A question for the Dremel afficionados

[Michael GilliganParticipant @michaelgilligan61133]

I give up

 

[HopperParticipant @hopper]

Dunno why the concept of nominal size is so hard to grasp. It’s a standard engineering practice.

[Michael GilliganParticipant @michaelgilligan61133]

O.K. … one last response

The concept of ‘nominal size’ is grasped !

So is the fact that by international agreement 1” = 25.4mm

Sometimes [for example Dremel shanks in Dremel chucks] ‘nominal’ is adequate.

Sometimes [for example whatever shanks in a proper, watchmaker’s style, 1/8” collet] 3.2mm would be inappropriately over-size.

Please feel free to continue the discussion amongst yourselves.

MichaelG.

[HopperParticipant @hopper]

Don’t forget your handbag.

[Robert Atkinson 2Participant @robertatkinson2]

Don’t give up Michael.

The other thing that matters is thectolerance they are manufactured to. No point in in sizing to a precision  that is smaller than the tolerance.

This is a particular peeve of mine with work documents where people put values to several decimal places just because their calculator or spreadsheet spits out that result.  A recent one was putting a reference temperature in a formula to two decimal places when the tolerance on the test pass / fail was +- 3 degrees. The number was correct but should have be rounded to the nearest degree.
Measuring to a hundredth of a degree at the range in question is not trival.

Robert.

[old martParticipant @oldmart]

The average user of this type of tool is not likely to be able to tell the difference in diameters.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

No point in in sizing to a precision that is smaller than the tolerance.

This is a particular peeve of mine …

A peeve shared …

[Neil LickfoldParticipant @neillickfold44316]

Michael, After reading, I looked at the 1/8 rivets. Yip called 3.2mm   Bunnings does have 1/8 drill bits though, and they also have the 3.2mm drill bits, double ended. Next I will get one of each and see if they are the same size or really are different as they should be.

The days of the mounted point shanks being a reliable accurate size are sadly long gone. Even the 3mm shank ones are all over the place compared to what they used to be.

Just a sign of the times and the cheaper lower specifications to get it out the door quicker.  The collets are not the same as they used to be either. With my original Dremel from 1987 came with the imperial collets, as well as the metric 3mm, 2.5mm and 2mm. Imperial were 1/16, 3/32, 1/8. all collets are steel.  My exact model , Dremel have no spare parts  for them anymore. So when it fails, will be the end of it. It also came with a very nice 3 jaw chuck that will hold upto a 4mm drill and all runs very true. Its a 240v50hz model made in the USA for the Aussie market and sold in NZ. I don’t think anything Dremel is made in the USA anymore.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the input, Neil … it’s much appreciated

I will be interested to see your findings.

MichaelG.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

…. give up Michael. …

 

….This is a particular peeve of mine with work documents where people put values to several decimal places just because their calculator or spreadsheet spits out that result.  A recent one was putting a reference temperature in a formula to two decimal places when the tolerance on the test pass / fail was +- 3 degrees. ….

Robert.

Eggzackerly.  Many journalists are story writers, not fact delivery agents.  Often they use already approximate values and convert those with a calculator to provide an apparent very precise value totally unrelated to the real facts.

Like the original estimate might be in metres to the nearest ten, but the reported story will be in feet to the nearest one!  Idiots, the lot of them, that do that!  Energy is yet another common misconception where journalists (and sales hypists) use power and energy units as though they are one and the same.

[not done it yet]

On not done it yet Said:

On Robert Atkinson 2 Said:

…. give up Michael. …

 

….This is a particular peeve of mine with work documents where people put values to several decimal places just because their calculator or spreadsheet spits out that result.  A recent one was putting a reference temperature in a formula to two decimal places when the tolerance on the test pass / fail was +- 3 degrees. ….

Robert.

Eggzackerly.  Many journalists are story writers, not fact delivery agents.  Often they use already approximate values and convert those with a calculator to provide an apparent very precise value totally unrelated to the real facts.

Like the original estimate might be in metres to the nearest ten, but the reported story will be in feet to the nearest one!  Idiots, the lot of them, that do that!  Energy is yet another common misconception where journalists (and sales hypists) use power and energy units as though they are one and the same.

Yes we get the same in metric Australia. 30-foot waves in a wire story coming in from the US end up in the local newspaper as 9.1 metre waves. 90mph car chases end up as 144kmh chases. Seems to be a complete lack of initiative in the conversion of such estimated measurements.

But journalists and numbers are like oil and water and don’t mix. They were all the kids at school who took English and Drama etc and no maths or science. When I swanned about at newspapers in the second half of my working life, I was considered the resident black magician because I could work out percentages mentally or with a pencil and paper.  Even simple things like 20 per cent being one fifth was a mystery to the younger ones.

Management meetings were no better. Unable to work out what percentage of the staff were female when there were 78 women out of 207 employees. “A bit less than half” was the consensus after much discussion — and my figure of 37.6 percent from doodling on a notepad in front of me was disregarded as “too low, can’t be right”. (This was back pre-smartphone and all-knowing Googlistas.)

[old mart]

On old mart Said:

The average user of this type of tool is not likely to be able to tell the difference in diameters.

The average user is far more likely to be swearing at how poor the actual tool and consumables are than worry about a couple of tenths of a mm.

[jimmy bParticipant @jimmyb]

Yes, this is the sort of thig that tends to annoy me too……

 

Jimb

[HowiParticipant @howi]

Well, This has brightened up my weekend (not!)

I think some folks have too much time on their hands.(Yawn!)

[Howi]

On Howi Said:

Well, This has brightened up my weekend (not!)

