I followed the direction from the valuable info gathered here; http://ourworld.compuserve.com/homepages/David_Pozzi/brakes.htm#Converting_Drums_to_Discs

The info was great but I now am trying to find the correct bolt that goes in the hole that is home to the "boss"I just had .600 machined off of!
Does anyone have a dimension for this bolt or a part #? Thanks.

Year One or Ground Up carry the bolt.

You still need brackets and dust shields. I never see brackets for sale without spindles.

i am pretty sure it uses the same bolt. the factory drilled and tapped them all the same depth so that after machining the same bolt would work.

I'm doing the same thing. You can get caliper brackets at Ground Up for $93/pr with your membership or $109 without. The steering arm mounting bolts for the drum spindles are 5/16 and 3/8 for the disc brake spindles so you either have to drill the holes out or shim the one hole in the caliper bracket. The bolt for the top hole in the drum brake spindle has a shoulder machined into it. The hole in the caliper bracket is larger in diameter than the threaded portion of the drum brake bolt and once you machine off the top of the boss, the original drum brake bolt will be too long. An original disc brake bolt is larger in diamerter than the threaded hole in the drum brak spindle. I'm not sure how I'm going to get around this but I think I can remachine the original bolt. I just haven't had time recetnly to work on it anymore but am up to discussing it.

Cam

I've seen drum spindles that use smaller diameter bolts. The ones I saw came off a Buick. There are drum spindles that use the same diameter bolts as the original disc brakes off a 72. I've pulled them, had the boss cut, and an original center bracket bolt screws into them.

John Muha-There is a drum brake 72 lemans at the local bone yard and I will go snag the bolts off that one! Do they need to be shortened to fit?
Cam- Good tip on the larger hole in the bracket!
I think I will go with a spacer there.
I wonder if GM still sells the correct bolt or at least lists its length?
Oh no,not another question.(I am sure the local parts guys flip a coin to see who gets stuck looking up old chevelle info for me.LOL!)
Thanks all!

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Not sure where Cam got the bolt sizes. Some drum spindles screw onto the steering linkage with 7/16-14 bolts. The ones I pull and fit the disc brake set-up are held in with 1/2-13 bolts.
Johnny check the 2 nuts that hold the spindle on your car. The nuts will either take a 11/16 wrench (small bolt) or a 3/4 wrench (large bolt). You want ones that the large bolt. If your car doesn't have the large bolt (my 64 doesn't), you should take the "C" shaped piece from the donor car that the bolts go through. Not sure that piece will fit a Chevelle but take it anyway.
The "smaller bolt" spindles are threaded with a 1/2-20 center hub hole. The "larger bolt" spindles are threaded with a 5/8-18 hole. These are the ones they used on late model Chevelles for the disc brake set-up. These are the ones you just have to machine down.
DG gave you a couple of source for the bolt.

John Muha-The spindles I had machined down are from my 70 parts car and also use the big 1/2-13 nut/bolt size to attach the steering arms to the spindle and the larger bolt is the 5/8-18 item!
Do you know the torque spec on these ?
A friend of mine said he thought that the smaller ones were 64 thru 67 drum cars and should be avoided if possible. Can you confirm this for me?
Thanks.
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Woops, sorry guys, You're right. My spindles are 64 and have the smaller 7/16 (not 5/16) bolts.

Cam

Originally posted by 67johnny:
Do you know the torque spec on these ?
A friend of mine said he thought that the smaller ones were 64 thru 67 drum cars and should be avoided if possible. Can you confirm this for me?
Thanks. I'll try and look it up in the morning. However, generally torque is dependent on the bolt size. That is, all 1/2" bolts are torqued the same.
I agree, avoid them if possible. However, they will only take more work. A skilled machinist on a mill won't have any problems opening up the hole sizes and tappng the 5/8 threads.

Pictures, pictures, pictures, the more the better. The ones in the link were helpful, but have any of you taken any pictures of your spindles, before and after machining?

Here's a torque chart. Print it out and save it. Too lazy to go out and see what those bolts are marked. Probably around a Grade 5.
I'll try and get the daughter to do something about pictures. I've got a "small hole" spindle uncut and a "large hole" drum spindle that's been cut. However, she's not around too much.
http://www.engineersedge.com/torque.htm

Originally posted by John_Muha:
Here's a torque chart. Print it out and
http://www.engineersedge.com/torque.htm Hmmm...I'm really surprised they list that equation without an asterics. My Machine Design book tells not to use it with bolts smaller than 1/2" diameter and the coefficient is listed with a range of material used when clamped.

Interesting....

Joe

Originally posted by 72SSAbody:
Hmmm...I'm really surprised they list that equation without an asterics. My Machine Design book tells not to use it with bolts smaller than 1/2" diameter and the coefficient is listed with a range of material used when clamped.

Interesting....

Joe Yeah, see what you mean. They really made it more simple than it really is. I took it as a layman's explanation of the factors involved, not something a BSME would use.

