Dusting off the cobwebs

[Mac]

Thanks for the suggestions, Guys!

I did a bit of searching on the web last night, and it seems likely that the product I used was a latex based adhesive. It's still being made, but not marketed in convenient squeeze bottles like the one I had.

https://www.freemansupply.com/products/ ... isc-cement



There are also stripable contact adhesives. Klingspor markets one.





The thing that most folks seem to default to is 3m's Feathering disc adhesive. It's a stripable adhesive that the auto body guys use for their discs. I watched a knifemaking video about it here, https://www.youtube.com/watch?v=U22HcM-cEHw and it seems like the sort of thing I need.



I've just been on the phone with my local Napa auto parts store, and they will have a tube of this stuff for my tomorrow morning.



Mac

[John Vernier]

I used the 3M feathering disc adhesive for a while years ago, before I could readily get PSA discs. It probably will work fine for you. I recall that it would remain an 'easy peel' adhesive for some time after application - a day or two - after which it became necessary to scrape the old disc off the pad, maybe using some solvent. Of course I was using cheap crappy paper-backed discs at that point.

[Jeremy.G]

Hey Mac,
I really like the spindle setup on your grinder shaft (with the 5/8x11 and the 'lock' bolt on end)
Is that something you found, or machined yourself?

[Mac]

I recall that it would remain an 'easy peel' adhesive for some time after application - a day or two - after which it became necessary to scrape the old disc off the pad, maybe using some solvent.

I am hoping that the stuff does not build up too much or require complete solvent removal too often.

That's the whole thing about these abrasive products and processes. There's so much experimentation to do, and nothing is ever cheep. Nor can you just go to the local Home Despot and get what you need, so there's always lag time and down time while you wait for the next (expensive) product to test.

Mac

[Mac]

Hey Mac,
I really like the spindle setup on your grinder shaft (with the 5/8x11 and the 'lock' bolt on end)
Is that something you found, or machined yourself?

I made that shaft on the lathe a number of years ago. I think that this one is the forth shaft I have had on this machine. The first two were cheep commercially available parts from polishing arbors like this one.



Mac

[Mac]

I got a box of goodies from Supergrit today. There are a couple of cork belts, a Trizact belt, some graphite cloth and a couple of backing pads in 5 and 6 inch.

So... I'll be doing more abrasive testing this evening.

First, though, I thought I would show what has to happen to the backing pads before they are fit to use. Just like those grinding discs I showed a couple of days ago, they have to be made to run true. Here is what the 6incher looks like in motion. It's out by over 1/16"!



On these guys, it's the face that gets chalked, rather than the back. I'm using blackboard chalk here, because it goes on better than the welder's chalk (soapstone). You can us a water soluble felt tip marker if you want, but this is what came to hand.



It's pretty much the same sort of thing as the grinding discs, but with two differences. The first that we don't have very free access to the mounting surface, and have to content ourselves to scratching away with the end of a small file. The second (and this is easy to forget) is that since the marks were made on the face, rather than the back, we need to remove material on the same side as the mark, rather than the opposite side.... Think it through... I always have to.



When you get it so that the marks show on both sides of the pad, that's the best you can do. I wish they would make these things to higher standards, but for most other craftsman's applications, it just does not matter. So, we get what we get, and have to be glad of it.



Mac

[Ungman]

I´ve always been a silent follower of your awesome work Mac and I really appreciate how much I learn from this thread!

I was just thinking, would it not be easier to glue a large washer on the surface and file that down when you can access the whole surface properly, or is there a downside to that?

//Erik

[Mac]

I was just thinking, would it not be easier to glue a large washer on the surface and file that down when you can access the whole surface properly, or is there a downside to that?

//Erik

If I understand you correctly, there are two things that make that idea troublesome. The first is making sure that the washer ends up in the correct orientation with respect to the pad. You could glue it in place with CA or epoxy, but that brings us to the second problem. If you fasten the washer down, you only get one shot at removing the correct amount of material.

Now.... perhaps one could introduce a locating pin on the bearing seat on the pad, and have a hole in the washer so that it ended up in the same place every time. (or vise versa, which may be easier) That would work, but it might well be more trouble than doing it the way I did.

