one piece axle for mk3 commando

"It's been several years since I converted my MK III to solid rear axle (BEFORE the original broke), and I merely made up spacers (two, I think) and filed the swingarm forks wider to accept the Honda 17MM axle. As I recall, the wheel bearings required no mods or replacements. <...> I've found that by sliding the axle out to the left side, the sprocket can be left in place while removing the wheel." (Frank Forster, 2012)

The simplest solution often IS the best solution. How often do you have to remove the rear wheel? The absence of a dummy axle just means you have to be a little careful when pulling the long solid axle. A mark on the axle will tell you how far out you can safely pull it. Who cares if the lone sprocket is a little wobbly on the protruding shaft end? You can always push the axle back in if you are worried about the sprocket and chain dropping to the ground. See entries #1, #20, #26-27 of this thread.
The solution looks very attractive to me!
Now I wonder which Honda model has (or had) a 17mm axle of suitable length?

= Knut

mdt-son said:

Now I wonder which Honda model has (or had) a 17mm axle of suitable length?

= Knut

Click to expand...

There are a ton of diff models out there with 17mm rear axles, altho i've come across a major issue that is problematic. There are a few guides out there but they conflict.

This one for 15mm shows pretty much mostly well below 500cc bikes, 17mm showing mostly 250cc up to 1,000+

pretty much the same here
--------------------------------------------------------

then this list shows many above 500cc bikes, that are the in the 17mm section above, but in the 15mm section below

then for the 3rd link (directly) above, there is this post, these last 2 links dated 2006

L.A.B. said:

The pre-Mk3 axle is 9/16" and so is the thread.

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.

andover-norton.co.uk

The Mk3 axle thread is 1/2" (UNF).
Edit: The Mk3 dummy axle external thread is 9/16"

Click to expand...

"The Mk3 axle thread is 1/2" (UNF).
Edit: The Mk3 dummy axle external thread is 9/16" UNF.
-------------------------------------
That would mean the left side mk3 swingarm axle slot would have to be opened up for the 17mm axle? Certainly it would for pre mk3.

That then gets into does the area then get weakened, requiring it to be 'beefed' up? I have come across suggestions yes, including a resulting part failure/crack/breakage there, altho in a racing situation.

- edit
comnoz said:

Common mod for racing or heavy loads. Basically you drill through the stub axle and use it as a spacer or make a spacer from bar stock. Then you go to the MC breaker and find an axle the right diameter and length. A lot of old dirt bike axles will work. You need to widen the slot in the left side of the swingarm and make it the same width as the slot on the right side. It makes tire changing a little tougher as you then remove the sprocket with the wheel. I have made up spacer sets in the past for people but I don't have the measurements anymore. Jim

74ok said:

That would mean the left side swingarm axle slot would have to be opened up for the 17mm axle?

Click to expand...

Yes.

74ok said:

That then gets into does the area then get weakened, requiring it to be 'beefed' up?

Click to expand...

I wouldn't think so as the Mk3 LH and RH axle plates are identical except for the narrower slot in the left-hand plate. Unlikely to be a problem on the pre-Mk3 either I would have thought.

Here's a post taking it back to 05

hobot said:

From Ken Canaga 1/5/2005 5:58 PM

As Mike and Frank, and others in the past have pointed out, it is a fairly
staightforward job to convert a Commando to a one-piece axle of same (9/16")
or slightly larger (17 mm) size. I used to race a Norton Production Racer,
and after breaking two-piece axles twice, did the same. I would warn
against going to a much larger diameter, however, unless you plan to modify
the swinging arm. As the bike progressed from a 750 production class racer
to a 920 Pro-Twins bike, I switched to 18" mag wheels from a TZ-250, and in
the process went to a larger 20 mm rear axle. To do so, I had to enlarge
the adjustment slots in the swinging arm to match. No problem, and it
seemed to work fine, until the swinging arm broke right through the
adjustment slot. It was kind of exciting, but at least I didn't crash. I
ended up makeing a new swinging arm out of rectangular tube, and all was
well from then on. I think it should be fine at 9/16" or 17 mm, but if the
urge to go larger strikes, think about beefing up the swinging arm. And
just to prove that you can never eliminate all risk, I also managed to break
one of the one-piece 9/16" axles during a race at Willow Springs. That's
actually what prompted me to go to the 20 mm axle. Didn't crash that time
either, but it was a wild ride off the track and across the dirt.

