I'm looking to attempt my first thread milling on some small parts that I need to make. They will be threaded 1/4-40 both on internal and external surfaces approximately 1/2 inch deep. These are mating parts in 4140 normalized steel.
Thread milling seems to be the way to go and I've never done it. I looked at both multi-tooth and single tooth cutters and I would really appreciate your collective input on the merits or faults of each.
I know that there are some threads on the subject here already and I will review them as I get into this. Right now I am just looking for suggestions as to which cutters I should order to get them in-hand. I'm probably going to use MSC if that helps.
While I'm at it, if you've got a recommendation for engraving cutters suitable for a 3K RPM spindle machine, I could use that information too!
1/4 40 will not allow you to use a normal inserted threadmill. You can use one on your external threads but I would look at Micro100 single point internal threading tools...Just helical interpolate and use three or four passes...I've used them to thread some pretty small bores in the past.
I also use 15deg misro 100 engravers (1/4" dia) for most of my engraving
They put out a catalog every now and then that I find most helpfull...
I have used cutters made by Scientific cutting tool before and been happy with them, they make both single thread and multi-thread cutters, I would work from the bottom of the hole to the top. With normal materials I would start at 150sfm and work out a 90 degree of arc ramp out to dia. then commence to threading. If you do all the threading code in incremental you can make it a subroutine and just call it up at each location.
I did use some from MSC but as I recall they were not nearly as nice as the scientific cutting tools. I have milled clear down to 8-32 with the Sci. tools. the 8-32 job was D2 and holding size was tough over hundreds of parts, we went back to tapping that job.
Depending on your engraving, if you can do what you want, I have used small carbide endmills and ball endmills that were leftovers from other stuff, the 1/16 and so we never had re-sharpened.
Scientific (SCT) makes the tool you need to thread mill the ID and OD threads. Click here. Get them coated and you'll be just fine. Its a multi thread with a 1/2 LOC.
As far as engraving, with your low rpm and mat. type, I'd go with a small, carbide 2fl ball mill.
I ended up ordering the micro100 tools. Frankly, what a pain in the ass trying to get someone to sell them to me. I called the manufacturer, they sent me to a distributor that sent me to another distributor that finally arranged to have a tool sales place call me. That guy was willing to take my money and promises to send me some stuff...what a test! Almost three hours to buy four little cutters.
I looked at the scientific cutting tools, but the price was almost four times as much as the micro100 tools and since this is my first attempt at thread milling, I didn't feel comfortable with the idea of wrecking a $150 tool.
The tool rep said that they should be out to me by the end of next week...we'll see how this goes.
Thanks for the help!
Just closing the loop on this.
The cutters arrived yesterday and the engravers were put to use last night. My immediate impression is that they are quality tools.
The tips broke after very little use in normalized 4140 steel at .005 depth, but they got the job done. I'm fairly certain that the breakage was due more to my low spindle speed (3000rpm) than to any quality issues with the tool. It suggests to me that I need to find a different shape tool for my engraving.
The thread mill for the 1/4-40 threads looks like an extra viscious dental instrument more than a cutting tool. I will be trying it out in some machine wax first and will post some pictures once successful.
I hope my last reply did not come across poorly to those that recommended the Micro100 products. I was/am frustrated with the multiple gyrations it took to buy the tools. I think I got spoiled by the ease of buying through MSC.
Well, that's it for now. Have a great day everyone!
Several of the catalog companies stock Micro tools. Shouldn't have been so painful to buy. But I'm lucky having several local shops that are competitive in pricing with any of the mail order outfits.
The engraving cutters won't take much in the way of feed rate. I chipped one at .001 per rev in aluminum, at about .008 deep. That was a 30° included angle. I've had better luck with the 60° tool, and can't see any difference in the appearance of the engraving at a shallow depth like this.
we generally run advent for solid cabide thread mills. I have thread milled down to 10-32. advent is good stuff, sct makes good stuff as well. I have used various other, but the advents have the widest selection I have found so far.
we run 2l inc engraving tools with pretty good success. they actually recomend the speeds range you are talking for theirs.