Minor Problem (well, fairly minor)

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Originally Posted by gromit

John,
3/8" UNF bolts have a 9/16" AF head. You mentioned a 9/16" head so is that OK ?
You could probably buy some bolts long enough to cut off the threaded section & then cut a BSF thread.
A cap head screw will most probably be HT so a bit harder to thread. Single point turning then then finishing with a BSF die may work.


Colin

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Yes to all of the above. You need a thin wall 9/16" socket (made by me by judicious use of a drill drive for 3/8" sockets and a bench grinder). Yes, the single point turning followed by a die was what I was thinking - I am pretty sure I have the right change wheels for my lathe. I think the cap screws would be better than the hexes.

I'll see if I have a cap screw at least suitable for trying this before going and buying a set to work on. Do you think they are likely to be soft enough to machine?

If they are soft enough to machine, will they be hard enough to do the job?

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Originally Posted by JDNSW

Yes to all of the above. You need a thin wall 9/16" socket (made by me by judicious use of a drill drive for 3/8" sockets and a bench grinder). Yes, the single point turning followed by a die was what I was thinking - I am pretty sure I have the right change wheels for my lathe. I think the cap screws would be better than the hexes.

I'll see if I have a cap screw at least suitable for trying this before going and buying a set to work on. Do you think they are likely to be soft enough to machine?

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Hi John,

Not sure if the originals were HT.
I've machined cap heads before but thread cutting is a bit harder with a die (needs to be HSS), single point turning may be good enough.
I'll check at work if they can hold a cap head, problem is you need to come through the back of the collet because of the head. Next problem will be all the threading tips will be 60degree (Metric) rather than 55.

I haven't single point turned for many years. Top slide set over at half the thread angle I remember but stopping at the same point for each cut is the bit I don't remember. A modern CNC is a doddle, shame I don't have the programming skills ! Someone at work owes me a favour though....

Colin

Hi John,

Are these the right thread?
403 Forbidden

A light touch of each hex on a grinder, might be easier than cutting new thread?

Tony

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Originally Posted by TonyC

Hi John,

Are these the right thread?
403 Forbidden

A light touch of each hex on a grinder, might be easier than cutting new thread?

Tony

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I presume there is some sort of a picture or link there, but it comes up as "403 Forbidden" so I really can't answer your question.

What is needed is 3/8" BSF, but there is not enough room for the standard BSF hex. Grinding a bit off is probably easier than cutting a thread, but begs the question of how to tighten them. Grinding the evenly to a hex that a 9/16" spanner can exert suitable torque on is probably more difficult than rethreding a bolt with the right hex (or a socket head.

The bolts do not need to be particularly strong - there are six of them, and they are at a large enough pitch circle. I have never heard of the bolts on the standard drive flange failing or distorting. While the free wheel hub bolts are much longer, the drive is taken right at the interface with the hub, so the extra length is pretty much irrelevant.

The link I posted works for me, but I guess I posted it.Here is a screenshot, but the link had many others that may suit. The spanner size was listed as 9/16 AF
Attachment 195146

Yes, they would work. I will have to check exactly what unthreaded length I want. Any of them should be off the shelf locally here. But not, of course, BSF with the "wrong" hex! I will see if I have one I can try my skills on before buying some though.

(I expect the problem with your link is the website you were linking does not allow it to be linked via another website, probably as a security feature.)

Works for me, on Chrome.