Washer bore sizes

[Parlo]

I've always considered this a feature, instead of a bug. I guess it's all about where your standing. Lol
I like Bills explanation. That sounds reasonable to me. Although from what I know, the punch diameter never changes. Just the length of the punch. I still like his notion.

Yes the punch diameter never changes, the length is always reduced to resharpen the face.
A cross section of the washer bore will show a slight depression around where the punch enters.
Below this, a shiny area where the shear occurs, this area is precisely the size of the punch and is about 1/3rd of the thickness of the washer.
Below this is where the slug breaks and is tapered from the punch size to the die size, generally 20% of the thickness bigger in diameter.
So there is some natural provision for the bolt head root radius to go, even at nominal size. The shiny nominal size area would be the only area that is a good fit on the bolt centering the washer.

 

[Parlo]

I suspect that washers are made that way because that's the way they were always made. Originally, they were made by a blacksmith pinching the hole over a bolster. He probably gave the punch an extra blow to make sure that it the fit the bolt. Since he didn't like having to check and repunch, he probably gave punch an extra hard final blow. By the time the process became industrialized, a standard was set and that's what we have today.

If there are any questions, ask me about the roast.

I suspect that if bolts were technically able to be machined, then simple washers would also be made using machinery.

 

[RJSakowski]

Yes the punch diameter never changes, the length is always reduced to resharpen the face.
A cross section of the washer bore will show a slight depression around where the punch enters.
Below this, a shiny area where the shear occurs, this area is precisely the size of the punch and is about 1/3rd of the thickness of the washer.
Below this is where the slug breaks and is tapered from the punch size to the die size, generally 20% of the thickness bigger in diameter.
So there is some natural provision for the bolt head root radius to go, even at nominal size. The shiny nominal size area would be the only area that is a good fit on the bolt centering the washer.

A blacksmith's punch is an entirely different animal. It is a tapered tool driven into red hot metal with a hammer. The punch will drive a small slug partially through the work and the work is flipped, the part is placed over a bolster, and the slug is driven back, completing the shear. The the punch is then driven further to create the final i.d.

We are talking about a process that far preceded the industrial revolution, where everything made of iron was made in a blacksmith's shop. There were no standards at the time. Every blacksmith had his own set of standards. Initially, screws were made by hand filing. In the 18th century, the first commercial screw cutting machines were developed. The USS and SAE standards didn't come about until the late 19th century.

Modern metric fasteners are governed by the DIN 125 specification. Looking at washer sizing, metric washers are closer to the nominal screw diameter than USS washers, being .016 " to .020" larger for smaller sizes and .039" for screw sizes 12 mm to 42 mm. This fairly well matches up with specifications for close fit clearance holes for metric screws. Clearance holes specification for a loose fit for UNC and UNF fasteners roughly corresponds to the i.d. for SAE washers.

 

[sdelivery]

When I was in the apprenticeship one of the first jobs I did was make flat washers for the machines(LATHES) we built.

 

[Parlo]

A blacksmith's punch is an entirely different animal. It is a tapered tool driven into red hot metal with a hammer. The punch will drive a small slug partially through the work and the work is flipped, the part is placed over a bolster, and the slug is driven back, completing the shear. The the punch is then driven further to create the final i.d.

We are talking about a process that far preceded the industrial revolution, where everything made of iron was made in a blacksmith's shop. There were no standards at the time. Every blacksmith had his own set of standards. Initially, screws were made by hand filing. In the 18th century, the first commercial screw cutting machines were developed. The USS and SAE standards didn't come about until the late 19th century.

Modern metric fasteners are governed by the DIN 125 specification. Looking at washer sizing, metric washers are closer to the nominal screw diameter than USS washers, being .016 " to .020" larger for smaller sizes and .039" for screw sizes 12 mm to 42 mm. This fairly well matches up with specifications for close fit clearance holes for metric screws. Clearance holes specification for a loose fit for UNC and UNF fasteners roughly corresponds to the i.d. for SAE washers.

I have never referred to the blacksmithing process, I simply asked why the holes in washers could not be a little smaller.
I very much doubt that internal threads could be filed before simple washers could be stamped.
Although the bores of metric washers closely match the reccommended clearance holes, is there any reason why the washers need to have the same limits?

 

[Bi11Hudson]

This conversation has gone further than I had expected. Let's look at washers for what they are. A part to fit between a fastener and the base. Its' purpose is to distribute the forces of the bolt as it is stretched. And some other purposes such as keeping the bolt 'head' from rubbing on the base as it is rotated. The end result is that the bolt (fastener) is the primary element in a multipart assembly. As in the washer is designed around the bolt.

