That "DUH!" Moment. Can I fix it?

R

Rob!

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Feb 9, 2000
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Just got my 9" disc and mounting plate from (sort of) Beaumont Metal Works. It took some doing to get it here, but with some kind help from Darren Ellis, it arrived. I really liked the idea of the crowned disc keeping the blade off the far side of the disc as it spins.

Now that it's in hand, I realize this crown means it is actually a cone and doesn't have a single flat spot on it. Does anyone have any experience in using one of these - and as a secondary question, can I flatten it without a lathe or should I just write it off and start over with a flat plate?

The idea of this was to get better machine refinement of polish and to flatten scales, bolsters and other parts for best fit and finish. I'm pretty sure, flat sanding will be less than satisfactory on a cone. Am I missing something?

Thanks for any guidance.

Rob!
 
Rob! said:
Just got my 9" disc and mounting plate from (sort of) Beaumont Metal Works. It took some doing to get it here, but with some kind help from Darren Ellis, it arrived. I really liked the idea of the crowned disc keeping the blade off the far side of the disc as it spins.

Now that it's in hand, I realize this crown means it is actually a cone and doesn't have a single flat spot on it. Does anyone have any experience in using one of these - and as a secondary question, can I flatten it without a lathe or should I just write it off and start over with a flat plate?

The idea of this was to get better machine refinement of polish and to flatten scales, bolsters and other parts for best fit and finish. I'm pretty sure, flat sanding will be less than satisfactory on a cone. Am I missing something?

Thanks for any guidance.

Rob!
Click to expand...

Rob,
Is the entire surface area curved, or is it a straight surface that comes to a point in the center? I attached a drawing. Is it like drawing "A" or "B"? I exaggerated the curvature and angles in my drawings.
 

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scott: he's talking about curvature in the other direction, if it was really flat there'd be no way for it to wrap around, for exaggeration imagine if the disc was an icecream cone, even though it is 'flat' it's still gonna put a hollow grind into the object, albeit an extremely shallow one for the disc.

rob: I'd try it it before you write it off, since the angle is so shallow the hollow should be un-noticable, nothing is ever really flat anyway :)

You'd need to use a lathe to flatten it and get it perpendicular to the shaft, but I wouldn't do that, I bet someone would trade you a flat one.
 
Luke Sheridan said:
scott: he's talking about curvature in the other direction, if it was really flat there'd be no way for it to wrap around, for exaggeration imagine if the disc was an icecream cone, even though it is 'flat' it's still gonna put a hollow grind into the object, albeit an extremely shallow one for the disc.

rob: I'd try it it before you write it off, since the angle is so shallow the hollow should be un-noticable, nothing is ever really flat anyway :)

You'd need to use a lathe to flatten it and get it perpendicular to the shaft, but I wouldn't do that, I bet someone would trade you a flat one.
Click to expand...

In my mind, the part being ground would be making contact from the letter marked side in my drawing. Is that correct?
 
If you can take a photo with a straight edge from the outer edge of the disk to the center. That way we know what your dealing with and can offer help.
Chris
 
It's a straight 1degree taper. Like your "B" drawing Scott. In a perfect world, I think having both on their own motor would be the way to go. In my shop, I've got both, but with just one motor/controller. I've only been using the tapered one since I got it... haven't felt the need to switch back to the other.

For handle material, I use a fly cutter to get it flat and then lap it on my granite plate to get the surface finish I'm after.

I recommend you try it out before you decide you don't want it.

I personally love the tapered disc for finishing out flat grinds. :thumbup: :)
 
Well if its a 1 deg taper to the center then it should be flat everywhere from the center to the edge of the disk.
Meaning you should have 4.5 inch of usable flat on your disk, now if you were expecting to be using more than that then sell it to me and get something else.
Chris
 
But those 4.5" are going to be slightly dished. I don't see why the tapered disk is needed when you can run the blade on the outside of the disk? I have only used very small disk sander, and you just have to stay out of the center area and it works fine. Actualy a hole bored through the disk, and a nylon rod would be handy to rest against sometimes?
 
