Member postings for Bill Phinn

Thanks for the replies.

I'm astonished that industry can realistically regard having a discreetly located and recessed imperial/metric toggle button at the top of the display as a source of error.

Does industry typically entrust a Mitutoyo digital caliper to people taking critical measurements who are so bovine, hung over or distracted that they can't tell whether their caliper is set to metric or imperial?

If these people can't be trusted to know what setting their caliper is on when the two settings are so clearly differentiated by the appearance of the readings, and changing from one to another needs such a deliberate press of a recessed button, how can they be trusted to distinguish between hundreds or thousands of settings on multi-axis digital readouts and in CNC software?

Does the seller of the Mitutoyo caliper listed two days ago realise that his caliper will almost certainly read in both metric and imperial?

If it doesn't, can anyone tell me which current model of Mitutoyo digital caliper that looks like the one being sold does not read in imperial as well as metric?

EtA: I see I'm out of touch with the current spec. of Mitutoyo digital calipers; it appears that there are now quite a few models that only read in metric. Why would Mitutoyo do that? Won't that deter American buyers and quite a few old world buyers too? I do mostly use metric, but I'd still want my caliper to be able to read in imperial as well.

Edited By Bill Phinn on 26/10/2022 18:45:09

Posted by Peter Greene 🇨🇦 on 25/10/2022 01:38:54:

It's the "point of need" in this context that I'm confused about (not the "free" )

The patient has a need for a health provider's intervention, in this case the NHS'. The patient gets that intervention at the point in time and space where his need for it arises, in theory if not always in practice, unless it's a trip to casualty.

I'm not personally familiar with the phrase "free at the point of need". I know it as "free at the point of use".

It means the cost is paid for by taxpayers, not the individual using the service, though the individual may also be a taxpayer, in which case he or she will contribute to the cost indirectly, i.e. through tax payments and not at the point of need/use.

One of the things that paper conservators are agreed on about foxing is that there isn't a single cause.

Having said that, I regularly see foxing of the kind Greensands has shown on the heads and fore-edges of modern mass-produced books printed on chemical wood pulp paper, especially when they have been stored in slightly damp and dusty conditions.

The quality of the paper is almost certainly the biggest factor. I've restored early 16th century books that have clearly been through the wars but their rag paper is still white as snow and largely unblemished five centuries later.

The rot really set in for books when the Industrial Revolution got into full swing: paper and leather began to be produced very quickly and cheaply, and quality suffered as a result.

The upside was that the written word began to be disseminated much more widely, and so knowledge, and with it the chance of acquiring wealth, influence and political power became no longer the preserve of the privileged few.

Thanks for the further replies.

If I can get confirmation from a couple of sellers of the shim washers what the actual rather than the nominal ID is of the 8x13x1 ones, I might give them a go.

Given the modest quantities I'm talking about, though, and the immodest price of these shim washers, my need for off-the-peg washers with those dimensions is correspondingly not very pressing.

Following other forum members' advice, I've just made some plain washers of the dimensions I want for M6, M8 and M10 cap screws.

M6 were made from Form A M5 washers drilled out to 6.4mm. No reduction of the OD was necessary as it is 9.95mm.

M8 were made from Form A M7 washers. ID was drilled out to 8.4mm, OD reduced by 0.4mm.

M10 were made from Form A M8 washers. ID was drilled to 10.5mm. Existing OD is only 0.1mm bigger than the cap screw head, so again no reduction was needed.

The task was a very quick one and these washers all now fit my counterbores.

I see that Drill Service Horley do sell at least 3 different sizes of counterbores targeted presumably at M8 cap screws: 13.5x8.4, 15.0x8.4, and 18x8.5. Their 14.0x9.0 would be another candidate.

It won't be one of those, V8; those aren't toothed [like the one in Philip's picture] but have diamond particles [or some sort of abrasive material, at any rate] embedded in them.

Edited By Bill Phinn on 20/10/2022 18:42:59

To address Hopper’s point, the main problem, as I see it, with omitting a washer under a cap screw comes when the surface in direct contact with the screw head is a lot softer than the screw, e.g. aluminium. It’s chiefly for use on aluminium that I wanted plain washers that fit my counterbores.

