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View Full Version : Making heavy hex bolt to finished hex bolts



cuemaker
08-19-2011, 10:00 AM
I have a customer who requires ASTM B8M spec for hex bolts, but in finished hex head pattern. To make it more difficult, the source of the steel must be either domestic or DFAR's compliant, or as an exception no India, China, Taiwan or Indonesia.

So I am down to having heavy hex bolts in B8M machined down to finished hex sizing. Quantities are not big, 70 to 300 a month, but the customer does not want to commit to a bulk manufacture, but would rather pay as the need arises..

Using a 1/2 bolt as an example:

Per IFI,
heavy hex bolt head size:
Width across the flats: .875 to .850
Head height: .323 to .302

Finished hex size :
Width across the flats: .750 to .725
head height .364 to .302


So for 5/8 and 3/4 I will have to reduce the head height some, and for sure the width across the flats.

I need to either pay a shop to do this or do it myself. I do not have a mill, but I do have a lathe.

Is a mill the best way to do this?

Carld
08-19-2011, 10:18 AM
Is he aware that will reduce the strength of the bolt?

rkepler
08-19-2011, 10:27 AM
Are you talking ASTM A193 or ASTM A320 here? Big difference here, the first could be met with cut thread, the latter less likely. If you're planning on thread rolling then you're OK either way.

winchman
08-19-2011, 10:37 AM
Why would your customer want high grade bolts which have had the markings removed from the heads?

You could machine the flats on the lathe if you made a fixture to hold the bolts on the tool post, and put a milling cutter on the spindle. You'd need a mill to make the fixture, though.

I'd farm them out, but I'd be very careful who I asked to do the work because of the fact that the bolts you get back will be indistinguishable from lower grade bolts without expensive testing.

vpt
08-19-2011, 11:07 AM
I've done hex on my lathe. Impossible to get plug for my truck so I made one. Mill the top and bottom of the hex, turn bolt and repeat.

http://img638.imageshack.us/img638/7311/heaterplug73010.jpg

http://img59.imageshack.us/img59/4375/heaterplug73012.jpg

cuemaker
08-19-2011, 11:30 AM
Is he aware that will reduce the strength of the bolt?


I am working with engineers drawings, so yes, I assume they understand what they are doing.

cuemaker
08-19-2011, 11:37 AM
Are you talking ASTM A193 or ASTM A320 here? Big difference here, the first could be met with cut thread, the latter less likely. If you're planning on thread rolling then you're OK either way.


ASTM A193.. not A320.. sorry... but you bring up a point of which I may not know of.. Does A320 not allow thread cutting and only roll threading for stainless?

I do know that B7M and L7M do not allow any mechanical work done after final heat treat...is that what you are thinking of?

rkepler
08-19-2011, 12:10 PM
ASTM A193.. not A320.. sorry... but you bring up a point of which I may not know of.. Does A320 not allow thread cutting and only roll threading for stainless?

The difference is in the spec strength, a weaker spec usually allows cutting of the head and threads, stronger specs usually require forming to meet the strength spec. I think in this case the heads are likely to be cold formed in either case. As long as you're not cuttng the head down far enough to affect the pull strength I'd expect that you're fine.

As to the method I'd setup an indexer for the flats and attempt to rig something to align the flats for the cuts. Precision of alignment depends on how much you're taking off - if your new size hex is less than the original flats then alignment doesn't matter at all. Not sure about thinning the head - you might actually need to take off the bolt markings with all the changes and might need to remark them, most of that depends on the use.

Either way I'd expect a bolt with a cold formed head to be pretty tough, a 316 cold formed head is going to be really fun to machine.

cuemaker
08-19-2011, 12:35 PM
Why would your customer want high grade bolts which have had the markings removed from the heads?

You could machine the flats on the lathe if you made a fixture to hold the bolts on the tool post, and put a milling cutter on the spindle. You'd need a mill to make the fixture, though.

I'd farm them out, but I'd be very careful who I asked to do the work because of the fact that the bolts you get back will be indistinguishable from lower grade bolts without expensive testing.


Winchman,

Customer dont care who makes them or markings, as long as we provide the MTR's and certify the county of origin.

As for tagging and separation, you bring up good points. The original bolts will arrive in a bag with proper labels indentifying the parts with heat codes. Those parts will then be inspected, re-packaged and re-labeled. Since all material will be B8M, I dont foresee the machine shop mishandling the product to much unless they happen to mix other jobs that require stainless and machined heads..

The parts will arrive back to me here, we will then again inspect insuring the head dimensions and then ship. Lots of hassle for 70 to 300 bolts a month. But if they are willing to pay for it, we are willing to do it.

macona
08-19-2011, 12:38 PM
You will need a mill or a lathe with polygonal cutting.

Or possibly a die that will shave off an outer ring of the head. But that is the most expensive option (Initially)

lakeside53
08-19-2011, 01:00 PM
This would be dead simple on a cnc mill, even my converted BP. I see a setup like a vertical 5C for the bolt, align off one flat, program to cut the top and sides to spec.

Given cold rolled 316, if surface finish is an issue, your head height may be a problem if it's just a whisker off (low depth of cut).

Are you going to manually debur/polish?

Maybe you can just send them out as a batch each month, and mark up the result?

cuemaker
08-19-2011, 04:33 PM
Well, I just got back from a meeting with a nicely equipped shop who is setup for this kind of thing.

They had 4 or 5 small hardinge chucker lathers, 2 big Warner Swasey lathes setup as chuckers, 2 (dont remember the name) old machines that were automated for similar operations and 2 CNC lathes with bar feeds...