For 'hardware store' bolts, the grade of toughness run the gamut from Grade 0 (ungraded) to grade 3. Metric fasteners have a different system but essentially the same end result. For more precision(?) there is a grade 5 (3 tics) that will stand up to a higher torque. For hydraulic assemblies, there is a Grade 7 (5 tics). There are higher grades (at higher cost) for more critical applications such as aircraft.

When the 'head' of the fastener is 'upset' in mass production or left after turning in a one off shop, there is a radius. It is a well known fact that when machining a smaller dimension into a larger, that a sharp corner is a weaker point than a radiused corner. The same concept applies to the head of a fastener. When producing a Grade 3 fastener, the process uses the lowest cost materials, weaker by nature. Thus a larger radius. As the Grade number increases, so does the quality (and cost) of the stock. And the radius is decreased as the material is stronger. There are other factors such as corrosion and whether the washer may be intended as a 'captive' part.

The end result is that the lower the cost of a washer, the lower quality of material it is made from. Allowances for the internal dimension will be based on the material (Grade) of the fastener. At its' simplist, consider looking at the local home center (Lowe's, Home Depot, Menards) for a Grade 5 bolt. You will find the Grade 5 fastener in a cabinet off to the side. (at much higher cost) Then for a washer, one tends to grab one or a box from the ungraded area. (much lower cost) A washer is considered less a critical part than the fastener so cost is a large issue.

Working in the steel mills, with a dedicated 'bolt room', Grade 5 fasteners were the norm. As were the washers and nuts. A Grade 7 nut, for example, is larger than a Grade 5. For 3/8-16 threads, the nominal size wrench is 9/16. For a Grade 7, the size was 5/8. Washers fall into the same catagory, a Grade 5 has a larger bore than a Grade 7. Greater grades were used for hydraulic systems, with washers with correspondingly smaller bores. The metric fasteners had similar grades versus sizes, just different designations.

I tend toward babbling when I get on a technical subject. Please forgive the length of this post. But bear in mind, quality of materials, hence cost, has a large bearing on most any material, be it a fastener or an airplane.

.

 

[mmcmdl]

You can just use these and do without the washers OR , align the oversize bore washers concentric up by eye and tighten your bolts . 27 posts on washer bore specs ?

flat head countersunk bolts - Google Search

 

[RJSakowski]

I have never referred to the blacksmithing process, I simply asked why the holes in washers could not be a little smaller.
I very much doubt that internal threads could be filed before simple washers could be stamped.
Although the bores of metric washers closely match the reccommended clearance holes, is there any reason why the washers need to have the same limits?

You actually asked why there is clearance on the bore of a washer and the short answer is that there are standards set for the i.d. As to why the standards are what they are, who knows? My answer was meant to be a tongue in cheek explanation. But seriously, many standards we have today were set by some arbitrary decision made decades or even centuries ago. A great example is the width of railroad tracks tracing back to the combined width of two Roman horse's rumps.

Once a standard is adopted, it is difficult to change. We in the US went along with an inferior standard for television for more than a half a century. Our CMDA cell phone standard which is used by the majority of cell phones in the US is inferior to the GSM standard that you use. We can't even convert to the metric system.

As to how were internal threads formed, that is an intriguing question. My guess would be that the male thread was formed and it was screwed into the hot blank, much like a modern thread forming tap or sheet metal screw. I have seen examples of screws used in medieval armor c.a. 15th century.

Regarding washer i.d., I see that there are multiple standards for metric washers. Washers made to DIN 125, DIN 433, ISO7089, or ISO7092 specifications are made to a smaller i.d while those made to DIN126 or ISO7091 specifications have a larger i.d. You might want to check with your supplier to see which you are getting regarding washer i.d.

 

[jwmay]

27 posts on washer bore specs ?

I felt the same way about some other thread. Now I can't even find it. It was near the top of the list for a week or more. I finally opened it because I just HAD to know what everybody was talking about to keep that thread alive. Anyways... you'll forget about this painful experience soon enough. In the meantime, we're ciphering here. Leave us to it. Lol
And Bill, I think you meant to say Grade 8 with 5 tics.
And I still find a loose fitting washer a handy feature. The only reason I can imagine it would matter is for aesthetics. If we're looking for better aesthetics, it might be better to make your own washers.

 

[RJSakowski]

I felt the same way about some other thread. Now I can't even find it. It was near the top of the list for a week or more. I finally opened it because I just HAD to know what everybody was talking about to keep that thread alive. Anyways... you'll forget about this painful experience soon enough. In the meantime, we're ciphering here. Leave us to it. Lol
And Bill, I think you meant to say Grade 8 with 5 tics.
And I still find a loose fitting washer a handy feature. The only reason I can imagine it would matter is for aesthetics. If we're looking for better aesthetics, it might be better to make your own washers.

Bill is correct. The grade is two more than the number of marks. A grade 8 bolt has six marks. I have never run across a grade 7 but they do exist.