CMT Ursus 250 Repair: 3) Carriage Hand Wheel

[RobinHood]

The hand wheel on the carriage was broken. I tried really hard to repair it, but without success. The material is White Cast Iron. It is considered non-weldable, non-brazeable because of its chemical composition (high chromium content). CMT uses this material extensively on hand wheels and dials as you can highly polish the surface or media blast it to give a nice soft satin finish. It also grinds very well - dial bearing surfaces are all cylindrically ground the lathe.

The wheel is in one piece now, but the aluminum bronze weld did not bond with the WCI as the surface does not wet. The reason it is staying together is because of the weld prep. There is no structural strength whatsoever.

Front view of wheel

And the back side

I don’t have any ductile iron stock big enough (8+” diameter), but I did find some 4330 of suitable size. Here the Carolina saw is slicing a 3+” wide disc off the log. I had it set for the slowest speed and light down feed. Took 90 min to get through. Neither the blade nor the log got appreciably warm - exactly what I wanted. This stuff can work harden pretty easily.

The 8.5” x 3.25” disc weighed just over 52 lbs. I’ll weigh the wheel once it is done.

Here we are roughing out the front.

And done. The OE is beside the billet for comparison. I am leaving the contouring of the hand portion to the end. I like to have flat faces for easier mounting to the rotary table to cut the two spokes. The sharpie marks roughly show what needs to be removed off the rim and what stays on the front.

And here is the back roughed out on the lathe. The OE center hub was cylindrically ground inside to fit on the shaft as well as the outside to accept the travel dial. I will probably use the tool post grinder to finish off these surfaces - not 100% certain yet, as 4330 turns really nice with carbide tooling. I may just go with turned surfaces.

More to come…

 

[RobinHood]

I did not grind the ID and OD with the TPG. Fine tuned speeds and feeds a bit more to get even better surface finishes and just turned the OD journal and the ID bore. Here it Is on the apron for a first fit-up.

Next I mounted the wheel to the 12” BP rotary table to start working on the two spokes. Started with the 4 “corners”. The radius of the OE’s spokes - to - circumference is just over 24mm. The location of the Center of the circle was determined by using geometry. I set the Y-offset on the mill table and the angle on the RT. As mentioned elsewhere, this RT can accurately divide the circle into degrees, minutes and seconds. Since the bulk of the inside of the hand wheel was removed on the lathe, I had to use an center cutting end mill to locate the corner circle because of the step (You can see it in the picture). Plunged a 1/2” carbide EM through first, followed by a 3/4” one. Then switched to the boring head to open the hole to dimension.

After milling the excess off the inside circumference and “stitch drilling” the roughed out wheel spokes look like this. I had previously machined the counter balance weight (6 o’clock position on the wheel) and drilled & tapped the handle mounting hole (12 o’clock position)

There is still a little extra material to come off the inside to blend into the corner rounds. In the picture above you can see that they don’t quite match yet.

The OE wheel has a circular cross section of the perimeter surface - both inside and out. The outside I can turn on the lathe with a form tool.

The inside is another story. It can’t be turned on the lathe because of the counterweight and the handle boss. I think I am going to move the RT onto the Deckel KF2 3D pantograph and see if I can do some contour milling using a ball nose end mill.

Stay tuned for that…

 

[YYCHM]

Could you not use a corner rounding endmill and the RT to do the interior rounding?

Corner Rounding End Mills - Results Page 1 :: KBC Tools & Machinery

 

[RobinHood]

Yes, that is an option.

I have to check, but I don’t think I have one big enough. IIRC, the largest one in my stash is 1/2”. The nominal diameter is 26mm. Plus, I only have imperial corner rounding end mills.

 

[RobinHood]

I did not use the KF2 for the next steps.

I did find a suitable round-over end mill to machine the inside surface. I also used a ball nose end mill to blend in the transitions from the circumference to the spokes.

Center finding on the handle bore to set up the axis of rotation to mill the boss.

All the blending done

That left the spokes themselves. Using a template on the KF2 would have been the best (and precise) option. Would have to make one and the mill is not fully operational at this time (needs all sliding surfaces inspected and spindle bearings repacked).

So I just scribed two lines and carefully milled to the lines. Some filing and the spokes are done.

Next will be a 6mm key way through the bore and rounding over the outer circumference. I could leave the outer contour as is, but it would not match the OE hand wheel.

 

[PeterT]

That's one good looking handle! All those machining steps to complete many interrelated features. Kind of illustrates why casting is used so much on machine components - where 80% of effort goes into the master pattern & at leaves machining to a lower number of critical surfaces & features.

 

[RobinHood]

My thoughts exactly wrt casting vs machining from billet.

Plus all the wasted metal. So far I machined off almost 40 lbs of perfectly good 4330 tool steel!

 

[John Conroy]

That is a work of art. Nice work!

 

[6.5 Fan]

Indeed a work of art. Excellent write up and pics to explain what your doing.

 

[Dabbler]

As usual, perfect work! every time you use it you can be proud.

 

[Brent H]

@RobinHood : a wheel of fortune!!! That is a beauty!! Nice work!

 

[RobinHood]

Thanks for the compliments. Much appreciated.

The lathe is made to very high standards - so it deserves a decent replacement.

 

[historicalarms]

Outstanding job man, thoroughly enjoyed the thread....but all the time reading through it I could hear my old mans " practical farmer voice" in the back of my mind..."I woulda fixed that in the time it took to cut through that log" and he probably would have said.
First he probably would have went out to some old retired piece of machinery out back and found either a chain gear or pully with the same bore as the handle. drilled a hole for the crank handle and slid er' on.
If not finding a suitable repurpose piece, his next move would have undoubtedly been to torch cut a suitably sized piece of flat 1/4" or 3/8 plate into a circle, run the rough edges over the bench grinder a couple passes, now torch cut a center piece out to accommodate the original hub, drill a hole on outer edge for crank handle...now drill through existing hub and just cut plate and bolt securely to each other...and slide er' on.

its amazing to me, two different philosophies that end up with exactly the same outcome....a working piece.

 

[kevin.decelles]

I thought about how badly I would have butchered a piece of 4xxx steel, and how my cheap tooling would have broke or squealed it’s way through the job

I appreciate the skill, equipment and tooling!

Much to learn, far to go, and looking forward to the journey


Sent from my iPhone using Tapatalk

 

[RobinHood]

Outstanding job man, thoroughly enjoyed the thread....but all the time reading through it I could hear my old mans " practical farmer voice" in the back of my mind..."I woulda fixed that in the time it took to cut through that log" and he probably would have said.

Thanks.

I did think like your dad at first, but only for a short while. Was going to burn out a ring from plate, weld in spokes & a hub. It would have been totally functional and the repair would have taken a whole lot less time.

But, as I mentioned above, this lathe is built to a very high standard/quality and it just would not have been right. To give you an example: the treading dial has the bore, the shaft and the mating flange cylindrically ground & bronze bushed! Everything on this machine is built like that. I am absolutely amazed at the quality and effort that went into it. You could not pay for this kind of thing today.

Here are some pictures of the threading dial:

Yes, it needs a bit of TLC (one gear tooth mangled a bit - I will make a new one), but even just after a cleaning, the dial runs buttery smooth.

That is my main reason to spend so much time and effort on refurbishing this lathe. (Plus I like challenges…)

 

[RobinHood]

I thought about how badly I would have butchered a piece of 4xxx steel, and how my cheap tooling would have broke or squealed it’s way through the job

I think I was lucky that the 4330 machined as well as it did with the tooling I have. I have learned a lot machining all sorts of SS for other projects and those experiences were directly transferable.

I have spent hours on this hand wheel, not just with set-ups, but also tinkering with speeds and feeds, DoC, and trying different inserts to get the finishes you see.

 

[PeterT]

Yes, you can see the quality in those parts. Look forward to the gear making

 

[YotaBota]

Beautiful work RH.
Do you have a melting pot to put the chips back together for the next project?
All I need is another 50 years experience and 7 tons of chips and I might get to this level. lol

 

[RobinHood]

Unfortunately no foundry capability. It would be nice…

 

[RobinHood]

Little more progress over the last couple of days…

Used a 1/2” corner rounding end mill as a stationary tool on the lathe to contour the OD of the circumference of the hand wheel. Careful manipulation of X & Z feed allowed me to nibble away the material. As we approached the 1/2” radius, it became increasingly more difficult to prevent chatter as an ever longer portion of the arced cutting edge started engaging. 72 rpm and light infeed followed by tool retraction as the harmonics changed seemed about the sweet spot.

Here you can see the end mill and the workpiece’s matching radius.

Since the corner rounding end mill was not rotating (as it normally would in a milling operation), the surface finish was an exact replica of the radius grind of the end mill’s one cutting edge. It was quite good, but nowhere near where I wanted it to be. (This is a reasonably high quality Butterfield CREM).

You can see the dull finish and the tooling marks here.

Next was to polish the surface to eliminate the tooling marks - did that with progressive finer sand paper.

And old vs new.

Need to make a tool to cut the 6mm key way as I don’t have any metric broaches. That will then complete the hand wheel.