They will be more than capable to handle the work based on who their current clients are (pump manufacturers) with the availability to do the odd rush jobs we get.

Only caveat is I have to provide material due the exactness, but thats only a slight pain in the ass compared to a capable shop.

tdmidget
08-19-2011, 08:14 PM
Well, I just got back from a meeting with a nicely equipped shop who is setup for this kind of thing.

They had 4 or 5 small hardinge chucker lathers, 2 big Warner Swasey lathes setup as chuckers, 2 (dont remember the name) old machines that were automated for similar operations and 2 CNC lathes with bar feeds...

They will be more than capable to handle the work based on who their current clients are (pump manufacturers) with the availability to do the odd rush jobs we get.

Only caveat is I have to provide material due the exactness, but thats only a slight pain in the ass compared to a capable shop.
So are you modifying existing bolts are having new ones made?

ScottyM
08-19-2011, 08:32 PM
I am working with engineers drawings, so yes, I assume they understand what they are doing.

Never, never, ever assume that an engineer knows what they are doing.

I once had one that wanted me to take 3" x 3" x 1/4" angle and mill off one leg to 2". I asked him why we couldn't just use 3" x 2" x 1/4" angle. Dead silence on the phone, and then do they make that?

I kid you not.

Scotty

Black_Moons
08-19-2011, 09:05 PM
Never, never, ever assume that an engineer knows what they are doing.

I once had one that wanted me to take 3" x 3" x 1/4" angle and mill off one leg to 2". I asked him why we couldn't just use 3" x 2" x 1/4" angle. Dead silence on the phone, and then do they make that?

I kid you not.

Scotty

Hahaha. All engineers need to be pointed to MCmaster.
Not because I think its a good place to buy parts.. Especialy if you don't live in the USA.. But it is a wonderful site to quickly determin if something 'exists' in a commonly made state.

cuemaker
08-19-2011, 09:11 PM
Scotty,

The plans are from a major firm involved in pump design.. Plus I am not given the option of changing or modifying, either its to their spec or they dont buy it.

Tim, we are going to be modifying existing bolts and nuts. Cheaper and easier I believe. Or at least thats the way I have it planned. I think on the per piece basis milling new bolts from solid bar would eat up to much time. I can buy 10-30 bolts to be modified (depending on size) compared to his making how many in an hour for $60/hr

tdmidget
08-19-2011, 10:15 PM
So this shop you found. Shall we assume that they have a mill? If the numbers are big enough one of those W&S turrets will make one in about a minute.

cuemaker
08-19-2011, 10:25 PM
So this shop you found. Shall we assume that they have a mill? If the numbers are big enough one of those W&S turrets will make one in about a minute.


Its kinda funny, the only mill is an older manual bridgy..

Hmmm, make one in minute... I might have to go back for a further consult....

tdmidget
08-19-2011, 10:55 PM
I'd say so. A real good man could set it up in an hour. If so then you're in $2 plus material for the first 60 or so. If it is a repeat then maybe do 150 or so. If it takes 4 hours then 150 is $1.60 ea. plus the material.
The other way you buy a finished part and it would take at least a minute, more like 2 in a Bridgeport really humpin'.
As an apprentice I was told that the Warner & Swasey turret lathe was the machine that won WWII. Thousands and thousands cranking out any thing they could make, unskilled operators and one machinist for maybe each 2 dozen or so machines. They are massive, rigid and bulletproof when set up properly.

rode2rouen
08-20-2011, 08:54 AM
I am working with engineers drawings, so yes, I assume they understand what they are doing.



That's funny......naive, but funny!!


Rex

armedandsafe
08-20-2011, 03:15 PM
We have a saying in electronics (my background) that an Engineer is a waste of a good technician. :D

Pops

tdmidget
08-20-2011, 03:38 PM
I'm assuming that the $60/hr was conventional machines. If they have time on the CNCs that would be even quicker. Probably a good bit more per hour tho....

cuemaker
08-20-2011, 06:03 PM
I'm assuming that the $60/hr was conventional machines. If they have time on the CNCs that would be even quicker. Probably a good bit more per hour tho....


Something else I didnt cover... Good point.

On Monday I will get his opinion of machine time vs modifying time and what is the most bang for the buck.

Although a consideration is that each pump kit contains at most 16 bolts and the pump manufacturer has been very careful not to say how many pumps they make as it waxes and wanes

J Tiers
08-20-2011, 07:48 PM
Engineers............

It varies....... One indicator is to check the hair color...... Gray and you figure they know something, absent conclusive proof of cluelessness.

At least a good chance they know what is available, and many of the usual "gotcha" type issues will probably be OK.

aboard_epsilon
08-20-2011, 08:14 PM
I've seen it somewhere ..I'm sure my friend Alwyn's got one

it's a device that goes in the tool post of the lathe ..holds a bar and allows it to turn 60 degrees after your first cut..you just keep turning it after each cut and eventually end up with a perfect hexagon.

all the best.markj

Rustybolt
08-20-2011, 10:04 PM
Hahaha. All engineers need to be pointed to MCmaster.



Oftentimes thats where the problem starts.

Peter.
08-21-2011, 03:19 AM
I've seen it somewhere ..I'm sure my friend Alwyn's got one

it's a device that goes in the tool post of the lathe ..holds a bar and allows it to turn 60 degrees after your first cut..you just keep turning it after each cut and eventually end up with a perfect hexagon.

all the best.markj

You could make something to do that easily enough.