Tapping questions

Minimum quality of tap is Hansen or Vermin America brand, I only use them 'cause I can get them on Sunday afternoon at the local hardware store. Anything better and/or non-standard, I have to wait for the brown buggy to deliver. Home Despot/Lowes/HF carry peculiarly ridged objects that they're pleased to sell as taps. Good taps can be had at fairly decent prices from the likes of MSC, better prices in quantity.

On aluminum, I back up every 1/4 or 1/2 turn to break the chips with straight fluted taps and use a proper cutting compound, Tap Magic is one brand I've used, Alumi-Cut is another. Extruded aluminum is gummy and will build up on your tap without it, you can get things so plugged that it will jam and you can't get it backed out without breaking it. Those small holes can be buggers to do sometimes, a tapping jig using a bushing can help a lot. I also like using a dogbone-type of wrench rather than a T-handle, there's less leverage there and I can get a little better control and less side pressure. I like a little Starrett unit I bought long ago for taps of that size, it's about 2 1/2" long. 2-flute taps are good, too, they've got a little more rigidity in those small sizes.

10-32 may be a bit too fine for extruded aluminum unless the extrusions have been hardened. You might find that when you torque your fasteners down that the holes will strip with fine threads in soft material. Without knowing more about your project and the load you want to apply, it's hard to say what you need. I'll repeat the old saw about needing at least 3 threads in the material to hold well.

Another alternative to get a small threaded hole is the threaded insert or nutsert, there's a number of different types of these, some are available in stainless or aluminum.

Stan

Reply to
Stan Schaefer
Loading thread data ...

Egads, I can't believe I'm the only one who noticed this (or perhaps the guy I heard this from is just full of it). Is this boat going into salt water? If so, DON'T DO THIS!!! A buddy of mine who does a great deal of ocean sailing tells me that you do NOT want to mix AL, SS and salt water. At least not if you want your parts to come apart ever again. I guess there's a pretty bad reaction among the three, and those things fuse together like a solid block. You will have to cut them to get them apart. He was referring to using AL nuts on SS screws, but the same would apply to this situation, I'm sure.

'Least that's what I heard...

Reply to
The other Thomas Gardner

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.