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View Full Version : Dremel Tool Arbor Thread size? Replacement Screws?



GNM109
11-13-2017, 11:39 AM
If you have a Dremel tool, you may have either broken or lost the miniature screw that holds cutting discs onto the standard 1/8" Dremel arbors. I tried measuring one but neither my US or Metric thread gauges have threads anywhere near that fine.

I have 4 or 5 of the arbors in a drawer that are without the little screw. If they fall on the floor, you could get lucky and possibly find it. I have a poor batting average when I drop something that small.

If anyone knows the thread or a source for the screws, please advise. AFAIK, Dremel does not sell these separately. They only come with a new arbor and I have several of those.

Thanks in advance.

CCWKen
11-13-2017, 01:53 PM
My collection of arbors and sanding drums are all different. Some are slotted pan head, cheese head or pan head Phillips. I just count those items as expendables. I sure wouldn't spend time searching for screws then pay $5-$10 shipping for them. Throw them in the trash and get new arbors.

Next time, don't be such a "clumsy bastard". :)

Dragons_fire
11-13-2017, 02:04 PM
i have no idea what size they are. Im thinking metric but not sure. have you tried an M2 in it? I wreck the screws also because i find if i dont tighten the screw enough, the disc slips a little and will eventually cut the screw, and if its over tightened, the disc shatters or will break easier when cutting.

GNM109
11-13-2017, 02:29 PM
i have no idea what size they are. Im thinking metric but not sure. have you tried an M2 in it? I wreck the screws also because i find if i dont tighten the screw enough, the disc slips a little and will eventually cut the screw, and if its over tightened, the disc shatters or will break easier when cutting.

They are no more than 1mm and almost certainly metric. I'll keep looking. LOL

mattthemuppet
11-13-2017, 02:31 PM
might be worth making your own using a readily availably screw size (2-56?). It'll take longer to set up the lathe than it will to make it :)

BCRider
11-13-2017, 02:49 PM
Measuring four arbors I've got one of the four is most certainly a 2-56 screw. But the others all appear to be #1-64. Measured sizes were .069, .071, .073 and .082. The .082 is the 2-56 which was confirmed by threading the screw into a 2-56 nut. Just a note to say that the last one I believe came in a cheap-o set and has always had a stone wheel on it. So the STANDARD would seem to be #1 screw size.

And while I can't find it just now I recall having a really old Dremel arbor that I'm pretty sure was a #1-72 thread.

In any event checking a couple of diamond saw discs shows that a .081 drill will "just" fit. But the abrasive discs and sanding discs will only take a .078. The .081 feels like with a twist or two it could easily enough "crunch" it's way through the abrasive disc though. But even so .081 won't take a #2 screw unless the threads were to be topped off to drop the OD down to fit.

GNM109
11-13-2017, 02:53 PM
Measuring four arbors I've got one of the four is most certainly a 2-56 screw. But the others all appear to be #1-64.

And while I can't find it just now I recall having a really old Dremel arbor that I'm pretty sure was a #1-72 thread.

In any event checking a couple of diamond saw discs shows that a .081 drill will "just" fit. But the abrasive discs and sanding discs will only take a .078. The .081 feels like with a twist or two it could easily enough "crunch" it's way through the abrasive disc though. But even so .081 won't take a #2 screw unless the threads were to be topped off to drop the OD down to fit.

Yes, I've measured them in the past, although I don't recall the size. I have some taps in that range but I could never get them to fit.

The mystery continues.

QSIMDO
11-13-2017, 02:54 PM
Got a model shop near you?

GNM109
11-13-2017, 03:14 PM
Got a model shop near you?

No. The ones I used to patronize went out of business.

A US seller on eBay has 5 of the arbors with screws for $8.95 and he states that they are a "1/16th inch screw". They are something close to a 1/16th" I guess but who knows?

It may be a moot point however, since I looked on eBay and a Chinese seller has them in a package of ten with the arbors for $1.96 with free shipping! I may just order them and forget about it. LOL.

BCRider
11-13-2017, 03:19 PM
For that much? Buy three packs of them and get on with your life.... As has been said it's not worth worrying about the ones with no screws.

GNM109
11-13-2017, 03:23 PM
For that much? Buy three packs of them and get on with your life.... As has been said it's not worth worrying about the ones with no screws.

That's what I'm doing. Believe me, this is not slowing my life down very much. It's just a minor inconvenience.

