fit a flange mounted motor and VFD, is there an option to fit it in line with the spindle axis and drive it with a Lovejoy or other flexible coupling instead of the belt? With the samll motor on these things, you will loose a lot in belt friction. That will reduce the maximum grinding wheel width significantly.
You can easily make up the speed loss by cranking up the frequency a bit (75Hz equals the 3:2 speed increase of the belt drive). That will keep the motor a little cooler....
at 4320rpm sounds like a 5" wheel diameter to me. I take it your flange mount motor is 2-pole (2880rpm)?

Thanks Joe
Direct drive is an option but would mean major modifications to the way the motor mounts and the slide it sits on. I hope to post some pictures of the disassembly the weekend but the carriage that the motor sits on is also the vertical sliding element, so any remounting of the motor could potentially add complexity.

Grinding capacity is not a big issue. I was planning on running 1/2" or a little wider wheels as the normal. As Peter's came with a 1/4 hp motor and I'm fitting a 3/4 hp motor because that's what I could easily get, a little frictional loss can probably be accommodated. The motor is a 2 pole.

Wheel size is one reason I would like to see some specs or a brochure or something. This grinder has come with no wheel guard and a 7" wheel fitted. Peter's machine also has no guard - as a result we have no way of confirming what the original maximum wheel size should be. Scaling from the picture I have of the complete machine suggests that 5" is probably about right. I have figures of 4000 to 6500 sfpm as a typical surface grinder speed, which equates to 3.6 to 5.8 inches in diameter. Of course that is not taking wheel and metal characteristics into account which may change things. I'm also not using coolant. Then again, I will have a VFD on there that should allow me to tickle the speed slightly if needed.

Michael

The grinder came home today and lacking anything better do, started stripping it down and doing an initial clean. It was filthy but under the muck looks to be some reasonable paint work. As I don't like painting and I find that beaten up looking machines attract less attention in the shed that's fine by me...
Work has just gotten a new parts washer (filters the solvent down to 0.1micron before recirculating it) and I was hoping that I could clean this up there in it but when we went to start it up this afternoon, the pump was DOA. Bugger. Back to kerosene, rags and a paint brush.
The motor is coming off - I've got a suitable motor and a suitable VFD is in transit. As previously reported there were some funny things happening with pulley drives. This is the old motor mount. Note the thinning of one side of the pulley, the stacks of washers, the pulley attached to the extension shaft with a SHCS and the list goes on. Elsewhere on the machine there are screws of differing lengths, missing screws, missing washers and a general lack of care for the machine. I can understand that someone with limited machine tool experience may repair a more common machine like a lathe like that because they did not know any better but surface grinders are a little bit more specialised and not the sort of thing I would have thought anyone would have if they did not know what it did or how to look after it. Simon said the seller claimed some engineering credentials but from what I've seen so far...

Attachment 310024
There was some speculation that Peter's machine was the standard machine and my motor mount had been machined down to take a foot mount motor. This is the plate that the motor mounts on and as can be seen, there is no evidence of a web once being there. I have inquiries in with Repco and a couple of other places that might have old sales literature but it might remain a mystery.

Attachment 310023
The next couple are the underside of the table showing the rack and pinion feed. The gear and rack don't look new, but at the same time do not look like they have had it. One day I hope to be set up to do racks, so when it gives up the ghost I'll be ready. An interesting thing is the little numbers stamped everywhere. I can only assume that they are item numbers in the assembly. I've seen it on military hardware, so whether this was made with the army in mind?
The side to side slides are lubricated with oil and as can be seen have felts in the holes to wipe oil on. A photo that Peter sent me had a felt missing and what looked like an oil tube in the well, so there might be something approximating a central lubricating system.
Attachment 310022 Attachment 310025
The next two are of the column. It needs to be stripped down further but even with a basic clean the paint is in remarkably good condition with just a few chips off here and there. I thought Peter was winding me up when he said that on top of the spindle there was a small reservoir for coolant, but there is. I need to clean this further but there is a tap on the opposite side of the spindle housing. I've always either ground dry or with flood coolant, so I'm not sure how a trickle will help. The second photo shows the surface of the column where it bolts onto the base. The base is recessed in this area to provide some clearance for moving parts, so there is a pocket around 5" wide and 1" deep. That was packed solid with greasy muck about half the height of those pads. In the muck were pieces of stainless rod up to 10mm in diameter, greasy swarf and pieces of shattered thin cut off disc. It looks like for a significant period of it's life this machine was being used as a cut off saw. Another mystery...

