Working DIY Micro Auto Disk

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LiveLife

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I wasn't affected when Lee Precision discontinued the Micro Auto Disk as most of my W231/HP-38 charges used were higher than 3.5 gr which I used for 147 gr 9mm loads.

Since I got a 380 pistol, now I need to consistently meter 2.5 - 3.0 gr range of W231/HP-38. I initially used Lee Perfect Powder Measure to conduct my load development (which dropped consistent powder charges in that range) but now I need to increase the production rate using the Pro 1000.

I heard of reloaders drilling the side of Auto Disk and tapping a screw to make an adjustable DIY Micro Auto Disk but never seen one illustrated so I decided to make one.

I went to the local Home Depot and bought a package of #10-32 x 1/2" brass machine screws with size of head that was smaller than the thickness of the Auto Disk. I used a drill bit slightly smaller than the screw and drilled about the center of the disk hole. After I screwed the brass machine screw in and out, the hole was nicely tapped with threads for "micro" adjustment. After cleaning up the hole burrs, I was ready for powder drop measurements.

- Initial powder drop test was done at 3.0 gr of W231/HP-38 with the machine screw thread just sticking out the hole. 10 drops were spot on the Ohaus 10-10.

- 1/2 clockwise turn of the machine screw dropped the powder charge to 2.7 gr. All 10 drops measured right at 2.7 gr.

- Another 1/2 clockwise turn of the machine screw dropped the powder charge to 2.5 gr. All 10 drops measured right at 2.5 gr.

I hope this helps other reloaders who needs to meter W231/HP-38 below 3.0 gr for smaller caliber reloading.


Brass machine screws (make sure the head is smaller than the thickness of the disk)

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.30 disk hole drilled and tapped with brass machine screw

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Shown at 3.0 gr W231/HP-38 setting

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Smaller head than the thickness of the disk allows for clearance during cycling

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Confusion Microdisk vs micro-adjustable

First of all, thanks for the report on our results, especially specifying what parts you used and reporting the measurements of results. It takes a lot of the guesswork out of it for those who are less than certain they want to risk one of their disks (or don't have an extra disk).

My subject line refers to the ease with which Lee Precision's two devices are confused

1) The Micro Disk which is a half-height version of the regular auto-disk and uses a shim to adjust the other half of the height and

2) The Micro-Adjustable Charge Bar which is a full-height single cavity version of the disk, but has a sliding block as one side of the cavity, thus making the cavity infinitely adjustable. (However, small charges are still its weakness)

Thanks for reading and again, thanks for your excellent report of results and detailed instructions.

Lost Sheep

p.s. On eBay, there is a someone who is selling copies of Lee's Micro-Disk for about $20, but, of course, they are not adjustable, but are a natural for the smaller charges.
http://www.ebay.com/itm/CUSTOM-CAST...588?pt=LH_DefaultDomain_0&hash=item3cdb98fe1c

Also, Check this out:
http://www.ebay.com/itm/CUSTOM-CAST...625?pt=LH_DefaultDomain_0&hash=item3cdba34ee1


p.p.s Then there is this: A micro-adjustable micro charge bar
http://www.thehighroad.org/showthread.php?t=741097
 
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OK, I uploaded the pictures again and you should see them now.


Also did more testing at 2.3 and 2.0 gr of W231/HP-38.

At 2.3 gr, W231/HP-38 continued to drop consistently.

At 2.0 gr, thread of machine screw is more than halfway into the hole and I noticed some powder on top of the threads. Still, powder drops were consistent with holes I use for larger 4-5 gr range so even with powder on top of the threads, powder charge that drops into the case must remain consistent enough.

Keep in mind that this testing was done with small flattened and coated ball powder W231/HP-38 and would not expect similar results from larger flake powders. I may try the test with Bullseye as it can be downloaded quite well.

Stay tuned, I will be back.
 
At the same setting as 2.0 of W231/HP-38, I replaced the powder in the hopper with Bullseye (I made sure remaining W231/HP-38 grains were cleared from the top of the thread in the disk).

When weighed, I got 1.8 gr of Bullseye. I weighed 10 drops and they were consistent (less than .1 gr variation I usually see at higher 4-5 gr charges). I then tried for 1.5 gr of Bullseye and weighed 10 drops. Hard to believe, but the drops were still consistent.

So the reloaders of 25ACP, 32ACP and 380Auto rejoice! With this simple modification to your Pro Auto Disk, you may now be able to more consistently drop powder charges (at least with Bullseye and W231/HP-38).

If you want more powders tested, let me know. In addition to Bullseye/W231/HP-38 tested, I have Clays, WST, Red Dot/Promo, Green Dot, Titegroup, N320, Herco, Unique, Power Pistol, Universal, WSF, AutoComp (but I probably won't test large flake powders like Red Dot/Promo/Unique).
 
Excellent write up and pictures. I had seen a pic of one, but not as good as yours.:)

You just did a pilot hole and screwed the the screw in. No tapping?
 
Since I was drilling freehand, I used a Forstner drill bit. If I was using a regular drill bit, I would use a pilot hole.

I used a drill bit slightly smaller in diameter than the brass machine screw and used the threads on the screw to tap into the hole. As you can see in the picture, it created nice permanent threads that I can now use to infinitely adjust the powder drop charge simply by adjusting with a Phillips screwdriver.

