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specs for machining sprockets to 520 chain #261491
06/27/09 7:20 pm
06/27/09 7:20 pm
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Melbourne Fl
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Terry_tr6 Offline OP
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Not being a machinist, If i was to take a set of stock sprockets to a good machine shop, what would i need to tell them in order for them to machine the sprockets to for 520 chain? And wold it be better to do both sides or just the inside of the sprockets. Just one side should be cheaper and give more tire clearance, but will it cause problems with chain guard clearance? I know my guard is pretty close to the chain

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Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #261503
06/27/09 10:14 pm
06/27/09 10:14 pm
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Asheville, NC
Mike Baker Offline
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Terry
I think you'd have to keep the centerline of the chain the same.
I've run certain 530 chains that have nicked the engine cases due to their width. A 520 o-ring is about as wide as a 530 standard chain. If you're going to a standard 520 you might get by machining one side, but whats the point in that?
My next chain and sprocket set will be 520 o-ring. Tired of adjusting every 400 miles.....
Mike

Re: specs for machining sprockets to 520 chain [Re: Mike Baker] #261507
06/27/09 11:09 pm
06/27/09 11:09 pm
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Virginia, USA
SBoyd Offline
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Terry
Bring them a good 520 sprocket from another bike.
Then they will know what to do.

If you don't have an assortment of 520's from other bikes, any nice repair shop should have several in the junk box and will give or lend to you. Get one that is not worn.
You should also bring a piece of 520 chain so they know how far towards the center to remove material.

As for the centerline, I think mblab is right.
For racing, I took the material off the inside to gain tire clearance for the wider tires, BUT that was going to standard 520 chain, not o-ring.

You have to dodge both the tire and the chain guard so the stock centerline may be best.


Stop the insanity.
Re: specs for machining sprockets to 520 chain [Re: Mike Baker] #261510
06/27/09 11:30 pm
06/27/09 11:30 pm
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Melbourne Australia
Tiger Offline
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You must machine both sids IME.

I use a DID 520 [VX?] X-ring and it is narrower than the 530 std chain but only by a few thou overall [which means half of a few thou each side].

The std 530 chain runs so close to that upper drive side 'case bolt that you cannot realistically move it any closer which would be the case if you tried to get away with grinding one side of the sprockets.

You need to reduce sprocket width by 1/8" overall which is of course 1/16" either side.
Be aware that the DID x-ring chain at least has press/taper fit link plates/pins on the joining link, this can be a PITA in the shed much less on the roadside.

I alleviated this issue by lapping the plate to the pins to reduce the force necessary to push the plate below the circlip groove on the pins.

Do not lap so much that you lose the benefit of the taper, the job can be made easier but the taper is there for a reason.

Your question has prompted me to think of a new tool, I have been using a pair of Jap OEM toolkit slip joint pliers to push the link plate onto the tapered pins, an awkward job at best.

But what if one were to drill a "socket" in one side plier pad to fit over the pin ?

This would drive the link plate squarely onto the pin and avoid the pliers slipping off a greasy chain.

It is necessary to crimp left/right [alternative sides of the plate/pins] to settle the plate evenly, you are not going to push one side of the plate fully home on it's respective pin without the other coming along.

Great conversion BTW, virtually nil chain wear and less vibration, I was told to expect slightly higher fuel consumption due to x-ring stiction but that has not proven to be the case, I reckon "normal" wear of a non sealed chain is probably worse for economy.

If you want std gearing [my preference] think about a 20T gearbox sprocket and four more teeth on the rear, the larger gearbox sprocket is easier on the chain, if my memory serves me the above will drop engine speed by only 40 RPM at 60 MPH.

The above sprocket sizes also allow you to machine and "re-band" an otherwise good integral sprocket brake drum.

The larger sprockets fit easily under a std dry frame chain guard.

Last edited by Tiger; 06/27/09 11:33 pm.

1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: specs for machining sprockets to 520 chain [Re: Tiger] #261518
06/28/09 12:04 am
06/28/09 12:04 am
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Posts: 731
Melbourne Fl
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Terry_tr6 Offline OP
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wow great info! I'm checking to see what britech and british spares charge for their kits(but i forgot to ask if it included the chain) so i can see if it makes sense to get the sprockets done locally
as to pressing on the side plate, would something like a C-clamp set in the middle of the plate work to squeeze the plate on? Maybe tack a couple tabs on the screw side to keep the swiveling pad from slipping off...
I'm going with towner and florida-tr6 on keeping the 47 tooth rear and try going up to a 20 tooth front on their TR6's. No hills here in florida, and they report being pretty happy.