Having thought about this a bit, I wonder if I am going about it all wrong. Maybe I need temporarily affix the backing pad to a faceplate on the lathe, and turn the seat true to that. Hmmm..... The only problem I see there is the difficulty (not insurmountable) of getting the pad's shaft to be coaxial to the lathe arbor. Ya know... the more I think about that, the better I like it.

Mac

[Sean Powell]

Having thought about this a bit, I wonder if I am going about it all wrong. Maybe I need temporarily affix the backing pad to a faceplate on the lathe, and turn the seat true to that. Hmmm..... The only problem I see there is the difficulty (not insurmountable) of getting the pad's shaft to be coaxial to the lathe arbor. Ya know... the more I think about that, the better I like it.

Mac

If you have a flat platen you can attach to the lathe spindle, especially one with concentric circles then all you need to do is mark north or 12o'clock and use a dial indicator on a magnetic base to find the high and low points. They should be opposite each other. Then shift the workpiece half the difference. repeat until you are within a few thousandths.

I'm not certain how you can attach the pad that will be stable enough to true up the socket. aren't the pads flexible and won't the socket move with pad flex while cutting it?

Before I bothered with truing up a pad I'd probably find the high point and then see if adding some shim-stock to the opposite side would correct things. Paper is ~.003" thick so that's sticky-notes. Scotch tape is ~.0015" thick. Either can be added or removed from the shoulder of the arbor with minimum fuss.

Luck!
Sean

[Mac]

If you have a flat platen you can attach to the lathe spindle, especially one with concentric circles then all you need to do is mark north or 12o'clock and use a dial indicator on a magnetic base to find the high and low points. They should be opposite each other. Then shift the workpiece half the difference. repeat until you are within a few thousandths.

I think I would chuck the disc or the backing pad into the tailstock and use the tailstock ram to offer it up to an adhesive surface on a true faceplate. That aught to get it close enough to concentric for the purpose.

I'm not certain how you can attach the pad that will be stable enough to true up the socket. aren't the pads flexible and won't the socket move with pad flex while cutting it?

On the packing pads, the seating surface is typically an aluminum plate. That should cut easily enough that the inherent flexibility of the pad would not be a problem. Only one way to find out.

Mac

[Mac]

I was going to try that procedure for for truing backing pads on the two 5" hook and loop pads I just got from Ebay. Unfortunately, the pads are defective in manufacture.... or something. They are labeled 5/16"-24, but they only thread about half 2/3 of the way into my arbor. When I check with a thread pitch gauge, I see that they are more like 25 TPI than 24. That sounds like it might be M-6, but they are too big to enter a die of that size.

In any case, I have opened a dispute with the Ebay vendor. I was sort of wondering why he had them so cheep....

Mac

[Arrakis]

Do you have access to a vertical mill? Could you mount the discs face-down flat on the mill table and just bring an end mill across perpendicular to the front face to true up the mating surface?

[Mac]

I was out of town for a week to visit my folks in sunny Fla., but I'm back and returning my attention to the grinding and sanding. Most of that is pretty boring and hard to photograph, but today I started the filework on the demigreaves and demicuisses.

Here are the demigreaves, along with the test piece I made up months ago.



I drew in some guidelines with a sharpy to indicate where to remove metal.....



.... and started in with the Dremel tool.



When the edges were roughly shaped, it was time for the file.



The tempered steel cuts pretty nicely under a good sharp file. It's a bit like sharpening a saw, but perhaps a bit softer than that, and a good deal quieter. I used an "extra slim" three-square file for the job, but a fine mill file would have done as well.



I started in on the demicuisses, but only got as far as dremeling out one of them tonight.



Mac

[Mac]

Do you have access to a vertical mill? Could you mount the discs face-down flat on the mill table and just bring an end mill across perpendicular to the front face to true up the mating surface?

Sometimes I think I'd like a mill, but I don't have one. There are some more backing pads on the way, and I will probably try truing them up on the lathe.

Mac

[RandallMoffett]

Mac,

Your work is so impressive that I am lost for words. Just amazing. I love how much detail you have put into the decoration. Just amazing!

