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Old 02-20-2020, 06:56 AM   #1
ct
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Default Rear hub bolts

I need to replace the rear hub bolts on the A. I have steel brake drums so the new bolts require machining as they are made to suite cast iron drums. According to Mac's website the shoulder must be reduced by 1/16 inch.
Questions arising:- (refer to attached photos)
1) Is the taper between points A and B an integral factor in the swedging process?
2) Does the taper need to be maintained or can the shoulder be squared-off?
3) If it can be squared-off, from which point is the 1/16" reduction measured?
4) Has anyone worked with a dimension (C) that the shoulder needs to be from the drum pre the swedging process?
Thanks in anticipation of your responses. CT
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File Type: jpg Hub bolt 2.jpg (26.4 KB, 15 views)
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Old 02-20-2020, 09:01 AM   #2
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Default Re: Rear hub bolts

1) Taper between A-B IS part of the swedging process. But only the outer fraction of the ramp A-B. After swedging the top part A of the ramp still exists, but the bottom part B has been pushed down and "out."

You can get a sense of where this cut occurs by looking at the ID of a new swedge tool and comparing it to the ramp. Keep in mind that swedge tools wear, and this diameter will change with wear.

2) Shoulder CAN be squared off, but one is advised not to as one creates a stress concentration point for lines of force, and this can become a potential crack. Better would be a radius, or maintain the taper.

3) Guessing here (I have not used CI bolts on pressed drums) but based on what I know the reduction should be "overall". (i.e. the whole A-B taper portion)

4) In C dimension, you mean for pressed drums - see reply above. The vendor of CI drums (Mel Gross among others) will probably be able to tell you what he likes to see as he does this regularly - and he has to filter out the potential errors including bolts made wrong, the drums inconsistent thickness, the hubs inconsistent thickness, something a burr or chip in the interstice between bolt and hub, warped hubs.

One might take the thought of the thickness of the bolt circle on a cast iron drum and comparing it to the thickness of the same spot on a pressed steel drum. The difference is how much you should reduce the shoulder A-B height (i.e. irrespective of dimension C)

I think given a pressed drum and a bolt, one would probably learn on the first try if too much or too little metal has been left. You want to buy bolts enough for at least a couple of re-do - consider the cost part of your "learning curve." And one bolt is only 1/5th of the 2/5 bolts needed to actually hold a wheel in place so if its not perfect you go onto the next one and change your setup/machining.

And - when you come right down to it, the swedging ONLY holds the drum in place long enough to get the wheel on and the lug-nuts tightened. Well, this once you get the brake drum surface "trued up" and centered.

As to the ramped portion and the nut/threading action - the ramp could be removed entirely as it has nothing to do with the bolting action.

Of course "back in the day" nobody swedged the bolts - instead they were tack welded in place! (Not recommended.)

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Old 02-20-2020, 10:05 AM   #3
BRENT in 10-uh-C
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Default Re: Rear hub bolts

Quote:
Originally Posted by ct View Post
I need to replace the rear hub bolts on the A. I have steel brake drums so the new bolts require machining as they are made to suite cast iron drums. According to Mac's website the shoulder must be reduced by 1/16 inch.
Questions arising:- (refer to attached photos)
1) Is the taper between points A and B an integral factor in the swedging process?
2) Does the taper need to be maintained or can the shoulder be squared-off?
3) If it can be squared-off, from which point is the 1/16" reduction measured?
4) Has anyone worked with a dimension (C) that the shoulder needs to be from the drum pre the swedging process?
Thanks in anticipation of your responses. CT

I looked at my copy of the A-1118 print, and the taper between 'A&B' is listed at 45.

The 'C' distance is not specified on the print however the specified length between the two 45 taper areas is listed as 29/64" (0.4531"). The OD of that area is listed at 0.625 - 0.628.

Now with all of that said, I will confess that I have never been successful at shortening the length in this area. The threads are -20" by about 0.625" in length. I tried to make a split collet to hold the stud in the chuck but even then I struggled with holding concentricity so the new taper would rivet (Ford used the term Rivet on the print instead of swage) evenly. I finally gave up and located some original studs to use. Maybe if you have plenty of time to keep indexing it to get the run-out down to less than 0.003" on the tapered end, you would be successful.
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Old 02-20-2020, 11:31 AM   #4
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Default Re: Rear hub bolts

Or put an ad in the classifieds and look for some original ones, I am sure they are out there.
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Old 02-20-2020, 09:28 PM   #5
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Default Re: Rear hub bolts

I have used the same studs on both cast and steel drums and both have worked fine . Have done 4000 cast ones and 150 steel ones in 37 years. Don’t overthink it.
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Old 02-21-2020, 12:53 AM   #6
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If you do want to over think it, the straight part is .220 between the two angles. (from the green book, 1928 to 1948 parts)
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Old 02-21-2020, 01:51 AM   #7
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Default Re: Rear hub bolts

Thanks all for your responses.
Joe K Thanks for the tip re: the need for a radius. I planned to leave a small radius on the internal corner if "squared-off".

Brent I would love to use original bolts but they seem to be rarer than hens teeth. Re: "the specified length between the two 45 taper areas is listed as 29/64" (0.4531")". Mine are that measured between the large diameters of the two tapers

Steve Correct me if I'm wrong. You didn't shorten the bolts for the steel drums.
I thought that the shoulder might interfere with the lug nuts or nut spacer washers.

redmodelt Re: "the straight part is .220 between the two angles" so that must be for the shorter bolt for steel drums?
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Old 02-21-2020, 10:42 AM   #8
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Default Re: Rear hub bolts

Yes that is what was called out in the 1948 Ford parts book so should be for rear steel drum. The fronts were a little longer at .380.
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Old 02-21-2020, 06:43 PM   #9
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Default Re: Rear hub bolts

Thank you all for taking the time to help.
CT
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Old 02-21-2020, 07:27 PM   #10
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Default Re: Rear hub bolts

No need to shorten them. When you swedge them they will fill the cavity in the drum and hold tight.
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Old 02-21-2020, 11:08 PM   #11
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Default Re: Rear hub bolts

SteveB31 Thanks for the follow-up.
CT
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