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Need some tight tolerance (+/-0.001 or similar) guide rods so looking at using drill rod. Does in normally come in non hardened state? Probably don't need high hardness for my application but it isn't clear from the descriptions I have seen what hardness it typically is. I could use other material if more economical with similar close tolerances.
Any Ground rod would do the same job, the drill rod is not hard and depends on what you want to run on it as to how hard it should be, you can get round linear rails that have a hard surface and are inexpensive depending on what diameter you needQuote:
Originally Posted by Jim27
Found some info indicating annealed M2 will be about Rockwell C of 24...
I normally use dowel pins for guide rods in small dies. Around RC60.
https://www.mcmaster.com/dowel-pins/
I have done that too but was wanting something a bit larger and longer. Now I see that they are available longer than I thought so that could work.Quote:
Originally Posted by Jim Dawson
I bought over and under size reamers for the dowel pin sizes I will use the most (mostly 1/4"). Wondering if I could get a close enough hole size for a one off project with a bigger one by cnc with a smaller end mill. I know I would have to sneak up on it as the accuracy would not be enough to just specify the hole size and expect it to be right on the first time. Would need to cut undersize and gradually increase until fit was right. But I don't have a way to measure hole size with the needed accuracy either so probably not going to work very well.
Typically for a dowel pin you want +0.000 to -0.0005 for the tight side, and for a slip fit on the mating part you want +0.0005 to +.003 or so depending on the required fit.
I normally do this with reamers. I guess I would buy the reamers to do the job properly, it's pretty hard to interpolate a dowel pin hole on a CNC mill, especially if you don't have pin gauges to test. The other option is to buy a set of small hole gauges, that will get you pretty close.
I have a couple true die sets with large guide pins. Trouble is I need a hole in one almost the size of the base to eject the part when formed. All the base pins look to be a press fit - are they heat shrunk to get a tighter fit? Thinking I might be able to use the base and make a new top plate since the linear bearings are a slip fit and are held by clips and machine screws. Or I might be able to eject the part by backing it out of the die rather than pressing through.
In real diesets, the smallest pins I have seen are 1 inch, the largest about 1.5 inch, this would be for like a 16x24 dieset.
Normally the lower pin holes would be reamed undersize -0.001 to -0.002 depending on the pin size. This would give a tight press fit. A tight press fit is normally -0.001 to -0.0015 per inch of diameter.
If the bottom die working area is so close to the edges that you don't have room for pins, then you maybe need to think about mounting it up on a larger backing plate.
Hi,
I went through a factory (Sutton Tools, Marybourgh, Australia) and they had many hundreds of rolls of tool steel, but literally coiled up like you might expect to see
mild steel reinforcing. It was about 32 RockwellC in that state. They stretched it a bit to straighten it then heat treated it. After hardening but before tempering it was as hard as the 'hobs
of hell', maybe 70 HRC plus, but after tempering it was back to about 66 HRC, what you would expect for a HSS drill. Then they ground the drill blanks. The final size and the straightness
depends on the grinding machine.
If you want some hard pins of precise size try some nitride hardened ejector pins. They are used in plastic injection moulding machines, available in different diammeters, precision
ground and harder than a HSS drill.
Craig
Mine are about 1.25 to 1.5" dia pins. The plates are roughly 8 x 8. Are you suggesting adding bigger plates to the die sets or remounting the pins to larger plates or something else?
I don't need super hard pins as these are just hobby shop type projects not dies that will run 10s or 100s of thousands of parts. Rc or 20 or 30 is likely sufficient and allows easier cutting and other modifications.Quote:
Originally Posted by joeavaerage
Hi,
ejector pins are offer in un-nitrided condition. The basic material seems to be about 40-45HRC. That would allow you to cut/grind etc.
Craig
You can just buy some Pins and Bushes to do the job, there are many suppliers, you may even be able to find a used Die set for cheap like this on Ebay 303162954152Quote:
Originally Posted by Jim27
Or here https://www.alibaba.com/product-deta...736704758.html
I was suggesting that if the actual die is too small to install pins, then mounting the die in a larger die set would be the way to go. If the die is 8x8, then it would seem that something around a 12x14 die set would be about the right size.Quote:
Originally Posted by Jim27