RPM

[Mac]

Randal,

Nothing I'm doing here is really "hard". It's fussy and there is a lot of it, but really, anyone who dedicates themselves to the craft can do it. It's all about breaking the task down into manageable steps and performing them in a reasonable order. None of the details is really "perfect", but the overall effect tends to mask that.

Mac

[Sean Powell]

Do you have access to a vertical mill? Could you mount the discs face-down flat on the mill table and just bring an end mill across perpendicular to the front face to true up the mating surface?

Sometimes I think I'd like a mill, but I don't have one. There are some more backing pads on the way, and I will probably try truing them up on the lathe.

Mac

Given that I spec things out for milling operations, I wouldn't spec this one out to a milling shop. The radius of curvature changes both in plane and through plane. The mill geometry that would be good on a straight flat section wouldn't necessarily work well on on a concave or convex curve. Same applies to a grinding disk with a special profile edge.

My default sense is to wire EDM as the thin material will cut quickly and each arc can be a custom shape... but that's not much different than a really really aggressive dremel wheel.

[Sean Powell]

Hey Mac,
I really like the spindle setup on your grinder shaft (with the 5/8x11 and the 'lock' bolt on end)
Is that something you found, or machined yourself?

I made that shaft on the lathe a number of years ago. I think that this one is the forth shaft I have had on this machine. The first two were cheep commercially available parts from polishing arbors like this one.



Mac

Another polishing arbor
http://www.ebay.com/itm/like/2816045437 ... ps&lpid=82

But it doesn't have Mac's drilled and tapped internal threads. I could add a second nut or thin jam-nut to mine instead.

Sean

[Mac]

I picked up where I left off last night by dremeling the other demicuise. Then I took the file to the fist one. I find myself switching the file back and forth between hands a lot more than I used to. This is probably a good practice, really.



I used the "three square" for most of it, but switched over to a small "barrette" file for the petals of the fleurs because I needed something narrower.

Here is what the filed one looks like next to the one that is only dremeled. The bevels look darker than one might expect because I ran the edges over a fine wire wheel to worry the filling burs away.



I'm taking a little break before doing the other one. I am so afraid of repetitive injuries these days that it has made a total wimp out of me.

Mac

[Mac]

Another polishing arbor
http://www.ebay.com/itm/like/2816045437 ... ps&lpid=82

But it doesn't have Mac's drilled and tapped internal threads. I could add a second nut or thin jam-nut to mine instead.

Sean

That's probably a very useful machine in its own right, but it's too fast for anything but buffing.

Can a motor like that be slowed down with some sort of digital magic? If so, will it have much torque?

Mac

[Sean Powell]

Another polishing arbor
http://www.ebay.com/itm/like/2816045437 ... ps&lpid=82

But it doesn't have Mac's drilled and tapped internal threads. I could add a second nut or thin jam-nut to mine instead.

Sean

That's probably a very useful machine in its own right, but it's too fast for anything but buffing.

Can a motor like that be slowed down with some sort of digital magic? If so, will it have much torque?

Mac

There is no motor. It's belt driven with a 3-stage pulley. Belt can come out the back or straight down. Mine is connected to a 1750rpm 1.5hp (from memory) that also has a 3-stage pulley. I can go from ~600rmp to ~5000rpm by playing 3:1, 2:1, 3:2, 1:1, 2:3, 1:2 or 1:3 with the belt. This pic isn't clear but you can see the motor with the light switch below the buffer in this picture.

http://i161.photobucket.com/albums/t239 ... 010547.jpg

Sean

[Mac]

Ah! No wonder it seemed so affordable!

It looks like a much better sort of arbor than the one I started with.

Mac

[Jeremy.G]

I've been looking at a lot of those lately. The trick (for me) is finding one with the 5/8-11 threads so I can mount a grinding disk like our friend Mac here. Tho, I would need to put a couple backing nuts behind the disk as Sean mentioned. Hopefully that would be enough to tighten the disk against.

The only arbor I've found that advertises the 5/8-11 threads is one by Grizzly. I wonder how the Shop Fox is threaded? It does look pretty nice...

[Mac]

It sort of looks like 1/2"-20 on both sides.

