The Stovebolt Site Forums The Shop Area Engine Shop bolt sizes and TPI

finally putting together the bolts and looking for threads per Inch on:
clutch housing, water pump, fuel pump, transmission to bell, the starter wishbone and starter.
thanks for any help and cheers to all bolters! Lynn

Pretty sure those are all going to be National Coarse thread. Get yourself a thread pitch gauge to confirm.

And remember...if it don't fit don't force it.
I purchased a string of thread checkers a few years ago, and it was both male/female along with being both metric and SAE. best money I ever spent. I think I paid 25 bucks.

Generally, Al and CI use NC threads, steel uses NF threads, so, if there is doubt, start there.

Ed

The only fine threads I know of on an AD truck are the door hinge bolts, the parking brake cable clevises, and maybe the adjuster for the clutch pedal.

Yeah there isn’t much fine on the whole truck
I think could add only:
Lug nuts are 1/2 inch fine
And there are two fancy screws holding the speedometer face onto the odometer housing, 5-40 or 5-48 not common thread at all. The spark plugs being metric 14mm is that fine for the size?
The bolts holding the universal joints together are fine
And so are the engine mounting bolts at the front of the engine into the frame rail
The back of the engine might be a fine larger bolt but I don’t recall at the moment
-s

Lynn this is not aimed at anyone. It is commentary. It's good time to give a perspective. I've said this before on other posts.

Figuring out the bolts and general hardware is about the easiest task in restoring, refurbishing, assembling a basket case or a case of forgotten where hardware goes.
Most bolts are UNC (coarse). A few are UNF....door hinges as said. They are Carbon steel. Gr 5 is plenty strong. Trim screws are SS. Not many, if any, are AL and I don't know what Cl is.

Hardware is a basic component found all over the truck. If you want to learn a basic skill and enjoy fixup up trucks and all things mechanical, Bolts, Nuts, Washers and screws are easy. You don't have to learn the decimal equivalent like I had to, fractions are OK. Vendors and Stores speak fractions.

The tools and tricks:
1. Buy a tap and die set with hex dies. The set will have a thread gauge. You need the set to chase threads, renew threads, cut the rust and gunk out. I always save and reuse hardware. You don't need a set of "thread chasers".

2.When you see a threaded hole that needs a bolt, use a thread gauge if you can see OK. Have yourself a collection of known bolts and nuts. One of each size normally seen on our trucks. You use as a go/no-go gauge.
A thread gauge, calipers and a few trial bolts and nuts is a cheap kit. Asking folks to tell you a size for this and that is making them do work you can do and should do.

3. For length, it's the calipers. You figure what is called the stack-up. For thru hole conditions it's the thickness of parts, including the nut and washers and a little stick-out. For Blind hole condition, it's depth of threaded hole, plus stack-up, minus clearance at bottom of hole. The calipers are also used for basic diameter of hole or bolt or nut thread.

After a while you get leaned and know threads and sizes by sight. Threads are delineated by no. or nominal diameter, then the pitch/TPI/threads per inch, UN classification, tolerance(accuracy) and gender. I.E. Drawing callout: 4-40 UNC-2B.... .250-20 UNC-2B..... .375-24 UNF-2A. Now we have GD&T to add to that.
Common UNC sizes are 1/4-20. 5/16-18, 3/8-16...then you will also be able to know the hex size by sight many times. Like socket or wrench to use. 7/16, 1/2, 9/16, etc.
It's kind of nice to learn. It makes things faster and easier. No waiting for some answers on the internet. All mechanics, Jr or Sr, know that basic stuff.

When I renew old hardware, which I like to do, I don't media blast them. It takes off some coatings and sometimes turns them gray. I want to maintain that good old "blackened" look of them. So I clean then with gas and a wire brush, then wash and scrub with soap and water, then wire wheel to super new clean, then chase if needed, then blast with brake-kleen. Albeit I live in an area where there is no rust. Metal hardware on the truck does not get old. Once in a while the threads are damaged or rusted beyond rethreading. Flat washers are reusable. Don't reuse a split lock washer if it's flat.

