Thread: Your latest project

Bought myself a Giant Talon ebike a month ago.
Need to get it sorted for a ride down Tassie later in the year covid permitting.
First off bent up a stainless adapter to attach my old rack to hang the pannier bags off.
Used 1.6 from memory, way overkill but I’ve been using it for shopping with probably up to 10kg each side. I’ve a lower mudguard rough shaped to fill the gap below, will put up a few pics when it’s done.AB87D2D4-7CD1-4B6B-8669-C4E1CDE1274E.jpg6665ED8B-7903-49A4-8254-EBFD17A62D06.jpg

My left shoulder has been playing up so I decided I’d better fit some more comfortable handlebars so I could sit more upright and get the weight off my shoulders.
I had a look online but there was nothing available with a 32mm clamp and 22mm bar.
I took the old one I’d fitted to my ride to work bike which used a 25mm clamp and made an spacer/adapter from some Al.

Someone in Victoria made up a bunch of sleeves that are meant to be an interference fit for a 2.813" roller bearing.
I.D. is about 2.811" at the mouth, and 2.809" at the bottom. They are 3" diameter, and bolt into the engine block.


Problem is that engine guy wants the sleeve to also be an interference fit in the block, and is worried that the two lots of crush will damage (crack) the block.


So, I tried to machine less than a thou from the inside of a thin sleeve of 4140:

1. Spent nearly an hour gently grabbing and clocking the sleeve in the 3jaw chuck. Achieved .00075" axial TRO by wiggling and tapping the jaws, but that was with nearly 1thou wobble on the front face. When I tried to correct that, TRO went up to over 2thou
2. In the end, used a thin piece of paper under one jaw to get about 1thou TRO
3. Put my newest/best cutter in the boring bar, a CBN tipped CCGT060202
4. Tried a very mild cut at 300RPM – cutting air at the mouth – about .0004" deep at the bottom:

IMG_1805.jpg

If you look closely, you will see it has only cut the high points created by the chuck jaws crushing the sleeve.
Note also the gentle chatter marks.



Tried a few deeper cuts, nearly 1thou at 100RPM. End result is a little rough, with 3 shiny spots from the original machining, up the back between the jaws, where I guess the diameter was slightly larger from the jaws making a slightly triangular shape.

Didn't think I had clamped it that tightly in the chuck



I might try cleaning this one up a little by clamping with the jaws on the shiny spots and re-cutting, but currently trying to work out a more secure way to mount it for machining. Either a larger sleeve on the outside with bolt holes, or bolted into parallels on a mill for boring.

(I don't think cylindrical grinding is possible, but that's only because I haven't seen a round magnetic chuck )

Put it on a mandrel and take the thou off the outside.

Steve

Textbook demonstration of why 6 jaw and collet chucks exist!

If you want to do ID turning, drill 4 holes in a disc you can hold in the chuck, face the disc off and bore the centre to larger than target diameter for a couple of mm (runout room for the boring bar, could even just be a groove). Bolt sleeve to that - either use the 4 bolt holes directly, or make the pcd larger and use clamps. This way works for either OD or ID turning if you have the sleeve facing out towards the tailstock....

Could also use a piece of square plate in a 4 jaw - I tend to have a heap of 10mm steel or aluminium plate kicking around, so I'd probably punch a hole right through the centre on the mill, and do an exact 4 hole pattern, then chuck in the lathe, indicate in, face, and bore the centre hole to a slip fit for the OD of the sleeve. Seems more likely that the 'back' face (the one you can't see) in your photo is true to the bore (or should be for the intended purpose, at least). Whether it is or not depends on how the part was originally run.

If you have a lot to do, might be worth figuring out how to bolt or clamp some 'pie segment' type softjaws onto your chuck, that can then be bored to exact size in situ and give a full 360 degree contact surface (minus a degree or two!)... Setup should then in theory be a matter of slap the sleeve in, and do the chuck up on the same pinion with a torque wrench every time, and indicating as a check rather than having to dial it in - depends on how good the chuck is I guess.

