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CMT Ursus 250 Repair: 3) Carriage Hand Wheel
- Thread starter RobinHood
- Start date
To broach the 6mm key way, I needed to make a single lip broaching tool. I found a suitable 1/4” piece of HSS and a 1/2” boring bar that I could then hold in a collet in the mill.
Since there was not enough room on the Clarkson T&CG for both a vise and the spindexer, I mounted everything on the mag chuck of the Ingar surface grinder.
The profile I was after looks something like this.
Set-up on the mill.
Turns out that this cutting edge geometry was too aggressive and required a lot of force to push through the 4330 steel bore. The tool kept digging in - when it did cut. Lots of tool deflection as well. I also lost the cutting edge about 1.5mm into the 3mm depth.
So back to the surface grinder to change the geometry. I basically went for a scraper style edge this time around, as seen here.
That worked much, much better. The cutting forces were greatly reduced with 1thou DoC. Also, the cut was totally controllable and no digging in of the tool. The cutting edge stayed very sharp to the end.
You can see the huge difference in the chips produced. Left is the negative rake edge chips, on the right are the scraper style edge chips.
Had to step-over 0.23mm on each side to get the key way width to just a shade over 6mm as the tool was intentionally ground to < 6mm wide.
All done & installed.
The final weight of the hand wheel is 8 lbs 4.5 oz. That is over 40 lbs of 4330 chips to whittle this thing out from a solid disc. Casting is definitely the way to go if you are making more than one…
Since there was not enough room on the Clarkson T&CG for both a vise and the spindexer, I mounted everything on the mag chuck of the Ingar surface grinder.
The profile I was after looks something like this.
Set-up on the mill.
Turns out that this cutting edge geometry was too aggressive and required a lot of force to push through the 4330 steel bore. The tool kept digging in - when it did cut. Lots of tool deflection as well. I also lost the cutting edge about 1.5mm into the 3mm depth.
So back to the surface grinder to change the geometry. I basically went for a scraper style edge this time around, as seen here.
That worked much, much better. The cutting forces were greatly reduced with 1thou DoC. Also, the cut was totally controllable and no digging in of the tool. The cutting edge stayed very sharp to the end.
You can see the huge difference in the chips produced. Left is the negative rake edge chips, on the right are the scraper style edge chips.
Had to step-over 0.23mm on each side to get the key way width to just a shade over 6mm as the tool was intentionally ground to < 6mm wide.
All done & installed.
The final weight of the hand wheel is 8 lbs 4.5 oz. That is over 40 lbs of 4330 chips to whittle this thing out from a solid disc. Casting is definitely the way to go if you are making more than one…
Very nice work. End result looks right at home on the machine. Keyways look so harmless from across the room, but there appears to be a lot of factors to get right for clean accurate results. So you opened up the slot to full width by alternating left & right a bit to the 'line' with each progressive depth stroke?
The cutter ended up 5.57 mm wide after I cut in all the relief angles (it started out as 1/4” = 6.35mm). The key way needed to be 3mm deep (1/2 of the 6mm width). I cut the key way 5.57mm wide to 3mm deep on the center line. That removed most of the material. Then I moved off center 0.23mm and cut the one side all the way down to the 3mm depth. Step over 0.23mm to the other side of center and clean up that side. Total width 6.03mm. Close sliding fit for a 6mm key.
Yes, all this was done on the mill using the manual quill down feed handle as a way to move the boring bar (with the broaching bit) up and down in the bore. The wheel was conveniently held in the vise using a V-block against the fixed jaw. The x / y axis of the table were then used to position the bore correctly under the quill. DoC (in-feed) was controlled with the y-axis. The broaching operation worked very well once the cutter geometry was correct for the material I was cutting.
Yes, all this was done on the mill using the manual quill down feed handle as a way to move the boring bar (with the broaching bit) up and down in the bore. The wheel was conveniently held in the vise using a V-block against the fixed jaw. The x / y axis of the table were then used to position the bore correctly under the quill. DoC (in-feed) was controlled with the y-axis. The broaching operation worked very well once the cutter geometry was correct for the material I was cutting.
historicalarms
Ultra Member
One-off Broach cutters can be made quite easily using HSS cutters of the desired size. Cut a piece of bar the same size as your bore that you desire to key. now mill a groove lengthways in the insert that corresponds with key cutter, now you have a guide same as any manufactured broach set.
