By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

3.5mm hex. head screws

All Topics | Latest Posts

Search for:  in Thread Title in  
JA21/11/2021 12:17:04
avatar
1281 forum posts
79 photos

The recognised metric replacement for a 4BA screw is a M3.5 x 0.6 screw. I am trying to find if such a mild or stainless steel hex. head screw is available. I have looked at Polly Model Engineering web site and some of the European model engineering suppliers' web sites without success.

Has anyone knowledge of the availabilty of such screws and nuts?

JA

Chris Gunn21/11/2021 12:43:16
412 forum posts
27 photos

Buy M3 x 3mm Full Thread Hexagon Bolts (DIN 933) - Stainless Steel (A2) | Save 80% | 500,000+ Components | Accu®

Chris Gunn

JasonB21/11/2021 13:36:59
avatar
Moderator
21964 forum posts
2531 photos
1 articles

I've not come across M3.5 hex head from any of the usual suspects here or abroard. If you don't need many then not to hard to turn down some round bar, thread and then machine the hex.

John Haine21/11/2021 13:37:07
4402 forum posts
261 photos

I think JA wanted M3.5 Chris?

Quite a few suppliers of M3.5 screws come up on Google but hex head don't.

HOWARDT21/11/2021 14:02:51
831 forum posts
28 photos

I think you will find them at PTS, Precision Technology Supplies. I got some M2.5 from them, usually use them for all my stainless screws.

Chris Gunn21/11/2021 14:42:51
412 forum posts
27 photos

JH, you are right, I searched for 3.5 hex head, and mistakenly believed Google took that on board, should have looked closer at the results. I thought it was too easy.

Chris Gunn

speelwerk21/11/2021 14:56:55
428 forum posts
2 photos

Not quite, because it is hex with a slot, but perhaps useable, Niko. **LINK**

https://www.ebay.de/itm/265158626286?hash=item3dbcaf8bee:g:YwIAAOSwHd5gnPZY

Keith Wyles21/11/2021 15:17:41
94 forum posts

Why not use 4BA?

Martin Connelly21/11/2021 16:15:13
avatar
1999 forum posts
214 photos

Fix a nut to a piece of stud and clean it up. If you use a machine screw for the stud you can run the nut up to the point where the thread finishes to have as much metal as possible filling the nut.

Martin C

JA22/11/2021 12:16:51
avatar
1281 forum posts
79 photos

Many thanks for the replies.

The ISO Metric 3.5mm Coarse thread is a standard thread and features in thread tables including the one in Tubal Cain's Model Engineer's Handbook. I know that it is used on some electrical fittings.

I asked the question because I am converting the design of a large well known model, with quite a few 4BA screws, to metric. Before going too far I thought it would be wise to check if the metric equivalent was available.

2mm, 2.5mm, 3mm and 4mm hex headed scews are readily available but I am going to assume that I will never see a 3.5mm hex headed screw.

JA

Juddy22/11/2021 12:25:07
avatar
94 forum posts

There are these:

Socket Head Cap Screws DIN 912 (ISO 4762) M3.5 in A4 Stainless Steel - Westfield Fasteners Ltd

or these:

M3.5 / 3.5mm Metric A2 Grade Stainless Steel Socket Cap Allen Bolt Screws | eBay

Vic22/11/2021 12:26:26
3012 forum posts
8 photos

I’m not sure what size Hexagonal bar (metric/imperial) is available but it shouldn’t prove too time consuming to make your own?

Michael Gilligan22/11/2021 12:30:51
avatar
19571 forum posts
994 photos

The awful truth appears to be here : **LINK**

https://itafasteners.com/products-bolts-hex-head-anchor-bolts.php

M3.5 is a standard … but not for bolts sad

I agree with Martin; but might be tempted to use hex-socket grub screws as the thread … thus providing optional tightening methods.

MichaelG.

JasonB22/11/2021 12:53:41
avatar
Moderator
21964 forum posts
2531 photos
1 articles

JA wants hex head not cap head. Though I have used m3.5 cap heads on models I reserve them for the modern aero and ic engines rather than anything period.

When I have made hex head bolts in M3.5 to keep them in keeping with the other model hex heads which are smaller than the usual ISO sizes I mill the hex to 5mm A/F which fits in about right with M3 with it's 4mm hex and M4 with it's 5.5mm hex. For the few I make it is not worth sourceing 5mm hex stock and the spin indexer makes machining quite quick.

No sure what engine martin is making but when doing others in metric I often find the suggested BA size a bit large for example the 2BA ones on the Stuart Voctoria, beam, etc are on the big side so use M4 rather than M5 which would be closer.

Edited By JasonB on 22/11/2021 13:30:52

peak422/11/2021 12:54:30
avatar
1587 forum posts
167 photos
Posted by Vic on 22/11/2021 12:26:26:

I’m not sure what size Hexagonal bar (metric/imperial) is available but it shouldn’t prove too time consuming to make your own?

M3 hex heads are 5.5mm spanner size, M4 are 7mm
It seems to me that 6mm hex bar would seem an appropriate midway approximation.
4BA AF hex size is 0.249", so not much larger than 6mm.

Both 1/4" and 6mm hex bar are readily available.

Bill

JasonB22/11/2021 13:11:33
avatar
Moderator
21964 forum posts
2531 photos
1 articles

The model ones tend not to use standard hex, see my comment above and this table Similar to many people using one size smaller BA fixings.

They are also taller so more in keeping with a period engine.

Michael Gilligan22/11/2021 13:26:26
avatar
19571 forum posts
994 photos
Posted by JasonB on 22/11/2021 12:53:41:

Martin wants hex head not cap head. […]

.

dont know

Do you mean JA ?

MichaelG.

.

Incidentally … My reference was to Martin Connelly’s suggestion.

JasonB22/11/2021 13:32:06
avatar
Moderator
21964 forum posts
2531 photos
1 articles

Yes, edited it now.

First part of my reply was to Juddy.

Though grub screws may be a bit limited on length depending on what is needed or if studs are being used for the majority of fixings.

Edited By JasonB on 22/11/2021 13:33:33

Michael Gilligan22/11/2021 13:35:40
avatar
19571 forum posts
994 photos

yes

Vic22/11/2021 16:59:53
3012 forum posts
8 photos
Posted by peak4 on 22/11/2021 12:54:30:
Posted by Vic on 22/11/2021 12:26:26:

I’m not sure what size Hexagonal bar (metric/imperial) is available but it shouldn’t prove too time consuming to make your own?

M3 hex heads are 5.5mm spanner size, M4 are 7mm
It seems to me that 6mm hex bar would seem an appropriate midway approximation.
4BA AF hex size is 0.249", so not much larger than 6mm.

Both 1/4" and 6mm hex bar are readily available.

Bill

Yes, sounds good Bill.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
Warco
cowells
Eccentric July 5 2018
walker midge
emcomachinetools
JD Metals
rapid Direct
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest