how do u identify bolts? - PeachParts Mercedes-Benz Forum

Ethan · #1 07-14-2006, 09:25 PM

what is proper bolt nomenclature,

I have a bolts I want to purchase more off.

Went to HomeDepot and sized the bolt in their display and it fit the M8 - 1 hole.
What does that mean?

The threads are 15mm in length and the head is 5mm in width for a total length of 20mm.

I assume my bolt is a 8 - 1 - 15 is that correct.

It is also a Torx head, are they described similarly as other bolts?

Scott

Monomer · #2 07-14-2006, 09:40 PM

"M8" refers to thread pitch.

I'm not to keen on metric fastoners - But I do beleive that "8-1" means 8 thread per 1mm.

Torx (with IS trademarked) is just the form of head on it. More commonly you'll see SHCS (socket head cap screw) FHCS (flat head cap screw) Carrage bolts, and Button head's. I recommend looking up "Industerial Fastoners" (with the correct spelling, of coarse) in your local yellow pages. The guy behind the counter will more than happy to assist you in finding the proper bolt, and depending on quanity, he might just give you it, and it's not even worth his time to ring up (their around $.08/ea.)

ninety300E · #3 07-15-2006, 11:43 AM

I do not know what the #1, is but metric bolts are identified as follows:

8mm (major diameter of threaded area, not head size or root of thread), 1.0 (thread pitch, crest to crest in mm) You will find thread pitchs of .5 (very fine), .75 (fine), 1.0 (average), 1.5 (medium), 1.75 (coarse).

American standards are identified by TPI (threads per inch), ie 5/16-18 (5/16 diameter X 18 threads per inch.

If in doubt do a google search on metric hardware.

Michael

EDIT:
Length does not include the head thickness, the only exception is with flathead hardware, flatheads are measured by total length.

mpolli · #4 07-15-2006, 02:41 PM

Ninety300E is correct. Also to be considered is material(alloy), grade(strength) and finish(plating). Metric nomenclature usually starts with "M" such as M8-1 x 15 Socket Cap etc. The book I have here (from Tacoma Screw Products) shows standard M8 to be pitch 1.25 and M6 to be 1.0. However that doesn't mean you don't have a M8-1. A pitch of 1mm = 25.4 TPI and 1.25mm = 20.3 TPI so you can measure how many threads in an inch and figure out the pitch. And the diameter is pretty easy to measure.

Mike

Ethan · #5 07-15-2006, 04:17 PM

Every know and then I like to just thank everyone for ALL the incredible answers to all my questions - lots of time I get private answers where I cannot write back and thank that individual.

I used a gauge at Home Depot to get the 8 - 1 size and after using the techniques here on this forum it may well be a 8 - 1.25 pitch.

I wanted to duplicate the Torx style head but at this time I just want an allen head due to the bolt location. On Monday I'll go to some supply hoses and see what I can find.

Stay cool and safe!

Scott
1998 C230 86K - best car I could imagine owning.

ninety300E · #6 07-15-2006, 04:22 PM

Ethan, check out www.mcmaster.com for your hardware needs as well as to gain all info needed on bolt grades, sizes etc.

Do not attempt to "change" metric to inch........metric is a superior method of measurement.

Michael

rwhyde · #7 07-15-2006, 06:01 PM

I think you got the idea on how to identify the botls but more importantly, be careful about the grade (strenght) of the bolt you are using. If is best to just to your local MB dealer and get the correct bolt for you application. Using a lower grade bolt might cause it to break in your application and then it just multiplies the problems you experience. I know this might sound like overkill and I too do things in a temporary fashion until I can get a proper fasterner, but just some friendly advice from the audience.

Wayne Hyde

Ethan · #8 07-15-2006, 09:25 PM

Wayne,

I've tried my dealer but they can't locate the bolt, it isn't shown on the computer database - it's two torx bolts that hold the speed sensor bracket to the steering knuckle on my 1998 C-230 - I've even e-mailed MB technical.

So for now I'll install any bolt that is the correct size

Thanks
Scott

Monomer · #9 07-15-2006, 10:52 PM

Quote:

Originally Posted by rwhyde

I think you got the idea on how to identify the botls but more importantly, be careful about the grade (strenght) of the bolt you are using. If is best to just to your local MB dealer and get the correct bolt for you application. Using a lower grade bolt might cause it to break in your application and then it just multiplies the problems you experience. I know this might sound like overkill and I too do things in a temporary fashion until I can get a proper fasterner, but just some friendly advice from the audience.

Wayne Hyde

A SHCS will be just fine, as most are rated grade 6 (I beleive)

ninety300E · #10 07-15-2006, 11:04 PM

Socket head cap screws (SHCS) are grade eight.....there is no such thing as grade 6. The confusion may be due to hex head grade 8 bolts (SAE) have six radial lines on them to identify them as grade 8. Three lines designates grade 5, this is sae and nf, nc, USA marks. Metric goes by numbers on the head.

Here is a simple chart: http://www.boltdepot.com/fastener-information/Bolt-Grade-Chart-A.aspx

Michael.............still serving my 30 year machinist apprenticeship

Ethan · #11 07-15-2006, 11:15 PM

do chk out www.mcmaster.com as mentioned above

socket head cap screw is what I'm looking at.

what happens when you put a 1.25 pitch screw in a thread that uses a 1 pitch?
and vice versa. do the threads strip? does the screw entre easily or not thread in at all unless you use lots of force?

hs_300e · #12 07-15-2006, 11:28 PM

Check out http://www.boltdepot.com/fastener-information/Default.aspx - all you wanted to about bolts and nuts is in here.

The following page - http://www.boltdepot.com/fastener-information/Printable-Metric-Thread-Gauge.pdf - has images of various metric thread pitches. When you print it, the images are printed to scale. So you can very easily compare your bolt's thread pitch with the print out.

Monomer · #13 07-15-2006, 11:56 PM

Quote:

Originally Posted by ninety300E

Socket head cap screws (SHCS) are grade eight.....there is no such thing as grade 6. The confusion may be due to hex head grade 8 bolts (SAE) have six radial lines on them to identify them as grade 8. Three lines designates grade 5, this is sae and nf, nc, USA marks. Metric goes by numbers on the head.

Here is a simple chart: http://www.boltdepot.com/fastener-information/Bolt-Grade-Chart-A.aspx

Michael.............still serving my 30 year machinist apprenticeship

dang, forgot to add two..

I'm going on two years machine experience here, fresh out of highschool.

mpolli · #14 07-16-2006, 02:03 AM

Quote:

Originally Posted by Ethan

what happens when you put a 1.25 pitch screw in a thread that uses a 1 pitch?
and vice versa. do the threads strip? does the screw entre easily or not thread in at all unless you use lots of force?

Is this a trick question? You will get about half a turn before damage begins.

Mike