Grind one side of the HSS cutter to a slight angle and notch some teeth into it with a dremmel ( how many you want is up to you, I used 3). Now you can cut a small amount out of your bore with every pass by shimming the back of the cutter.
I have used both hyd press & arbor press....arbor requires more effort but hyd takes longer to retract & reset for each pass.
The use of a backing insert makes cutter angle a lot mot forgiving....no "deflection problems". Although hogging out a keyway is a lot less demanding, precision Barrel rifling cutters have experimented with cutting angles for decades and every one I know claims the thing that has to be right first is the cutter holder has to fit the bore exact to counter any tool deflection. If the boreriding tool holder is perfect, the cutting angle is a lot more forgiving ( one of the most respected cut rifling barrel makers in NA, I have watched him grind a cutter by hand & eyesight).
Grind one side of the HSS cutter to a slight angle and notch some teeth into it with a dremmel ( how many you want is up to you, I used 3). Now you can cut a small amount out of your bore with every pass by shimming the back of the cutter.
I have used both hyd press & arbor press....arbor requires more effort but hyd takes longer to retract & reset for each pass.
The use of a backing insert makes cutter angle a lot mot forgiving....no "deflection problems". Although hogging out a keyway is a lot less demanding, precision Barrel rifling cutters have experimented with cutting angles for decades and every one I know claims the thing that has to be right first is the cutter holder has to fit the bore exact to counter any tool deflection. If the boreriding tool holder is perfect, the cutting angle is a lot more forgiving ( one of the most respected cut rifling barrel makers in NA, I have watched him grind a cutter by hand & eyesight).
@historicalarms , I do agree with your points on home made broaches and the fact that a “backed” tool will deflect less (or not at all) when used in a broaching operation.
I don’t have an arbour press. I do have a little bench top hyd press. I have successfully used the hyd press with my DuMont SAE broaches. I have even used the broaches in the lathe applying pressure using the tail stock. It all works.
I have broached using a shaper - which I no longer own.
And I have used the mill spindle with a single lip cutter - like in this case.
It basically came down to what would give the highest probability for success without going out to buy a commercial 6mm broach (I would have to make a custom bushI. and backer pins regardless, as the bore is overly long and a non-standard diameter). Keeping all this in mind, I decided on the single lip broaching tool held in a 1/2” boring bar using the mill spindle as a ram. Except for the faulty cutting edge geometry initially, I was pretty confident that it would work well. And it did, after the cutter was corrected.
I had a lot of time invested in this part and really did not want to screw it up during the last operation. So I fell back on a procedure I am very familiar with and know that works. Plus, I had all the components of the tool on hand (other than it needed the cutting edge ground) to complete the job.
I always like to hear about other methods of doing operations - makes me think and evaluate what I could do differently next time. So thank you.
I don’t have an arbour press. I do have a little bench top hyd press. I have successfully used the hyd press with my DuMont SAE broaches. I have even used the broaches in the lathe applying pressure using the tail stock. It all works.
I have broached using a shaper - which I no longer own.
And I have used the mill spindle with a single lip cutter - like in this case.
It basically came down to what would give the highest probability for success without going out to buy a commercial 6mm broach (I would have to make a custom bushI. and backer pins regardless, as the bore is overly long and a non-standard diameter). Keeping all this in mind, I decided on the single lip broaching tool held in a 1/2” boring bar using the mill spindle as a ram. Except for the faulty cutting edge geometry initially, I was pretty confident that it would work well. And it did, after the cutter was corrected.
I had a lot of time invested in this part and really did not want to screw it up during the last operation. So I fell back on a procedure I am very familiar with and know that works. Plus, I had all the components of the tool on hand (other than it needed the cutting edge ground) to complete the job.
I always like to hear about other methods of doing operations - makes me think and evaluate what I could do differently next time. So thank you.
