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Trust (that it is), but verify (before cutting any metal).

Not any more!

John

I haven't finished the pocket for the valve seat because the ½" boring bar I've been using isn't quite stiff enough to avoid making it slightly oval. Unfortunately, although I have a set of 1" boring bars for a different boring head, they have brazed carbide tips with whose geometry the bronze isn't happy. So, the final machining awaits delivery of a 1" boring bar that takes carbide inserts appropriate for bronze and cast iron. The difference in diameter might not sound like much, but for the same length bar the deflection will be 16× less.

On the drive-side bearing front, the steel needed to make a sleeve arrived a few days ago in case I want to go that direction, but first I'm going to try welding the walls to take the 62 mm bearing as-is. First, though, I'll measure the location of the bearing with respect to the outer flange as carefully as possible given the wear, to try to decide if it was originally Concentric with the flange. If so, and if there isn't too much problem welding the old casting, the next step will be to mount the case on the 12" faceplate shown in a recent post. As I think I've written before, my lathe is 11" but I have an unusual accessory for it that increases the swing 16", which is very useful at times like this.

However, all work is on hold until the weekend because of other commitments.

Yes you have written it before......Why don’t you just copy and paste that into your signature line?

You are helping to reinforce my aforementioned irrational fear of boring heads. Thinking I should seek out some carbide cutters for this. Rigidity was likely a major factor in their evolution. As difficult as it is, I’ll refrain from using some juvenile analogy.

E658012E-3660-4BC0-9B2F-84F02CA2994B by First Last, on Flickr

The boring head wasn't at fault, it was the relatively flaccid ½" boring bar. If you put yourself in a rotating reference frame, the same boring bar would have had the same problem on a lathe because from its perspective the two situations are identical.

That flaccid thing can really dampen your spirits.... my condolences. Not that I derive any pleasure in depleting your war chest funds.......

I would have sent the link by PM, but unlikely anyone else on here is nutty enough to buy it. Make an offer.... and you can one up me by 10 pounds with free shipping to boot.


https://www.ebay.com/itm/45-lbs-Cerrobend-Low-Melting-Temp-Alloy-Woods-Metal-158-Degrees/153780833382?hash=item23ce0d4c66:g:7EEAAOSwy1VeCoDu

Would the lowly flycutter be stiff enough?



I bored this hole in my Triumph head for and exhaust spigot adapter to 1.675". I could have used the next size which is 1.403 shoved up into the tool holder which would seem to be quite stiff because of its short shaft and heavy head.

Tom

I would think a fly cutter would do... just a matter of finding one small enough and robust enough at the same time. MM’s situation seems to be a little unique in that he is cutting 2 different materials. I’d say the ones used by the pros are basically fly cutters. I haven’t used the one in the photo that I posted, but it runs on a pilot which would help to reduce chatter.

In principle a flycutter would do, but in practice there are two limitations to overcome. One is adjusting the cutter to give the precise diameter to within no worse than 0.001", and the other is the need for the right cutter geometry to deal with both the bronze and the cast iron. It might just have been my own inability to grind a HSS cutter that would do the job, but it wasn't for lack of trying. A boring head with a stiff boring bar and a carbide insert designed for Al lets the diameter bore easily be dialed in to the desired bore.

It looks like I'll make it into the garage today after all. I had written off the entire day assuming I would be stuck in long lines to get vaccinated along with my wife, whose appointment was two hours after mine. But, 45 minutes after we arrived we were in the lot waiting the necessary 15 minutes to be sure neither of us had a bad reaction to the vaccine. I have my second appointment scheduled and am on track to have developed the maximum immunity before the end of February.

Although I understand I should expect a sore arm and headache later, my present feeling is best expressed by the following socially-distanced video:

I know the feeling, MMan---my wife and I got our first shots earlier this week.
Second shot appointments for mid February so maximum immunity by end of February.
I think every motorcycle event this spring and summer is going to swamped by people rebounding from the restrictions and events having had to be cancelled over the last year.
Bring it on!

