Bolt thread experts...HELP!

[loathar]

I picked up a Dremel drill chuck to hold micro drill bits. It won't fit my Chinese Dremel knock off. (imagine that!)Different thread pattern. All is not lost! (I hope) I can still use it as a pin vise if I get the correct thread bolt to screw in it. Dremel said the thread pattern is .28 by 40.
I'm assuming this is metric but I've never heard metric measured this way. My hardware store only has things like 8mmx1 or 6mmx .5 Any advise on what they are talking about???

[GAPPLEG]

I assume they are saying it's .28 of an inch in diameter with 40 threads per inch. Just a wild guess. Not a standard thread pattern anywhere in the world.

Just measured my dremel it's .28 inches in diameter , I have a thread guage somewhere, If I find it I'll check.

Found my thread guage , yep 40 threads per inch on a dremel shaft.

[steemtrayn]

Take the chuck to the hardware store and try to find a bolt that fits.

[Beowulf]

That would be .28 inch diameter and 40 threads per inch.  I just measured mine.  The threads mate perfectly with those of a 4-40 bolt.  I know you can't find such in a hardware store but it will take someone with machine tool experience to tell you where it can be found.

Good luck.

[loathar]

I took it to True Value. The closest thing I found was a 5/16x24, but thread was too coarse. Do they make a 5/16x28 or a 5/16x30? My True Value is run by an old coot that won't let you touch anything and hovers over you saying "that won't work!" "that won't fit!" "We don't have anything like that!" Drives me crazy!(only hardware store in town)

[GAPPLEG]

If your really determined to make a pin vise out of it , I'd get a dowel and thread that sucker onto the dowel. You wouldn't ruin the threads that way and don't have to worry about metal working to get something to fit.

[tstage]

Loathar,

5/16 only comes in 18 (coarse) and 24 (fine).  Depending on the hole and what fits in it, you could drill it out and tap it with the next size larger tap.  Of course, that will increase the size of the bolt you'd need, which may not work for you if that bolt passes through another hole.

Tom

[loathar]

The thing is...Screwing the bolt in and out will open and close the jaws on the chuck. A dowel rod might work. I'll have to give it a shot. At least I know what to look for now.
Thanks!

[GMTRacing]

Lothar - if you don't have any joy with the dowel, I'll look tomorrow and see if I can find a listing in my machinists handbook. There are all sorts of special threads out there in the real world for special applications. If a listing is found the next step is to find a bolt to suit or make a suitable threaded shaft on a lathe.  The 5/16" bolt would likely be too big with a major diameter around .31"    J.R.

[loathar]

Lothar - if you don't have any joy with the dowel, I'll look tomorrow and see if I can find a listing in my machinists handbook. There are all sorts of special threads out there in the real world for special applications. If a listing is found the next step is to find a bolt to suit or make a suitable threaded shaft on a lathe.  The 5/16" bolt would likely be too big with a major diameter around .31"    J.R.

Thanks. If I end up having to order a box online, it might almost be cheaper to buy the least expensive Dremel tool. Or just order a pin vise for $5. I was just hoping to find a bolt that worked for $1.

[GMTRacing]

No worries. We have lots of expensive stuff we made to try to save a buck. At any rate you've piqued my curiosity and now I need to know what is a .28 x 40 thread.  J.R. 

[Newyorkcentralfan]

I picked up a Dremel drill chuck to hold micro drill bits. It won't fit my Chinese Dremel knock off. (imagine that!)Different thread pattern. All is not lost! (I hope) I can still use it as a pin vise if I get the correct thread bolt to screw in it. Dremel said the thread pattern is .28 by 40.
I'm assuming this is metric but I've never heard metric measured this way. My hardware store only has things like 8mmx1 or 6mmx .5 Any advise on what they are talking about???

Since it's Chinese made, it's most likely metric. Since you're saying it's close to 5/16th I'm thinking 8mm.