I can’t really see why using cap screws in counterbored holes should do away with the need for one of the common functions of washers, i.e. to prevent chewing up of the surface of the thing that is in direct contact with the underside of the fastener head - a surely important consideration, particularly if frequent disassembly and reassembly takes place. It’s not primarily aesthetics I‘m thinking of here.

It seems I’m not the only person to have felt the need for plain washers under cap screw heads:

https://www.practicalmachinist.com/forum/threads/is-there-such-a-thing-as-a-washer-for-a-shcs.316893/

An additional reason why I’m sceptical whether it’s right to say there's commonly no point to using washers [spring or plain or otherwise] under cap screws in counterbored holes is the content I’ve managed to find [from a fuzzy image] of DIN 974 part 1:

“DIN 974 , part 1. Diameters of Counterbores

1 - …
2 - Counterbore Diameters

This standard specifies six series of counterbore diameters as a function of screw type, of whether used with or without washer, and, if used with washer, of the washer type…

Where there is the risk of the edge of the hole being damaged by the screw underhead fillet, the edge shall be chamfered. This, however, will increase the pressure on the head bearing face.”

What I can’t find mention of is quite what diameter counterbores DIN 974 recommends in these six cases and what these six cases are. It may well be that counterbores on the wide side are advised for use on softer materials, so that washers such as DIN433 [or even wider] can be used to spread the load.

If this is so, my wish to use narrower and perhaps non-standard counterbores with aluminium and have the narrower than standard washers to go with them may ultimately be misguided, though perhaps not as misguided, in this case at least, as using no washer at all.

Many thanks for the further replies.

My counterbores are branded SWT, made by a big company in Xinan, China. They’re sold by many sellers on eBay, which is where I acquired my set of M3-M12. The dimensions chart I’ve posted clearly shows they’re sold as metric.

I had already seen the Engineer’s Bible pages showing the many different standards for counterbores. It confirmed my perception that standard metric counterbores are very oversized for the fasteners they’re intended for. I’d not read the Unbrako pages before today [and they do look interesting], but I was aware that the Unbrako name was acquired a few years ago by an Indian company called Deepak Fasteners Ltd.

I was surprised to read in my 17th edition of Machinery’s Handbook that “Counterbores for screw holes are generally made in sets. Each set consists of three counterbores: one with the body the size of the screw head and the pilot the size of the hole to admit the body of the screw; one with the body the size of the head of the screw and the pilot the size of the tap drill; and the third with the body the size of the body of the screw and the pilot the size of tap drill”.

I’m sure I’ve never seen counterbores sold that way.

I wasn’t aware of the existence of shim washers. Their dimensions fit the bill but a casual search suggests they're rather pricey.

I remain forlornly hopeful that manufacturers of metric counterbores and reduced diameter washers will see sense some time soon and start producing both with smaller diameters that more closely correspond with the real-world dimensions of metric cap screws.

Thanks to everyone for your replies.

My post in this thread:

https://www.model-engineer.co.uk/forums/postings.asp?th=177296&p=2

will explain why the DIN433 cheese-head screw washers Jason and others are referring to will not fit my counterbores. The metric counterbores I use aren’t rare anomalies dimensionally speaking but are widely available in the marketplace. Their closer clearances (e.g. 13.4mm for the 13mm head of an M8 cap screw) give a much better appearance, I think, than the standard ones Jason refers to.

Michael’s mention of imperial cap screws led me to look into the relative dimensions of imperial cap screw heads and the counterbores that exist to accommodate them. Obviously what I’ve unearthed in a brief search isn’t the whole picture, but…

Mc-Master-Carr’s 5/16” cap screws have 15/32” (11.90625mm) diameter heads. Mc-Master-Carr’s standard 5/16” counterbores have a cutter diameter of 0.475” (12.065mm). Their 1/64” and 1/32” oversized counterbores, for “when the screw holes in sheets or layers of material are misaligned”, have cutter diameters of 0.491” (12.4714mm) and 0.506” (12.8524mm) respectively.

Hence, with their standard counterbore, a 5/16” cap screw head’s diameter is 98.7% of the diameter of the counterbore.
With the 1/64” oversized counterbore, the 5/16” cap screw head is 95.5% of the diameter of the counterbore.
With the 1/32” oversized counterbore, the 5/16” cap screw head is 92.6% of the diameter of the counterbore.

