SURFACE GRINDING SNAP RINGS

[Oldtimer]

Can a snap ring be ground on a surface grinder without compromising its integrity?

The D20 T Shift Transfer Case uses a C6TZ 7070-B snap ring the retain the main drive gear on input shaft.
The C6TZ 7070-B snap ring is no longer available.
The 8A-7064 snap ring is available. It has the correct ID and Width, but is too thick.
Tom’s 4015B is too thin and too narrow.

C6TZ 7070-B -- ID 1.222 -- TK .064 -- W .157
8A-7064 ------- ID 1.220 -- TK .093 -- W .156
Tom’s 4015B -- ID 1.170 -- TK .058 --- W .089
JBG 11624 ---- Not in stock, no dimensions

 

[73azbronco]

google size as a snap ring. too thin, use two thin ones?

https://americanring.com/products/snap-ring.aspx?item=XSC-149

 

[jamesroney]

Can a snap ring be ground on a surface grinder without compromising its integrity?

Yes.

Especially if you flood cool it. If you are only doing a few, no problem.

The steel is heat treated before finishing, and is thru-hardened. You just need to make sure you don't anneal it.

Factory snap rings are finish sized on a double disc lapping machine, but if you are only making a few...no problem on a horizontal spindle mag mount chuck.

But if you are going to the trouble of machining your own snap ring, why not go ahead and widen the shaft snap ring groove? Then you can use the fat snap ring.

 

[Oldtimer]

I think I will have better success finding a machine shop to surface grind snap rings than one willing to make an interrupted cut in a hardened shaft.

If they grind all 10, I will have a part (and solution) that others can use.

 

[Broncobowsher]

My understanding, yes it will work. Even through you see sparks as it is ground, it is still considered a cold process.
I'm trying to get a surface grinder put back in service at work. I'm still learning about these things.

 

[Jason Miller]

Good call getting all 10 done, you're about to become the D20 snap ring guy and the forum will owe you one.

To echo the machining wisdom above: yes, surface grinding is fine here because these rings are thru-hardened, so you're not skating a thin case off a soft core. The only thing that can bite you is heat. The rule of thumb is watch the temper colors. A light straw is no big deal, but if the ground face goes blue or purple you've locally annealed it and the hardness in that spot is gone. Flood cooling, like mentioned, keeps you well clear of that, and taking a few light passes beats one heavy grind every time.

One thing worth doing once they're back: deburr the ground edges and actually measure one with a mic before you trust the batch. And double check the .064 lands in the groove with a hair of clearance, you don't want it proud.

On the "stack two thin ones" idea from earlier: I'd skip it for a retained gear. Two rings can rotate against each other and you lose the solid shoulder you're after. The ground single ring is the cleaner answer, which is exactly the route you took.

Post up the final dimensions and the shop you used when they're done, the next guy with a dead C6TZ 7070-B will thank you forever.

 

[ba123]

There has got to be a snap ring available to match.

Worst case, I'd bet Advance Adapters has one.

If not, JBG will tell you what their part is if you call or email and ask.

There is literally no way that there isn't a clip available somewhere.

 

[Grey owl]

You would have to grind it to the correct specific thickness. Thats important to prevent a possible failure.

 

[DirtDonk]

I must have missed something. Is the correct ring not available? Do we have anything at WH that you wanna try?

 

[ba123]

I saw one or two on the WH site but there is no info.

 

[DirtDonk]

Too bad I waited till Friday. I’ll have to find out more about them.

 

[Oldtimer]

Paul,
WH only has the large internal snap ring that goes in the extension housing, and retains the OD of the input shaft Bearing. Tom's & Jeff's both carry this snap ring.

There are also 2 small external snap rings, one for the main drive gear on the input shaft, and the other for the front drive constant mesh gear to the output shaft.
The 1966 Ford parts have been discontinued for years. There are no NOS parts in the country, and the rebuilders use the old ones (after reforming), or harvested ones from cores they have.
Some of the other Bronco vendors sell snap rings that might work, but they are thinner and narrower then the original Ford/Spicer parts.

