Enlarging hole in sight disk, . . . Non Bubba

[Jeff R]

I would like to gradually enlarge the aperture in this disc, until it is "just right." I don't want to just drill it out and then wish it was smaller.
194454

Is there a bit, or tool that would do this? I was thinking of coating a round toothpick in lapping compound and spinning it with a drill. I don't want it to take hours. Any suggestions are welcome. I know somebody knows.
Thanks!
Jeff

[waksupi]

I would just use a set of number drills, graduating in thousandths.

[NSB]

Does Anschutz make an adjustable disc for their sight? Most "modern" sights have either screw in aperture or a "leaf" that rotates over the hole to change hole size. Is this a possibility? I've got a number of guns with adjustable apertures from various makers. The problem with what you want to do is that the hole size will never be right for all distances and lighting conditions.....I know, I've been there/done that. Check into it before you proceed any further. Good luck.

[MostlyLeverGuns]

There is an adjustable aperture, the Merit aperture. It adjusts. Midwayusa, Brownells, EABCO all list them. Available in different sizes and for different sight brands. Screws in like standard fixed apertures. Useful because aperture size can be adjusted for different light conditions.

[country gent]

There is the merit disc that's a camera shutter type adjustable appeture. Anshultzs, Gehman, and a couple others that depending on the appeture have adjustable appetures, color filters, diopeter adjustment.Yo just need to know the thread size and pitch, along with length of the thread.

[Cap'n Morgan]

A tapered micro reamer would do the trick and make it easy to gradually open the the hole to the right size (which should be done from the front for a sharp edge towards the eye) It may be over-kill for a single hole, but here goes:

http://www.micromark.com/mini-hand-tools/reamers

[Nueces]

I've used Merit iris disks for nearly 50 years. The opening can be adjusted for light conditions, from a tight target one to a wide ghost ring one. It's a fine sighting accessory.

I have an old set of Parker Hale tapered sight reamers, complete with a nickeled case. They're either 5 sided or 7 sided, and similar to some of the ones the Cap'n linked to at MicroMark. Included is a tiny conical deburring cutter, to take off the fuzz.

[waksupi]

Come to think of it, I believe I have aMerit around here I would part with.

[Hick]

I opened mine up using numbered drills. I started with one that was almost exactly the size of the original opening and ran the bit through by hand (turning it). Then I looked through it to see what I thought, and went to the next number bit. that one did it for me.

[Ballistics in Scotland]

Jeweller's reamers are tapered but just pentagonal in section, and very slow in steel. The best tool is a taper pin reamer, which has a taper of ¼in. per foot in imperial or one in fifty for metric. eBay is full of them, and here is a table of sizes. They will go into a tubular front section of the disc, and the taper is enough to avoid light shining on the side of the hole.

But for anyone who has a Dremel tool, there might be more benefit in a ⅛in. shank carbide burr with a long conical point. It might be cheaper, and a lot more useful for other jobs than the taper pin reamer. For the aperture I would use it by hand rather than under power.

[KCSO]

As Waksupi says use the numbered drills and don't forget to deburr the holes front and back before rebluing.

[samari46]

I've wrapped the threads in teflon tape to prevent damage to the threads and set it in a three jaw chuck for my lathe. Used a selection of numbered drills to get the hole where I needed. Used a slimmed down wood dowel with a tiny bit of silicon carbide paper to remove any burrs than cold blue on a q tip. Old eyes and need all the opening I can get. Don't need to crank down on the 3 jaw as the stub with the threads is thin enough as it is. Frank

[waksupi]

I generally use the small aperture to sight in, and then remove it all together for general shooting and hunting.

[KenH]

I think one of those adjustable apertures would be nice. I ordered a Pedersoli and it came with a .030" hole in disk - too small to see anything for my 70 yr old eyes! I opened it to .043" with numbered bit, helps a LOTS. I got a Lee Shaver economy sight which came with a .050" hole (per Lee Shaver) which is really nice. I'm thinking I just might open the Pedersoli disk up to .050" also.

easy to open up, just using numbered drills of right size.

Ken H>

[JSnover]

I was thinking of coating a round toothpick in lapping compound and spinning it with a drill. I don't want it to take hours. Any suggestions are welcome. I know somebody knows.
Thanks!
Jeff
I've lapped, polished, and honed a lot of things a lot of different ways and the abrasive toothpick seems like it would take a long time. If you can't find the right replacement disc, the drills or reamers would be the way to go.

[country gent]

I have used the 45* coned single cut carbide burrs to open appeture holes up with good results. I wrapped behind head with tap to slip fit in appeture tube so it was centered closer. then turned by hand. This gives a nice knife edge on the hole for a crisp edge. Keep in mind when cutting at the angle it dosnt take a lot to change dia of the hole. Work slow and carefull. A small stop collar on the shank similar to a case trimmer might be really helpful.

[gzig5]

The Merit apertures have an odd English thread that fit Redfield and Lyman sights. The European sights have a metric thread (9mmx1?) and accept apertures from Gehman, Anshutz, Centra, etc.. there are adapters to fit Merits to the Euro sights. I use drills to open fixed apertures up, reamers are expensive and not warranted. Best done in a lathe if you don't want to Bubba it, but a steady hand with a drill or pin vise can do it.

[imashooter2]

How will you know what just right is until you go past it? [smilie=1:

[Col4570]

Make a square Taper Reamer out of a Small round File by carefully grinding and keeping a sharp edged square.Do not overheat during grinding.The reamer will gradually open up the aperture to your requirements.Finish by removing burs with a drill larger than the aperture.The same type of reamer can be made for Flintlock Touch holes.