Ken
----------------------------------------------------------

- It should be pointed out, a few big fish have suggested/commented against going with stainless steel.

Vincent axles , front and rear, are Stainless Steel, from the factory. I've never heard of one breaking. Many are still running on the original 70-80 year old SS axles. I'm reasonably certain my Rapide is still on its original axles. That bike has done huge mileage over the years, somewhere over 300,000.

Glen

74ok said:

That would mean the left side mk3 swingarm axle slot would have to be opened up for the 17mm axle? Certainly it would for pre mk3.

That then gets into does the area then get weakened, requiring it to be 'beefed' up? I have come across suggestions yes, including a resulting part failure/crack/breakage there, altho in a racing situation.

Click to expand...

I don't see a problem. It's a marginal change, and the RHS already has the 17mm slot, as pointed out by Les.

- Knut

no details..

Madnorton said:

Had a stainless one break in 2002, but no problems with the AN one fitted to replace way back then.

mdt-son said:

Now I wonder which Honda model has (or had) a 17mm axle of suitable length

= Knut

Click to expand...

no details other than
norbsa48503 said:
file the slots in the swingarm, and use the 17mm
rear axle from a Honda 350

part #2 shows 2 options

covers a range of 350 - 60 models including 1 year (77) 400/4 (Use up to Frame SN 2222576)

Dunno what the diff part# is about, may or may not be relevant/significant (Use up to Frame SN 2222576)

74ok said:

- It should be pointed out, a few big fish have suggested/commented against going with stainless steel.

Click to expand...

Applicable steels should be selected based on ASTM D790 Flexure Testing using a 4-point fixture and subjecting a circular solid specimen to simple (non-reverse) bending. The endurance stress limit (in MPa) for steels is the statistical median performance measured at 10E6 cycles. In addition the material must exhibit ductility in the post-yield range. A starting point is found here:

I have no tables in front of me, but a quick search indicates a fatigue endurance limit of AISI 316 (a common stainless grade) specimens subjected to reversal bending tests is in the order of 270 MPa while a case hardening steel such as AISI-SAE 4316 or 4320 will endure reversal bending stress cycles of almost 700 MPa. Alloy 4320 may be tuned to much higher endurance stress levels if sulphur and phosphor inclusions are kept low.

There is no doubt fatigue performance of most case hardening steels far outperforms common stainless grades. If the maker specified such a steel for production parts, I would be anxious about replacing it with a spindle made of a common grade stainless steel.

I have queried Don about the material spec for his axles. No reply so far.

- Knut

​

Looks like a honda cb350 axle is too long & needs modding, at least in the usual way. Haven't seen mention of going with a spacer and or washers at the bolt head, to shorten excessive length, prior to insertion.

Bruce MacGregor said:

" I installed a solid axle made from a Honda 350/450 axle 17 MM as per Frank Forster/ Mike T's instructions.
Basically the axle needs to be cut down to fit and threaded for a 5/8-18 castellated nut. the axle is inserted from the drive side swing arm which needs to be enlarged as well as the speedo drive & bushing. A new bushinng needs to be made to match the bushing on the dummy axle. (Note The honda axle is very hard, you will need a machine shop or a good lathe to do the threading).
And I found the Honda chain adjusters to be exact same as the Norton ones except much , much stronger. I currently have one Honda chain adjuster on the drive side and have had no problems. I will need to machine about an 1/16" off the other swing arm in side face in order to fit the other chain adjuster. Next Winter "

Click to expand...

