Summer Project #5: Back To The Grind, Completed!

Joined: January 1st, 1970, 12:00 am

May 24th, 2018, 8:41 am #1

Yep, adding more fuel to the fire! 😁

Very nearly a decade ago (!) I downloaded some free plans for a DIY "KMG" style 2x72" belt grinder, intending to build myself one. I bought the steel from one of the local suppliers, and... well, let's just say I proceeded to work on it in my spare time. 😋

I'd managed to assemble the main frame and mill part of the slack-belt platen by 2010, and a year after that had found a motor and made a pulley.

Apart from collecting a couple of contact wheels, snagging a bag of miscellaneous belts by lucky chance from the local secondhand shop, and moving the pile of parts around at least a dozen times in the intervening years, that's about as far as I got.

I have decided that, due in no small part to the happy circumstance of getting some of the big parts ground, finally, that I would spend some time this summer endeavoring to also complete (or at least make significant gains upon) several of these other half-finished projects of mine, that I'm in many cases truly sick and bloody tired of looking at. 😁

The grinder, besides being a tool I could have used many dozens of times over the years, is also largely complete, just needing finish machining on several of the parts. And since I don't even have to "invent" anything, I just have to follow the instructions in the plans, it should be quick and simple.

So, this afternoon, after completing and mailing my customer tasks for the day, I sat down to figure out what needed to be done next. Here's how it looked, and how it has looked for five or six years now, sitting off in a corner:




While I still had the plans printed out in the shop files, and a copy saved to my archive drives, it was lucky that I'd marked each piece back in the day- that helped me keep track of the pieces, and not wind up using them on some other project.



I only had a short while to spare (and even that only thanks to being 'stuck' while some paint dries) so today it was just the tensioner/idler arm. First, the upright support was slotted, drilled and tapped...



And what will become the arm itself drilled, tapped and countersunk.



And assembled:



The four holes will hold an adjustable pivoting block which will control the belt tracking, and a spring underneath will put tension on the belt. (A common mod I recall from back in the day is to use a "gas spring" cylinder- I may try and pick one up if I can fins a short, stiff one. The regular spring apparently tends to pop out or kink.)

The black handle is something I spotted at that same secondhand store many years ago, and picked up specifically for this. The small serrated contact wheel was... donated? Or I bought from? A Guild regular, roughly half a million years ago. There's also a larger 8" wheel I bought last year, off another board.

Apart from possibly the gas springs (or a regular spring) the only thing I need is a VFD for the 3-phase motor. And I either need to buy a 'spensive sealed one, or I'll have to also get an enclosure of some sort for it, to keep the grinding grit and dust out of it.

Doc.
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Joined: September 16th, 2014, 7:01 am

May 24th, 2018, 7:05 pm #2

You're going to have to build a shop addition just so you have a "clean side" for paint booth and assembly tables and a "dirty side" for grinding blasting sanding and welding, and the shaper, lathes and mills go somewhere in between. 

Perhaps pour a simple footing and drop a 40' Container or two outside?  The Reefer style should also be cheaper to heat in the winter...
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Joined: January 1st, 1970, 12:00 am

May 24th, 2018, 7:59 pm #3

Yeah, that's starting to be an issue all right.

The primary plan is to have the machine on a cart, kind of like a hand truck. When set down, it's on solid feet, but when tipped back, it's on a set of rubber wheels, and can be moved around like a load on a hand truck. And for any serious grinding job, just roll it outside and do the work out on the shop apron.

Rainy days and winter days obviously put a damper on that kind of thing, so I'm looking into picking up another dust extractor like the woodworkers use, and setting it up specifically for this thing.

The problem there is the classic "thermite" issue. Grind both aluminum and steel on the same machine, and let it all collect in the same bag, and you form a crude thermite. Too many sparks from the next steel-grinding job could then set it off, causing a serious fire.

So what's the fix? Get two dust collectors, and set each one up for separate materials? I was considering using a dust-collector style squirrel-cage fan, and just venting it straight outside. That makes for an easy setup and use, with the only real drawback being that during long grinding sessions, it'll pull a lot of the warm air out of the shop on a cold winter day.

