cowanrg said:
I am nice. To wit:
http://www.diyaudio.com/forums/showthread.php?threadid=58952
Is it my lot in life to be remembered for the critical side of my nature? Grrrrr.
I would use either a steped bit in a drill press or a reamer. that said, here are two small tips which could make other ideas work:
For Nylon hardware (software??), use threadlock. It will keep it from loosening.
If you want to thry the grinding bit in the Dremel again, put a dap of oil on the hole before you grind, and keep the dremel at it's lowest speed (which isn;t very low). You could try the same bit in a hand drill, but definitely use the oil to keep things cool. The bits are dying because you are melting the aluminum to them.
For Nylon hardware (software??), use threadlock. It will keep it from loosening.
If you want to thry the grinding bit in the Dremel again, put a dap of oil on the hole before you grind, and keep the dremel at it's lowest speed (which isn;t very low). You could try the same bit in a hand drill, but definitely use the oil to keep things cool. The bits are dying because you are melting the aluminum to them.
Peter Daniel said:
Yes, they are called helicoils. I did a Google search and didn't find any that small but I'm sure someone makes them. Since they are basically a coil that threads into a tapped hole I would think that the thread count in the larger diameter hole would still need to be the same as the new smaller diameter. Hence for a 4-40 bolt, you would need maybe a 6-40 threaded hole, not 6-32. I don't believe I've seen a 4-32 bolt.
I meant to look at some TO-3's last night and see how much meat is around the holes. I would think if there is enough meat there that enlarging them with a Unibit would be the way to go.
Blessings, Terry
EDIT: I found these.
Wouldnt it be a lot easier if Mr Green sent you the TO3's by mail, you drill the holes larger and send the stuff back, Terry ?
You Californian dudes should stick together, you know !!
Eeh,Terry, do you own a drill press ?
btw: seen the prices of those coils?
A week ago i needed a few 3/8" x 2.5" unc bolts, the Fabory center overhere charged me $54 for 6 bolts !!
You Californian dudes should stick together, you know !!
Eeh,Terry, do you own a drill press ?
btw: seen the prices of those coils?
A week ago i needed a few 3/8" x 2.5" unc bolts, the Fabory center overhere charged me $54 for 6 bolts !!
Cool ideas. Helicoil usage is explained here.
I have no idea what a "steped bit" is or a "unibit" ?? More googling necessary. Got some hits on "stepped bit" looks like the same as a unibit. Thanks, I'll do some reading.
FYI, from my massive research, the holes in a TO-3 (actually Onsemi says its a TO204AA), vary from about 3.8 to 4.19mm in diameter (.14961 in to .16496 inches).
I need to get this up to .17 inches to fit the smallest available shoulder washer, which from the hundreds of web sites and charts I have looked at contains an ID of .14 in, so a #6 screw at .1380 in will fit, and and OD of .17 inches, to fit the enlarged hole-- if I go that way.
Or I could order a custom washer-- those are available but for quantity of about 40 it would be an ugly price.
So enlargement of the TO-3 holes will not need to be very much (from .14961 - .16494 up to .17 inches), if this makes a difference for those who have advised against, let me know.
Also, looking very closely at the TO-3 package, the hats are not flat but are very slightly rounded, might make it a little tricky to put the bar over them.
I have no idea what a "steped bit" is or a "unibit" ?? More googling necessary. Got some hits on "stepped bit" looks like the same as a unibit. Thanks, I'll do some reading.
FYI, from my massive research, the holes in a TO-3 (actually Onsemi says its a TO204AA), vary from about 3.8 to 4.19mm in diameter (.14961 in to .16496 inches).
I need to get this up to .17 inches to fit the smallest available shoulder washer, which from the hundreds of web sites and charts I have looked at contains an ID of .14 in, so a #6 screw at .1380 in will fit, and and OD of .17 inches, to fit the enlarged hole-- if I go that way.
Or I could order a custom washer-- those are available but for quantity of about 40 it would be an ugly price.
So enlargement of the TO-3 holes will not need to be very much (from .14961 - .16494 up to .17 inches), if this makes a difference for those who have advised against, let me know.
Also, looking very closely at the TO-3 package, the hats are not flat but are very slightly rounded, might make it a little tricky to put the bar over them.