There are a few different options for 8mm diameter screws. 

http://www.gewinde-normen.de/en/iso-coarse-thread.html

ISO (International Standards Organisation) Metric Coarse Threads

Nominal Dia[M x mm] Pitch [mm]  Tapping Drill Size[mm]
8,0                         1,25          6,80

Thread Profile Drawing


ISO (International Standards Organisation) Metric Coarse Thread Profile
r = Basic Radius = 0.1443 p
hn = Basic Height of Internal Thread and Depth of Thread Engagement = 0.54127 p
hs =Basic Height of External Thread = 0.61344 p
p = Pitch = 1/t.p.i.
Angle of Thread = 60o Degrees


ISO (International Standards Organisation) Metric Fine Threads

http://www.gewinde-normen.de/en/iso-fine-thread.html

Thread profile drawing


ISO (International Standards Organisation) Metric Fine Thread Profile
r = Basic Radius = 0.1443 p
hn = Basic Height of Internal Thread and Depth of Thread Engagement = 0.54127 p
hs =Basic Height of External Thread = 0.61344 p
p = Pitch = 1/t.p.i.
Angle of Thread = 60o Degrees

Nominal Dia [M x mm] Tapping Drill Size [mm] Nominal Dia [M x mm] Tapping Drill Size [mm]
8,00 x 0,50               7,50                         30,00 x 2,00             28,00
8,00 x 0,75               7,20                         32,00 x 1,50             30,50
8,00 x 1,00               7,00                         33,00 x 1,50             31,50


ISO (International Standards Organisation) Metric Special Pitches Threads

Diameter mm Pitch mm Root Dia Internal Threads Root Dia External Threads Tapping Drill Size
8                 0.75       7.188                           7.08                              7.2 mm (0.2835")

Thread profile drawing


ISO (International Standards Organisation) Metric Special Pitches Thread Profile
r = Basic Radius = 0.1443 p
hn = Basic Height of Internal Thread and Depth of Thread Engagement = 0.54127 p
hs =Basic Height of External Thread = 0.61344 p
p = Pitch = 1/t.p.i.
Angle of Thread = 60o Degrees

Is the chuck thread too big or small? If it goes on a threaded shaft on the tool that's larger, then maybe it can be drilled out and retapped to fit the motor tool's shaft? If it's bigger,  you might try wrapping some plumber's teflon tape around the shaft and building it up a bit.

 

I took it to True Value. The closest thing I found was a 5/16x24, but thread was too coarse. Do they make a 5/16x28 or a 5/16x30? My True Value is run by an old coot that won't let you touch anything and hovers over you saying "that won't work!" "that won't fit!" "We don't have anything like that!" Drives me crazy!(only hardware store in town)

When dealing with this store, bring a friend with you to keep said coot busy by whatever means necessary while you try nuts on your drill.

[GMTRacing]

Lothar,   The thread on the Dremel in understandable terms is 9/32 - 40 and is available so far as I've found only as a tap or die from places like MSC. Your best bet at this point is the junk pile at a swap meet or flea market and someones' burnt up Dremel tool. You're probably right in thinking a five dollar pin vise is a better bet as I found no listings for ready made bolts the size you wanted. The only alternative is to have a shop single point a thread on a piece of round bar to suit your needs and that will get silly in a hurry. Sorry I couldn't help.   J.R.

[Virginian]

I think you should have one made out of maraging steel !!  It will outlive us all.  Good grief, that is a standard #4-40 machine screw thread size.  It is not the most common around, but they are available.

http://www.hobbyoutlets.com/store/hobby/127-dubro-mount-boltnuts-4-40-4.html

 

[GAPPLEG]

I think you should have one made out of maraging steel !!  It will outlive us all.  Good grief, that is a standard #4-40 machine screw thread size.  It is not the most common around, but they are available.

http://www.hobbyoutlets.com/store/hobby/127-dubro-mount-boltnuts-4-40-4.html

 

Virginian, you missed the point , this is a quarter inch in diameter with 40 threads per inch

[loathar]

I've E-mailed 3 companies that MAKE bolts and none of them have that thread in stock. One said to try MSC or Carr. Believe it or not-No Flea Markets close by. Living in the country can have it's dis-advantages!

