I am working on a project that I want to press fit, an aluminum cylinder into a brass ring.
The hole in the ring is 0.5 inches in diameter how much larger do I need to make the aluminum for a tight permanent pressure fitting?
I have done a couple pieces and they worked out ok but I cant find any chart somewhere that says .001 larger for loose fit .003 larger for tight…something like that.
Any help would be greatly appreciated.
0.5005" is about the right target for a decent press fit. You can get by with 0.501" if you first heat up the brass part to ‘enlarge’ the hole first.
As you may notice, the target diameter difference is very low. That means you need to know the diameter of the hole quite precisely. If the hole was simply drilled, then it is likely not a good candidate to be used for a press fit, since, a) the size will not be what you think and b) it is likely not really round.
BTW, the answer to all these questions is the Machinery Handbook. A copy of which is on the cart in the Machine Shop.
I’ve used this calculator before for sliding fits, got good results.
I believe you would look at the LN fits (Interference locational fits), but don’t quote me on that!
Stainless steel is a hardenable material, and depending upon the grade of the bolt, it might be hardened. If so, HSS and our tools are not going to work very well.
Do you know what grade stainless your talking about? They vary greatly in machinability. In any case, I would pick up some extra center drills, since they break easily and stainless will likely break one or two.
What size hole? If large enough, boring on the lathe is likely a better bet, not sure if our reamers are still useable, they get damaged quickly if misused.
Missed then when originally posted.
You have another option used quite commonly: take the .500" bar and knurl it. It will expand the diameter a bit. It will more easily press fit and induce less stress because the displaced metal has some place to go. Add a drop of Locktite to it both as a lubricant when pressing in and them locking it in.
How thick is the material? You’ll want to ream the hole so it is nice and round and has good wall finish. Do it on Bridgeport if possible so it is also perpendicular.
CDC over in Richardson. If that is inconvenient, let me know and I will run by there to get them for you.
A bolt used on a antenna like that is likely not grade 8, so it should be machinable. 3/16" can not use a boring bar, so it will have to be reamed.
I would use the lathe. Use some scrap stock in the lathe. Drill a tap size hole. Tap for the 3/8"-24 then screw the bolt into that hole. This ensures maximum egocentricity and squareness of the hole.
@TBJK has been getting a tan from all the TIG practicing he’s been doing. It’ll be fit for use as an axle when he’s done!
Agree and Stick TIG are fun. Love Oxy but not here.