For reference, a common harley axle size is 3/4" = 19.05 mm


SS thread
https://www.accessnorton.com/NortonCommando/stainless-steel-axles.500/

Thoughts on going with a 9/16 axle in 17mm swingarm slots?

Similar threads​

74ok said:

Looks like a honda cb350 axle is too long & needs modding, at least in the usual way. Haven't seen mention of going with a spacer and or washers at the bolt head, to shorten excessive length, prior to insertion.

Click to expand...

It's hard to find decent cores at Fleebay. Does anyone have the OEM spindle and dummy axle on the bench? Please take a reading of the combined assembled length, from under the bolt head to end of threads.
According to RGM, spindle under head length is 8-1/4" (209 mm).

-Knut

Found another front axle list, that confirms the 3rd link below,

It was news to me, what size axle Norton went with 9/16 (14.2875) pre mk3, in comparison to jap axles that start @ 15mm. That size also applies mostly to well under 500cc bikes.

17mm then covers a range from ~ 250 to 1,000+cc

Then hardness levels & type threads (rolled for 1 being better) came in the discussion, including metal composition.

From what i've read or come across, I don't think nearly enuff emphasis has been made of the history with the 2 piece axles. Altho apparently mostly considered 'rare' & ~ 'you can do something' about it, some folks have said specific things, that to me, put the 2 piece norton axle deal, on another level, including highly problematic failure modes.

I will elaborate with further specifics, but here's a start with some history & major specifics.

Oct 21, 2010 comnoz said:
Torque them to spec. Don't use stainless axles and if you ride aggressively or carry a big load put a one piece axle in it. Jim

- note the last sentence
Oct 22, 2010 comnoz said:
Dave, I have used both diameter axles but I think it will be easier to find a 17 mm axle. 350 Honda or several Yamahas used the right length. It is nice to use a milling machine to widen the swingarm slot but I have done them carefully with a carbide burr on the bike. Clean off the paint and scribe lines before you start.
I have broken several of the stock axles in the past. I have never broken a solid axle. Do not modify an axle by shortening it or cutting threads. The roll and finish at the threads and head is important. Hard washers can help spread the load and make things more rigid. I have modified any Norton that I have planned on putting much time on. I have been known to use them hard and I don't like having to worry about that. Jim

Jan 30, 2012 hobot said:
Oh yeah, btw Colin Sharpe on BI list just posted his SS axle upgrade fractured. It's Radioactive fissioning back there, how lucky to ya feel...

74ok said:

There are a ton of diff models out there with 17mm rear axles, altho i've come across a major issue that is problematic. There are a few guides out there but they conflict. It was news to me, what size axle Norton went with 9/16 (14.2875) pre mk3, in comparison to jap axles.

If a few lists out there are accurate, even mostly under 500cc bikes have 15mm axles that go up from there to 17mm

This one for 15mm shows pretty much mostly well below 500cc bikes, 17mm showing mostly 250cc up to 1,000+

Axle diameter size list

Compliments of "a member on another forum", Sorted by rear and front then size. Just find yours and you can see what else shares the same size for a swapping donor. Jap Bike Rear Axle Diameters 15mm Honda CB250 Nighthawk 91-92, CM250 Custom 82-84, CMX250 85-86 & 96-97 Rebel (right), CX500...

www.dotheton.com

pretty much the same here

Rear axle diameters

www.customfighters.com

--------------------------------------------------------

then this list shows many above 500cc bikes, that are the in the 17mm section above, but in the 15mm section below

Axle diameter chart glommed from chopperunderground forums

Axle diameter chart glommed from chopperunderground forums

kzrider.com

then for the 3rd link (directly) above, there is this post, these last 2 links dated 2006

Axle diameter chart glommed from chopperunderground forums

Axle diameter chart glommed from chopperunderground forums

kzrider.com

Click to expand...