[GAPPLEG]

I have a lathe in my work shop. I haven't tried making my own threaded stock with it , I have to change out gear sets for different thread rates. I will see if I have a gear set for 40 tpi , if so I'll try to make a barrel for you. No promises ! At work right now so it will have to wait till I get home.

[steemtrayn]

I have a lathe in my work shop. I haven't tried making my own threaded stock with it , I have to change out gear sets for different thread rates. I will see if I have a gear set for 40 tpi , if so I'll try to make a barrel for you. No promises ! At work right now so it will have to wait till I get home.

Wouldn't it be easier to just send him a pin vise?

[loathar]

I have a lathe in my work shop. I haven't tried making my own threaded stock with it , I have to change out gear sets for different thread rates. I will see if I have a gear set for 40 tpi , if so I'll try to make a barrel for you. No promises ! At work right now so it will have to wait till I get home.

Wouldn't it be easier to just send him a pin vise?

Where's the challenge in that?

GAPPLEG-I really appreciate the thought! Don't go out of your way unless that's something you enjoy doing. Realistically, I can get 2 pin vises online for $5. I just didn't think this thing would have such an odd thread pattern. Guess that's what I get for having a Chinese Dremel. 
(it was a gift)

[TheK4Kid]

If it will mate perfectly with the threads of a 4-40 bolt., then try a hobby shop, they usually sale  hardware for RC airplanes and 4-40 bolts-nut-etc are common RC engine mounting hardware.

OR

Try finding a tap and die set for a 4-40 thread.I know Sears sells a nice tap and die set in their tool department, and it's backed up by Sears guarantee of free replacement if it breaks.,They may also have a metric set. I have one of these sets and use it constantly, not only for model airplane work, but have used it for my model trains also.A good addition to any workshop.I bought a used loco several years ago (Rivarossi) that had 6-32 bolts in it and both were slighhlty worn  , so I got out my tap and die set, and redid both the bolts and the threaded holes they came out of, and was back in business in 15 minutes.I allso replaced a couple of boltsdd in another engine by retapping the holes with a 4-40 thread, and used 4-40 bolts instead of the weird metrics that were in them originally because no one had them available.
However a tap and die set can come in handy for many around the house projects from vacuum sweepers, to lawnmowers, car, bikes, etc.

TheK4Kid

 

 

[GAPPLEG]

HEY , it's just like building something you can buy I kit of ,( ie: my strip mall project )  THE CHALLENGE !!

[loathar]

Thanks K4. It's NOT a 4-40 though. It's around a 9/32 with a 40 count thread. MUCH larger diameter than a 4-40. I was thinking about the dowel rod idea and just tried a pencil. Perfect fit! I think I'm on to something here! I just have to find a dowel that's the right size and a little harder wood (or plastic) and I should be in business. Still going to order a pin vise though.

Thanks for the help everyone.

[GMTRacing]

The collective groan you heard came from the forum members standing by their lathes, thread cutting gears and 60 deg tool bits in hand ready to make chips for you.  But it's been fun. J.R.

[Anonymous]

.28 is 280 thousands of an inch in diameter, which is thirty thousands over 1/4 inch in diameter, which is pretty big for micro drill bits, and Chinese dremels are only good for what they are good for; they don't adapt well, and 20k rpm is a bit fast for drilling holes, and you're not even past step one yet.  Don't expect things to get better anytime soon.

 If you want to drill a hole today; I suggest putting your micro drill into a pin vise, chuck the pin vise into your drill motor, and drill away.

-rr

[Semper Vaporo]

MicroMark lathe gears for 40tpi

20  (40)  50

30 50-40 60

30 60-40 50

40 50-30 60

40 50-40 80

80 50-20 80