BTW-- I had a sore arm for 24 hours--no headache and no other side effects (Moderna vaccine).

I'm signed up for the Irish Rally at the end of August so fingers crossed the Irish get their situation under control so that the event doesn't have to be cancelled. Also, that scientific studies find that vaccinated people can't asymptomatically transmit the virus, so that travel restrictions can be lifted. Unfortunately, the present lack of such findings makes it unlikely I'll be allowed into Australia before the Brisbane exhibition ends on 26 April.

Not sure if these qualify as fly cutters, but the only thing standing in your way is $1849.99

https://goodson.com/products/adjustable-counterbore-cutter-kit

Hmm, other than the price...

While waiting for the 1" indexable boring bar to arrive (due later today) I turned to the drive-side case. The raised flange in the center of the case is out of focus in the first photograph, but is shown in the second.





As the indicator indicates, the outer edge of the center flange is round to within no worse than 0.001". Not shown is the same is the case for the inner edge. As the third photograph shows, with the case in the same location as for the above photographs, the battered wall for the bearing cavity is Concentric with the raised flange to between ~0.000" and ~0.002" depending on the height of the probe in the cavity.



From these measurements, plus expected machine shop practice when the case was machined, it seems highly likely the bearing cavity was machined at the same time as the flange. This means re-machining the bearing cavity using the flange as the reference surface is likely to be more accurate than using the ID of the timing-side bush as the reference surface.

Do you have that case held in such a way that you can pop the timing side on and verify that bushing is Concentric with the flange/ bore on the D/S?

I can't thank you for asking that because "verify" is such a troublesome word in the present context. Had you asked if I could "easily pop the timing side on" the answer would have been a firm 'no'. However, after I go to all the trouble of machining the case and installing the bearing it then will be relatively easy to verify that it is Concentric. Assuming it is Concentric...

Au contraire!.....MM, you better step away from the mill for a moment. Brain fog is a Covid symptom. Could it be a Covid vaccine symptom too?

Once the case is nicely fixtured with custom made expansion dowels screwed into ally blocks and clamped to the mill table, and dialed in to a gnat's patootie.....

Then you could easily "pop" the TS case atop the whole mess, carefully bolt them together and check for agreement.

I think that's what Cyborg was getting at. No need to cut metal first.

But a question. How are you calibrating your Blake indicator for the variation in arm length and arm angle? Compare dial reading to DRO maybe? It seems important given the precision you wish to achieve.

Yes.... in the reasonably unlikely event that you might want to move the bushing bore or the bearing bore because of a line bore issue.

My inherent lack of diplomacy makes it difficult for me to make myself understood without offending anyone. That’s why I earned the nickname “Gas Pipe” at work.

Hi All,
With those Blake indicators I found that any tiny error in the mill collet is magnified significantly at the end of the feeler finger
I have not done the Math to prove or disprove how this happens????
I prefer to use a setup with a 3/4in. round bar in the collet, it's cross drilled 3/8in. a length of drill rod through the 3/4in. bar can be clamped at any position with a grub screw at 90 deg to the cross drilling
The fittings from a Mag base DTI fit the 3/8 rod and hold different DTI's depending on the face that's to be dialled in
My thinking is that if the DTI is as close to the surface being trued up the less chances of error
A little back button Starret DTI has become a favourite doing similar setups , but a finger indicator would be better to follow the crankcase lip ?

John

IDK, I understood you just fine.

And hey buddy, I thought I was the "undiplomatic" one around here.

Oops. Sorry...We're having a rainy day here and I am finally ready to paint the house. I think it's making me testy.

I'll see your Au contraire! and raise you two Sacre Bleus!

Sacre Bleu! A general principle of machining is if you want to make something round, use a lathe. I won't be bolting it to the mill, which means I won't need to make those expansion dowels. It also means the way I'll bolt it to the lathe will have bolt heads projecting above the flange so it won't be possible to attach the timing-side case.