Aug 5, 2017 #18

mdt-son said:

Don and all,
Mk3 rear axle is really poorly designed. In the interest of safety i would suggest altering the swingarm by machining (milling) the LH swingarm slot to the same shape as the RH slot, thus providing a 17mm axle dimension right through. Sure, this is a non-reversible action, but a spare swinging arm may still be purchased by those wanting to return to originality in the future ....
Going by the image in the parts book, the S/A axle supporting plates are of identical outer dimensions. Maybe someone can confirm this as my bike is in a remote workshop.

Don, if you would like to make an initial sample along these lines, I volunteer as tester.

-Knut

Click to expand...

Click to expand...

o0norton0o said:

I did exactly what you suggested. I bought a second swingarm and had a machinist mill the slots out to use a one piece 17mm axle. In my case, I modified the swingarm slots to use a yamaha cast wheel who's axle size was 17mm.

IF the only part of the MK3 rear wheel assembly which is not 17mm is the axle slot, then it might be easy to convert an MK3 to a one piece 17mm axle. The 17mm yamaha axle I used in my modified swingarm is available on ebay for about $15. I also bought the axle spacers on ebay too.

I never had an issue with the 2 piece axle on my commando, but I always thought it was weird. Now that I have a 1 piece 17mm axle I have one less flaw to worry about.
--------------------
o0norton0o said:

82 seca 550 in my case, but as I said there are even better choices that I discovered in later research.






GRM 450 said:

Is bright steel 4130 ok to make an axle ?

Graeme

lcrken said:

Short answer is yes. 4130 is a pretty common material for race bike axles here in the US. 4140 is also pretty popular. 4130 is readily available in hardened, normalized bar with hardness around RC20, which machines well (with sharp tools). 4140 in hardened, normalized bar, is typically RC25 - RC30, and has higher tensile strength than the equivalent 4130. Either one will work fine for motorcycle axles. Both alloys can be had in higher hardness condition, with higher tensile strength, but the machining gets more difficult, and at really high hardness levels the material becomes too brittle for an axle that needs to be able to flex a little. Not sure what passes for "bright steel bar" down under. There's more than one definition of that term. But probably the same stuff we get here as pre-hardened, normalized bar. There are all sorts of other specifications for various 4130 conditions, but the stuff you usually get from a reputable metals supplier is likely to be what I've described here. If in doubt, ask what the specs are for the material before deciding.

If you just google "4130 motorcycle axles", you'll find lots of additional info, and some examples of currently available 4130 axles, although most of what you see will probably be for the Harley crowd.

Ken
-------------]

Rohan said:

Commandos have somewhat of a reputation of breaking these axles.

BSA use almost the same design, and don't.
The BSA ones look to have a much better/tougher grade of steel.

i had the stock standard original axle strip its thread back almost when these things were new - that says to me the axles could have been made out of a much better grade of steel , even the original items were too low spec ??

The thread also looks like it is cut in to the axle - not a rolled thread, which is much stronger...
-------------------------

- Haven't run across detailed specs of the C'do axles?

bobnorsaki said:
the mk3 two piece axle is 17mm. If you cut the stud off the stud shaft and open it up to 17mm you can insert a one piece axle. I have used the axle from a 1983 kawasaki gpz 750. one must redeuce the length of the shaft and put threads on it for it to fit the swingarm.
--------------------------------------

I'm not clear on the need to "cut the stud off the stud shaft and open it up to 17mm you can insert a one piece axle"

Why not just remove the dummy axle (i think OP is calling 'stud shaft')?

part #26


This post is suggesting the same
"The simplest solution often IS the best solution. How often do you have to remove the rear wheel? The absence of a dummy axle"

Then it seems to me, the original spacers would still work (part#s 11 & 30). OP also makes no mention of changes there.