Attachment 310026 Attachment 310027

The next two are of the handwheels. Originally they had an attack of flight rust but as the first picture shows, wire brushed up alright. Notice again that apart from some wear the paint is still basically there. The cross feed is graduated in thous and each division is around 3mm wide. The down feed handle (only attacked locally with emery) is also graduated in thous but the divisions are approximately 8.5mm wide. That does suggest to me that a suitable vernier scale could make it very easy to down feed in 1/10ths. Why I'd want to do that I have no idea but it is a thought.
Attachment 310029 Attachment 310030
The last photo is of the base. The cross feed runs in V ways and is driven by an 8tpi screw (so much for the seller's assertion that it was a metric machine). Simon mentioned that the seller did pick up the machine by the cross slide and Simon was worried that the lead screw may be bent. Well, he was right. The leadscrew is bent, so that is another task to add to the list. Phil also reported a stiffness in the cross feed, so that may have contributed. The bend is only slight but it is there and can be felt, so needs to be straightened. The base is something like 8" high and as can be seen has substantial ribbing in it. While bench top grinders can be sneered at as not being "real" machines, this one seems pretty darn heavy and rigid to boot.

Attachment 310028

The plan for the next session is to finish the general clean up, straighten the screw, check (and document) the lube points, fabricate a bench for it and do some basic tests to gauge wear.
(Should have it knocked off by lunchtime if I don't hang about...)

Michael

Originally Posted by Michael G

(filters the solvent down to 0.1micron before recirculating it)

Is that the USA mic? .001mm would get rid of bacteria. 0.1 would just about stop a virus...... or have a I slipped some zeros?

As far as wheel size goes. If you knew the factory spindle rpm wouldn't that give you an idea of wheel size.... or has the max rpm of wheels has gone up over the years........?

Stuart

Originally Posted by Stustoys

Is that the USA mic? .001mm would get rid of bacteria. 0.1 would just about stop a virus...... or have a I slipped some zeros?

They are claiming 0.1 micron -
https://envirofluid.com/worksafe-env...fit-filter-kit

Originally Posted by Stustoys

As far as wheel size goes. If you knew the factory spindle rpm wouldn't that give you an idea of wheel size.... or has the max rpm of wheels has gone up over the years........?

That's my bind. I have a non original part fitted and no indication of what spindle speed should be. If I put in the ratio that I'm guessing the maximum size that the pulley was I get a spindle speed around 4300rpm. As per Joe's calculations that would mean a 5" wheel (the 7" fitted says a maximum rpm of 37xx. Was the previous user an idiot? Oh wait - I think we covered that).

Looking at a supplier web site the maximum speed for a 6" Norton wheel is 4140rpm, for a 7" 3600rpm (5" is not listed for straight wheels). Now based on that I should probably make up my guard so that it can't take a 7" wheel (that is, 6" maximum) and knock the pulley size down to give me say 4000 to 4100rpm when running at 50Hz. Here's where I need the data for M series belts because at the moment I'm only guessing what the PCD of a M pulley is so getting the size right to get the speed right is still not straight forward.

Incidentally, now that it has been established that a 7" wheel is too big for this machine, does anyone have a use for one? 7" OD, 31mm ID, 1/2" thick, white.

Michael

Originally Posted by Michael G

Incidentally, now that it has been established that a 7" wheel is too big for this machine, does anyone have a use for one? 7" OD, 31mm ID, 1/2" thick, white.

Michael

If you're fitting a VFD, why can't you use it?

Originally Posted by Bryan

If you're fitting a VFD, why can't you use it?

