Thread: On Sharpening Twist Drills

Hmmmm......
So there workshop must have been very well climate controlled to get that sort of accuracy in timber. I'm amazed there is no immediate outcry in that thread, as a .0005" pin gauge could easily be pushed into a hole that was .001" small in timber.
Just the fact that the timber is not a consistent medium means that 10 holes drilled in the same piece but 10 different places and grain directions means you will get 10 different sized holes, no matter how good the drill.
If the timber was ebony and ivory (but more likely the timber for the hammers etc, not sure what they use there) then better tolerances could be achieved but i still don't think they could be that good.

Ew

Originally Posted by Ropetangler

There is this thread http://www.model-engineer.co.uk/foru...s.asp?th=95436 on the English 'Model Engineer' website that makes for interesting reading on drill sharpening. There are quite a few pages and I have not read them all, but on the first page, the moderator recounts his earlier career working for a company making piano movements. They drilled thousands of holes a day into wood, and the positioning was often to within a half thou, and hole sizes would be to within tenths of thous. No commercial drills would drill to size from the packet, so they would be graded, and remachined and resharpened to size. When they were installed, test pieces would be done and it might still take some hours of tuning before the machine was passed by the inspector for work. Some of these drills would then go on to drill over 30,000 holes before they were changed out. Well worth the read if the weather is as drizzly as it is here
Rob.

Tenths of thousands of a foot, maybe.

In short, I don't believe it. Someone is dreaming, as Ewan says, not in a material as subject to movement as any wood out there, not outside of a climate controlled environment.

PDW

The tolerances are somewhat irrelevant in my mind, although I do agree with the comments already made in this regard. The important thing to consider is that the drills needed a labour of love applying before they were considered accurate enough and thereafter they would last a long while.


Thx
Jon

Maybe you have been reading the April 1st edition of the Magazine or someones having a lend of someone.

The 1/2 thou reference on timber and then the 1/10 thou hole tolerance on a piano hole sizing.
Last time I looked,the piano was a musical instrument not a scientific one.

Overall I think many metal workers are duped into thinking they must have a drill doctor when in truth the application for the majority of drilled holes is for a bolt clearance or tapped holes.
I do concede, however, there are some applications for precisely sharpened drills for drilling accurate holes.

Maybe its just me thinking the that the old well regarded hand skills are fast disappearing.

Grahame

Does anyone keep in mind that when you are sharpening drills, all you are doing is grinding a clearance angle onto the drill... The actual cutting angle is fixed by the helix angle of the groove..

Originally Posted by Grahame Collins

Last time I looked,the piano was a musical instrument not a scientific one.

I will say, but...... If the goal is to produce pure clean sound tones that are fully repeatable.. It may amaze people to what extent some go to to get the best results. Or maybe to what extent you have to go..

Look at the price of some extreme high quality electronic audio equipment...

Originally Posted by Grahame Collins

Maybe you have been reading the April 1st edition of the Magazine or someones having a lend of someone.

The 1/2 thou reference on timber and then the 1/10 thou hole tolerance on a piano hole sizing.
Last time I looked,the piano was a musical instrument not a scientific one.

Overall I think many metal workers are duped into thinking they must have a drill doctor when in truth the application for the majority of drilled holes is for a bolt clearance or tapped holes.
I do concede, however, there are some applications for precisely sharpened drills for drilling accurate holes.

Maybe its just me thinking the that the old well regarded hand skills are fast disappearing.

Grahame

To be honest, I would have expressed much the same views everyone has expressed here myself, but if I am right, prety well every time John Stevenson has popped up on some metalwork forum, he sounded like he knew his stuff, and was generally held in high regard. I can only suggest that you all read the link posted for yourselves. I know nothing about the making of pianos, but I have no reason to think him untruthful when he described the procedures at his old workplace. I just reported the link, because I found it interesting and somewhat against the prevailing wisdom on these matters, but that company made the movements for many of the top names such as Steinway, Kemble, Kimble Bechstein, Baldin and Bosendorfer, so they must have been doing something right. JS goes on to mention that "any moving part on an action ran on pins 0.0505" in diameter, a standard reached in the late 18th century but unfortunately a size no drills exist for. In the early days of the 20th century they made drills by filings tool steel wire down, hammering and filing into a spade bit then hardening. In my day we bought HSS drill blanks in exact size then hand ground these into spade drills". Go ahead and read it all, there is plenty of thought provoking stuff there.

I realise that it would be easy to push a gauge pin 1/2 a thou bigger than the hole in wood into that hole, but that is also the case with a micrometer set a thou smaller than the true diameter of a shaft, being easily pushed over that shaft. It is repetition and lots of practice that make a machinist able to measure with his tools and instruments to high standards of accuracy, or in other words to develop the feel in his hands to get it right. That inspector did nothing but check and sign off on machine adjustments for quality control, so he would be capable of making these judgements with all the years of experience, the same with a piano tuner really, - he could possibly give an adjusting screw a 90 degree turn, and chances are that most of us wouldn't be able to tell the difference, but another piano tuner or a concert pianist would have no trouble detecting it.
Rob.

