The Ford Barn

big job · 08-18-2023, 05:50 AM

What I gather you want to shorten it only .850 no problem all you need is a lathe. I believe the spider gear and shaft OD, taper, and thread is the same on 1940 to 1948 I think If so, you have all the measurements. Order of operations: #1 cut .850 from the threaded end & machine .850 thread size to the taper and pick up the thread pitch and re thread re drill for the cotter pin thats done. now machine the taper .850 longer re-machine the shaft for outer bearing. Now the key way. easy and fast is a milling machine or a shaper. any shop can cut a key way. This is exactly how we machine marine prop shafts same thing. hope I said this correctly for my brain to transpose into typing kind of like explaining how to tie shoe laces LOL sam

Bored&Stroked · 08-18-2023, 07:18 AM

While a competent machine shop should be able to accomplish the task, it would be much cheaper to just find the right axle.

Mart · 08-18-2023, 07:55 AM

It can be done and has been done. I broke a shaft in my 41 pickup (same as a 40) and was able to obtain one that was a shortened 46-48 shaft. It was not quite right and I skimmed the taper a little more to position the drum correctly.

I didn't do the initial machining but was able to take a light cut. I made sure the hub was well lapped to the axle afterwards.

I don't believe any heat treatment was carried out. The metal is tough and needs good quality tipped tools.

My axle had been welded at the mid point and snapped.

I showed it in a video mini-series.

part 1: https://youtu.be/t0AfzS5OLYE
part 2: https://youtu.be/i26ZSqwFIF0
part 3: https://youtu.be/8ToEl7O01P0
part 4: https://youtu.be/MOVxQP0aZhg

Mart.

Mart.

deuce_roadster · 08-18-2023, 08:47 AM

Just get a correct good appearing used axle and have it magged at the inner end of the keyway. A used axle with no cracks can be lapped to your hub. By FAR the cheapest solution.

19Fordy · 08-18-2023, 09:13 AM

Bored&Stroked got it right. Machine shop work these days is not cheap.

Ricosan · 08-18-2023, 09:15 AM

Sponsored Links (Register now to hide all advertisements)

Alchemy, there is a detailed video doing this online at Iron Trap garage. Lots of other videos at this site too.
Richard

alchemy · 08-19-2023, 07:41 PM

Rico, I can’t find the video you are talking about. Can you post a link?

Mart, I watched your videos and it looks like exactly what I want to do. Can you tell me any more info about the process, or if there was any heat treat in the axle?

Pete, can you elaborate on the process you used? Just a lathe and no grinder? You didn’t have chatter problems as you cut into the hardened surface (if it IS heat treated)?

Pete · 08-19-2023, 08:11 PM

Quote:

Originally Posted by alchemy

Pete, can you elaborate on the process you used? Just a lathe and no grinder? You didn’t have chatter problems as you cut into the hardened surface (if it IS heat treated)?

It is heat treated. I used ceramic tool bit (carbide works also) and fairly high spindle speed. No grinder. Probably machined 30 to 40 finish and then lapped from there.

The splined late model axles were cut in the middle and welded to shorten for an econo blown Olds powered dragster. Around 400 hp. Only required 3 for all season. (broke one)

Ricosan · 08-19-2023, 08:52 PM

Alchemy, google “Iron trap garage”. Then click on “videos”
Richard

Yoyodyne · 08-22-2023, 01:46 PM

I'm discussing this with a friend, we'd like to do some calculations. Does anyone have the dimensions of the Ford taper handy? I'm looking for the large end diameter, the small end diameter and the length of the taper. The angle would be nice too, but we can calculate that from the above dimensions.

What thread is in the axle nut? And what is the factory recommended torque?

Unfortunately the only axles I have are in my truck.

BTW, I've seen axles successfully shortened by cutting extra long ones, or 2 axles, so that they can be sectioned together in sort of a broomhandle break fashion. That way the weld is not 360° around the axle, it also runs along the length. This way you don't have the embrittlement all around the axle in a circle and the weld is not all in shear. 3" section has always worked.

Mart · 08-22-2023, 02:17 PM

Threads are 5/8 -18 SAE UNF.

I believe the taper is 7 degrees. In my video I mention that it is an 8:1 ratio. You reduce the diameter by 1/8 of the dimension you want to shorten by.

It is tricky to measure a taper. You need to make sure you are measuring at the same place along the shaft. I tried to show some of this in my videos.

