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Screwdriver Sharpening

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On 6/18/2018 at 12:16 PM, milotrain said:

Gunsmiths have run into this problem a lot because external screws are decorative.  In order to protect the top edge of the screw's groove you don't want a tapered screwdriver or a hollow ground screwdriver you want a parallel ground screwdriver.  At the size you guys are working with this may be a moot point as Deggsie has said but it's valuable to know what you are going after.  Tapered and even hollow ground screw drivers can engage the top or leading edge of the notch which is it's weakest point, this is what causes deformation of the screw notch.  Ideally you want to engage the whole slot, or the base of the slot, not the top edge.

100% agree....but in the common vernacular, hollow ground is used to describe the resulting parallel, and desired, end you describe- i.e. the curve is a hollow vs the flat side of a regular screw driver.  Its what Wheeler and Brownels call them (this the set I have, and recommend it)  https://www.btibrands.com/product/professional-gunsmithing-screwdriver-set-89-pc/

I've do a lot of work on old machines and lathes (Schaublin 70's, Holbrook B8, rivett 608 etc) and a lot of these are put together with slotted head fasteners; some predate socket head cap screws.  Its really a shame to some of the nicest machines man's ever made scarred because some hack took a screw driver to them.  The trick is one  of those large gunsmith screw driver kits with hollow ground blades of different widths and thicknesses.  For stubborn ones you can put a wrench on the bit and it loosens without damaging the screw heat

Having said all that, I haven't weighed in on watch screws as (from lack of experience with watches specifically) I'm not sure of the necessity as it may be that the torque/contact ratios are different such its not required, and secondly the world best makers of watchmakers tools don't bother (although Bergeon does offer hollow grinding rig irrc) nor do many watchmakers who I view as highly competent.   I've a lot of books on watchmaking and cant' recall reading it (at least that I remember).  You'd think if it was important, given screwdrivers are the most used tool in this craft, tied maybe with tweezers, that if it was oh so important, hollow grinding them would be the first chapter in every book, yet it seems rarely or never mentioned.

bit of a zombie post.....didn't realize how old that one was :)

 

 

 

 

 

Edited by measuretwice

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Hollow ground screwdrivers are really only of use if you work on the same model of watch all the time.

The reason is if your flat ground screwdriver is too thin you just stone a tiny bit off the end to make it fatter.

On a hollow ground screwdriver you need to remove a lot more material to make it fatter, and then hollow grind it again to suit the screw you want to undo, so its harder to swap between brands of watches that you need to adjust your screwdrivers for.

If you worked as an 'in house' watch repairer of an expensive brand of watches, and always did the same movements then hollow ground is the best, but for most of us that works on what ever watch comes our way the flat ground is best being a compromise between time taken to reshape screwedrivers and the risk to 'chewing' screws.

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In school we uses this one, also to make hollow blades on a screw driver.

 

https://www.beco-technic.com/werkzeuge-verbrauchsartikel/schraubendreher/zubehoer-fuer-schraubendreher/schleifwerkzeug-fuer-schraubendreherklingen/schleifwerkzeug-profi-fuer-schraubendreherklingen.html

 

But is very expansive.

 

This one is cheaper, but don't know if you can use it on al screwdrivers from the Bergeon set, because it only have 3 holders.

 

https://www.cousinsuk.com/product/screwdriver-sharpener-tool-horotec

 

But this is wat you really need:

 

209445_4_3.jpg.c5076ef26f6e7fd03f7f084641b50624.jpg

Edited by Koen

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On 10/3/2018 at 2:57 PM, Tmuir said:

Hollow ground screwdrivers are really only of use if you work on the same model of watch all the time.

The reason is if your flat ground screwdriver is too thin you just stone a tiny bit off the end to make it fatter.

On a hollow ground screwdriver you need to remove a lot more material to make it fatter, and then hollow grind it again to suit the screw you want to undo, so its harder to swap between brands of watches that you need to adjust your screwdrivers for.

If you worked as an 'in house' watch repairer of an expensive brand of watches, and always did the same movements then hollow ground is the best, but for most of us that works on what ever watch comes our way the flat ground is best being a compromise between time taken to reshape screwedrivers and the risk to 'chewing' screws.

I agree. From what I know, The British Horological Institute and watchmaker schools in the Netherlands teach to work on watches with flat ground screwdrivers.

Hollow ground is useful for screws made of a softer metal such as gold and convex screws that you sometimes see in older watches and also sometimes used as case screws.

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Well because with hollow screwdrivers, you have more grip the teacher say ( Omega service center ) and les chance to slip away or to damage screws...

 

You don't want to damage movements, especially now with open case backs. But thats what we learn the first lesson, I am only the pianist. ;-)

 

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I have never heard such tommy rot. I well dressed screw driver blade and the correct size for the screw and you need a steady hand is all that is needed. The more expansive screwdrivers have a easier rotation in the fingers then cheap ones.   

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1 hour ago, Koen said:

Well because with hollow screwdrivers, you have more grip the teacher say ( Omega service center ) and les chance to slip away or to damage screws...

See above the good postings by Tmuir and measuretwice. Parallel blades drivers aren't given that much importance, for whatever the right and wrong reasons. Good that you are being exposed to comparison at school so you can base your own judgment, I want to do the same. 

Edited by jdm

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Well because with hollow screwdrivers, you have more grip the teacher say ( Omega service center ) and les chance to slip away or to damage screws...
 
You don't want to damage movements, especially now with open case backs. But thats what we learn the first lesson, I am only the pianist. ;-)
 

What is a hollow screwdriver?

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I also find it odd to immediately have everyone's screwdrivers hollowed. 

A friend of mine is also an Omega certified watchmaker but has never used a parallel blade in his life. The same goes for Anthony from NoBSwatchmaker, who's certified for Rolex, Breitling, JLC, and Omega.

No doubt that parallel blades are useful in some cases but it sounds like a personal thing from the teacher.

*edit The great George Daniels was also all about flat ground screwdrivers.

Edited by Nutiborskoku

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Like I say, I am only the pianist.

But hey every body will have there thought about something... Only time will tell my experience... but for now I am a rookie and just follow the pack. ;-)

But I can understand the point that hollow blades fit better in the screws and so you wont damage them.

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Like I say, I am only the pianist.
But hey every body will have there thought about something... Only time will tell my experience... but for now I am a rookie and just follow the pack. ;-)
But I can understand the point that hollow blades fit better in the screws and so you wont damage them.

Again, what is a hollow blade


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31 minutes ago, Nutiborskoku said:

I also find it odd to immediately have everyone's screwdrivers hollowed.

Quite normal in watchmaking schools, one have to do a lot of filing and tool making before undertaking actual horology subjects.

Good for building dexterity and machinist skills but really there is whole lot more than that to make, at least, a good repairer. 

 

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12 minutes ago, jdm said:

Quite normal in watchmaking schools, one have to do a lot of filing and tool making before undertaking actual horology subjects.

Good for building dexterity and machinist skills but really there is whole lot more than that to make, at least, a good repairer. 

 

Ah, that makes sense. Thanks.

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1 hour ago, oldhippy said:

I have never heard such tommy rot. I well dressed screw driver blade and the correct size for the screw and you need a steady hand is all that is needed. The more expansive screwdrivers have a easier rotation in the fingers then cheap ones.   

  what would a "flat ground" look like?    it might make the tip too long and weak.   have you ever twisted the tip off a tight screw?  a compromise is hollow grind.  vin

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