How about adjusting chain length, is it any harder to cut down an x-ring down than a standard chain? I'd think that the stock chain length is OK with a 20 tooth front, but sometimes the best price isn't for the exact length.

Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #261530
06/28/09 1:27 am
06/28/09 1:27 am
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Melbourne Australia
Tiger Offline
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The sliding clamp which you describe would work fine I reckon, the reason I lapped the pins/plates is that roadside the slip joint pliers will be in the toolbox.

It would be best to grind the ends off two pins to shorten a chain.

Been thinking about drilling into one pad of my pliers, probably quite hard material, grinding a slot across may be more practical.


1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: specs for machining sprockets to 520 chain [Re: Tiger] #261535
06/28/09 3:13 am
06/28/09 3:13 am
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georgia
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Conical rear hub? Pretty sure a 520 sprocket from a T25/B25 is a direct bolt on, no mods required....would greatly simplify the conversion!


1974 TR5T
Re: specs for machining sprockets to 520 chain [Re: trumpetloon] #261547
06/28/09 5:21 am
06/28/09 5:21 am
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Posts: 731
Melbourne Fl
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Terry_tr6 Offline OP
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all i see listed for the t25 is the 53 tooth

Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #261597
06/28/09 2:24 pm
06/28/09 2:24 pm
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georgia
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trumpetloon Offline
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I have seen aftermarket sprockets listed from 50 to 60 teeth. Finding a 47 toother might be a challenge... these were not particularly popular (or long lived) models. Still worth a bit of a search I would think?


1974 TR5T
Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #261598
06/28/09 2:35 pm
06/28/09 2:35 pm
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Norfolk, UK
L.A.B. Online content
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Originally Posted By: Terry_tr6
If i was to take a set of stock sprockets to a good machine shop, what would i need to tell them in order for them to machine the sprockets to for 520 chain?



The 520 sprocket width is 0.227". http://www.gizmology.net/sprockets.htm

Re: specs for machining sprockets to 520 chain [Re: L.A.B.] #261766
06/29/09 11:17 am
06/29/09 11:17 am
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Bega NSW Australia
Mark Parker Online content
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Pushing the sideplate onto the DID 'X' ring joining link; I use vice grips and a tiny ring spanner or socket, just pressing it gently over one pin then the other till the plate is on enough for the clip. The vice grips are adjustable to whatever you use to push the sideplate on and can comfortably give sufficient pressure. I rivet mine because the link with the clip is slightly wider and on the BSA the front sprocket is ground offset so it just skims the chain near the case and the other side is very close to the tyre.


mark
Re: specs for machining sprockets to 520 chain [Re: L.A.B.] #261770
06/29/09 11:49 am
06/29/09 11:49 am
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Melbourne Australia
Tiger Offline
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Originally Posted By: L.A.B.
Originally Posted By: Terry_tr6
If i was to take a set of stock sprockets to a good machine shop, what would i need to tell them in order for them to machine the sprockets to for 520 chain?



The 520 sprocket width is 0.227". http://www.gizmology.net/sprockets.htm


When you get the sprockets back you may want to gently dress off any burrs from the edges, a cylindrical stone would be ideal but I used a chainsaw file.


1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: specs for machining sprockets to 520 chain [Re: Tiger] #261804
06/29/09 2:45 pm
06/29/09 2:45 pm
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Westminster, MD, USA
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J. Charles Smith Offline
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I would machine the inside only so you have additional tire clearance. The clearance on your chaiguard will not be affected unless the chain thickness on the outside is considerably thicker - which it may be if you are going from standard 530 to o-ring 520. Otherwise, the outside run of the chain is not affected.

Re: specs for machining sprockets to 520 chain [Re: J. Charles Smith] #261857
06/29/09 5:47 pm
06/29/09 5:47 pm
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Scotland
kommando Online content
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47T 520 rear is a common fitment to the B50 to gear it better for road use, its a 520 as the cycle parts are commonish with the OIF B25.

Re: specs for machining sprockets to 520 chain [Re: kommando] #261925
06/29/09 10:12 pm
06/29/09 10:12 pm
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Regina Sk, Canada
Coco Offline
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Been looking at doing this to my Triumph build so this interests me. What about 520 X ring compared to O ring?

My Norton has had the 520 X ring conversion done.


Colin
--------------------------
1975 MKIII Norton Commando
'73/'70 Triumph 750 chop in the works
Re: specs for machining sprockets to 520 chain [Re: Coco] #261946
06/30/09 12:31 am
06/30/09 12:31 am
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Melbourne Fl
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Terry_tr6 Offline OP
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everything i've seen makes o-ring look like it is way surpassed in performance by x-ring.
Also, i just ordered a rear sprocket for my 71 tr6 (when did sprockets go to $50 and up?? and no one on eBay had any conical hub sprockets)from MAP and was told they have 19 tooth/4 speed front sprockets for 520 chain in the pipeline. no word on price and availability is some weeks out. rear sprockets are supposedly being made next but no timeframe estimate, What good a 520 front sprocket is without a matching rear, i don't know, but it looks like the popularity is spreading..

Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #266092
07/21/09 7:54 pm
07/21/09 7:54 pm
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Melbourne Fl
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Terry_tr6 Offline OP
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got my sprocets finished, but i'm puting the install aside till my current chain and tire need replacement in a month or 2.
The front sprocket must have been a real bear to turn on a lath because when i mentioned to my friend who did it that there might be a bit of a market out there for doing this and what would he charge, he changed the subject....

Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #266133
07/21/09 11:25 pm
07/21/09 11:25 pm
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DMadigan Online content
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Your machinist went about it the hard way. Front sprockets are hardened so even using a carbide bit will be tough cutting and chatter when skipping across the sides of the teeth. I used a body grinder mounted in the tool post. You only have to narrow the sprocket to the depth of the chain side plates (unless you are a racer).
Widths of 520 sprockets vary, one I measured was 0.235". It obviously has to be narrower than the chain and have the sides of the teeth champhered to guide the side plates as the rollers enter the pockets.
X ring seals are more compliant being cantilevered arms rather than a round rod in compression.

Last edited by DMadigan; 07/21/09 11:25 pm.
Re: specs for machining sprockets to 520 chain [Re: DMadigan] #266134
07/21/09 11:33 pm
07/21/09 11:33 pm
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johnm Offline
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Yes. Grind them.

Re: specs for machining sprockets to 520 chain [Re: johnm] #300277
02/24/10 3:59 pm
02/24/10 3:59 pm
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Regina Sk, Canada
Coco Offline
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Anywhere selling these chainring kits? I'd buy an x-ring kit now if they were available.


Colin
--------------------------
1975 MKIII Norton Commando
'73/'70 Triumph 750 chop in the works
Re: specs for machining sprockets to 520 chain [Re: Coco] #300296
02/24/10 6:48 pm
02/24/10 6:48 pm
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John Healy Online content

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Triumph and after market sprockets can easily be machined on a lathe with an ordinary carbide cutting tool. These sprockets are case hardened to a depth of only .010 to .020" thousandths. Just make your first cut .050" so you get under the hardnening.

Support the sprocket in the lathe's chuck using the high gear. (Use the one from the bike or one that is laying around the shop). Mount the sprocket on the high gear, place the sprocket's seal holder surface in the chuck (covered with tape to protect the surface), slip the high gear's splines into the sprocket and run a live tail stock center into the open end of the high gear's main shaft bushing. This will hold the sprocket rigid and help prevent chatter.

Because the reference point in all of this will typically the inside face of the rear sprocket, material will have to be taken off the outside of the transmission sprocket. This keeps the alignment correct. If you cut the inside, and don't move the rear sprocket, the chain will be traveling at an angle.

If you want more chain clearance on the tire ( as when a 5.00x16" tire is mounted) and you want to accomplish this by cutting the transmission sprocket on the inside, the rear sprocket has to be moved out to suit.

Because when you cut of the side of the sprocket (either side) you are exposing steel that is no longer hardened. Expect excessive sprocket wear on the side that has been cut.



Last edited by John Healy; 02/24/10 6:51 pm.

Re: specs for machining sprockets to 520 chain [Re: John Healy] #300304
02/24/10 8:15 pm
02/24/10 8:15 pm
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Regina Sk, Canada
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Thanks for the info John. I have no lathe or mill or anything of the like and have no experience using such machinery. I was hoping to just buy the front and rear chainrings so I'll have to look into this further and see if any machine shop around here is competent enough. I have everything apart on the primary side to install a belt drive so I figured while all of that is apart, now would be the time to swap out that front sprocket. Rear hub is a cotton spool type.

Bike is a hardtail chopper thingy but I'm using a narrow 18" rear wheel so no offset is needed for a fat tire.


Colin
--------------------------
1975 MKIII Norton Commando
'73/'70 Triumph 750 chop in the works
Re: specs for machining sprockets to 520 chain [Re: Coco] #300305
02/24/10 8:22 pm
02/24/10 8:22 pm
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DMadigan Online content
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There is a product called Kasenit that will allow you to reharden the steel sprocket after machining.

Re: specs for machining sprockets to 520 chain [Re: Terry_tr6] #431137
04/22/12 6:12 pm
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This is a great and informative thread, thank you. I just thinned my sprockets and installed a 520 o-ring chain on my BSA Gold Star restoration. See images and text of the sprockets and chain here.


1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville

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