Having problem milling 120 degree sections

[want2drive]

Hello all

I am a new member and just starting out in the hobby.

I purchased a mill and a lathe to start both PM, mill 932V, lathe 1236 and I am trying to make, new, longer, handles for the mill. I turned down the stock to the correct size drilled the proper holes using the lathe and proceeded to mill the ends of the extensions to match the machine. This is where I am having difficulties. I laid out the handle extension, set it up in a rotary table and messed it up basically. I indicated the rotary table locked the table, set up the extension, indicated it off the center bore, not moving the table or rotary table. Set up for 120 degree cuts, 6-60 degree 120 degree on center. I tried to fit the pieace from the original handle into my new part and it did not fit. I then proceeded to remove material to get the existing handle to fit the new extension.

That's where I think I am loosing the dimensions. once I get the existing handle to fit the new extension the new extension don't fit where the existing handle is suppose to fit. My new piece is sloppy in the existing location. It works but don't look good.

I attached some pictures to illustrate.

Any advise on my procedure, set up, lay out, old age and inexperience is greatly appreciated.

Thank you all

 

[pontiac428]

Huh, the way you laid it out, it should have worked. Unless... unless that gap is equal to your EM diameter, which would be tool radius error on two edges.

 

[solo]

That’s what I’m thinking, you forgot to subtract your tool.

 

[RJSakowski]

You need to offset your cutting path by the end mill radius. Set your x axis zero at the RT cneter position and offset the x axis by the tool radius. Make your first cut at 0º This will cut one side. Then you can either rotate 120º and make the next cut or move the x position by the cutting tool radius in the other direction for the second cut. Rinse and repeat.

 

[want2drive]

Thank you pontiac428 and solo

I thought I did offset the cuts for the tool diameter, .125" end mill, the diameter may still be an issue, my first attempt was from two different diameter pieces that the factory used so this attempt was two of the exact diameter. Same results however. It seems that I need to open the notched portion of the new piece to get the original piece attached to the handle to fit. Unless the factory piece that is attached to the handle is somehow cut different than the piece on the mill. But it looks like they are symmetric.

Its a mind twister for me as I am not experience enough to determine my error. As obvious as it is when I put it together

Thank you again I will keep reviewing my steps to try to figure it out.

 

[benmychree]

Clutch teeth are cut radially, one such as is shown can be cut in only 3 through cuts and 3 indexings.

 

[want2drive]

Thank you RJSakowski

That seems to be the consensus here, Im not sure what other offset to do. I set up to remove material only on the portion of the area that needs removed, cutting along the line not through it. so the edge of the tool in on the line cutting the area that is to be remove. Follow that along all cut areas. Then when I fit the part of the handle it dont fit. So I remove just enough so it does and bam, all dimensions fall apart and the piece is sloppy. However, the two factory pieces fit nicely.

Interesting stuff this hobby is, I keep looking.

Thank you

 

[want2drive]

Thank you benmychree

If I am understanding correctly, the 6-60 degree scribe are 180 degree apart producing 3-120 degree sections that are raised. I cut out the 3-120 degree sections by turning the rotary table so I am only cutting the area to form the clutch. If that is what you are asking/explaining?

Is that my error?

Thank you

 

[extropic]

In the photo of the "factory part trying to duplicate", it looks to me like the sides of the protrusions are not parallel with the opposite sides.
It also looks to me like the plane of each side does not include the center axis. In other words the sides don't look like they are precisely radial.
It may be an illusion caused by the camera, however please lay something straight across two opposing walls to see if they are parallel.
If they are not parallel then you have been working with false design assumptions.

 

[extropic]

Another attempt to understand the OEM design:
Is there more than one of the subject handles on the machine?
If there are two, try to mate them to verify that the notches and the teeth are nominally the same size/shape.