Now let’s compare DIN 912 M8 cap screws. The head is usually 13mm diameter. Standard M8 counterbores of the kind Jason has in mind typically have cutter diameters of 15mm. This means the head of an M8 cap screw is only 86.7% of the diameter of the counterbore. When measured by the standards of typical imperial counterbores, therefore, these standard metric counterbores produce massively oversized recesses for the heads of cap screws to sit in.

The question is why they are "standard" when they are so oversized?

In the case of the apparently non-standard M8 counterbore I have chosen to use, the head of the cap screw is 97.01% of the cutter’s diameter. This puts it dimensionally about midway between Mc-Master-Carr’s standard and 1/64” oversized counterbores. Isn’t this a sensible sizing decision, far more sensible at any rate than the unaccountably “standard” M8 counterbores with 15mm cutters?

Yes, I can make plain washers to fit, and have done, but the question remains why, when square section spring washers are practically the same diameter as the cap screw heads they are intended for and commonly available, isn’t there such a thing on the market as a plain washer with essentially the same dimensions?

To answer David's suggestion of Schnorr washers, although it seems these will fit my counterbores, I wouldn’t want to use these washers very often, partly because of cost and partly because they may leave gouges on the surfaces of parts, just as spring washers do when you disassemble connections they’re used with.

I sometimes use square section spring washers under the heads of cap screws, not so much to prevent loosening* [Junker demonstrated that spring washers under screw/bolt heads do not prevent loosening when parts are subject to transverse loads], but

a). to allow the underside of the screw head to turn against the washer not the part, and

b). because there is sometimes a small radius where the shank of a cap screw meets the head, and this radius can prevent the underside of the cap from sitting absolutely flush with the part.

My question is why are there such things as spring washers that fit under the heads of cap screws without protruding laterally [enabling them to be used in counterbored holes] but there is no such thing on the market as a standard plain washer that can fit under the head of cap screws without protruding?

*Though spring washers do not prevent loosening in all conditions, I believe they more often prevent complete separation, because once a bolt loosens enough to release the spring tension on the washer, the splayed ends of the washer dig into both the underside of the screw head and the surface of the part, and in some circumstances this can act as a brake to prevent further loosening, at least temporarily.

Edited By Bill Phinn on 19/10/2022 03:27:41

I was non-committal, Nicholas, on whether it should be described as "food" or "what passes for food" firstly because I'm aware that a worrying number of adults find it repugnant, and secondly because I've never tasted it, so must reserve judgement on the matter.

I must confess I did go into a 麥當勞 once when I was in China, but I only had a cup of tea there. The Chinese menu is very different from the Western one*, from what I could see.

*Or at least it was twenty years ago, when I went.

Edited By Bill Phinn on 18/10/2022 21:43:53

To discuss the rights and wrongs of the case, presumably. Naming names would do nothing to change those.

Decide what you want, John, and tell him: either that you're prepared to wait indefinitely, or you want the goods within a certain time frame, or you want an immediate refund.

If it's one of the last two and he doesn't comply, initiate a charge-back on your card. There seems no reason why you wouldn't get it.

Am I the only person here who's never had food, or what passes for food, at McDonalds?

There's also UNF 10-32, but that's unlikely too given the presumed age of your stove.

I expect the relative scarcity of 3/16" BSF is explained by the fact that the BSI encouraged the use of BA threads rather than BSF below 1/4" diameter.

I asked them a question about the availability of an item in an email last night, and I got a message this morning saying it wasn't in stock.

An "email exchange" sounds more time-consuming; was the seller likely to feel he had a high probability of getting a worthwhile order out of it ultimately?

The 100-hole round plastic ones look ideal, but I wonder whether the fact that they're rotatable, plastic [and therefore light] makes them inclined to move about undesirably when you're getting drills out or putting them back.

Can Roderick let us know, because the idea looks appealing at least?

I've got a large, recentish Dormer drill stand in plastic for metric drills, including holes for many of the tapping sizes, but it's rectangular and has a substantial footprint, so it doesn't move about when you use it.

Edited By Bill Phinn on 07/10/2022 23:14:23

I think part of the problem is that the magic bullet is available to them, but they are determined to get their hands not only on the bullet, but on the secret behind its magic.

Your opening response to Michael's not unreasonable criticism of one of the many bizarre vagaries of eBay did come across as gratuitously unsympathetic, Howi, to me at any rate.