I think some folks have too much time on their hands.(Yawn!)

The words “Dremel” and “afficionados” in the same sentence should have been a giveaway.

Anyway, model engineering is a pastime. It passes the time. That is its purpose.

[Michael GilliganParticipant @michaelgilligan61133]

BEFORE THIS DESCENDS ANY FURTHER … Please permit me a few words:

1. My choice of title was very deliberate: I was posing a question for “the Dremel aficionados” … on the assumption that there might be some on this forum.
2. I would not for one moment include myself in that group … my naivety being the reason for posting the question !
3. The question was specifically about the shank diameter being supplied by [Bosch] Dremel … not about the machines, or their chucks, or average-users.
4. Thanks to various snide personal comments, and some perhaps innocent misinterpretation, the spirit of my question has been lost in the muck.
5. As for the ‘pastime’ point … I invite anyone interested to have a look at my forum Profile [which has been there for a while, for that very purpose].
6. Finally … the background to my question, although it should be of no concern to any ‘participant’, is that I was wondering whether there was any point in purchasing Dremel-branded cutters for use in the BCA with its 1/8” collet. … This is, of course, just ‘research’ whilst my tools continue to remain un-homed.

MichaelG.

[DiogenesParticipant @diogenes]

Michael, make an enquiry to someone with an interest in precision grinding (as opposed to DIY store box-shifting) like Tyrolit.

[JasonBModerator @jasonb]

No 6

 

Is there any closing range on your BCA collet?

If Mine and Nick’s measurements are anything to go by then you should be able to use them in the BCA without risk of over expanding it provided you can close the collet down a couple of thou below nominal.

Failing that you could make a sidelock type holder to fit a larger BCA collet or even with the outer shape to fit the BCA spindle direct. Or use a straight shank ER collet chuck into the BCA which I have seen people use

[Nicholas Farr]

On Nicholas Farr Said:

Hi Dave, maybe you should read this post again, (all the way through) 10.25 

Typo’s excepted.

Regards Nick

Hi Nick,

I don’t see any incompatibility between what we’re saying.   Can you explain where I went wrong please?  Admittedly I’m not on top-form at the moment and am always happy to take responsibility for blunders!

Dave

[JasonB]

On JasonB Said:

No 6

 

Is there any closing range on your BCA collet?

If Mine and Nick’s measurements are anything to go by then you should be able to use them in the BCA without risk of over expanding it provided you can close the collet down a couple of thou below nominal.

[…]

Yes … but I wouldn’t even consider forcing 3.2mm [or any + tolerance on that] into a BCA/Lorch collet … which is why I asked the question in the first place.

Thanks for restoring some sanity to what was becoming an increasingly ridiculous discussion.

MichaelG.

.

Ref. __ I don’t have this many … but what I have are precious to me

https://pennyfarthingtools.co.uk/bca-sigma-collets/2023/07/07/

[Diogenes]

On Diogenes Said:

Michael, make an enquiry to someone with an interest in precision grinding (as opposed to DIY store box-shifting) like Tyrolit.

Thanks for the thought, Diogenes [but] I have no problem sourcing 1/8” cutters … the question was only posed because Dremel ones might occasionally turn-up at an attractive price.

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Dave, firstly you said my image was MichaelG’s, and then you asked what the minimum diameter the Dremel collet in question could hold, which I said that it could hold Nos. 36 to 30 twist drills, it would not even try to grip a No. 37, which is only 0.05mm smaller and had a tiny noticeable amount of wobble.

Regards Nick.

[DiogenesParticipant @diogenes]

Aah..the light dawns..

..weren’t ?Chronos?RDG? doing cheapy (sacrificial?) collets?

[HopperParticipant @hopper]

The original question was about whether Bosch are ” incapable of expressing numbers to 3 decimal places”, no mention of BCA collets etc.

Probably best thing you can do is buy a Dremel grinding point – they are not that expensive — and try it in your BCA collets. If it turns out to have the feared extra 0.025mm (0.001″) in diameter and absolutely won’t fit as a result, 20 seconds with a bit of emery paper should knock that much off the soft zinc plating on the shank and Robert is your mother’s brother.

[Nicholas Farr]

On Nicholas Farr Said:

Hi Dave, firstly you said my image was MichaelG’s, and then you asked what the minimum diameter the Dremel collet in question could hold, which I said that it could hold Nos. 36 to 30 twist drills, it would not even try to grip a No. 37, which is only 0.05mm smaller and had a tiny noticeable amount of wobble.

Regards Nick.

Ah with you.  The image mistake was brain fade – Michael never provided one!  Was misattributing the clip I took from Nick’s packaging really a problem?  My point was about nominal sizes and tolerances implied by the packaging, and the image source doesn’t matter,

Nick’s minimum diameter numbers are useful.  Looks like the collet in his Dremel will grip anything between 2.7mm and 3.264mm, a range of 0.564mm:

• No 30 is 3.264mm, bigger than 3.2mm nominal, and ⅛” (3.1750mm)
• No.36 = 2.705mm
• No.37 = 2.642mm (too small)

One for the mathematically minded.  Michael’s OP was based, I think, on what he saw as a misleading conversion from ⅛” to 3.2mm.  Does going the other way from metric to imperial cause similar mayhem?   Nick’s collet has a range of about 0.564mm – what’s that expressed as an imperial fraction in inches.  Is it a common value, like ³⁄₁₂₈”?

I think not.  A fraction calculator suggests 5551181/250000000″, which is hard to simplify.    Representing the fraction as a decimals helps,  giving 0.022204724″, close to 22 thou.

The main lesson to be learned from all this is avoid converting between systems!!!

Dave

 

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