This is something I'm really interested in, because once the spindles are done, then all you have to is locate a set of caliper brackets. The rotors and calipers can be bought at most auto supply stores. Then you would only need to buy a master cylinder, prop valve, and booster and of course, you have to deal with the plumbing. This looks like something that can help save quite a bit of money.

THe caliper brackets are available as Cam said, at Year One, Ground Up or OPG. The price has been coming down lately. They used to cost more than a whole setup from the classifieds.

Last time I checked, Sardeson Racing had the disk spindles for 99.00 each. Handy if your drum spindles are worn where the bearings ride.

K

Chevello-$99-. is the best deal I have heard of to date but its the little stuff that adds up.
The 5/8 bolts I am looking for are $15 a pair and I still cant locate the round seal that goes behind the backing plate!
All said and done,spending $15-ea. to machine the drum spindles(that I had) and bead blast the used parts I think I will be into a disk setup for about $350-with new hoses/bearings/brakets/plates and rotors. and thats fairly reasonable.
Randy-I can send you pic but I have yet to figure out how to post a pic here although I might have that figured out by next week as I did manage to put a pic of my 71 in the TC showroom!

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posted for John


Here they are:

The Newer Style Chevelle spindle can be found on the later year cars as David points out. The one shown was a drum spindle before it was cut.
http://www.chevelles.com/showroom/Dean/NewerStyleChevelleSpindle.jpg
I have a 5/8-18 tap sitting in the hole. This is now identical to a disc spindle. I used an original disc spindle as a pattern. After it was machined I ran a bottom tap into it and carefully cut a few more threads on the bottom.
This spindle, like the original disc brake spindles, has 2 mounting holes that accept a ½ inch bolt. Notice how GM changed the casting around the 2 mounting holes making the area larger by adding more material and gusseting the area for strength.
The Older Style Chevelle spindle is an uncut drum spindle.

http://www.chevelles.com/showroom/Dean/OlderStyleChevelleSpindle.jpg

Even though this one was pulled off a Buick, it’s identical in shape to the one on my 64. I have a smaller ½-20 tap sitting in it. It would need to be drilled larger and fully tapped to accept the 5/8-18 bolt. The backing plate or dust shield has 2 metal tabs on it to prevent the proper size bolt from backing out. The 2 mounting holes will only accept a 7/16 bolt. Notice that the area around the 2 mounting holes is much thinner than the newer spindles. This thinner area, along with the extra work, are reasons to avoid modifying an older style spindle.
Shown below is a picture of the c-shaped piece of the steering linkage that attaches to the spindle. Not sure of it’s real name. This one’s from a 72 Chevelle and has holes to accept ½ bolt. Best I can tell it is the same as the older years except for the hole sizes.

http://www.chevelles.com/showroom/Dean/Clinkage.jpg

Easiest way to check a parts car is with a wrench. Check the 2 nuts that hold the spindle on the car. The nuts will either take a 11/16 wrench (small bolt) or a ¾ wrench (large bolt).

Dean-Thank for sharing your pics with us!
Did you find that milling .600 off your spindle boss was the correct amount? I noted that David Pozzi had a couple of different numbers mentioned when he was comparing some of the stock disk spindles he had so I assummed that there was a fair bit of tolerance involved on the assembly line when they were making them! Thanks.

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Not sure if Dean Call has ever done this. The figure of .50 to .60 is correct. Need to mike from the surface where the oil seal sets to the cut area of the spindle. My cuts match an original disc spindle.

Originally posted by 67johnny:
Dean-Thank for sharing your pics with us!
Those are John Muha's pictures, I just posted it for him.

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Originally posted by John_Muha:
Not sure where Cam got the bolt sizes. The "smaller bolt" spindles are threaded with a 1/2-20 center hub hole. The "larger bolt" spindles are threaded with a 5/8-18 hole. These are the ones they used on late model Chevelles for the disc brake set-up. These are the ones you just have to machine down.
When you say late model, are you talking about 68 to 72? Am I good to go since my car is a 71 model?

Originally posted by Randy Mosier:
</font><blockquote>quote:</font><hr />Originally posted by John_Muha:
Not sure where Cam got the bolt sizes. The "smaller bolt" spindles are threaded with a 1/2-20 center hub hole. The "larger bolt" spindles are threaded with a 5/8-18 hole. These are the ones they used on late model Chevelles for the disc brake set-up. These are the ones you just have to machine down.
When you say late model, are you talking about 68 to 72? Am I good to go since my car is a 71 model? </font>[/QUOTE]I think it’s 69–72 for the Chevelles but seem to recall seeing the 7/16 inch bolt hole spindles on a Buick during those years. Maybe GM wasn’t consistent with their models. Maybe someone replaced them. Not real sure. That’s why I mentioned measuring the nuts with a wrench. That can be done before you pull anything apart by reaching around the tire. Every factory disc brake spindle I’ve seen has the ½ bolts through it.
One day I’ll go pull another drum spindle to keep as a spare for my discs. A lot of the ones I see have some heavy grooves in them so best find a good one while they are still out there.

Yep, they're 1/2 inch bolts. Looks like we're in business!