Planeman41
11-14-2017, 11:14 AM
All of this could probably have been avoided with the use of a simple device called a "jeweler's apron" made from an old towel and a few thumb tacks. As a long time model builder I have been using one for years. Just fold the old towel in half and tack one edge beneath the front edge of your workbench. When you sit down, simply pull the towel over your lap and up your front. Small parts that slip out of your fingers will fall into the towel and the rough towel and creases will keep them from rolling onto the floor. In addition, the towels keeps your pants and shirt clean of oil, drips, paint, etc and you can wash it out when needed.

GNM109
11-14-2017, 11:44 AM
All of this could probably have been avoided with the use of a simple device called a "jeweler's apron" made from an old towel and a few thumb tacks. As a long time model builder I have been using one for years. Just fold the old towel in half and tack one edge beneath the front edge of your workbench. When you sit down, simply pull the towel over your lap and up your front. Small parts that slip out of your fingers will fall into the towel and the rough towel and creases will keep them from rolling onto the floor. In addition, the towels keeps your pants and shirt clean of oil, drips, paint, etc and you can wash it out when needed.

That's an excellent suggestion.

I went up to my second floor shop yesterday and did some reconnaissance on this matter. They are not 0-80, 1-72, 2-56, 1.4mm, 1.7mm, or 2.0mm. The threads are much finer than any of those. It's clearly a proprietary thread and they are not sold separately.

One alternative to use my approximately 10 screwless arbors collected over the past 40 years will be to drill them with a #51 drill and tap them to 2-56. I have hundreds of those in stock as I use lots of them for my model railroad scratch building.This is slightly larger than the hole in the #409 or 420 ceramic cutting discs that I use, but the screw will readily thread into the center of the disc and can then be attached.

Life goes on. ;)

Puckdropper
11-14-2017, 02:21 PM
This is slightly larger than the hole in the #409 or 420 ceramic cutting discs that I use, but the screw will readily thread into the center of the disc and can then be attached.


If 1-72 will fit, I'd use that over the 2-56 for this reason. You're running those things up 15-30k RPM, you don't want any more stress on them than you have to have.

I may be worrying about something that will never happen, it's just a rational fear of broken spinning cutting discs.

J Tiers
11-14-2017, 03:14 PM
I....

I may be worrying about something that will never happen, it's just a rational fear of broken spinning cutting discs.

Broken discs are a given, and that is nothing to do with the screw size etc......

GNM109
11-14-2017, 03:16 PM
If 1-72 will fit, I'd use that over the 2-56 for this reason. You're running those things up 15-30k RPM, you don't want any more stress on them than you have to have.

I may be worrying about something that will never happen, it's just a rational fear of broken spinning cutting discs.

Note my post above. 1-72 won't fit. I'll probably just forget about this project. since it's really just a waste of time. LOL.

Doozer
11-14-2017, 08:12 PM
The Dremel non-reinforced emery discs do use that small screw to secure to the mandrel.
Whatever it is, you guys seem to have figured it out. One interesting thing I have found
with those fragile emery cutting discs, is I started using them with my air turbine die grinder
that spins 60,000 rpm. I must tell you, they are much stronger and last a lot longer at
that rpm. Night and day difference. I forget exactly what I was doing, maybe some buggered
thread repair with them, but they really cut at that speed.
But for the electric Dremel tool, I have switched to the .035" thick and 1-1/4" diameter fiber
reinforced cut off discs. I get them from McMaster Carr. They have a 1/8" hole, so I make
my mandrels using a 5-40 screw, which measures .125" on the nominal. You can buy mandrels
from McMaster, but I make them from silver drill rod.

--Doozer

Andre3127
11-15-2017, 12:11 AM
About 5 years ago I switched to Dremel EZ lock wheels. They're expensive, but they last a lot longer than any regular cutting wheel with the silly screw arbor.



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Paul Alciatore
11-15-2017, 12:17 AM
That jewler's apron sounds like a nice idea, but this is what you really need:

http://www.practicalmachinist.com/vb/attachment.php?attachmentid=212828&d=1510722509

It makes finding dropped screws easy:

http://www.practicalmachinist.com/vb/attachment.php?attachmentid=212829&d=1510722560

It was written up in the August/September 2011 Machinist's Workshop. I can't tell you how many dropped screws I have found with it.

It started with a standard telescoping, magnetic retrieving tool and I added an angle bracket to hold a flashlight head that can be adjusted to any angle. A couple of extra neo magnets and it is done. By adjusting the angle of the light to almost parallel to the floor, small screws, nuts, and other parts will cast a long shadow. That long shadow makes them stand out from the dust and dirt on the floor as well as the tile patterns that are intended to hide dirt. Then, if it is steel, the magnets pick it right up.