YOU MUST DOUBLE CHECK ALL INFO FOR YOURSELF. Do not take my numbers as gospel.

Mart.

Yoyodyne · 08-22-2023, 08:07 PM

Thank you Mart. I determined long ago that the tie rod end tapers are 1.5" per foot, which matches your 1/8 per inch figure. So there's a real good chance the axles are measured the same way. That taper is used a lot in automotive, or at least older automotive. 7° is very close to that.

Do you have a figure for the axle diameter at the big end of the brake drum taper or how long the taper contact is?

alchemy · 08-22-2023, 08:46 PM

The goofy part of measuring the taper is that it rounds off as it meets the full diameter of the shaft. You will need to determine a different point to cut to. I’m guessing you pick a certain diameter near the fat end, then a certain diameter near the skinny end. Then measure between to confirm? Or are there machinists gauges with a perfect circle that could be used?

I think some weekend soon I’ll just make a trip out to my buddy’s shop and show him what I’m thinking about. He likes a challenge.

Rico: I looked through every single Iron Trap video on YouTube and couldn’t find one pertaining to shortening an axle. Quite a few on how he shortens a drive shaft, but I must be too dense to find the axle video.

Pete · 08-22-2023, 08:46 PM

https://www.engineersedge.com/hardwa...sign_15009.htm

Mart · 08-24-2023, 01:20 PM

Quote:

Originally Posted by Yoyodyne

Do you have a figure for the axle diameter at the big end of the brake drum taper or how long the taper contact is?

No. But the shaft you have has all the right dimensions. You just need to move them all along the shaft by whatever the difference is between a 40 shaft and a 48. (years quoted just as a example.

In my video I described where I used a bearing race to hold the calipers at a specific point and got a reference dimension. I was able to then measure the oversize shaft at the same point relative to the housing and work out how much over size it was.

My point is that you need to work things out for yourself based on the established principles.

Mart.

Yoyodyne · 08-24-2023, 01:51 PM

Thanks, but I'm trying to do some engineering calculations on paper, I don't have an axle in hand.

08-18-2023, 05:50 AM	#21
big job Senior Member Join Date: Sep 2013 Location: Dighton, Mass Posts: 1,230	Re: Has anyone shortened a rear axle shaft? What I gather you want to shorten it only .850 no problem all you need is a lathe. I believe the spider gear and shaft OD, taper, and thread is the same on 1940 to 1948 I think If so, you have all the measurements. Order of operations: #1 cut .850 from the threaded end & machine .850 thread size to the taper and pick up the thread pitch and re thread re drill for the cotter pin thats done. now machine the taper .850 longer re-machine the shaft for outer bearing. Now the key way. easy and fast is a milling machine or a shaper. any shop can cut a key way. This is exactly how we machine marine prop shafts same thing. hope I said this correctly for my brain to transpose into typing kind of like explaining how to tie shoe laces LOL sam

08-18-2023, 07:18 AM	#22
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,070	Re: Has anyone shortened a rear axle shaft? While a competent machine shop should be able to accomplish the task, it would be much cheaper to just find the right axle.

08-18-2023, 07:55 AM	#23
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,755	Re: Has anyone shortened a rear axle shaft? It can be done and has been done. I broke a shaft in my 41 pickup (same as a 40) and was able to obtain one that was a shortened 46-48 shaft. It was not quite right and I skimmed the taper a little more to position the drum correctly. I didn't do the initial machining but was able to take a light cut. I made sure the hub was well lapped to the axle afterwards. I don't believe any heat treatment was carried out. The metal is tough and needs good quality tipped tools. My axle had been welded at the mid point and snapped. I showed it in a video mini-series. part 1: https://youtu.be/t0AfzS5OLYE part 2: https://youtu.be/i26ZSqwFIF0 part 3: https://youtu.be/8ToEl7O01P0 part 4: https://youtu.be/MOVxQP0aZhg Mart. Mart.

08-18-2023, 08:47 AM	#24
deuce_roadster Senior Member Join Date: Oct 2011 Location: Shelton, WA Posts: 3,800	Re: Has anyone shortened a rear axle shaft? Just get a correct good appearing used axle and have it magged at the inner end of the keyway. A used axle with no cracks can be lapped to your hub. By FAR the cheapest solution.

08-18-2023, 09:13 AM	#25
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,950	Re: Has anyone shortened a rear axle shaft? Bored&Stroked got it right. Machine shop work these days is not cheap.

