A question for the Dremel afficionados

[Michael GilliganParticipant @michaelgilligan61133]

Has Bosch really changed the tool shank diameter from 3.175mm [1/8”] to 3.2mm, or are they just incapable of expressing numbers to 3 decimal places ???

It may not matter to you, but it matters to me.

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, I’ve had this unopened Dremel grinding stone for at least five years, which states that the shaft is 3.2mm diameter.

Although I haven’t tried it in the 1/8″ collet, I’m sure it will fit, as the 1/8″ collet that I have, will hold twist drills firmly, and without undue force on the collet nut, from Nos. 36 to 30. Most of the 1/8″ tools that I have, are actually 3.5 to 3.7mm diameter shafts, and a few are about 3.8mm. So I guess they just round up the stated size to the closest metric equivalent.

Regards Nick.

[Maurice TaylorParticipant @mauricetaylor82093]

Hi, Why does a difference of 0.025 mm matter ?

Maurice

[Michael GilliganParticipant @michaelgilligan61133]

It’s the truth that matters, Maurice

MichaelG.

[JasonBModerator @jasonb]

Have you measured one of the 3.2mm ones Michael? it would confirm if they are telling the truth or rounding it up then you may be able to sleep easy tonight.

At least they are consistent as the collets are also given as 3.2mm so you should not need to worry about fit and if anything like mine they will close down quite happily onto 1/8″ and 3.175mm shanks as well as any 3.2mm ones.

[JasonBModerator @jasonb]

Well all I can say is does it really matter to you? If it did you would have checked your facts before your opening post as it would seem from checking a dozen of my Dremel brand bits some at least 10yrs old and never used that none are 3.175mm or 1/8″ in old money. Sorry if that has ruined your world

I suppose that is the difference between a true practical aficionado and one who just plays with words and numbers😛

Interestingly the 3.0mm shank ones from other sources are a lot closer to 3mm than the Dremels are to 3.175mm

[JasonBModerator @jasonb]

If the 3.2mm ones are made to similar tolerences then they should be closer to 3.175 than the old 1/8″ ones as they would be that little bit bigger!

 

 

 

[JasonBModerator @jasonb]

Oh that’s a new one I did not know about, you can insert multiple images in one go if you select and drag a group.

[JasonB]

On JasonB Said:

Have you measured one of the 3.2mm ones Michael? it would confirm if they are telling the truth or rounding it up then you may be able to sleep easy tonight.

At least they are consistent as the collets are also given as 3.2mm so you should not need to worry about fit and if anything like mine they will close down quite happily onto 1/8″ and 3.175mm shanks as well as any 3.2mm ones.

Thanks for all the input, Jason … but perhaps not for your abrasive tone.

It was just a simple question

I am well-aware that Dremel’s shanks fit Dremel collets.

MichaelG.

[bernard towersParticipant @bernardtowers37738]

I think ill go back to sleep now

[not done it yetParticipant @notdoneityet]

Anyone who worries about a dremel shank size varying by that microscopic amount needs to chill out, IMO.  Most normal people are likely to not notice, or bother about, a one thousandth of an inch.  Only precision fits, like shrink fitting, or similar, actually need to measure to better than that.  Poster will just have to lap the shanks by that odd thou (if necessary) and also should check the collets are actually to that same precision (which I very much doubt).

Only if the shanks will not fit the collets is there any worry whatsoever.  Even ER-8 collets (precision items) accommodate shanks with a 0.5mm range – and nobody moans about that.  They understand that the stated precision will only be at the specified collet size and not the whole usable range).

Further, expressing the dimension to two significant figures means that the actual third significant figure value could be anything between 3.15mm and 3.24mm? (simple maths convention for rounding numbers🙂).  That might/should indicate the collet would accommodate any shank size in that range.

As an aside, I wonder what exactly was the tolerance for the value 1/8”?  Plus or minus 1/16th, 1/32nd, 1/64th, 1/128th, or ….?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, okay, I’ve opened the grinding stone with the 3.2mm shank, and measured it.

It’s much the same size as most of mine are.

The measurements 3.7 and 3.8mm, I’ve stated in my post above, should be 3.17 and 3.18mm

This maybe of interest Dremel 4485 Collets & Chucks

Regards Nick.

[SillyOldDufferModerator @sillyoldduffer]

Truth or inexactitude?  More what the packaging doesn’t say than a deliberate fib or cock-up I feel.  We aren’t told he all important tolerances, and without them the dimensions we’re given are just guidelines.  Both the hole in the collet and the diameter of the shaft were made within manufacturing tolerances,

I suggest there’s no particular need for the collet in a hand-held tool to be high-spec.    For example, 3.175mm is within tolerance for an H9 shaft in a 3.2mm H8 hole.   As a user convenience this is a ‘Free Running Fit’ allowing tools to be inserted and removed easily.