Thanks for all the guidance and suggestions. Yes, it is like picture B and yes, it has a straight line, but what I bougfht for was a flat plane. Any way you grind something like a bolster or scale, it's going to have - not just a radius, but a changing radius.

Now, this is a well made product, exactly as described. That's why I bought it in light of the manufacturer's reputation. Understand that I'm not upset at anyone but myself - but I'm now in a spot where I can either hand it to a machinist (reputation and capabilities unknown - or I can spring another $150 and order the correct thing this time. Either way, I'm feeling pretty stupid.

The radius is not really insignificant. You can see it with the naked eye just over the length of a credit card. I may set it up just to get a feel for what it's good for.

Thanks to those who suggested swapping, but it's not really practical since it costs so much to ship.

Thanks again. Just needed to share my "doh"!

Rob!
 
NickWheeler said:
It's a straight 1degree taper. Like your "B" drawing Scott. In a perfect world, I think having both on their own motor would be the way to go. In my shop, I've got both, but with just one motor/controller. I've only been using the tapered one since I got it... haven't felt the need to switch back to the other.

For handle material, I use a fly cutter to get it flat and then lap it on my granite plate to get the surface finish I'm after.

I recommend you try it out before you decide you don't want it.

I personally love the tapered disc for finishing out flat grinds. :thumbup: :)
Click to expand...

A couple of things, if you would, Nick...

Would you describe how you use the 1deg. disc to finish grind flat ground blades?

Do you have a picture of your two discs/one motor & controller set up you would be willing to put up?

Thanks, Nick...

Mike
 
Mike- I forgot I was going to take some pics for you back on that other thread.

I misspoke about my set-up. I didn't mean to say I have a set-up that runs two discs at once on one motor. I meant I've only got one motor, so I have to switch the discs out.

As far as the finish grinding... I just go to the disc between ascending grit belts on the belt grinder. I can try to take some pics of it the next time I grind a big blade. :)
 
Let me fry your noodle a bit more. Even with a flat disc, the outside is going faster than the inside, so it will always have a tendency to remove more material.;) But seriously, I don't think that we have to be quite that precise in most of our applications (unless your last name happens to be Wheeler) and if you have a job that requires that type of precision, then you probably need something other than a grinder or sander of any type to do it.
 
I could name at least 5 Mastersmiths that have and use that 1 degree tapered disk for finishing. The main thing to ask is are you capable of grinding that precise with a hand held item?
 
NickWheeler said:
Mike- I forgot I was going to take some pics for you back on that other thread.

I misspoke about my set-up. I didn't mean to say I have a set-up that runs two discs at once on one motor. I meant I've only got one motor, so I have to switch the discs out.

As far as the finish grinding... I just go to the disc between ascending grit belts on the belt grinder. I can try to take some pics of it the next time I grind a big blade. :)
Click to expand...

OK... I've get the 'switch disc' set-up now.

I've been trying to make a picture of grinding flat on a convex surface. I understand the blade only touches at the highest point unless held in that position a long time, which is unlikely. The problem is I've only ever seen a disc used to flatten (flat disc) and to finish short folder blades (same flat disc).

And thanks, Nick...

Mike
 
Will Leavitt said:
I could name at least 5 Mastersmiths that have and use that 1 degree tapered disk for finishing. The main thing to ask is are you capable of grinding that precise with a hand held item?
Click to expand...

Simply put yes. The effect is less near the outer edge - (greater radius, so less acute curve), but still unacceptable if I can see a visible gap along a short straight edge. Nearer the center, it will be just plain useless for flattening. I can see it might have value for polishing as long as it the piece was kept moving, but that is not my required application.

Rob!
 
$10-$14 bucks will ship the disk in a flat rate priority mail box. Seems a lot less than re-machining would be. Plus, two people get happy with the swap!
 
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