The dual-material thing might work with a pair of trash-can cyclonic separators. One blower and bag, but two separators- wouldn't be perfect, as some dusts will still get into and mix in the bag, but the steel-can separators also act as a pretty good spark-arrestor.

I'd love to have a "dirty room" specifically for the grinders and welders and whatnot, but I simply don't have the room, and definitely don't have the funds to build any kind of an addition or outbuilding. (Local connex prices are $4K for a 40-footer, plus delivery, plus a gravel or concrete pad, plus insulation, plus heating, lighting and electrical, etc.)

Doc.
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Joined: July 12th, 2017, 12:19 am

May 24th, 2018, 8:09 pm #4

Hey Doc;

You may want to look at something like this: http://www.rockler.com/workbench-caster-kit-4-pack

You push them down and it rolls around, left them up and the machine sits on it's own feet (i.e. NOT a locking caster). Biggest drawback, they're only rated for 100 lbs each. I suspect 400 lbs wouldn't do it for a lot of your toys.

Tim
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Joined: January 1st, 1970, 12:00 am

May 24th, 2018, 9:04 pm #5

TimoRu wrote:You may want to look at something like this: http://www.rockler.com/workbench-caster-kit-4-pack
-The problem with something like that is my floor is not the most level, nor is it always the cleanest, despite my best attempts. There's also a nearly 2" lip between the garage floor and the concrete apron outside (or a door sill going through the man door.)

I need a bigger, softer tire to make moving it around easier.

The problem with my setup is that the grinder will be top-heavy. I may have to redesign the system to mount the motor lower.

Doc.
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Joined: August 16th, 2016, 11:47 am

May 24th, 2018, 10:17 pm #6

Re mixing dusts: Somewhere in the back of my ravaged memory is a "water pipe" type of dust collection. Used a shop vac and plastic trash can inside a galvanized trash can. Plastic held water, galvanized didn't crush due to vacuum. Long pipe from dust source to below water level. Hose out to vac from above water level. Stopped sparks from getting to paper filter on vac.
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Joined: January 1st, 1970, 12:00 am

May 24th, 2018, 11:21 pm #7

I see a lot of knife makers basically forego any dust collection at all, and just have a sheetmetal chute under the wheel to aim the sparks at a plastic bucket that has about 6" of water in it.

Of course, they also tend to have a closed or dedicated "grinder room", and will of course wear a respirator as they're working. (And generally don't have to worry about mixing dusts- they do 98% of their work in one manner or another of steel.)

Doc.
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Joined: January 1st, 1970, 12:00 am

May 27th, 2018, 7:33 am #8

Part of today's distraction was getting the belt tracking mechanism put together.



A pivoting mount, another idler wheel (that I'd machined roughly seven or eight years ago 😁 ) and a quickie adjuster knob. After that, for the first time in, like, ever, I was finally able to mock it up with an actual belt!



No, we're still a ways from makin' sparks with it, sorry. We still need a spring for the tensioner, the tool rest, a mounting pad for the motor, a clamping bolt for the tool arms, wiring for the motor, and a few other things.

But like all these projects, I just need to keep chewing away at them. 😁

Doc.
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Joined: January 1st, 1970, 12:00 am

June 2nd, 2018, 8:12 am #9

Getting back to this for a moment, I was temporarily stuck last weekend, when I discovered I was short a bearing. The two idler wheels on the working head of the machine each have two bearings, lightly pressed into a turned aluminum roller.

Well, as I was assembling everything again- for the first time in years- I discovered one roller was empty. I was pretty sure I had bearings in both rollers at one point, but I looked around where I'd stashed all the grinder parts, and they weren't there.

Well, it's been years since I really last did anything with this, and it's been moved a couple of times over those years too, so I figured I'd lost or misplaced them somehow, and went ahead and ordered two more bearings.

Fast forward a bit to Wednesday, and I was cleaning the shop, which, as I've said, is an absolute wreck in large part because I had to heavily dismantle three major machines, AND move stuff around to have access to move the parts in and out. Just generally putting tools away, picking up random offcuts or old parts, putting away pieces, organizing, etc. Typical stuff.

Well, I had a lot of junk in the chip tray of the Logan lathe, as that is all-too-convenient a spot to set stuff when working with the Exacto mill. As I was picking up those tools, I looked at some of my mods in a wistful, I-really-need-to-get-back-to-this-one-too way, and a little lightbulb when on in my head.