Grip is achieved later by tightening the collet, and it is how well the collet and collet holder are made that determines alignment and run-out.   I don’t recall the collet system being fully specified in my Dremel manual; only the basics.

The simple message in this diagram from Michael’s packaging tells me the collet is a notional 3.2mm, therefore don’t  shove a 3.3mm twist drill into it and expect the Dremel to still be good!  The shaft on the tool should be 3.2mm or a little under.  3.175mm should be fine,

Collets are easily damaged by pushing even slightly oversized rod into them.

Rod smaller than nominal collet size is less of a problem, unless of course a Gorilla deforms a collet by forcibly squeezing one below it’s minimum diameter.  Anyone measured the minimum diameter a Dremel collet can grip?

Dave

[Nicholas Farr]

On Nicholas Farr Said:

Hi, okay, I’ve opened the grinding stone with the 3.2mm shank, and measured it.

It’s much the same size as most of mine are.

The measurements 3.7 and 3.8mm, I’ve stated in my post above, should be 3.17 and 3.18mm

Regards Nick.

Many thanks for making that sacrifice, Nick … and for correcting your previous typo.

What you have done seems to support my initial suspicion that 3.2mm is a convenient bit of “Metric presentation” rather than a manufacturing reality.

MichaelG.

[SillyOldDuffer]

On SillyOldDuffer Said:

[…] The simple message in this diagram from Michael’s packaging […]

🙁

Nick’s packaging

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

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

Typo’s excepted.

Regards Nick

[not done it yet]

On not done it yet Said:

[…]

Almost all of which is irrelevant to my reason for asking the question.

[ which I intentionally did not disclose, because I was simply seeking information ]

If you feel the urge to make gratuitous insults, there are plenty of  ‘social media’ sites available.

MichaelG.

[JasonBModerator @jasonb]

Dave My 1/8″ nominal or 3.2mm collet happily holds 3mm metric shank cutters. If I want a bit less than that I have the drill chuck for it or smaller collets.

Interesting that the Chinese supplier of my cheap burrs that I use in the dremel seems to have managed to get a lot closer to 3mm ( 0.1181″) than Dremel can manage to get to 3.175mm. None of the other various 3mm shank tools measure less than 0.1175″ or over 0.1182″ and at a fraction of the cost of the branded Dremel items.

[Another JohnSParticipant @anotherjohns]

Sort of off-topic, but Jason – thanks for the mental exercise as I sit here with my morning coffee.

It has been maybe 30-35 years since I used an imperial micrometer; I got “converted” in the mid ’90s when living in Europe, and don’t own any inch micrometers.

Thanks for the flash-back to my youth!

JohnS.

[BazyleParticipant @bazyle]

Given that it was originally a German company why would they have made the parts 1/8″. Probably not going to change for the American connection. Or maybe it is some round figure in 64ths.

[Michael Gilligan]

On 19 September 2024 at 23:14 Michael Gilligan Said:

Has Bosch really changed the tool shank diameter from 3.175mm [1/8”] to 3.2mm, or are they just incapable of expressing numbers to 3 decimal places ???

 

Neither. Bosch is not stupid. Both 1/8″ and 3.2mm are the nominal shank size. To specify a mass produced non-critical shank size to 3 decimal places of a millimetre would be plain stupid.

 

[Bazyle]

On Bazyle Said:

Given that it was originally a German company why would they have made the parts 1/8″. Probably not going to change for the American connection. Or maybe it is some round figure in 64ths.

I suppose it was to suit the existing industry standard Die Grinder bits etc that are 1/8  and 1/4

Mr Dremel also invented his handheld machine in America so that would also tie in with fractional bananas

[Bazyle]

On Bazyle Said:

Given that it was originally a German company why would they have made the parts 1/8″. Probably not going to change for the American connection. Or maybe it is some round figure in 64ths.

Dremel was originally an American company. Hence the nominal 1/8″ shanks. Bosch bought the Dremel company out in recent years. 3.2mm is the internationally accepted and used equivalent nominal size to 1/8″.

All sorts of things from pop rivets to metal plate are sold as nominal 3.2mm rather than change machinery and rolling mills etc to make them a round 3mm and then have a problem where new pop rivets or plating would not fit together with old mating components etc.

 

[Michael Gilligan]

On Michael Gilligan Said:

Many thanks for making that sacrifice, Nick … and for correcting your previous typo.

What you have done seems to support my initial suspicion that 3.2mm is a convenient bit of “Metric presentation” rather than a manufacturing reality.

^^^ Job done, so far as I am concerned

MichaelG.

[HopperParticipant @hopper]

Not “convenient metric presentation” at all. Just a nominal size, as per standard practice worldwide.

What next? Measure the hole up the middle of a piece of half-inch water pipe and wonder why it does not measure 0.5000 inches?

Interestingly, the metric equivalent to 1/2″ water pipe is 15mm water pipe, because that is closer to what the hole in a nominal 1/2″ pipe actually measures.

 

 

[Author]

Posts