 

[Oldtimer]

@Kalex asked about WH#7215 , large internal snap ring . I have not touched it or the ones the other vendors sell, so I can't comment on dimensions.

If you google the Ford number C6TZ 7070-A you will find NOS parts on EBAY.

The large internal snap ring does not get as beat up when removing, so they can be reused.
The small external ones get deformed when opening up to slide off of their shafts.
The one on the front output shaft is trapped between a gear and a bearing, so it has a high mortality.

 

[ksagis]

@Old Timer, I poked around and see what you mean on availability. Seems like the C6TZ 7070-B is a bit of non standard size.

Are the dimensions you state above as measured, or stated on in spec writeups? Have you put calipers on snap ring groove on the shaft and is it roughly 0.004 to 0.006" wider than the ring you have now? Similar question on the ring you removed, is it 0.064" thick?

 

[Oldtimer]

I poked around and see what you mean on availability. Seems like the C6TZ 7070-B is a bit of non standard size.

Are the dimensions you state above as measured, or stated on in spec writeups? Have you put calipers on snap ring groove on the shaft and is it roughly 0.004 to 0.006" wider than the ring you have now? Similar question on the ring you removed, is it 0.064" thick?

The ring I removed is .064" thick, and .157" wide.
The the groove in the shaft is 1.252" OD, and it is .083" wide. The shaft OD is 1.375.

EDIT: With bearing and main drive gear installed on input shaft, the available gap for a snap ring is .067", not the total .083" groove width.

The ring sold by Tom's is only .058" thick and .089" wide, which sent me on the search for something closer to stock.

 

[ksagis]

Wow, that snap ring groove is a lot wider than I expected - when I've spec'd snap ring grooves they're generally about 0.005" larger than the thickness of snap ring for GD&T allowances.

That seems to jive with what James said that this is a not a highly loaded joint else I'd think they'd hold the groove to be a lot smaller (assuming it hasn't worn wider during use).

You're adding 0.008" of gap to what was a 0.019" gap.

I did the math fast but think you lose about 0.060" of snap ring width due to depth so the one from Tom's seems borderline wide enough... Feels like the width is more important than the thickness.

 

[Oldtimer]

That snap ring sees no load except when reversing in 4wd. (or engine braking in 4wd) It's mostly along for the ride in 2WD.

The thrust side of the tooth forces the gear against the bearing in the forward direction. I've seen old dana 18's with the nut loose, and that gear stays put.

If you are in a pinch, the 3-4 synchro hub snap ring from a 64-73 Toploader is the right ID, and thickness. It's not nearly as wide though. I'm not saying it's exact, but there's more than a few Dana 20's that I have built with the smaller OD snap ring.

James.

@jamesroney , Thanks for explaining load condition against snap ring.
Which Toploader model did your snap rings come from?
All the snap rings from my 72 Toploader (RF-D2AR-7006-CB W1) are too thick to fit in the groove of my T-shift D20 input shaft.
In fact the MPC calls out the 8A 7064 for 65 on Toploader 3-4 syncro hub.

 

[Oldtimer]

Edit to post #16:

With bearing and main drive gear installed on input shaft, the available gap for a snap ring is .067", not the total .083" groove width.

 

[jamesroney]

@jamesroney , Thanks for explaining load condition against snap ring.
Which Toploader model did your snap rings come from?
All the snap rings from my 72 Toploader (RF-D2AR-7006-CB W1) are too thick to fit in the groove of my T-shift D20 input shaft.
In fact the MPC calls out the 8A 7064 for 65 on Toploader 3-4 syncro hub.

I looked at the kit, and it is generic. It has about 25 more snap rings and thrust washers than a single trans can possibly use. I thought it was the 3-4 synchro hub, but your MPC says no. David Kee Toploaders also says no. So I can't be right. Sorry.

 

[Master Chief]

Quite surprised that Jon at JB Custom Fab has not chimed in on this thread yet. He may have a solution.

https://jb-custom-fabrication.myshopify.com/