I think it was certainly well worth the slightly more than a dollar I spent for the brass machine screws.
 
Excellent write-up; currently I'm using the adjustable charge bar. Even so, I think I'll try the disk mod just because.

Thanks bds!

Joe
 
Instead of worrying about the size of the screw head, just use a set screw.
 
Could you please test some throws with Unique. It's one of go-to powders for .380. I use the micrmeasure charge bar but it becomes a real PITA for reduced loads <3.5gr. I would like to know if this mod can get me down to around 3.0gr consistently.

Thanks for posting this.
 
I missed work today due to sickness, probably back at it tomorrow.

Figured I would give the disk mod a try.

I ended up using a spare 5mm screw I had lying around (about the same size you used).

I run some bullseye through it to test. My results were mirror of yours. Tried 2.2gr, 2.3gr, 2.5gr, and 2.6gr and all weights were very consistent. I experienced no variation with any weight in my small test.

Very satisfied with the mod, thanks again for sharing.

Joe
ImageUploadedByTapatalk1394656157.685023.jpg ImageUploadedByTapatalk1394656167.656902.jpg ImageUploadedByTapatalk1394656178.916483.jpg
 
This is extremely useful information. Thank you! Do to the current severe powder shortage and my recent start in reloading, I only pistol powder I have is Hodgdon Titegroup. I would like to be able to drop 2.5 and 2.8 gr of Titegroup. I get 3.2-3.4 gr with the .30cc disk currently. I would very much appreciate it if you could test and report consistency for Titegroup using the machine screw to reduce loads to 2.5.
 
Bullseye will meter well through just about anything. I get .1gr accuracy through my micrometer charge bar. Bulky powders are more problematic. Still interested to see if anyone has tried unique with this mod.
 
FrankTalk said:
if you could test and report consistency for Titegroup using the machine screw to reduce loads to 2.5.
I did some testing with Titegroup today and found something interesting.

While higher than 2.8 gr dropped fairly consistently, as I got lower down to 2.5 gr where more of the thread was inside the hole, I noticed Titegroup did not flow as well as Bullseye/W231/HP-38 and this led to more or less powder on top of the threads that varied the powder drops. At one point, I was getting around 2.5 - 2.6 gr for about 10 drops but when I turned the screw more to get smaller powder drops, my drops varied from 2.3 - 2.7 gr. When I looked on top of the threads closely as I cycled the Pro Auto Disk, I noticed Titegroup powder building up on top of the threads in different amounts, which explained the swings in powder drops.

Replacing the powder in the hopper with Bullseye/W231/HP-38 did not reproduce the inconsistent powder buildup on top of the threads.
evan price said:
I just used a hex-headed self tapping sheet metal screw, screwed all the way in... Drops exactly 2.5 gr of Titegroup, my preferred 32 S&W Long load.
Perhaps the self-tapping tip of the sheet metal screw with less threads in the hole helped with 2.5 gr drops of Titegroup? BTW, I did get consistent drops down to 2.5 - 2.6 gr so perhaps 2.5 gr is the lower limit for this mod with Titegroup?

So, my recommendation would be if you are using powders other than Bullseye/W231/HP-38, be careful and weigh powder drops on accurate scale (preferably one tested with check weights of similar powder drop weights) to ensure you can get 10-20 consistent drops.
 
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Mad Chemist said:
Bullseye will meter well through just about anything. I get .1gr accuracy through my micrometer charge bar. Bulky powders are more problematic. Still interested to see if anyone has tried unique with this mod.
Yes, Bullseye/W231/HP-38 metered within .1 gr with this mod down to 2.0 gr (1.5 gr for Bullseye) and would be the powders I recommend for the mod to throw smaller powder charges.

I will not be testing Unique or larger flake powders (like Red Dot/Promo) for this mod as I get .2 - .3+ gr variations with Auto Disk holes in my Pro Auto Disks and I figure powder drop variations will likely increase as screw threads inside the hole may aggravate powder bridging.
 
OK, did some testing with Red Dot which I can meter around 1.8 - 1.9 gr with .30 cc disk hole and Pro Auto Disk.

With the mod's thread screwed in less than halfway of .30 cc hole (mod setting that Bullseye/W231/HP-38 metered consistently), I got the following 10 drops (to prevent partial disk hole fill, I double-checked that my bead chain was tight and the spring compressed when the shellplate carrier was at the bottom).

1.5 gr
1.2 gr
1.1 gr
0.6 gr
0.8 gr
1.3 gr
1.0 gr
1.2 gr
0.8 gr
0.5 gr

To me, this is too much of drop-to-drop variation. Since Red Dot meters best of Red Dot/Unique/Promo, I don't think I need to test either Unique or Promo.
 
I think if you were to carefully file off (or lathe it, if you have a lathe) the threads that protrude into the hole it might help with the inconsistency of some powders. That's just a semi-educated guess though as I don't have an Auto-Disk measure nor have I ever modified one. It just seems to me that it would give the powder less to stick onto to cause inconsistent drops. It should be very quick and easy to do with the proper small file. But I'm not sure if it would leave enough threads to thread into the disk and hold the screw in place. Might be worth a shot though with the screws bein so cheap.
 
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