Comments from Terry Zollinger and Mike Morgan (our USU machinists)
1. Always use the same DATUM POINT!
a. When dimensioning a drawing reference all measurements within a plane to the same reference point (a DATUM).
2. Use relative dimensions when applicable.
a. You can't measure to air, give something to measure so the dimensional tolerance you specified can be verified.
3. Give pertinent information when needed.
a. If a cutout is for a bearing, tell them it is for a bearing, it changes how it is made.
4. Consider machining techniques and specify realistic geometries.
a. Not everything you will draw can be made!
5. Use common materials
a. You can save considerable costs and speed up manufacture times if you use materials that are commonly available. If don't know what is avalible use websites such as www.mcmaster.com.
b. Most materials warp if you cut a lot of thickness off.
6. When manufacturing a part, order matters.
a. This will make your part take longer because the machinist needs to consider what order to build your features.
7. Consider Tolerance Stack
a. Take time to think if the tolerance one dimensions will affect other dimensions. This can become a significant problem when relative dimensions are used. Consider the following situation (see picture). The length of the part is 100.00mm. If a tolerance is placed on all dimensions on +/- 0.05mm the overall length of the part could come out as 99.7mm or 100.3mm which is outside your tolerance. However it is you that have made the mistake, not the machinist.
8. Kits and material to be machined or welded should not be cut exactly to size.
a. Make sure when you give the machinist material that there is enough room for clamping, chucking and distortion from welding.
b. Machining costs can be significantly higher than those of the material.
9. Remember Form, Fit, and Function
10. Close tolerances equals high expense.
a. Only specify a tight tolerance when it needs to be tight.
11. Give the machinist your latest print with all current revisions.
a. It is best if they can work from a print with a date stamp from the last 24 hours.
12. Follow all blueprint protocols for views.
a. This includes specifying all dimensions, tolerances, and material types.
13. Maintain a single measuring system.
a. All dimensions on a drawing should be metric or standard, don’t mix them together.
14. Don’t tell the machinist how to make a part.
a. If you specify a threaded hole don’t say they must tap it, or drill with a #X drill bit before tapping.
b. The machinist (even though you might think highly of yourself) knows a lot more about manufacturing processes than you.
15. Get an idea of actual size of your project before you have it made.
a. Telling the machinist “wow, this is a lot bigger than I expected” makes you lose credibility.
16. Give credit where credit is due.
a. If you have a project and you need help thinking how could these things fit together, give your help the proper credit.
b. If you take advantage of your machinist they will not trust or help you again.
17. Plan ahead to avoid crunch time.
a. It will cost you or your company significantly more money if you “have to have this now.” You could be paying for the machinist’s cabin, airplane or hunting trips.
b. Our USU machinists are very busy year round working on senior design projects as well as funded research projects for our faculty.
c. High tolerances and surface finished can take considerably long to make.
18. Get to know your machinist
a. Here at USU both Mike and Terry are very friendly and want to help you.
b. Before you submit a drawing to be made go talk to them about it, you will be surprised at how much they can help you have a better result.
c. They will often try to determine what features are critical and which ones are not. Be open to their ideas.
d. It never hurts to have a good relationship with the people you depend on to succeed.