That's where those bearings went. These bearings! 😆

I can't recall how or why, but at some point one of the grinder rollers wound up on my workbench- I took it off for some reason, and now can't remember why. (I can damn near hide my own easter eggs these days.😋 ) The bearings weren't a tight press fit, and either slid out or I'd tapped them out for some reason, and so were sitting at the back of my bench, near the roller, for several years.

I used them for the encoder mount having completely forgotten the reason for them or why they were there.

No big, really, had plenty to do in the meantime while waiting for the replacements.

At some point over the week, I put together the tool rest- a chunk of plate and a chunk of bar, the bar gets a slot for adjustment, the plate gets bolted to it. Well, there's no reason for the bolts as opposed to other methods of joining the pieces, so I got out the TIG and just ran a couple beads instead of drilling and tapping (as the instructions suggest) three countersunk 1/4"-20 bolts.



20 minutes drilling and tapping, or 90 seconds welding. Go fig.

That bolts on like so, using holes I put in there about 10 years ago.



And then a bit later in the week, I did the platen and mount.



The "platen" is simply the working surface- the flat plate behind the belt that you can push the work into, without causing the belt to bow inward and grind your part round. That flat face- as opposed to a round contact wheel- is why some people call these "square wheel" grinders.

It's worth noting that people do, in fact, deliberately run without a platen for certain jobs- called "slack belt" grinding- specifically TO cause rounded surfaces, in order to make smoother, more flowing parts.

Anyway, the platen mount is a simple chunk of angle with a couple slots in it...



Although this one of several errors I've found with this set of instructions (which admittedly I downloaded a decade ago- they may well have been corrected since then.) The dimensioned drawings for this piece to be 7.5" long, and the platen bar to be 8" long. The "parts list" given- a "shopping list" for you to take to the steel supplier- lists these pieces as 6" and 7".

I made do. The platen is "consumable"- the backside of the belt eventually wears the platen face, eventually making it "cupped" right at the level of the tool rest. So it's supplied as a separate piece, which can be swapped or replaced as necessary. (People make ceramic heat-resistant platens, and/or offer stick on low-friction sheets to help reduce heat buildup. I may try one or the other eventually, but that kind of thing tends to be only important to knifemakers and others who put five or six hours at a stretch on their machine every day.)

The mount bolts on like so...



And the platen face itself just gets the ends ground at a fair radius to smooth the belt transition, and two holes drilled and tapped in it.



That bolts onto the mount like so...



Which gives us this- which will win no prizes for beauty and sophistication, but is sure starting to look a lot like a real live grinder now. 😁



Doc.
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Joined: January 1st, 1970, 12:00 am

June 5th, 2018, 5:25 am #10

At this point the main frame is just about done, needing only two more things: The tensioner spring, and a way to lock the sliding tool arm.

The spring was first- I'd already picked up a suitable-appearing spring from the local hardware store, and the plans have a fairly simple way of affixing it: When the top plate of the tool arm holder was made, the instructions had me add this extra 1/2"-13 hole on the top. What you do is screw a short chunk of allthread in there, with a nut to lock it in, and a washer for the spring to seat on:



No, that's not a bolt sitting there upside down. 😁 The idea is, the extra length of the stud also helps retain the spring, and you can add or subtract nuts or washers to fine-tune the spring preload.

Now, I was supposed to have drilled a similar hole in the tensioner arm, but skipped that. Instead I turned up this plug out of a bit of offcut steel from my parts bin.



That, using a handy nearby MIG that just happens to be right there and set up, gets welded to the arm like about so.



Assembled, it looks like this:



Not the prettiest or best-engineered thing, but it works. After that, all that was left was to add a locking bolt to the tool arm. So I popped the side plate out of the tool arm holder assembly, and drilled a couple more 1/2"-13 holes in the side.



Then, for the time being, I just threw a spare bolt in there- I'll order a proper handled locking bolt shortly, but this gets us going.



And finally, for the first time, I can actually set the tool arm and tensioner, properly install a belt, and roughly set the tracking. There's still some small bits to be done, but the main chassis is effectively complete.



Too bad I don't need it anymore. 😁

Doc.
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