Buying stock for 5c collets
I'm running into an issue when buying stock. Most of it is at least a few thou oversized, sometimes more. I can jam it in there if I really force it, but there's no way my bar puller is gonna be able to handle that. This is mostly aluminum bars, some brass. How are you guys dealing with this? Are certain suppliers better about on size or slightly under size stock? I would think going a 64th up in size on the collet may work, but it can't be optimal since it's only gonna grip at the nose. Only other option I can think of is turning some emergency collets like 5 thou over my common stock sizes, but I thought I would check and see how others are dealing with this
Re: Buying stock for 5c collets
I've had the same oversize problem, I actually had to grind a couple of my 16C collets to fit the material we are getting, ~1.505 and ~1.230. We did get some precision aluminum stock in one order that was on size, but if you ordered that as precision stock I suspect it would be expensive. The last batch of 1 1/4 that we got measured at around 1.249. We buy from a large vendor, but we are buying by price rather than precision.
Hardinge will make collets in any size you want....... for a price $$$$ They might stock some over size collets.
Using emergency collets might be the best option.
Re: Buying stock for 5c collets
In my opinion Service center brand aluminum is the worst I have lot of bars oversize I can't use.
The chips don't break very well to gummy ,I avoid it like the plague.
I have always used Alcoa bought out by Sapa and then bought out again and now called Hydro.
I have NEVER in 30 years had a bar not fit in a collet, Chips breakup very well I always specify Hydo when ordering
material .
Re: Buying stock for 5c collets
with aluminum material there is extruded and cold drawn
the extruded has a lot more tolerance to the spec's then the cold drawn
cold drawn 0-.500 is +/-.0015
.501-1.000 is +/-.002
1.001-1.500is +/-.0025
1.501-2.000 is -/*.004
extruded starts at 0-.125 dia. at +/-.006and goes up from there
there is a price difference between them though the extruded is cheaper
Re: Buying stock for 5c collets
So I was thinking i would just start buying cold drawn for better tolerance, but what downside would there be to just buying emergency collets and boring to fit the cheaper stock? I can get cheap import emergency collets for 8 bucks. Obviously runout doesn't matter since I'm boring them. Possibly even better runout than a sized collet since it will be loaded in the spindle the same way while it's being bored as it will be while being used for holding since I use the index pin. As for the reduced hardness, I only run aluminum and brass so that shouldn't really be a downside either right? Even cold drawn stock isnt always gonna be a perfect fit in a sized collet. I really want a perfect low resistance slip fit so my bar puller can be reliable and boring my own collet will allow me to really fine tune that.
What would be the downsides to going this route? I haven't bored any emergency collets yet, is it harder than I think to bore a nice concentric low runout collet?
Re: Buying stock for 5c collets
Quote:
Originally Posted by
QuinnSjoblom
What would be the downsides to going this route? I haven't bored any emergency collets yet, is it harder than I think to bore a nice concentric low runout collet?
There really isn't any downside. No problem boring your own, the ones I have done machine very nicely. One note, the only time a collet (or chuck for that matter) needs to be perfectly concentric is when re-chucking a part that is partly done and needs a second op. When cutting raw material, the part will always be concentric to the spindle center of rotation. Even the stock is not going to be perfectly round unless you are buying TG&P stock, and even then it has a roundness tolerance.
Re: Buying stock for 5c collets
Looking forward to the videos :)