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Screwdriver Sharpening

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41 minutes ago, Nutiborskoku said:

Careful, guys!

Not many things make watchmakers lash out more than screwdriver blade shapes and which oils and greases to use where :D

But, the picture make sense, so imo I understand why we are doing this.

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As with so many things, there's no good or wrong. This has been debated for decades and it won't be settled with 1 picture. The best thing is to have multiple sets of screwdrivers so you can use the best one for the job.

The picture makes sense but only because the one on the left is a perfect fit. If the slot in the screw is only a fraction wider, it doesn't work. So, you'd need a different screwdriver. 

Edited by Nutiborskoku

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20 hours ago, Nutiborskoku said:

The picture makes sense but only because the one on the left is a perfect fit. If the slot in the screw is only a fraction wider, it doesn't work. So, you'd need a different screwdriver. 

Actually that is not true. If the slot is wider there will be no full contact between driver blade and screw, but there will be two shorter points of contact, since these are parallel to the axis of the blade they  not tend to lift the tool, which is good. In addition there will be some friction between the tip of the blade, and the bottom of the slot. As a result, he screw will be driven properly.

Compare to a wedge shaped (aka flared) driver. In theory there are always two thin strips of contact, which are as wide as the blade. The down side is that the blade tends to cam out because there the surface asre not paralled are inclined, and there is no friction contact to the bottom.

Parallel tip drivers are also somehow common in general mechanic, from small to big sizes. These are usually considered better, and are more expensive. 

In the comments of this article https://www.cnccookbook.com/8-brands-to-consider-for-the-worlds-best-screwdriver you can read about paralled, plus JIS and Pozi cross types, which are unknown to many.

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15 minutes ago, jdm said:

Actually that is not true. If the slot is wider there will be no full contact between driver blade and screw, but there will be two shorter points of contact, since these are parallel to the axis of the blade they  not tend to lift the tool, which is good. In addition there will be some friction between the tip of the blade, and the bottom of the slot. As a result, he screw will be driven properly.

Compare to a wedge shaped (aka flared) driver. In theory there are always two thin strips of contact, which are as wide as the blade. The down side is that the blade tends to cam out because there the surface asre not paralled are inclined, and there is no friction contact to the bottom.

If the slot is only a fraction wider, the two points of contact will be on the opposite corners of the blade on the diagonal of the slot. This causes tensile stress which can cause more damage than a traditional v-shaped blade in the correct size because it evenly grips the full length of the slot.

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6 minutes ago, Nutiborskoku said:

If the slot is only a fraction wider, the two points of contact will be on the opposite corners of the blade on the diagonal of the slot. This causes tensile stress which can cause more damage than a traditional v-shaped blade in the correct size because it evenly grips the full length of the slot.

It seems to me than tensile stress, assuming it could be an issue, happens on the blade which is thin and subject to torsion, it may chip. On the other hand, even tapered blades do chip, and I can show from threads here that even first brand ones do.  The screw head by contrast has ample mass at the point of contact and I don't see how it can be damaged.

Anyway, I was just trying to go a bit more in depth on the theoretical aspects of the debate, without taking any side. You certainly made clear which you one you've adopted, the question is, from real direct experience? Have you ever damages some screw (watch size or other) using a parallel blades driver? Certainly I did't.

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Just now, jdm said:

It seems to me than tensile stress, assuming it could be an issue, happens on the blade which is thin and subject to torsion, it may chip. On the other hand, even tapered blades do chip, and I can show from threads here that even first brand ones do.  The screw head by contrast has ample mass at the point of contact and I don't see how it can be damaged.

Anyway, I was just trying to go a bit more in depth on the theoretical aspects of the debate, without taking any side. You certainly made clear which you one you've adopted, the question is, from real direct experience? Have you ever damages some screw (watch size or other) using a parallel blades driver? Certainly I did't.

I haven't taken any sides either. I have three sets of screwdrivers and one set has parallel blades. I was simply reacting to other statements that seem to think that parallel blades are gospel and that tapered blades are wrong.

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I think one thing that everyone can agree on is that maintaining your screwdrivers is a must, which ever method you prefer, as soon as you notice the tip is damaged it time to sharpen them.

I originally had a cheap Asian set of screwdrivers, but the metal the blades were made from I think was actually cheese as they would need reshaping pretty much after evry second screw I undid. In frustration I decided to replace all the baldes with blue steel, but when I went to remove the first blade one half of the grub screws snapped off, at which point I invested in a good set of Horotec screwdrivers that I now just love.

For me working on different ages and brands of watches and pocket watches and even the occasional WWII aircraft clock the tapered suite me better, but do agree if you worked in a repair shop that specialised in one brand parallel sharpened blades would be better.

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5 minutes ago, Tmuir said:

I think one thing that everyone can agree on is that maintaining your screwdrivers is a must, which ever method you prefer, as soon as you notice the tip is damaged it time to sharpen them.

I originally had a cheap Asian set of screwdrivers, but the metal the blades were made from I think was actually cheese as they would need reshaping pretty much after evry second screw I undid. In frustration I decided to replace all the baldes with blue steel, but when I went to remove the first blade one half of the grub screws snapped off, at which point I invested in a good set of Horotec screwdrivers that I now just love.

For me working on different ages and brands of watches and pocket watches and even the occasional WWII aircraft clock the tapered suite me better, but do agree if you worked in a repair shop that specialised in one brand parallel sharpened blades would be better.

    100% contact of a screw driver IN THE SLOT is what we are shooting for and the wedge is as close as we get.   as far cheezy steel,  that ia another story.   vin

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3 minutes ago, vinn3 said:

    100% contact of a screw driver IN THE SLOT is what we are shooting for and the wedge is as close as we get. 