Yes a unibit is what I meant when I said step bit. The beauty of them for drilling sheetmetal is that the bit stays centered in the hole as it drills the next size so the hole always stays centered and round. A standard bit will many times oval out a hole and/or bind up in it. The unibit is much better for enlarging holes in sheetmetal. Unibits used to cost about $40 each but I bought a set with three different size bits at "Costco" for less that $20. One of them is very thin and works great for smaller holes. That is the approach I would take if I were you. I think "Harbor Freight" carries them as well. A drill press would make it a little easier but if you can clamp them in some way, a hand held drill should work fine.
Blessings, Terry
Blessings, Terry
Thanks. I've got a bit for making countersunk holes, is this the same or different? It looks conical, so would appear to keep everything centered when drilling a preexisting hole. If this is no good, its off to Costco this weekend. I may try it first, if the holes are leaning towards the larger size, I only need to widen them by a wee small amount.
http://www.shopoftools.com/store/UNIBIT.html
The unibit drills in steps. A countersink tool cuts a beveled hole and you would have to gauge the depth just right to get the right size hole. With the Unibit, each step is a precise size.
try to find one like the one pictured in the center of the add I linked to above. That should work perfectly for what you have in mind.
Blessings. Terry
The unibit drills in steps. A countersink tool cuts a beveled hole and you would have to gauge the depth just right to get the right size hole. With the Unibit, each step is a precise size.
try to find one like the one pictured in the center of the add I linked to above. That should work perfectly for what you have in mind.
Blessings. Terry
Cases
I thought that TO-3 cases were steel, not aluminum?
But yes, a few hundredths or thousandths of an inch is all I will need.
I have experienced drills binding when used to enlarge preexisting holes in metal, so am a little concerned about the last post. But have to try it and see; I've got some old devices around for experimenting with.
I thought that TO-3 cases were steel, not aluminum?
But yes, a few hundredths or thousandths of an inch is all I will need.
I have experienced drills binding when used to enlarge preexisting holes in metal, so am a little concerned about the last post. But have to try it and see; I've got some old devices around for experimenting with.
i may have lost the original point of this thread, but could someone basically describe to me the reason why we need to expand the hole in the case?
cant we use a smaller screw?
cant we just use a clamp bar instead?
given all things equal, it seems a LOT easier to just mount it some other way than try and risk the chip's life. im looking out for the life of this poor defenseless TO-3!
cant we use a smaller screw?
cant we just use a clamp bar instead?
given all things equal, it seems a LOT easier to just mount it some other way than try and risk the chip's life. im looking out for the life of this poor defenseless TO-3!
cowanrg said:
I believe lgreen's heatsinks are already tapped for 6-32 screws. He wants to use shoulder collars to isolate the TO-3 cases from the heatsink. The holes in the TO-3's need to be enlarged to allow for the collar. Otherwise he is going to have live heatsinks.
One concern I would have is the depth of the shoulder portion of the collar. If it is at all deeper than the TO-3 case is thick, you will not get enough pressure on the case to properly seat it against the heatsink.
Blessings, Terry
Terry has it right, the heatsinks are pretapped for 6-32 screws and these are too thick to be used with any existing shoulder washers that have the right inside diameter because their outside diameter is larger than the hole of the TO-3 case.
Absolutely not, it would destroy the threading. Also, one side is inaccessible from the back so without the threading the TO-3 can not be fastened, you would not be able to put a nut on the other side of the screw.
This will work to hold down the TO-3 but If a clamp was used you now have the problem of how to electrically connect to the collector of the TO-3 and whether you want your clamp to be electrically live or not. You could additionally add some nylon screws at the standard holes with a solder tab connector, but the nylon screws are not very strong and your connection might be suspect.
Good! If the heatsinks were live there would be no problem, but I'm trying to avoid that for reasons explained elsewhere.
From Terry-
I have looked at this is a lot of detail, depth will not be an issue; have some washers right here that will do the trick once the holes are widened.
Not to be a pain, but I am betting nylon would provide plenty of pressure. You really don't need all that much. And use a threadlock compond on the threads to keep them from loosening up on you.
Edit:
I just found this while looking for torque specs for TO-3 cases (which I didn't find), but this is some good reading!
http://www.onsemi.com/pub/Collateral/AN1040-D.PDF
Edit:
I just found this while looking for torque specs for TO-3 cases (which I didn't find), but this is some good reading!
http://www.onsemi.com/pub/Collateral/AN1040-D.PDF
BrianDonegan said:
For some reason, I have always been of the impression the one of the reasons why the TO-3 has an advantage over the other style Transistors is because of the ability to snug them down to the heatsink better and therefore get better heat transfer. I would think that nylon bolts would defeat that. It certainly looks as though there is ample metal around the mounting holes to enlarge them slightly.
Blessings, Terry
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