08-18-2023, 09:15 AM	#26
Ricosan Senior Member Join Date: May 2018 Location: Tallahassee Posts: 375	Re: Has anyone shortened a rear axle shaft? Sponsored Links (Register now to hide all advertisements) Alchemy, there is a detailed video doing this online at Iron Trap garage. Lots of other videos at this site too. Richard

08-19-2023, 07:41 PM	#27
alchemy Senior Member Join Date: May 2010 Location: middle of Iowa Posts: 647	Re: Has anyone shortened a rear axle shaft? Rico, I can’t find the video you are talking about. Can you post a link? Mart, I watched your videos and it looks like exactly what I want to do. Can you tell me any more info about the process, or if there was any heat treat in the axle? Pete, can you elaborate on the process you used? Just a lathe and no grinder? You didn’t have chatter problems as you cut into the hardened surface (if it IS heat treated)?

08-19-2023, 08:52 PM	#29
Ricosan Senior Member Join Date: May 2018 Location: Tallahassee Posts: 375	Re: Has anyone shortened a rear axle shaft? Alchemy, google “Iron trap garage”. Then click on “videos” Richard

08-22-2023, 01:46 PM	#30
Yoyodyne Senior Member Join Date: Nov 2010 Location: Lancaster PA Posts: 535	Re: Has anyone shortened a rear axle shaft? I'm discussing this with a friend, we'd like to do some calculations. Does anyone have the dimensions of the Ford taper handy? I'm looking for the large end diameter, the small end diameter and the length of the taper. The angle would be nice too, but we can calculate that from the above dimensions. What thread is in the axle nut? And what is the factory recommended torque? Unfortunately the only axles I have are in my truck. BTW, I've seen axles successfully shortened by cutting extra long ones, or 2 axles, so that they can be sectioned together in sort of a broomhandle break fashion. That way the weld is not 360° around the axle, it also runs along the length. This way you don't have the embrittlement all around the axle in a circle and the weld is not all in shear. 3" section has always worked.

08-22-2023, 02:17 PM	#31
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,755	Re: Has anyone shortened a rear axle shaft? Threads are 5/8 -18 SAE UNF. I believe the taper is 7 degrees. In my video I mention that it is an 8:1 ratio. You reduce the diameter by 1/8 of the dimension you want to shorten by. It is tricky to measure a taper. You need to make sure you are measuring at the same place along the shaft. I tried to show some of this in my videos. YOU MUST DOUBLE CHECK ALL INFO FOR YOURSELF. Do not take my numbers as gospel. Mart.

08-22-2023, 08:07 PM	#32
Yoyodyne Senior Member Join Date: Nov 2010 Location: Lancaster PA Posts: 535	Re: Has anyone shortened a rear axle shaft? Thank you Mart. I determined long ago that the tie rod end tapers are 1.5" per foot, which matches your 1/8 per inch figure. So there's a real good chance the axles are measured the same way. That taper is used a lot in automotive, or at least older automotive. 7° is very close to that. Do you have a figure for the axle diameter at the big end of the brake drum taper or how long the taper contact is?

08-22-2023, 08:46 PM	#33
alchemy Senior Member Join Date: May 2010 Location: middle of Iowa Posts: 647	Re: Has anyone shortened a rear axle shaft? The goofy part of measuring the taper is that it rounds off as it meets the full diameter of the shaft. You will need to determine a different point to cut to. I’m guessing you pick a certain diameter near the fat end, then a certain diameter near the skinny end. Then measure between to confirm? Or are there machinists gauges with a perfect circle that could be used? I think some weekend soon I’ll just make a trip out to my buddy’s shop and show him what I’m thinking about. He likes a challenge. Rico: I looked through every single Iron Trap video on YouTube and couldn’t find one pertaining to shortening an axle. Quite a few on how he shortens a drive shaft, but I must be too dense to find the axle video.

08-22-2023, 08:46 PM	#34
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,409	Re: Has anyone shortened a rear axle shaft? https://www.engineersedge.com/hardwa...sign_15009.htm

08-24-2023, 01:51 PM	#36
Yoyodyne Senior Member Join Date: Nov 2010 Location: Lancaster PA Posts: 535	Re: Has anyone shortened a rear axle shaft? Thanks, but I'm trying to do some engineering calculations on paper, I don't have an axle in hand.