Holistic Drill Gauge

[mklotz]

You live in the USA, home of the inferial idiocy, and you need to drill a hole that's a close fit to your part.  The closest fractional drill doesn't quite match so you have to use a chart to find the nearest number/letter size. You have metric drills so maybe one of those would be better.

Wouldn't it be nice to have a gauge with holes of all sizes (both inferial and metric) arranged in order of increasing size.  You could just test your part in the best fitting hole and read the drill size off the chart.

If this scenario sounds familiar to you, you need a Holistic Drill Gauge (manufacturer's name, not my choice). The smaller one covers hole sizes from 1/32 (0.031) to P (0.323)...

https://www.amazon.com/Holistic-Drill-Bit-Gauge-Gauges/dp/B0C55MQGBL/ref=sr_1_1?crid=5VD706NQNF7Z&dib=eyJ2IjoiMSJ9.l4aYAuY7xmAVzmLx5uFTNp4Rq4uSOuzGchC_I6q12TbIw0fSpc4ppBq6AzJUCvoSkmTbO6spvho0zEYcMtIZX-ptFaoupZRRrB-_znfJbILzPhOmGSdxZAOkr92zx1VDFVQDiUh1MlKRWguZL2QO2-z8xEHTiUaIhd7vdQF44YUJpH3EM5RWT1Z1l9q4BAPpGD5eill6Q-OA-vQuz1SWZhzlw43iZooxGeuHVLYn0YE.0dh6BXmoOfuAK-Lm-75Hu7WO1Vfy0qO-9IcfzOgsWEI&dib_tag=se&keywords=holistic+drill+guide&qid=1756485382&sprefix=holistic+drill+guide%2Caps%2C175&sr=8-1

The larger size covers from 6 mm (0.236) to 5/8 (0.625)

https://www.amazon.com/Generic-Holistic-Drill-Bit-Gauge/dp/B0D64D53P4/ref=sr_1_2?crid=5VD706NQNF7Z&dib=eyJ2IjoiMSJ9.l4aYAuY7xmAVzmLx5uFTNp4Rq4uSOuzGchC_I6q12TbIw0fSpc4ppBq6AzJUCvoSkmTbO6spvho0zEYcMtIZX-ptFaoupZRRrB-_znfJbILXXHnZ3X-0oDDROAIgZs3sv1v5DFE5YOFEx_sA_OBa5ez8xEHTiUaIhd7vdQF44YWCt9goYh_mGWjcLsUfG1kc3RYbDyY_uOGbLLiJrCjcih9vdz3KGFYZRe0tG5t95ww.ZD9P6EGyq15b5WCQ47aPQ1C_-AuAYrz0H8XoAoCXm0o&dib_tag=se&keywords=holistic+drill+guide&qid=1756485433&sprefix=holistic+drill+guide%2Caps%2C175&sr=8-2

Standard disclaimer:  My only association with Amazon is as a customer. 

[Vixen]

I have my doubts about the "Made of rigid, durable miltiary-grade fiberglass."

Gauge steel would be so much better.

Mike

[Jasonb]

They seem to have missed out that those of us of a metric persuasion have our drill sets in 0.1mm increments not whole mm.

[mklotz]

I have my doubts about the "Made of rigid, durable miltiary-grade fiberglass."

Gauge steel would be so much better.

I had the same concern but mine is very rigid.  It's an infrequently used tool and will probably outlive me.

One of the programs on my website provides a mathematical version.  Given a size, it will report the closest fit as well as the next three smaller and the next three larger - see sample output below.  Of course, it doesn't provide test holes into which to fit your part and it does need a computer in the shop - the gauge is far better.

SAMPLE OUTPUT

number of drills read from data file = 371
D    find Drill designation given hole size
S    find hole Size given drill designation
T    find Tapdrill for any tap and dot
F    find tapdrill for thread-Forming tap
X    step drilling calculations
H    display this Help/Menu
M    display this Help/Menu
Q    Quit (Esc also)

(D,S,T,F,X,H,M,Q) ?
{[d].dd or [d-]d/d (e.g. 1.5 or 1-1/2)}  Hole Size ? 0.235

(5.80 mm) with size 0.2283 (-0.0067)
(5.90 mm) with size 0.2323 (-0.0027)
(A) with size 0.2340 (-0.0010)
***** (15/64) with size 0.2344 (-0.0006) *****
(6.00 mm) with size 0.2362 (+0.0012)
(B) with size 0.2380 (+0.0030)
(6.10 mm) with size 0.2402 (+0.0052)

[CI]

Sometimes I use the drill bit holder for a quick rough check.
I have metric and Imperial metal thread checkers, and those are really handy with identifying unknown bolts and screws.
There are tap charts for normal bolt/screw threads, and also for pipe threads.

The tap charts give the tap drill size, and also a clearance hole size.

And they make under and over reams too, which are very handy if you don't want to overshoot a hole size (typically 0.001" over and under).

.

[mklotz]

They seem to have missed out that those of us of a metric persuasion have our drill sets in 0.1mm increments not whole mm.

Since you don't live in the former colonies, you would not have much use for such a gauge.  You measure directly in millimeters and then go to drill indices labeled in millimeters; no need to wade through number, letter and fractional stercus.

Drill sets with steps of 0.1 mm are rare here and would be an expensive, seldom used luxury for a home shop. My set is the more common variety - 1 to 10 mm in steps of 0.5 mm and many of the drills have never been used.

[ShopShoe]

Once I had a chart that someone once passed out for free that gave the closest fractional or number/letter size that could substitute for a metric size drill. I don't know where it is because I now have a set of metric drills matched with metric taps, which meets most of my metric needs.

I happily live in both worlds and use whatever is called for. I just wish the guy who manages the bins at the hardware store would stop mixing up the systems when restocking: Particularly hard to accept when they have rulers, screw-checkers, and calipers handily available on the top of the stock cabinets.

ShopShoe

[Krypto]

Once I had a chart that someone once passed out for free that gave the closest fractional or number/letter size that could substitute for a metric size drill. I don't know where it is because I now have a set of metric drills matched with metric taps, which meets most of my metric needs.

Something like this? (See attachment).

[john mills]

local manufactures  in melbourne still hand out size charts you can see if what you have will fit or do

[AVTUR]

I am not sure whether I understand this subject. I have never felt the need for a drill gauge plate and as for a chart of imperial, number/letter and decimal drills I now use Tubal Cain's "Model Engineer's Handbook". I have two copies, one in the workshop and the other in the office.

AVTUR

[ShopShoe]

Krypto,

I have a similar chart.

I downloaded your example to add to my collection anyway,

Thank You,

ShopShoe

[petertha]

Drill sets with steps of 0.1 mm are rare here and would be an expensive, seldom used luxury for a home shop. My set is the more common variety - 1 to 10 mm in steps of 0.5 mm and many of the drills have never been used.

I bought some (what I consider) reasonably priced 0.1 mm sets from AliExpress. Prices shown are CAD so multiply by 0.73 = USD. Luckily they are of excellent quality. I use the heck out of them. I machine in IMP because my DRO & dials are set up that way, but fasteners & tooling are predominantly MET because of availability & proce.

[bent]

All this reminds me to put my Machinery's Handbook in the box to take home come Retirement Day...