There are many ideas and methods use by members here. They all work and have merit.

For decimal/caliper measuring: screws 2, 4, 6, 8, 10. start with .086 for no. 2 and add .026 each size up. .086, .112, .138, .164
1/4 and up is easy. Just decimal equivalents.

Sheet metal screws are caliper measured and are same nominal sizes as UN. 2, 4, 6, 8, 10, 12. If they have a taper, measure at the head end.

Bottom line, it's not learning a thing to ask what size bolt to use. It's arm chair mechanic'in. Figure it out, make a list and go to the store. Kits are too expensive but if you copy their lists it gives you a ball park location and size for bolts.
Merry Christmas everybody.

Great write-up and solid advice. The one thing I would like to add is a thread chart and this is coming from my machinist background. I know you said you don’t have to learn decimals like you and I did, but unless you have a calipers that read in fractions, (yes they do make them), most calipers read in thousands or tenth of an inch (I have a cheap plastic one that reads in tenth’s) you’ll have to convert from decimals to fractions. As a career machinist, I have most common ones in my head but a thread chart makes this easy, in addition it will give you the drill size for taping a new hole.

I’ve attached photos of mine. Just my two cents!

For the sheetmetal joints, large diameter flange head bolts really make a difference in the look. Nothing looks worse than hardware store bolts holding the fenders on.

Good info guys. I forgot to mention a cheap bolt sizer could help some folks. Click
Alvin was the first to mention

These two thread checkers are sort of what I was talking about, just get some bolts and make your own "go/no-go" set, as I called it.
Click
Click

Here is the thread gauge I use that came with tap and die set. Click

SAE threads (Society of Automotive Engineers) is standard American threads. UN Unified National. Sometimes called "inch". As opposed to Metric threads. The Automotive industry actually started the whole Engineering world to evolve and begin to standardize.... today we have ANSI specs and etc..
Also a shout out to Andrew Carnegie for his early Engineering and Technical schools where my Dad went in the 1920's/30's.
Henry Ford for his assembly line process and his use of tolerances, to be able to use any part in the bin to fit any part in another bin, is an overlooked massive advancement. He was the champion of interchangeable parts back then. I am the champion of TMI.

Phil,
Machinists: When I worked, I made sure I was good friends with the machine shop. I learned a lot from them about how to design for manufacturing needs and the tolerances they and their machines could hold. Those guys did not get much credit except from guys like me. They found my errors.
Once we got it down, a part was released to a vendor for quantity production.

Ken, Ed was referring to what the bolts screw into - AL = Aluminum of course, and CI = Cast Iron.
Very detailed writeup on your part, and good recommendations. It's been said that if you have a Chevy, you only need a 1/2 -9/16 wrench. That's pretty close.
Merry Christmas to you as well.

Thanx Kevin. For some strange reason I was thinking Cl was CL.

Sorry Ed. I see your point now.

the front engine mount on the 216 has 7/16-20 x 2
the outside bolts in the mounting assembly are 3/8-24 x 2
is it best to go with the fine or course to replace - i see a Denny Graham write up
and it states course thread @ 14 - trying to match the black oxide but should i switch
from the fine to course and replace with new castle on both or nyloc nut? thanks for your advise, Lynn

I found the correct 7/16 carriage bolts for the front engine mount on Amazon. They were zinc (or maybe cadmium) plated. Unless you want to drill them for cotter pins, I would use Nyloc nuts on them (or another prevailing torque style nut.) 7/16-14 is coarse thread and 7/16-20 is fine thread. Either will work, but fine nuts are probably harder to find, as 7/16 is a fairly uncommon bolt size.
What's interesting is that the 1929-1954 Parts catalog doesn't even list 7/16 carriage bolts, but does list 7/16 nuts in all types (including the castellated lock nuts) in both coarse and fine thread.