Also, this axle (no mention of mods) has been in use a few years & has come up as candidate, but had ltd use (a few yrs seca 550 only), or wasn't widely shared among models with yamaha.


Lastly, i think there are swingarm dimensions out there, that could help find a suitable length Axle Bolt, that hasn't been determined yet. Finding this makes a candidate AB ready to use vs cutting to length then also re tapping threads, if it can even be done (likely not) without a mill.

Partzilla is handy for finding jap part #s along with what model(s)/year(s) may be covered, Part #s can be very useful for ebay searches. Finding a widely used candidate part usually makes it easier to find & cheaper.

74ok said:

I'm not clear on the need to "cut the stud off the stud shaft and open it up to 17mm you can insert a one piece axle"

Why not just remove the dummy axle (i think OP is calling 'stud shaft')?

Click to expand...

If the Mk3 dummy axle is removed then either the 'head' would need to be cut off and used with the 17mm axle or a spacer fitted in its place as it is the spacer between the double-row sprocket bearing and hub bearing.

For the complexity (extra double row bearing, et al) does the MK3 cush actually perform any better that previous models?

mdt-son said:

"It's been several years since I converted my MK III to solid rear axle (BEFORE the original broke), and I merely made up spacers (two, I think) and filed the swingarm forks wider to accept the Honda 17MM axle. As I recall, the wheel bearings required no mods or replacements. <...> I've found that by sliding the axle out to the left side, the sprocket can be left in place while removing the wheel." (Frank Forster, 2012)

The simplest solution often IS the best solution. How often do you have to remove the rear wheel? The absence of a dummy axle just means you have to be a little careful when pulling the long solid axle. A mark on the axle will tell you how far out you can safely pull it. Who cares if the lone sprocket is a little wobbly on the protruding shaft end? You can always push the axle back in if you are worried about the sprocket and chain dropping to the ground. See entries #1, #20, #26-27 of this thread.
The solution looks very attractive to me!
Now I wonder which Honda model has (or had) a 17mm axle of suitable length?

= Knut

Click to expand...

I did this using an axle from a Honda CB350. It's a bit long, but I just use some spacers to get the castilated nut in the correct place. It lacks flats on the other end to hold it when tightning it, uses a through hole instead, which requires you to carry a suitable screwdriver or similar to use as a tommy bar instead.

It's not a difficult project, but I don't think I would do it again if I was planning on keeping the original rear hub. I have a cunning plan to use a modern lightweight hub at some point though.

SteveBorland said:

I did this using an axle from a Honda CB350. It's a bit long, but I just use some spacers to get the castilated nut in the correct place. It lacks flats on the other end to hold it when tightning it, uses a through hole instead, which requires you to carry a suitable screwdriver or similar to use as a tommy bar instead.
It's not a difficult project, but I don't think I would do it again if I was planning on keeping the original rear hub. I have a cunning plan to use a modern lightweight hub at some point though.

Click to expand...

Thanks for your input, Steve.

The absence of a proper hex head is a point of nuisance to me. I have yet to find an axle off a jap bike which has this feature. Apart from the problem finding a decent axle at all.
45 year old axles are mostly looking tatty, with bearing wear marks etc. . The axle to use is off a Honda 350 Four I guess. How much too long is it, approximately? I hate dragging unnecessary weight along, apart from the design annoyance.

The spacer issue addressed by Les (#56) may be solved by a suitably shaped spacer shrunk into the sprocket. Having a loose spacer there (in lieu of the dummy bolt head) is a bit cumbersome - to me at least.

Why wouldn't you do the conversion again if you planned on keeping the original rear hub? The rationale for the conversion was/is safety.

-Knut

mdt-son said:

The spacer issue addressed by Les (#56) may be solved by a suitably shaped spacer shrunk into the sprocket. Having a loose spacer there (in lieu of the dummy bolt head) is a bit cumbersome - to me at least.

Click to expand...

The spacer, however, is static as it's a bearing spacer but the sprocket rotates.