Hi,
We're interested in producing (in relatively large numbers) 1/4-28 UNF 1/2" Long screws with a quadruple-start. We're thinking of buying an older (cam-type) screw machine to dedicate to this part. The question is, can these cam-type machines (e.g. Acme-Gridley, Brown & Sharpe, etc.) cut screws with multiple starts?
Thanks in advance, James
I can't help you, but I do have a naive question: Does 1/4-28 4-start mean that there are 28 threads in each inch (with the thread lead being
1/7 of an inch) or does it mean that the lead is 1/28 inch and there are 106 of them?Either answer is impressive, in its own way...
Tim, it means that the pitch remains at 1/28 but the lead is 1/7 (4:1 ratio), which means that turning a nut on this screw advances the nut four-times the distance that would be travelled by a regular nut on a regular 1/4-28 screw, but both nuts would have the same number of threads engaged.
According to James H. :
I believe that these machines don't have a thread-cutting leadscrew and gearbox, so threads are most often cut with something like a Geometric die head.
You'll have to get in touch with Geometric (or any of the other people who make chasers for such die heads) to find out whether they can make a special set of chasers to do this.
I suspect that they can -- and may provide the chasers for about double the cost of standard chasers.
Good Luck, DoN.
Where I used to work we rolled threads with an automatic thread roller. As I recall, we had it mounted at the twelve o'clock position on an eight spindle Conomatic. We had a few Acme's set up for thread rolling as well.
Multi-start thread rolling dies might be available already, or could be ordered I suppose.
Hope this helps,
Tinker
Large numbers of threaded screws are most often done by thread rolling. The threads are better then cut threads. I remember running a 1000 piece order of threaded 17/4 stainless rod ends that called for a 5/16 left hand fine thread . And by mistake we had then threaded right hand. So we talked to the thread roller and he rerolled them straight then rerolled them to the correct left hand thread. These parts were aircraft parts. Which makes me think you might be able to use stock 1/4 bolts to do the same thing if the thread rollers can make a die for your parts. If I remember correctly the thread rolling company was called Ace Grinding in the Los Angeles area. Hope this might be of help to you. Jim
I understand you and Gunner don't like each other much, but unless it's about survival machining, please cut out the cross posts. Thanks.
-- W§ mostly in m.s -
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