Nice job and write up Rudy. I wonder what a metal 3D print for this part would cost? Not as fun or interesting but still. The US navy was looking for a way to rapidly characterize the measurements of hand wheels on ships - valves and such - to enable quick replacement. It’s a similar problem - they also need one custom hand wheel at a time. I’ll see if I can find that link.
US Navy Challenge: Rapid Design Tool for Advanced Manufacturing
US Navy Challenge: Rapid Design Tool for Advanced Manufacturing
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Rudy I was re-reading your discussion of trying to weld/braze the old wheel. It got me thinking about TIG welding CI - I did a little research and it seems people claim it's possible with a nickel filler rod. Welding CI Not that I've tried this myself. Do you do any TIG welding?
My guess is outsourced 3DP metal would be insanely expensive because it's mostly a function of mass (more material cost, more print time, more structure stuff, more baking, more post-finishing...).
A while back I was interested to just get a ballpark $/cc type cost metric. Even that was not straightforward. If anyone has seen a chart like that I'd be interested. I can see vendors not wanting to commit online without firs seeing a CAD file because of so many potential variables. But still...
Have you ever submitted something for a (metal) quote, Janger? I've always been tempted to upload one of my model engine parts just for the heck of it. I'll do it on a dare LOL
support.shapeways.com
A while back I was interested to just get a ballpark $/cc type cost metric. Even that was not straightforward. If anyone has seen a chart like that I'd be interested. I can see vendors not wanting to commit online without firs seeing a CAD file because of so many potential variables. But still...
Have you ever submitted something for a (metal) quote, Janger? I've always been tempted to upload one of my model engine parts just for the heck of it. I'll do it on a dare LOL
How are prices calculated?
By uploading your 3D model through the model upload page, you'll get an instant quote for your 3D printed product in various materials. Our system will quickly analyze your model and show you the p...
John, thanks for the links. Interesting that the Navy has similar problems with one-off wheels for valves.
Yes, I did try to TIG weld it. As a matter of fact I tacked the individual pieces together with just the heat of the tungsten. That held well enough for the wheel to be in one piece and that is when I took most of my measurement. When I then tried to finish weld the cracks, i discovered that the CI was not really wetting - when I did get a puddle, the material just flowed away, ie it was too hot and the CI had reached its melting point. The “no puddle” problem steered me towards using Aluminum-Bronze as a filler (mainly because of the lower melting point). Unfortunately it did not stick, as, again, I could see any wetting action.
I then tried welding using O/A - same problem: by the time I got a puddle, the CI was just flowing away. Also no wetting action.
I have not tried hi nickel rods. It was suggested by other members here. Now that I have a new, functioning wheel, I will most likely try it. What do I have to lose?
I am pretty sure that the material is White Cast Iron — most folks consider it non-weldable, as I have learned. The article in your link draws the same conclusion.
Metal 3D printing would most likely work. I don’t have CAD software to design the part so that I could even send out a file to a printer to get a quote. I think prices have come down, but I suspect it would still be quite pricey.
Yes, I did try to TIG weld it. As a matter of fact I tacked the individual pieces together with just the heat of the tungsten. That held well enough for the wheel to be in one piece and that is when I took most of my measurement. When I then tried to finish weld the cracks, i discovered that the CI was not really wetting - when I did get a puddle, the material just flowed away, ie it was too hot and the CI had reached its melting point. The “no puddle” problem steered me towards using Aluminum-Bronze as a filler (mainly because of the lower melting point). Unfortunately it did not stick, as, again, I could see any wetting action.
I then tried welding using O/A - same problem: by the time I got a puddle, the CI was just flowing away. Also no wetting action.
I have not tried hi nickel rods. It was suggested by other members here. Now that I have a new, functioning wheel, I will most likely try it. What do I have to lose?
I am pretty sure that the material is White Cast Iron — most folks consider it non-weldable, as I have learned. The article in your link draws the same conclusion.
Metal 3D printing would most likely work. I don’t have CAD software to design the part so that I could even send out a file to a printer to get a quote. I think prices have come down, but I suspect it would still be quite pricey.
Dabbler
ersatz engineer
I don't know a way to braze white cast iron, but reading this article helped me to understand the differences:
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