OK, guys, I only used that Blake to confirm to my satisfaction that the bearing was originally machined Concentric with the flange. Having accomplished that, it's the last the case will see of the mill's bed, since I'll install it on the lathe to do the machining. Once on the lathe I'll dial in the outer flange using the most sensitive test indicator that the surface quality of the Al allows.

Once I have the bearing recess refreshed and ready for the bearing -- see below -- I'll install a faux bearing along with a faux crankshaft to check the timing-side bush. If the bush isn't properly coaxial, I'll make a new underside bush and use the appropriate Sunnen mandrel to line hone it into perfect alignment.

Mon dieu, with that out of the way, it's time to turn to the task at hand. The problem is the walls of the bearing cavity have been hammered oversize so wouldn't work even with an original 2.5"/63.5mm ball bearing, let alone the 62mm roller bearing I intend to use.



Some ways to deal with this problem, each with advantages and disadvantages, are:
-- machine a steel sleeve with the necessary 1.5mm/2 = 0.75mm/0.029" wall thickness (ignoring interference fits for the moment)
-- machine a 6061-T6 Al sleeve with the above specifications
-- build the walls of the case up with weld and machine to size

Although I bought a length of 4140 Cr-Mo hollow tubing for this purpose, I changed my mind and am going with an Al sleeve. Unless I change my mind again, that is. Briefly, a quick search confirmed the TIG filler would be softer than the 6061-T6, and a sleeve also has the advantage of being easily removable and replaceable if the machinist screws up. And welding assumes there wouldn't be any issues with whatever is in the alloy that was cast 92 years ago. As for steel, the wall of the sleeve will be so thin I can see no advantage to it over Al. If the bearing ends up moving again you can all tell me "I told you so," even though there's no way to know that a steel sleeve wouldn't have moved as well.

Britbike doesn't have nearly enough machining photographs, so I'll show all the steps. The next photograph shows I started with a length of 3" OD Al.



I bored it with a series of ever-larger bits up to the maximum 1½" drill bit I have.



I then used a boring bar to increase the ID to ~2mm less than it will need to be for an interference fit for the 62mm bearing.



I left the ID deliberately small to give added stiffness to the sleeve for when I press it into place. Also, any resulting distortion, tilt, etc. will be removed after it's pressed in the case and back in the lathe, where I'll do the final machining for the interference fit of the bearing in it.

I then reduced the OD to 0.003" greater than the largest ID of the present battered bore.



This means it will have 0.003" interference fit over much of the length, but ~0.005" for a band in the center. Yes, I could machine the walls of the bearing cavity smooth, but that would remove Al that I would much rather leave in place on the case. Anyway, after final machining the wall thickness of this sleeve will be just 45% of that in the photograph above.

This is where things sit at the end of the day.

Are you going to rely on interference fits?---bearing into ally sleeve and ally sleeve into ally case?

Good question. I'll use some form of Locktite on the Al-Al interface, and then put a few spot welds around the circumference at the top mmediately after installing the sleeve, before machining to the final dimension to receive the bearing. If the alloy of the case is happy with the welding I might continue around the entire circumference.

You're absolutely right about using the lathe. (And I think you secretly wanted to see "patootie" in at least one more post.) However, I'm sorry to see you edging away from such an elegant fixturing system.

But wait, it would work on a faceplate too! Adjustments would be a breeze and it would relieve you of the hassle of 4 fiddly bolts, spacers, nuts and all the shims and washers.

You could then do Cyborg's suggestion with the TS case and dispel all that uncertainty before cutting metal. Just think of it! I am and I like it, for when I repair my DB cases.

But......On another tack yet again, what does all this recent info tell anyone about mismatched cases? I was told long ago that it was a serious no no because nothing would line up quite right. But it would seem that the deck height is the most likely, and probably small discrepancy, not the main bearing housing alignment.......Even on twins.

Hmmm..... Any thoughts?