If I were building a grinder around that, I would start by turning a new shaft on the lathe. The alternative is to turn up an adapter that threads onto the end of the shaft. If the socket of the adapter is were about three shaft diameters deep and the threads were tight, it might run true enough.

Mac

[Jeremy.G]

No lathe for me I'm afraid. I'll have to build my grinder from parts "off the shelf".

Here's the arbor I've been eyeing lately. I think it's got the threads I'm looking for:

http://www.grizzly.com/products/Bench-M ... ring/G5549

[Mac]

That has 2/8"-11, but if you want to mount a grinding disc on it you need a shoulder for the disc to seat against. A pair of nuts tightened against one another might render a shoulder that ran true. If it didn't, you might be able to true it in place with a graver and a steady hand.

I guess I would use lock nuts for that, so they would not work loose. This sort here....



...rather than the Nylock sort. I'd also bathe them in an anaerobic thread locker for good measure.

Mac

[Mac]

I got some goodies in the mail today! The good folks at Cincinnati Dowel and Wood Products have sent me some 180 grit 5" diameter wavy edged discs. I have been cutting my own waves in my discs, and this will be a welcome relief.



The fleurs are pretty much done the demi-cuisses. I hope to go back and touch them up some day when I feel fresh, but for now this is how they look.



I spent the rest of the day searching for the best way to get from 180gr. to black emery. There is a great gulf fixed 'tween them. My 3M deburring wheel (8S Fn..... that's "8" hardness, Silicon carbide, Fine grit) will do the job, but it is slow going and requires a lot of pressure. I hope to find something a bit easier, but find myself thwarted. Everything else I try is either too course for the jump to the sisal buff, or else it won't remove the 180gr. scratches. I have a tiny 3M 5A Fn ("5" hardness, Aluminum Oxide, Fine grit) wheel that seems to do the job, but I can't find a big one for love or money.

Mac

[Mac]

Pursuant to my above quandary about not being able to find a large 3M 5A Fn wheel.... I don't know if the important thing is that the 5A Fn is softer than the 8A Fn or whether the aluminum oxide is more aggressive than the silicon carbide. So, I have ordered up two different wheels form Ebay vendors to test. The one is a 7S Fn, which will be softer, but with the same grit. The other is an 8A Fn, which is the same density, but with a different grit. When those arrive I will have to make up aluminum mounting hubs on the lathe before I can put them to the test.

Mac

[Mac]

I started polishing the knee lames this evening as a sort of test. The jumping off point is a 320 belt which has been "greased" with black emery cake. From there it's BE on a sisal buff.

The going is slow, and I am having trouble getting all the scratches out. I am also getting too much abrasive on my side of my respirator. I am contemplating taking a drastic measure..... that is shave my beard to get a better fit with the respirator.

Mac

[coreythompsonhm]

Is it a full face respirator? If so, one of those respirator hoods would help.

[Andrew Bodley]

Getting a goo face fit with aaabeard is very difficult. I like using the 3m air feed respirators. Expensive new but they do come up cheap on evil bay. Think I paid about £100 for mine. Just check that you can still buy spare.
The visor never fogs up, in summer you have a cool breeze over your face. Only avoid farting it wearing the filter pack on your belt.
Andrew

[Mac]

I just had a look at full face respirators on Ebay. For the most part, it looks like I would be trading a beard-seal problem for a glasses-seal problem.

I'll go back and see if I can find the type that Andrew B recommends.

Mac

[Andrew Bodley]

If you look for any of the versaflo or Jupiter 3m models. There are different face masks available depending on protection required. The can also be used with the speed glass welding make with the appropriate filters.
Andrew

[Kristoffer]

I have this:



And it is great. I neither have a beard nor glasses but I believe both would fit. If you consider buying it I could do some tests for you.

Its pretty expensive but I am sure ebay could produce something for you.

[Mac]

I've just spent some time cleaning and messing with my respirator. I am pretty sure that my exhaust valve is not closing tightly. There's no sense worrying about the beard if air can come in through the exhaust.

It's one of these.



The face piece fits comfortably enough, and I think it is sealing as well there as can be hoped. I think I'll try to find a replacement for the valve an see if that improves things.

Mac