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Messages - Jan

#16
I hope the upgraded SW will be corrected soon again.

In the past KG was issuing incorrect sharpness certificates saying that 100 on BESS ≈ 1 micron. After some time and several interventions from different sites in the world it was corrected by dividing the apex width by five! The initial error was not a misprint, it was done intentionally. The motivation was to speak the language of the local customers. The current KG certificate is OK.

The great role of constructive feedback, provided e.g. by CBWX, is to keep everyone on track and help to avoid major mistakes, namely in the concept.

Jan
#17
CB, thanks for your analysis of the upgraded SW.

You are correct, but I am wondering why you did not mention that the upgraded SW still uses the old Dutchman formula? It is incomprehensible, isn't it?

Jan
#18
The jig is my prototype of a self-centring knife jig for Tormek which was inspired by the knife clamp for Lansky controlled-angle system. It was described here: https://forum.tormek.com/index.php?topic=3834.msg25694#msg25694

Jan
#19
Yes, CB, you are correct!  :)

For a knife maker it is nice to have the grind length under control. The picture shows how it was done. Initial belt grit was 40! After the heat treatment the blade is mounted in the jig in the same way for the finial grinding.

The knife design was inspired by Bob Loveless iconic 4" drop point knife.

Jan
#20
Last week I was shaping a new blade for an outdoor knife. I used the TormekCalc2 to calculate the length of the hollow grind (HR). My blade was 3 mm thick and for primary bevel angle of 3⁰ per side I calculated 14 mm length of the grind. The wheel diameter was 252.5 mm.

Jan
#21
Knife Sharpening / Re: Rock hard felt wheel
June 20, 2020, 09:17:54 AM
I agree with CB. I would look for an error in setting the angle for the felt wheel. You can also try to use an alternative sw, e.g. TormekCalc2. Good luck.

Jan
#22
HTK 706 includes Small knife jig also.  ;)

Jan
#23
JVH, thanks for sharing the updated version of TormekCalc2. Highly appreciated!

As an occasional knife maker I invite the new sheet with material parameters. I could imagine also basic heat treating info here.

Jan
#24
Knife Sharpening / Re: Polishing angle calc
June 02, 2020, 03:36:47 PM
Quote from: Gilles on June 02, 2020, 11:22:50 AM
Hi Jan,
This is exactly the conclusion that I have done from this study and you explain it very well: "The consequences are important, both, the real grinding angle and the real honing angle are biased in the same way. This allows successful deburring despite the fact that the bevel angles are biased. "

It is also interesting to notice the effect of thickness and the effect of tapered blade on the bevel angle asymmetry (grinding angle and bevel height).

Tapered blade angle have often more impact than the blade thickness itself. The thicker the blade is, the higher the tapered blade angle can be and the higher the asymmetry can be.

Gilles   

Gilles, thanks for your assurance, I am glad to see that we interpret the results in the same way!

As far as I know you are the first who geometrically described the impact of blade thickness and tapper on the bevel angle asymmetry. Those are things that affect everyday life of every Tormeker.

Thanks again for sharing your valuable Excel script with us! Highly appreciated!  :)

Jan
#25
Knife Sharpening / Re: Polishing angle calc
June 01, 2020, 09:27:15 PM
CB, you are talking about the sheet Polishing Angle, but I am talking about the sheet Thick Tapered Knife Edge.

In my example the honing angle is by 1.5⁰ larger than the grinding angle and for all realistic wheel diameters there is no danger that heel of the bevel could collide with the honing wheel. (I assume that the honing angle is larger than the minimum grinding angle.) 

The results from the sheet Thick Tapered Knife Edge clearly show that thick blade is source of bevel angle asymmetry which does not depend on stone diameter or the magnitude of the grinding angle. The consequences are important, both, the real grinding angle and the real honing angle are biased in the same way. This allows successful deburring despite the fact that the bevel angles are biased.

Jan

#26
Knife Sharpening / Re: Polishing angle calc
June 01, 2020, 11:49:17 AM
The Excel script Polishing Angle Calc is really useful tool. Recently I used the sheet Thick Tapered Knife Edge to quantify the impact of blade thickness on the bevel angles.

I assumed flat 4.5 mm (0.18") thick blade mounted in knife jig with projection distance of 139 mm and the USB set up geometrically for the grinding angle 15⁰. The script revealed that instead of the desired grinding angle 15⁰ we will get 15.5⁰ for the jig in the Up position and 14.5⁰ for the jig in the Down position. So the discrepancy between the desired grinding angle and the real grinding angle is 0.5⁰ for each side and does not depend on stone diameter or the magnitude of the grinding angle.

This has important consequences for advanced, jig guided, deburring. Assuming that the deburring wheel was geometrically set up to 16.5⁰ in reality we will hone 17⁰ for the jig in the Up position and 16⁰ for the jig in the Down position. It means that despite the fact that the bevel angles are slightly biased the deburring of each site will be done as intended.  :)

Jan
#27
Knife Sharpening / Re: Blade angle
May 25, 2020, 06:41:40 PM
James, I fully agree with the opinion expressed by CBWX. In my thinking grinding the edge of a blade is a trade-off between pivoting and handle lifting. In some situations raising the handle is enough in other situations pure pivoting is sufficient. In every day practice, I think, it is a combination of both.

This is in full compliance with Tormek handbook which shows pivoted blade whereas the text recommends to rise the knife handle near the tip.

Jan
#28
Knife Sharpening / Re: Polishing angle calc
May 24, 2020, 08:05:05 PM
I also use the USB top to stone distance because is simpler and more universal approach.

Jan
#29
Ken, all UPS cause some harmonic distortion of the voltage/current. Inexpensive UPS units usually have significant departure from sinusoidal form. See the attached picture! The inverter "chops" the voltage in square waveform output which is rich in harmonics. Passive filters can reduce the harmonic distortion to some 10% at full load.

More sophisticated and more expensive UPS units can produce almost pure sine AC voltage.

Jan

#30
Larry, thanks for sharing your issue with us.

When the problem continues also with the new Tormek machine than it is probably caused by the voltage generated by your inverter.

The inverter does not generate pure sine AC voltage but only quasi-sine AC voltage accompanied with spikes. This voltage unbalance can increase motor power consumption by 15 to 20%. This increase can lead to motor overheating. Common voltmeter is not able to detect the voltage unbalance.

My recommendations are:
1)   improve motor cooling by lowering the ambient temperature
2)   do not run the machine idle, because it generates more heat than under load.

Jan