Actually is is not so, by square surface the parallel tip type has more contact in the slot, refer to the drawing above.

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16 minutes ago, jdm said:

Actually is is not so, by square surface the parallel tip type has more contact in the slot, refer to the drawing above.

  not so? i have never heard of a screw of a " parallel tip" screw driver.   could you mean "hollow ground tip"?  i have only been sharpening screw drivers for 50 years.   vin

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If you've used properly fitting hollow ground blades for larger fasteners you know they can handle a lot more torque than a regular screw driver without damage fasteners.   The difference is so pronounced you just should not work on antique machinery/equipment with slotted fasteners without using hollow ground blades or you will botch up the fasteners.

However, relative to the current debate, two things occur to me

1)  To get the performance noted above, the bit has be a very good fit in the slot.  My set has I think 85 or 90 pieces.  Without that selection and ability to find a perfect fit, their advantage pretty much disappears.    Is a watchmaker going to have a similar selection to ensure that perfect fit and futz about constantly checking microscopic differences in fit? 

2) Performance is superior, but the metric is torque handling ability.  Does this even matter in watching making?   My limited experience suggest no.  otoh, if you are  regularly damaging heads of screws with taper blades than yeah, figure out how to get an assortment of hollow ground bits that work for you....but otherwise, why worry about it?  

imo there is no debate to be had on what is superior, the debate is simply whether it matters given the torques involved.

A young guy I know worked for Roger Smith for few years (talk about a learning opportunity!).....I'm curious on he was taught

 

 

Edited by measuretwice

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2 hours ago, vinn3 said:

  not so? i have never heard of a screw of a " parallel tip" screw driver.   could you mean "hollow ground tip"?  i have only been sharpening screw drivers for 50 years.   vin

To quote measuretwice from a previous posti g:

In the common vernacular, hollow ground is used to describe the resulting parallel

No matter how many years one has done something is always good to try to understand what others mean. Searching the Internet alsio helps

https://toolguyd.com/lee-valleys-parallel-tip-screwdrivers/

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1 hour ago, measuretwice said:

 

1)  To get the performance noted above, the bit has be a very good fit in the slot.  My set has I think 85 or 90 pieces.  Without that selection and ability to find a perfect fit, their advantage pretty much disappears.    Is a watchmaker going to have a similar selection to ensure that perfect fit and futz about constantly checking microscopic differences in fit? 

I don't think that microscopic difference matter that much, and not even that they are so pronounced when going from a watch brand to another as someone suggested. While it's a fact that generally speaking Swiss screw slots are narrow than Japanese for a same width, I suppose the parallel drivers makers have calibrated well the blade thickness to be the best average size. 

Quote

2) Performance is superior, but the metric is torque handling ability.  

For me the metric isn't just that. A very important aspect is the ability to grip well for the initial turn on long screw that has just put on its place, always tilted. on one side by some amount. 

Since I don't think there are available videos about that I will make a comparison one as soon I have the opportunity, and update this thread. 

Edited by jdm

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3 hours ago, measuretwice said:

If you've used properly fitting hollow ground blades for larger fasteners you know they can handle a lot more torque than a regular screw driver without damage fasteners.   The difference is so pronounced you just should not work on antique machinery/equipment with slotted fasteners without using hollow ground blades or you will botch up the fasteners.

However, relative to the current debate, two things occur to me

1)  To get the performance noted above, the bit has be a very good fit in the slot.  My set has I think 85 or 90 pieces.  Without that selection and ability to find a perfect fit, their advantage pretty much disappears.    Is a watchmaker going to have a similar selection to ensure that perfect fit and futz about constantly checking microscopic differences in fit? 

2) Performance is superior, but the metric is torque handling ability.  Does this even matter in watching making?   My limited experience suggest no.  otoh, if you are  regularly damaging heads of screws with taper blades than yeah, figure out how to get an assortment of hollow ground bits that work for you....but otherwise, why worry about it?  

imo there is no debate to be had on what is superior, the debate is simply whether it matters given the torques involved.

A young guy I know worked for Roger Smith for few years (talk about a learning opportunity!).....I'm curious on he was taught

 

 

   if IMO means what i think;  "right you are".   tourk (sp) is a different matter.   when i find a good steel driver,  i hone it to fit the slot.  if it starts to bend the tip,  i stop and re group.    cheers,   vin

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3 hours ago, jdm said:

For me the metric isn't just that. A very important aspect is the ability to grip well for the initial turn on long screw that has just put on its place, always tilted. on one side by some amount. 

 

Thats a point.  to be more exact I should have said based on my experience with larger fasteners, why hollow ground is better, and how you'd measure that, is how much torque it can apply without damaging a head.   There could well be other factors in watchmaking sized work.  Pet peeve of mine - taking apart some 100 year work of art and some hack before you has messed up all the fasteners :(

Edited by measuretwice

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I have the Hormec hollow grind sharpener, and a roller sharpener for wedge shape, and a large diamond file.

I hate the Hormec and hollow ground blades (like them for clocks and other stuff though, PB Swiss make my old Snap-On stuff look like toys).

I sharpen regularly with the diamond file. Wedge shape, not too shallow. I recall Hamilton recommending 15 degrees, I do a little more. Been meaning to sell the Hormec but after loaning it out try-before-buy to several folks they lose interest after actually trying hollow ground. I know one watchmaker who uses mostly hollow ground, but has 3 or 4 sets and is always messing with them.

It doesn't really matter as long as the screws (and nearby parts) survive unscathed. When doing final assembly of a new watch with flat polished screws, where each screw gets hand polished on tin, I use a nickel (german silver) blade, which needs dressing every 3 or 4 screws.

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