I could, but the VFD is there for my convenience. I would rather set it up so that if at some stage in the future if the VFD was removed (for example I got more than one 3 phase outlet or I sold it to someone) I would know that if it was run on 3 phase mains power it would function safely.
The VFD may get used for smaller wheels but normally I don't intend to adjust the frequency.

Michael

Originally Posted by Michael G

.. at the moment I'm only guessing what the PCD of a M pulley is so getting the size right to get the speed right is still not straight forward.

Michael,

I do have data on M series sheave dimensions ...somewhere.
In the mean time, I believe the geometry of 'conventional' v-belts is consistent across the size range (M, A, B, C etc).
Given that the nominal width of an A series belt is 1/2 inch, and an M series belt is 3/8 inch wide, you should be able to simply scale down the sheave dimension data for A series belt drives to get the data for M series drives. I presume the info you need is sheave OD vs PCD, so multiplying A series dimensions by 0.75 should get you close to the mark. Or was that your guessing procedure?

Cheers,
Bill

Originally Posted by Michael G

They are claiming 0.1 micron -
https://envirofluid.com/worksafe-env...fit-filter-kit



That's my bind. I have a non original part fitted and no indication of what spindle speed should be. If I put in the ratio that I'm guessing the maximum size that the pulley was I get a spindle speed around 4300rpm. As per Joe's calculations that would mean a 5" wheel (the 7" fitted says a maximum rpm of 37xx. Was the previous user an idiot? Oh wait - I think we covered that).

Looking at a supplier web site the maximum speed for a 6" Norton wheel is 4140rpm, for a 7" 3600rpm (5" is not listed for straight wheels). Now based on that I should probably make up my guard so that it can't take a 7" wheel (that is, 6" maximum) and knock the pulley size down to give me say 4000 to 4100rpm when running at 50Hz. Here's where I need the data for M series belts because at the moment I'm only guessing what the PCD of a M pulley is so getting the size right to get the speed right is still not straight forward.

Incidentally, now that it has been established that a 7" wheel is too big for this machine, does anyone have a use for one? 7" OD, 31mm ID, 1/2" thick, white.

Michael

Michael
Yes, I could use the 7" by 1/2" wheel for my surface grinder.
regards
Bruce

Originally Posted by Abratool

Yes, I could use the 7" by 1/2" wheel for my surface grinder.
regards
Bruce

It's yours. I'll post it early next week if I can.

Originally Posted by WCD

I do have data on M series sheave dimensions ...somewhere.
In the mean time, I believe the geometry of 'conventional' v-belts is consistent across the size range (M, A, B, C etc).
Given that the nominal width of an A series belt is 1/2 inch, and an M series belt is 3/8 inch wide, you should be able to simply scale down the sheave dimension data for A series belt drives to get the data for M series drives. I presume the info you need is sheave OD vs PCD, so multiplying A series dimensions by 0.75 should get you close to the mark. Or was that your guessing procedure?

Yes - that was my guessing. For A series I know the PCD is a 1/4" less than the pulley OD. 3/16" sounds reasonable but it would be good to have that confirmed (Hmm. Rule of thumb? - half the belt width is the amount taken from the pulley OD for the PCD. Can anyone confirm that for other sizes?). I've seen angles listed for belts as 38 and 40 degrees but pulley angles of slightly less than that, so all the geometry you can muster please.

Michael

Haven't got time to post more ATM but the motor pulley is 3.75" dia. I pulled mine out yesterday.

I still think the spindle pulley is very close to 2" dia.

As my motor is definitely original and 2800 rpm you can calculate spindle speed from that.

Can't get the pulley groove dimensions until maybe Monday or Tuesday but I can get them next week.

The base of mine is full of crap but mainly grinding dust etc.

I took off the motor connection block cover out of interest, to see if all 6 wires had been brought out. No, only 3, but it was a good thing I looked. The wiring from the motor to the switch (running through flex conduit) was the old rubber insulated type and - it had serious rubber rot just like the belt. In fact the rubber rot was so bad there was *no* insulation on the wires which were resting against the motor casing.

Might have dodged a bullet there....

Still the bloke I bought it off had never used it (some 'projects' get moved on many times) and at the price I paid, I still think it was a bargain. They're quite robust little machines.

PDW