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Yet another use for the BGM-100

Started by tgbto, March 27, 2023, 08:53:53 AM

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tgbto

Here's my setup for quick reprofiling of heavily damaged knives, or for convexing. The BGM-100 + FVB combo is admittedly more expensive than the cheap, small belt sander, but it does the job. For large knives, I use the larger USB.

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Cheers,

Nick.

3D Anvil

Great idea!  I use the same machine with leather belts for deburring and honing.  That system depends on one's ability to hold a blade perfectly level, which is not so easy if you're trying to hold an angle with less than 1° variation. 

tgbto

Definitely, I'd even say that whatever slack is in the belt will make for a deviation of more than 1°, especially with the non-stiff belts. However this setup allows for greatly increasing the consistency compared to using it handheld: the edge remains more easily in the same place on the belt, and according to an eyeballed measurement with an anglecube the jig shaft remains horizontal well within a degree.

Aside from very specific cases (blades that need to be convexed, or if I have like 5 minutes to get a blunt piece of steel to 15-18 dps around 100 BESS), I set the angle @-1.5dps compared to my target edgle angle and finish the knives up on the Tormek using the standard SG + leather honing wheel with PA-70 routine. I quickly get a burr on the Tormek this way, and the microscope does not show a significant secondary bevel, so the apex angle is about right.

And my favorite option for honing with this setup is ... the leather belt with PA-70. I found that with the micro-mesh belts on standard stainless steel knives I would end up with a foil edge that gets folded from side to side and not really cut. The fabric belts with PA-70 or diamond spray work quite well too.

The next step is to add a vacuum table because there quite a lot of metal dust flying around, especially when doing heavy-duty reshaping (repairing broken blades, heavy thinning, etc.).


3D Anvil

I also use PA-70 with leather belts.  Perfect for kitchen knives and low-carbide folding knives.  For wear-resistant steels I start with a leather belt using 2 micron or .5 micron diamond and then finish with PA-70.  But I almost always sharpen on the Tormek first.  With CBN or diamond wheels I find it to be just as fast as the Worksharp, with better results and no chance of overheating.

Sir Amwell

Interesting.
Like 3D, for low end knives I generally set an edge on the T8 and hone on leather with Tormek paste on the WSKO. It's always a bit of guess work to find correct honing angle on the belt, especially taking into consideration the taper of the blade.
I guess this set up could take out some guesswork but I'm wondering how you set the angle here?
Are you setting the belt at a particular angle and ensuring the usb is set so that the tip of the blade is hitting perpendicular?
Or somehow using a calculator?
Some clarification would be handy. Thanks.

3D Anvil

I recently started using a Sharpie to confirm the right honing angle with the WS, which was illuminating.  Seems I'm pretty good at nailing it on my right side, but what *looks* to be horizontal on my left side is actually a degree or two too shallow.  Now that I know that I can compensate and I get a more consistent result.  Lord knows why I waited so long to try this.   :-\

tgbto

#6
Quote from: Sir Amwell on March 28, 2023, 12:25:40 AMInteresting.
Like 3D, for low end knives I generally set an edge on the T8 and hone on leather with Tormek paste on the WSKO. It's always a bit of guess work to find correct honing angle on the belt, especially taking into consideration the taper of the blade.
I guess this set up could take out some guesswork but I'm wondering how you set the angle here?
Are you setting the belt at a particular angle and ensuring the usb is set so that the tip of the blade is hitting perpendicular?
Or somehow using a calculator?
Some clarification would be handy. Thanks.

I use an anglecube twice, referenced to the horizontal surface you're supposed to lay your knife on :
- once to set the angle between horizontal and the pulleys (the angle indicated by the dial is rather consistent with the measure). I set it @-1.5 target dps because that's what seems to compensate for the slack in the stiff belts, and I don't mind the increased angle for honing on more flexible belts
- a second time, after I've set up the blade in the jig and the position where it will contact the belt. I put it on the blade if I can (and average the top and bottom measurements), or on a block on the shaft of the jig if I can't. The goal being to have a 0° angle this time.

Quote from: 3D Anvil on March 28, 2023, 12:59:06 AMI recently started using a Sharpie to confirm the right honing angle with the WS, which was illuminating.  Seems I'm pretty good at nailing it on my right side, but what *looks* to be horizontal on my left side is actually a degree or two too shallow.  Now that I know that I can compensate and I get a more consistent result.  Lord knows why I waited so long to try this.   :-\

I found - using a sharpie as well - that I had both the tendency you describe and a proneness to twisting my wrist slightly on long, curved blades. The BGM/FVB/USB setup allows me to consistently get sub-100 BESS which didn't happen before.

cbwx34

FWIW, someone made a 3D file of a horizontal surface that you can mount right next to the belt...

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https://cults3d.com/en/3d-model/tool/work-sharp-ken-onion-blade-grinder-riser-2-5-with-slider-thinner-potranko28-2
Knife Sharpening Angle Calculator-(Works on any platform)
(or Click HERE to see other calculators available)

3D Anvil

The tool rest idea is pretty clever.  I need to get me a 3D printer.

RickKrung

#9
This is a bit of an old post, but I have just recently done something quite similar, using a Vevor 1x30 Belt Grinder.  These pictures only show the setup with the XB-100, the MB-120 and a USB, but it should be clear enough. 

I've tried using the platform pictured for freehand knife sharpening, both edge-trailing and edge-leading.  I've never liked free-hand and this is not much different.  Hard to keep the blade in position on the platform when in edge-trailing (the safer manner).  Not bad edge-leading.  The Vevor variable speed can bring the belt speed down to about 2/3 the surface speed of a 10" Tormek wheel, but I've been using it a good bit faster than that. 

Using a knife in a Tormek knife jig is much better, pretty much just like using one on a Tormek, edge-trailing (which I just about only do for honing). Edge-trailing, the belt keeps the knife/jig combo in position and the grinding motion/action is just like on a Tormek, except narrower working surface.  Have not tried it edge-leading, but I suspect it will have the same issue with holding position as does free-hand edge-trailing.  Maybe that is just a muscle memory thing that can be learned-away. 

I do not plan on abandoning my T8.  This belt grinder is intended to replace two other belt grinders and two bench grinders, at least as far a presence in my one-car garage shop is concerned.  Just not enough space for all that I had when in a two-car garage.  The belt grinder will live and play in the garage shop. The T8 lives and plays in the back bedroom, that I've turned into a workroom.  I do not want grinding dust from any belt or bench grinder in the workroom. 

Thought I'd check sharpness on the one knife done so far, in setup and testing.  Using only a 100 grit Cubitron belt (@15ºdps), honing on the T8 composite honing wheel at (+2º), finishing on a hanging leather strop:

BESS sharpness tester, grams of force:
After grinding, with burr:  650
After honing:                173
After leather strop:        113
Quality is like buying oats.  If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.