[Closed] Quick Engineering Q - clearances on bolt heads

Sorry if I've missed the point, but 30mm measured where?
And the socket, drive size presumably?

All the information about bolt head clearances is here;

http://www.roymechx.co.uk/Useful_Tables/Screws/Head_Clearances.html

Errrm, assuming the 30mm head is AF on a metric screw, that would be an M20... Why on earth would you need to 'design' a socket?

Are you one of those annoying OEM designers who f*cks about with bespoke parts to stop us using easily obtainable spares and instead come crawling back to you to pay £17M for a slightly modified M6 set screw?

Or as above, are you talking drive size, in which case you need to mention the torque you're expecting to use (I use <10Nm on a M24 thread in one application so it's not as straight forward as it sounds!)...

Why on earth would you need to 'design' a socket?

I would guess he/she needs to leave clearance around the nut so a standard socket can be fitted. Sounds like a good thing to me.

What richmars said - op is designing a recess around where a bolt head will be, and needs clearance for a socket set to get in.

What lerk says..

if you have to ask, you should not be 'fiddling' with cad.

wot they all sed but only the comments relevant to what you're actually trying to achieve which isn't clear.

if you have to ask, you should not be 'fiddling' with cad.

A bit harsh. I use CAD all day and I don't know the figures in the link irelanst posted.

Way to over complicate some things there. Basically I'm getting a 30mm hex wrench laser cut from 4mm sheet. Torque of 15nm required for the pedantic.
So the diameter of the head is 30mm what size should I make the cutout in the sheet to allow a tight fit. 30.1/2mm?

Ah, you mean Tolerance?

Though I'm struggling to work.out how you cut a 30mm hex wrench (Allen Key) from 4mm sheet.

Not sure I understand the question, but this....EDIT - scrap that more info added while I was typing....

cheez0 - Member

What lerk says..

if you have to ask, you should not be 'fiddling' with cad.

is bobbins.....

I'd say 30.5 was a little sloppy but not by much and will work fine for a 30mm nut at low torque. Depends how precise the nut is made, though.

I should have just asked in reality how wide is a 30mm socket to allow for tolerance?

ISO 691 is the official standard for metric sockets. I'd go with around +0.2-0.4mm

You mean, how wide are 30mm spanners? I think the talk of clearance is making folk think of recessed bolts (like in fork stantions)

I've probably totally misunderstood the question but a 30mm A/F will have a bigger diameter you need the across corners dimension. Then decide on standard or slimline socket.

scotroutes - member

Ah, you mean Tolerance?

Clearance, surely? Not tolerance?
Tolerance would be 30.5 -0/+0.5 for example.

The across flats size of a nut (assuming 30mm in this case, so an M20 nut...) is made so the upper end of the tolerance is 30.00.
As above, 30.5 might be a bit loose, but if it's only for a infrequently used item it would be OK (so long as you aren't torqueing it massively.
I'd probably go for 30.2 -0/+0.1 and if it's an open spanner make sure you have a decent rad on the leading edges to help guide it around the nut.

0.1mm clearance would be what I would go for, but your tolerance on the laser cutter may be +/- 0.1mm. I would probably get it cut at 29.9/30mm then grind or EDM wire erosion to the size you need.

Whatever it is, I would probably design it so the nut is a standard size, then you can use a standard wrench or torque wrench.

I can use a standard 30mm socket, its purely from the convenience of not having to carry around a gert great socket and ratchet I want to get it cut.

Like [img] [/img]

Why not buy a spanner, which will have been forged and heat treated?

In fact thinking about it 4mm thick is a bit weedy for an M20 thread (unless it is fine thread?)

The ISO standard for smaller size sockets are listed just over 1/2 way down this page

http://www.eng-tips.com/viewthread.cfm?qid=160993

Tried posting the data here but formating screws up.

I can't find the details for larger sockets without paying for access to the standard.

I assumed it was for a special application that had low clearance or something similar.

Can't you just get one of these:

http://www.powertoolsuk.co.uk/draper-36930-combination-spanner.html?gclid=CPvN57ezjsQCFTDKtAodS1cArQ

[img] [/img]

Cant use a standard spanner as the height of head is only 3mm and the spanner has a bevel which leads to slipping and sockets have to be ground down too. Plus I want different sizes at each end. 24mm one 30mm the other. I thought inc that would confuse matters.

Gotcha....

I see exactly what you are afte. Putting tge photo on the first post might have helped 😉

Ive only just found that after much googling

The irony of your username hasn't escaped me.

Ah now I see. If you keep tolerance nice and tight you may have to cut some corner relief. You only want the flats doing the work.