Here's my thoughts. Why did you make the stop from Cast Iron? I realize the original was made from cast. I'm sure they did this for economical reasons. They were going to make thousands of them, this was both a material saving and a machining savings. I'm sure they just did some clean up passes on the "business" surfaces and drilled the hole. The "V" groove also should have a radius in the "V". If you look at the lathe the mating part probably isn't a sharp corner. Even if it is if you drilled a hole on center to the "V" you won't have that inside sharp corner condition, which is where they probably always break. Making it thicker like you did probably dosen't help that much. It's like scoring a piece of glass it always wants to break at the sharp corner. My suggestion would be machine these from any steel and relieve or radius the sharp corner and it'll propbably be the last one you'll ever need to make.
Mark Rerynaert Mark Mold and Eng> My first summer project was making new carriage stops for our lathes. >
Why cast iron? Well the original was cast and I got it into my head to follow that example. My real preference would have been to make a pattern and cast the things myself but that would have needed a furnace and all the associated "stuff" so I settled for the Dura Bar. Which by the way is just lovely stuff to machine. Not a hard spot or void in it at all.
As to the radius a the apex of the V I thought about that and but at that point I was well into it and didn't want to change course so to speak. I don't think that these are going to break at they point and if they do I have enough material left over to make more and the person who breaks it will do the machining to replace it!
At the NEMES meeting last Thursday several fellows wanted to know why I didn't make a form cutter to do the radius cuts. Well, I already knew how to do that and wanted to learn, or improve my skills, on the CNC mill and CNC programming.
Sometimes I get it in my head to do things one certain way just because that is the way I want to do it. A personality quirk I guess.
Errol Groff
Instructor, Manufacturing Technology H.H. Ellis Technical High School
Looking through that, it is an excellent job, leaving me with just one puzzle. The white numbers on the pieces in the photo showing the ten with the V-grooves just finished. What is the significance of the numbers? Matching specific lathes which have the same numbers? The visible numbers seem to leave gaps in the sequence, and really seem to serve no visible purpose. Let's see:
48 57 58 73 75 92 (or is that one 26?)
Also -- what did you use to mark them?
Please do so.
Indeed so.
Are the ones who are going to make the necessary pieces by any chance the ones who broke the most stops? :-)
We do have 90 degree cutters and I could have used the horizontal mill for that operation but when I got to that point I didn't have interest in indicating in the table of the HM or mounting a vise and indicating it in etc.
Of course I woulnd up doing all that a few days later to mill the slot for the thumbwheel.
Well, I am not sure about those numbers. Probably when I got the parts mostly squared up I measured each of then and marked them for how much over they were from finished size.
It is a paint marker that comes in a toothpaste sort of tube with a spring loaded ball in the tip. Press on the ball and the paint flows. The paint dries in not too many minutes I can look at the thing on Thursday to see the brand name. I won't be going into the shop tomorrow.
Posted
Most of these broken stops have accumulated over the years so I don't really know who did the deed. Except for the one I broke last year that is. Just because one has been doing this for 40 years doesn't mean that big time screw ups don't happen. Actually, I was showing a student a threading operation and didn't realize that the stop was locked down. Err in haste, repent in leisure!
O.K. Sot then that last one is more likely to have been 26? (It all depends on which side you considered the top when you were marking. :-)
O.K. No rush -- it sort of looked like soap, and I was wondering.
Thanks. Now to go see what remained of them. I can't do e-mail reliably today, because some spammer did a major spam run forging my domain, and my mail servers are overloaded with the bounces. I've had to add a script to watch the system load and if it gets above a certain point to shut down incoming e-mail until the system recovers. (I've got two systems doing this now. waiting for all the bounces to end.)
Cast iron works well as a bearing surface against hardened bed ways. Steel has a tendancy to bind and score when slid over hardened materials (over long periods). Cast iron is ideal in this case.
I would use a disc grinder to create a rad in the v (about 10 seconds of grinding each, plus 20 seconds to clamp/unclamp in a bench vice). That's the rub with cast iron. Our die shoes are made of cast iron and everything has a rad purposely. In the die and mold industries, radii are very important for strength.
Sometimes I get that way. And then I get yelled at if it happens to be the "wrong" way.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.