The other catch is less than a thou off? Modifying an existing part like that, I reckon its 50-50 I'd overshoot that cut just trying to touch off.... I suppose if you've got a repeatable fixture, once you've nailed the first one, you can go to the same handwheel setting (or preferably DRO number!) for each one afterwards... In my book, absolutely NOT a CBN job, and not really a job for carbide unless maybe you're talking CCGT, or a CCMT that has been honed on a diamond wheel (or other variants of positive insert following those rules).

This seems to me more like a HSS type job if you really want to turn it - I'd try experiments with a vertical shear tool (supposedly very good for exactly this) if you go for OD on a mandrel like OxxAndBert suggested, or some sort of bizarre high rake grind (I'm excellent at creating bizarre grinds for one-offs, sometimes they even work) for ID turning. If the sleeves are actually hardened, then I guess back to a CCGT/reground CCMT (the cutting load from a CBN insert on a thin sleeve is unlikely to bode well for getting good results IMO). Realistically though, it strikes me as ideally a toolpost grinder or painful emery paper type job?

Interested to see what happens/what others think, as I'm almost certainly wrong and overcomplicating it...

CBN is the wrong insert to be using. CBN inserts are prepped with a strong but dull edge and are really only suitable for materials over 45Hrc, using them in softer materials and at slow speeds will damage the inserts. for small cuts you want a cermet insert, that is finish honed rather than just sintered like most inserts.

Originally Posted by Jekyll and Hyde

Textbook demonstration of why 6 jaw and collet chucks exist!

Realistically though, it strikes me as ideally a toolpost grinder job?

Interested to see what happens/what others think, as I'm almost certainly wrong and overcomplicating it...

This is probably the right tool and the right way for this job !

Originally Posted by snapatap

CBN is the wrong insert to be using

Probably. I tried it because, even though it has no rake,
it is the sharpest insert I had handy
(because of the ground sides).


Much sharper than my cheap CCMTs
(which have some rake in the chip breakers,
but have a dull corner radius from a sad old sintering press)



(plus, I bought this insert for machining a hardened press die, and it arrived yesterday, so was on hand)

I've only been using inserts for many years and they seem to love high rpm for a better finish.
Your rpm seems very low for carbide, more in the ball park of HSS rpm's in my experience.

Sent from my 5007U using Tapatalk

Originally Posted by Dave J

I've only been using inserts for many years and they seem to love high rpm for a better finish.
Your rpm seems very low for carbide, more in the ball park of HSS rpm's in my experience.

Would normally run that diameter at 300-500, but was trying to stop the juddering/chattering marks.

I have ground a lot of bearing housings similar to these using a simple fixture bored to allow the housing O/D to fit neatly into it and retained by screws through the holes in the flange. The fixture is pulled back against a faceplate using a drawbar through the spindle of the cylindrical grinder or lathe if using a toolpost grinder.
This method relies on the O/D's of all of the housings to be accurately finished to size first. This is probably the only way to get this job done successfully but it will not be easy, especially the one that has already been attempted.

Hardly a project, but
Before:
20210814_182713.jpg
After
20210815_150839.jpg

Finally the s/s panel from some old fridge came in handy...

These are printed with PLA, so I don't know how they will handle the Rapid Tap cutting fluid I use.

Rotated pic (again). My iPhone was being held in the normal orienation when the pic was taken, so I can't understand why this happened. I see Russ had the same problem above. Surely this can be sorted out mods?

Originally Posted by jack620

These are printed with PLA, so I don't know how they will handle the Rapid Tap cutting fluid I use.

Rotated pic (again). My iPhone was being held in the normal orienation when the pic was taken, so I can't understand why this happened. I see Russ had the same problem above. Surely this can be sorted out mods?

That's cool, I only wished my crosslide had them to add protect, or a thickness in it to accommodate machining them in.

I looked into adding then for a rear toolpost years ago, and I would have to drill and tap steel T sections to add them, but then reduce swing over crosslide diameter.

Sent from my 5007U using Tapatalk

If I had a milling machine I probably wouldn't miss the slots Dave. I only use them for securing a Myford milling attachment or angle plate (and prior to today, for accumulating swarf).

Originally Posted by jack620

These are printed with PLA

I have seen moulded (extruded) ones that clip in from above(on a mill).
This is the first time I have seen solid ones that slide in.


P.S. I assume this is just to keep the slots clean?