Help with drawing a part

[TomG]

Darren,

Unless I'm missing something without the part in hand, it can actually be drawn using only 5 views. That silly slot requires an entire view of its own and probably isn't even necessary. With a part like that it can be difficult to decide what features are primary and which ones are just there as a result of machining the casting. That tends to make the drawing more complex than it needs to be.

Tom

[PixMan]

I measured a few features on my 1982 vintage Alliant V42, and here's what I found:

Center distance between the two mounting holes, 43mm/1.700", 10.5mm counterbores, but the screws were actually 1/4-20UNC.
The slot measured 6mm wide. The "slider" measured .6265", so either and oversized 5/8" or an undersized 16mm. I didn't have time to disassemble it (and am disinclined to do so because I may need to use the machine soon.)

[Mayhem]

Tom, no you're not missing anything. I have more views than necessary as I was trying to figure out what was needed in each view. As already stated, I was worried about the clarity being shown. I'll download your drawing and study it when I get home. Difficult to do so on my phone.

Ken, thanks for the dimensions. I'll check mine when I get home. The bore on mine measures 16.18mm and the shaft is quite a loose fit (less than 16mm if I recall correctly). Please don't disassemble anything. Pity your old BP isn't still sitting outside your shop!

[Mayhem]

I haven't progressed this drawing any further, as Kondia are looking into whether they are still able to produce these. I've asked for the drawings if they are not going to make any more (I don't like my chance but you never know your luck! [besides, they are clearing stock of old manual machine parts]).

In the meantime, I have been drawing up the elevating screw and nut, as Ken has very generously offered to make them for me. I wish I could be there to see but alas, I only get to the US in September/October.

Since drawing is not something I have any training in or other experience with, I thought I'd share them here and I welcome any feedback on things I am doing wrong or could improve.


  Kondia FV-1 Elevating Screw and Nut.pdf (Size: 416.94 KB / Downloads: 20)

[EdK]

Looks good to me Darren. The only thing I see is the thread for the nut is not called out. I see it on the screw but not the nut. Of course it would be the same as the screw so maybe it's not necessary.

Ed

[TomG]

They look pretty good Darren, but there are a couple things I would suggest.

Other than what Ed pointed out, I don't see any tolerances on critical dimensions. Without them there is no way for the machinist to know whether a hole can be drilled, or if it should be reamed for a press or slip fit on a dowel. The same goes for the slot in the first part. If it's for a key, then it should have a tolerance to ensure that the key will fit. Any external diameters should also be toleranced if they are to fit in a precision bore.

One of the two views on the nut drawing is incorrect, but the information is all there (except for the internal thread as Ed pointed out). Oh, and what is the size on the thru hole for the 1/8" pipe?

Tom

[PixMan]

Darren sent me PDF's of the prints and the assembly as shown in a parts manual. The Ø 20mm shaft section fits a bushing over it then into a double row angular contact bearing. I think it should be a tapered roller bearing but that's not worth a redesign.

I find odd the size of the screw. I have to wonder if the screw threads have been distorted to have that odd O.D. of Ø 1.265". Any reason for not simply making it a standard 1-1/4"-5 ACME?

[EdK]

(01-30-2014, 07:53 AM)PixMan Wrote: ...

I find odd the size of the screw. ...

I also thought that dimension seemed a bit odd but don't know enough about the part to question it.

Ed

[Mayhem]

Thanks for the comments guys!

Ed - the thread call out was an oversight, probably because I know Ken is going to match the nut to the screw.

Tom - I have absolutely no idea how to determine when a tolerance is required and what that tolerance should be. This is where I need help. As for the nut, which view is wrong (and why)? The thru hole is 3.5mm, as indicated but I wonder if you mean the hole that needs threading for the 1/8" oil nipple. Again, this is a lack of knowledge on my part in measuring a tapered hole. I had meant to discuss this with Ken but I forgot.

Ken - I too found that dimension strange and I checked it several times. I took the measurements at the end of the thread closest to the ø20 section, as this would have the least amount of wear. I'll check it again. I would have no problem with it being ø1.250. I simply wrote down the measurements that I got.

[TomG]

Darren,

Standard tolerances can be found in the Machinery's Handbook or similar references. They simply determine whether two parts will slip together or press together and by how much. For instance in the ANSI standard, there are the following fits:

• RC Running or Sliding Fits
  
• LC Locational Fits
  
• LT Transitional Clearance or Interference Fits
  
• LN Locational Interference Fits
  
• FN Force or Shrink Fits
  

Each fit has a class associated with it to determine the allowance which is applied to the hole and the shaft. I believe it's done a bit differently in the metric world, but the outcome is the same.

I see the 3.5mm dimension now. As far as the views go, for the right hand view to be correct, the left hand view should be rotated 90º CCW.

Tom