cutting M5 thread on 5mm steel rod - thread loose

  • Thread starter Thread starter Don4
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The nuts are stamped with a 5 and an 8 which I take to be M5 / 0.8. The nut certainly fits the M8 tap.
 
If I remember correctly a metric bolt stamped with an 8 simply meant that it was high tensile. I can't say whether that's the same for a nut.
 
Isn't M5 the gauge, ie, 5mm?

The pitch will be .8




Aye, pitch. I know what I meant! :):)


Mr. HandyAndy - Really
 
But if the pitch is wrong it will jam rather than wobble wont it?
 
the 0.8 refers to teh pitch, 8.8 on a bolt head referes to the tensile strength.

The link you posted says the rod is stainless steel, a cheap carbon steel die won't last long cutting that but should not give a loose thread.

Are you using a mass produced hex nut as this will have been machined to give 75% thread engagement, only way to get it tighter would be to make a custom nut.

If you are using a nut to take a hex key like the one in the link and it was sourced from america then its not likely to be a metric thread, probably whats termed "10-32" which is very close to M5 at 4.83mm x 0.79

Jason
 
for a job like this, the nut serves to be the thread gauge.

assuming he has the correct die it sound as if he is closing it up to much. back off the two screws a little, that will give a closer fit.

take your time cutting the thread as well. keep well lubcicated :)
 
Thanks for the input. I'm using the die with only the centre screw which is screwed in to open up the die as much as I can.

Interesting about the 75% thread engagement oif mass manufactured nuts but logic tells me that the die should open up enough to compensate. I'm not using an american nut.

I've ordered a new die and I'll see where I can get to with that.

Thanks for all the information and help. I'll let you know how I get on. The info here has already helped produce a big improvement. Thanks
again.

Don
 
good luck

you dont need to tighten the screw too tightly, its only a matter of a through thousandth of an inch between a sloppy fit and a tight fit.

unless your die was knackered i dont think that is the problem (the steel rod may be of a low quality as well), but you should still be able to get a thread that will suffice.

Just take your time when cutting the thread.

IWS: It Will Screw :)
 
It might be worth taking it to a local engineering shop - probably take them 5 seconds in exchange for a beer.

It might also help to cut both the rod and nut yourself from a high quality tap & die set.
 
good luck

you dont need to tighten the screw too tightly, its only a matter of a few(!!) thousandth of an inch between a sloppy fit and a tight fit.

unless your die was knackered i dont think that is the problem (the steel rod may be of a low quality as well), but you should still be able to get a thread that will suffice.

Just take your time when cutting the thread.

IWS: It Will Screw :)
 
Thanks Ponty.

Thanks Mr Grim Nasty. I Know your right. I know I could get it done but the problem is that now it's personal.

Don't worry I'll get it to work..

Cheers

Don
 
is the bar definitely 5mm? (ie have you actually measured it with a micrometer, or even verniers) does your thread have sharp peaks or flat ones? is the thread you have made true to the bar? it can be hard starting the die true and they don`t tend to pull themselves true as you go along. sometimes swarf can just clog and over-cut the thread as you go, if you liberally wax the die and bar with candle wax and go softly softly that may help. or pack the die out with lard to catch the chips. generally you always get some problems, whether tapping or dying thread, from the chips/swarf generated.

my best guess is the cheap mass produced nut problem suggested earlier, and beware, .75mm is also a common m5 pitch.
 
Don, you say your making a custom scale one. Is this for a bass guitar or ordinary 6 string? Usual scales for ordinary 6 string is either 24 3/4" (Gibson )or 25 1/2" (Fender) Truss rod length for either is usually around 17 -18". I usually make mine out of 3/16" bar. Fitted into 10mmX10mm channel with a piece of rosewood the width of the channel but around 1/8" thick in the middle tapering to nothing at either end. All fitted together into the neck before the fingerboard goes on. Good piece of advice here. always put plenty of grease on the threaded end before glueing the fingerboard on. Otherwise you could render the trussrod useless (unable to be adjusted) :)
 
Thanks folks for all the input on this.

Joiner John it's a six string but the scale is going to be slightly shorter than the Gibson size. However the rod conforms pretty much to your description. (good advice about the grease)
Thanks to the advice received here I am getting pretty good results now cutting the thread.

Interestingly (at least if your as sad as me)Tubal Cain in his workshop book Drills, Taps and Dies states that HSS dies will not be as sharp or as long lasting as carbon steel in manual usage. There advantage comes when machining threads and generating a lot of heat. (I'm just quoting here. The book was published in 79 and doesn't show much sign of being updated although it's been re-published every year or so).

I had heard that HSS would be preferable.

Anyway I have two dies one from a Screwfix set which came with a one screw die stock and split dies (with a grub screw in the die) marked HSS.

The other set from H****s and marked Made in China came with a three screw die stock and split die.

The rod is mild steel and using a vernier it is bang on 5mm thick (haven't got a micrometer).

There is a little slack in the thread engagement but I don't think its going to strip out so the problem is SOLVED. Thanks again.

There are differences though and I have to say that the die from the not-screwfix set cuts a visibly better thread than the screwfix die marked HSS.

I am going to try a Dormer split die and 13/16ths three screw dies stock for comparison.

On thread engagement, apparently 100% would not be desirable even if achievable, (Tubal again). He also states that it is the flank of the thread that takes the load put on the joint (that is one side of the thread).

Also he shows a graph depicting joint strength against thread engagement and above 75% thread engagement the additional strength added to the joint for further degrees of engagement becomes rapidly less such that increasing degrees of engagement give less and less additional strength.

Thanks for all the help .

Don
 
Well I must be sad as well because I am finding this thread (excuse the unintentional pun) fascinating not just because I love learning about anything engineer related but also because I play guitar.

I admire anybody who has the determination to build a guitar from scratch particualry when there are so many cheap copies available which actually play extremely well.

I bought a secondhand Strat copy from a colleague of the sort that would usually retail with an amp for about 120 quid and I swear it plays better than my genuine USA Strat. (albeit a 90s HM which probably weren't the best Strats ever built)
 
agree with you about learning stuff, you can never know too much and the folks here are really helpful.

If your interested I've started a thread on a guitar forum

www(dot)Guitars(dot)co(dot)uk/Forum as user Mike3124.

Agree about cheaper copies. check the forum above for a link to my e-bay telecaster (£30) to baritone conversion.

Did cost a couple of hundred quid in the end for new pickups and the conversion neck but I actually like it better than my 50th anniversary strat.

And that's probably quite enough of that on an engineering forum!!!

Don
 
I tried the Dormer die in the 13 / 16ths dies stock and the result is ever so slightly better than the "made in china
" on HSS die which in turn is markedly better than the S-fix own brand.

Truss rod now threaded and fitted so thanks to everyone for advice and input

Don
 
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