Are you using metric or SAE stuff to build rockets?

[rharshberger]

I don't like Phillips when compared to square (Robertson) or star (Torx) screws. No camming out. And I hate slotted screws. I own 2 VWs and everything is metric. Lots of hex caphead bolts and Triple Square bolts.

I prefer Robertson drive when available they are less likely to strip the head than just about any other fastener, the one I dislike the most is double square drive (8points) used on Audi CV shafts among other parts in the same area of the car.

Triple square are also known as XZN. Imagine taking a square drive & rotating it 3 times, 30 degrees each time. You end up with 12 points. On my 2000 & 2005 Golfs they are used to attach the drive shafts to the transmission and a few other places.View attachment 431572

Triple square is used on VW's is interesting since Audi used double square fasteners on at least the 2000 Audi A6 Quattro's drivetrain (I had one and hated working on it).

 

[Greg Furtman]

Here's a good chart you can print out & put on the wall to remember things. First page is a calendar, 2nd page is a fractional/decimal.metric conversion chart.

https://www.bokers.com/userfiles/file/Bokers-Calendar.pdf

 

[prfesser]

Here's another chart from Starrett, it includes number and letter size drills, pipe threads, etc. I just finished enlarging it to 11x17 so I can read it from five feet away. The long google URL is because I couldn't find the file on Starrett's web pages.
https://www.google.com/url?sa=t&rct...tin-1317.pdf&usg=AOvVaw3M9jDH1rg_5uq1MBvCLD9F

 

[KilroySmith]

prfesser -
I looked at a lot of those charts to find a good one for my garage, didn't really like any of them, so I made my own. It is aimed at drilling/tapping holes, and synchronizes English and Metric drills, taps, and clearance holes. Need to drill a hole to tap an M2 fastener, but only have English bits? Well, this one has you covered. It's an Open Document spreadsheet for OpenOffice/LibreOffice so you can easily modify it , but maybe Microsoft Excel will open it these days.

 

[gna]

I'm so old I have two sets of tools: Metric and Imperial. I still look at a 14mm bolt and go, 'Well, that's about 9/16ths.'

Working with both systems is easier than a lot of people think, and if I win the Lottery I'll be buying a Triumph X-75 Hurricane and then I'll need those Imperial tools!

I work on older English Bicycles, so I have three sets of tools: Metric, SAE, and Whitworth.

I grew up in the 70s, when everything was Here Comes the Metric System
https://getyarn.io/yarn-clip/26701b47-72b9-4722-821d-f17164403f0cThat said, I don't know the system that well, so inches/oz, altitude in feet when working on rockets.

 

[OverTheTop]

Sutton Tools do a good chart. I have the earlier ones of these on my workshop wall. They are referenced frequently. Saves getting my Machinery Handbook (#22) off the shelf.
https://www.aimsindustrial.com.au/sutton-tapping-drill-wall-chart-free

 

[Blast it Tom!]

Crikey, that looks like a nice chart by Sutton, and it's free, but it's $56 to mail it to the US... Back to the old Machinery's Handbook. Thanks anyway, down-under OverTheTop! Did I miss a PDF link?

My 2 cents' worth - some 30 years ago, when I joined my company, we used heat transfer units in watts/(inch-°C) and the like because typically the range of values we used didn't require scientific notation. Even when Mathcad came along, the practice persisted because Mathcad can handle units so well. Certainly the rockets don't care if it's 1 inch or 25.4 mm!

 

[heada]

I was looking through my parts drawers for screws and found just about the perfect ones. #8 3/4 inch. Quick lookup on the drill chart and drill size for #8 is 1/8 inch. Huh...then I looked up #6 and it was 3/32 inch. #10 is 5/32 inch. Then it dawned on me. The # size is the number of 64ths. So a #2-56 is a drill size of 1/32 inch. Who knew the size told you the drill size?

 

[Javelin]

Reminds me of when I was working with small light bulbs. G was for globe and often the numbers told you the size measured in eights of an inch. For screws it’s 64ths of an inch. 6/64, 8/64, etc.

 

[Kelly]

For screws it’s 64ths of an inch. 6/64, 8/64, etc.

Would be nice if that were true, but it's not. For example a #6 screw has a thread diameter of 0.138, which is ~9/64. #8 is 0.164, or about 10/64. You might expect a #12 to be twice the diameter of a #6, but it's actually 0.216, about 1-1/2 times as big.