Got the front end apart on my '26 Coupe. Every bushing is shot, so I'm replacing them. I roughly measure the kingpin holes in the axle at .510", while the kingpins measure about .4996" (in a 55° garage). I know I need to ream the spindle bushings, but can anyone tell me what the axle boss diameter needs to be? Thanks.
Kingpin to axle boss clearance
- Thread starter Taint
- Start date
rotorwrench
Well-known member
Clearance between pin and bearing journal have to be close enough that the pin is a light push fit. This is the ideal clearance but that largely depends on the type or reamer and what size a person starts with. A spiral flute reamer that gets it very close is a start. From there, it's best to use either an expandable reamer that is made for king pins or purchase an expandable journal lapping tool with yellow time saver. Cheap adjustable straight flute reamers tend to bugger up the bores.
To avoid that, take the parts to a machine shop with a Sunnen hone or equivalent and let them do it.
To avoid that, take the parts to a machine shop with a Sunnen hone or equivalent and let them do it.
Thanks for the response. I have a milling machine and tooling. So maybe a couple of thousandths? The bushings are to be reamed or honed to .502-.504", so I'm guessing it's the same. I wasn't sure if there was some strange reason the axle boss had to be a little looser, but .010" seemed excessive. I can heat shrink/ream or bore and bush the axle, I just haven't been able to find a stock specification to take it to. The two options I've found have been "chuck it and find a good axle" or "use a Stevens Tool".
rotorwrench
Well-known member
Since a light push fit is not a an exact decimal number, I always treat it as a trial fit with any number of slightly increased clearance numbers until it fits by push. The actual number is likely within a range of .0008" to .0012" +.0003". Anyway, you can see where I'm coming from if you have done a good bit of machine work. Getting close clearance in more of an art form than a number.
I have expandable fluted reamers for king pins. These are the types that have slotted hollow shaft with an internal taper that a cone or ball can be forced into for slight expansion. They are extended to act as a pilot. My stuff is old but well made for it's time. I make very slight adjustments after the initial non-expanded pass. The internal bushing finish after reaming is very smooth with no signs of chatter. I see this stuff used on flea-pay now and then but the prices may be high for ones that are in good condition. Custom made fluted reamers are better than fixed size if the fixed size give too much clearance. A lot of the ones available are a bit too large for me. A bore lapping tool is an alternative and the yellow time saver compound works well with soft metal bushings. Here is a link:
https://www.msdiscounttool.com/cata...MI-L_X04zQigMV2CjUAR1S0AuHEAQYBSABEgL1h_D_BwE
I have expandable fluted reamers for king pins. These are the types that have slotted hollow shaft with an internal taper that a cone or ball can be forced into for slight expansion. They are extended to act as a pilot. My stuff is old but well made for it's time. I make very slight adjustments after the initial non-expanded pass. The internal bushing finish after reaming is very smooth with no signs of chatter. I see this stuff used on flea-pay now and then but the prices may be high for ones that are in good condition. Custom made fluted reamers are better than fixed size if the fixed size give too much clearance. A lot of the ones available are a bit too large for me. A bore lapping tool is an alternative and the yellow time saver compound works well with soft metal bushings. Here is a link:
https://www.msdiscounttool.com/cata...MI-L_X04zQigMV2CjUAR1S0AuHEAQYBSABEgL1h_D_BwE
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rich b
Well-known member
Sounds like the eyes on the axle have become worn, stretched, or elongated or a combination of all three over the years.
Kingbolts should be a relatively tight fit in the axle.
Guess I would heat shrink them with an old old kingbolt, torch, and hammer; just be sure to knock the pin out while the eye is still red so the pin doesn't seize in the hole.
When done, resize the eyes for a tight fit.
Kingbolts should be a relatively tight fit in the axle.
Guess I would heat shrink them with an old old kingbolt, torch, and hammer; just be sure to knock the pin out while the eye is still red so the pin doesn't seize in the hole.
When done, resize the eyes for a tight fit.
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super flat
Senior Member
Taint please fill out your location so sombody can fit them with a Sunnen hone.
rotorwrench
Well-known member
I found this link to the Model T Ford Forum that lists the sizes of the axle to spindle support bores. It shows a bore size of .5045" to .505" so it may be a bit loose on a 1/2 inch bolt.
http://www.mtfca.com/discus/messages/506218/518049.html?1423984071
A person never knows how the fit is until it's all put together but the way the spindle bolt fits in there and is secured then that might be OK. Its the spindle bushings that need to be tight on the bolt for the most part. The spindles do have to turn smoothly so surfacing the thrust faces is also a part of that. The model T was definitely old tech.
http://www.mtfca.com/discus/messages/506218/518049.html?1423984071
A person never knows how the fit is until it's all put together but the way the spindle bolt fits in there and is secured then that might be OK. Its the spindle bushings that need to be tight on the bolt for the most part. The spindles do have to turn smoothly so surfacing the thrust faces is also a part of that. The model T was definitely old tech.
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Awesome, thank you! I did search around quite a bit. I might have bought an adjustable reamer like you describe; I'll post it once the mail starts running.
10-4. I'm in Elizabethtown, KY, but will update my profile.
Thank you! I guess it's time to get some more bottles for my torches.
I forgot I can't post pictures yet, but it is an L.O. Beard Tool Company expandable reamer, like you described with the cone.