Originally Posted by Ropetangler

To be honest, I would have expressed much the same views everyone has expressed here myself, but if I am right, prety well every time John Stevenson has popped up on some metalwork forum, he sounded like he knew his stuff, and was generally held in high regard. I can only suggest that you all read the link posted for yourselves. I know nothing about the making of pianos, but I have no reason to think him untruthful when he described the procedures at his old workplace. I just reported the link, because I found it interesting and somewhat against the prevailing wisdom on these matters, but that company made the movements for many of the top names such as Steinway, Kemble, Kimble Bechstein, Baldin and Bosendorfer, so they must have been doing something right. JS goes on to mention that "any moving part on an action ran on pins 0.0505" in diameter, a standard reached in the late 18th century but unfortunately a size no drills exist for. In the early days of the 20th century they made drills by filings tool steel wire down, hammering and filing into a spade bit then hardening. In my day we bought HSS drill blanks in exact size then hand ground these into spade drills". Go ahead and read it all, there is plenty of thought provoking stuff there.

I realise that it would be easy to push a gauge pin 1/2 a thou bigger than the hole in wood into that hole, but that is also the case with a micrometer set a thou smaller than the true diameter of a shaft, being easily pushed over that shaft. It is repetition and lots of practice that make a machinist able to measure with his tools and instruments to high standards of accuracy, or in other words to develop the feel in his hands to get it right. That inspector did nothing but check and sign off on machine adjustments for quality control, so he would be capable of making these judgements with all the years of experience, the same with a piano tuner really, - he could possibly give an adjusting screw a 90 degree turn, and chances are that most of us wouldn't be able to tell the difference, but another piano tuner or a concert pianist would have no trouble detecting it.
Rob.

I used to argue at times with John Stevenson on r.c.m 20 years ago. I agree he's a smart man and very knowledgeable in his field, but that doesn't mean he's always right. Like Rich King on PM, sometimes he has the tendency to think that because he does things in a particular way, that's the best and only way, simply because that's how he & his father before him have done it, and it works. Not what I regard as meeting any scientific methodology.

Now WRT small holes in wood, the 2 things that cannot be avoided are temperature fluctuations and humidity fluctuations. We all know what happens to holes in metal with temperature changes. Wood is no better and has the very large compounding factor of humidity as well. Even very dense woods like iron bark and blue gum move. I've been working with blue gum cut and air dried in a shed for over 8 years now; the cross cuts just look polished off the saw due to the density. It still moves when you get down to measurements with vernier calipers and micrometers.

So *maybe* you can drill a hole using a drill made to tolerances of tenths of a thousand of an inch, and *maybe* that hole will be on size to a similar tolerance level at the moment that the drill clears the work.

Anyone want to bet what size the hole will be, say, 3 months later, when the item may well be in a completely different country? Say, a shift from the north of England to Singapore?

PDW

Originally Posted by .RC.

Look at the price of some extreme high quality electronic audio equipment...

and the best are still using valves I believe

Originally Posted by eskimo

and the best are still using valves I believe

While beauty is in the eye of the beholder, so too with sound to peoples ears. You will never when an argument with valve amp audiophiles that mosfets (or whatever) are better because they like valves!

I would almost go out on a limb and say that of these people, 1% may be able to spot the sound difference while the other 99% are just hanging onto the past, similar to what we do when we admire fine old machine tools.

Persoanlly I can't tell the difference.

Enjoying the thread on drilling holes in timber though!

Originally Posted by eskimo

and the best are still using valves I believe

Not the best. Like those people who believe that music played from vinyl records is better than from digital media, there are some people who prefer the sound of valve equipment. It is my understanding that it is simply a matter of personal taste.

Dean

If accuracy of the order claimed was required, you wouldn't be drilling it, not as a final operation, and definitely not with a twist drill, irrespective of the material (and I agree strongly with the above regarding wood). Twist drills only came in to use IIRC at the beginning of the 20th century, prior to that other drill designs were used, some of which remain a more accurate way to bore a hole, albeit with other disadvantages. The point being if they are claiming no twist drills existed of that size in the 18th century, I'd suggest that's about the only piece of fact there; since NO twist drills existed at that time.

Originally Posted by Pete F

If accuracy of the order claimed was required, you wouldn't be drilling it, not as a final operation, and definitely not with a twist drill, irrespective of the material (and I agree strongly with the above regarding wood). Twist drills only came in to use IIRC at the beginning of the 20th century

No I'm pretty sure it was earlier than that - 1860 to 1880 era I think.

But your point is still valid. There were no spiral drills before that, and the design was under patent when first brought out, so other manufacturers still had straight flute drills.

PDW

Originally Posted by PDW

No I'm pretty sure it was earlier than that - 1860 to 1880 era I think.

But your point is still valid. There were no spiral drills before that, and the design was under patent when first brought out, so other manufacturers still had straight flute drills.

PDW

Spiral pattern augers go back way further than that, but, to stay on topic, I'd think that augers with straight sided flutes would drill a more accurate hole in wood than twist drills.

Ray

Originally Posted by RayG

Spiral pattern augers go back way further than that, but, to stay on topic, I'd think that augers with straight sided flutes would drill a more accurate hole in wood than twist drills.

Ray

So, how many 1.3 mm augers have you come across?

As I mentioned, there were other drill designs before the modern twist drill, and some of them are much more accurate, though rarely seen these days, however claims were being made that are difficult to justify on a number of fronts. Ewan mentioned wood movement (and I fully agree), I mentioned that if they're claiming that accuracy from twist drills, they didn't exist before 1860ish, at best. No disrespect to the OP, just pointing out where things don't add up.