thread milling ?

fugdbdt said:

I just now got around to trying my milling bits from Hightower.
Beautiful threads but i cant seem to make the male and female match.
5/8 x 14 tpi is what i was trying for but i would settle for anything in
that range. My tennon size was .625 an my hole size was about .562.
Id say my male thread depth was about .070 and the female was about
.100 deep. What am i doin wrong? Any advice? thanx

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When you cut the threads, did you dial in .070 per side or total?

Kelly

Where did you get the idea for a 5/8x14 thread?
You can use any thread you want as long as you're cutting both the male and the female at that pitch.
SS joint collar threads are offered from Atlas in 5/8x11 & 5/8x18, no 14.

http://www.cuestik.com/store/product.asp?DEPARTMENT_ID=85&ITEM_ID=5756

You'll notice there is also a 3/4x16 but that's for the thin-wall collar.
Since you mentioned a 5/8 tenon I'd assume you're using one of the first 2 collars.

KJ Cues said:

Where did you get the idea for a 5/8x14 thread?
You can use any thread you want as long as you're cutting both the male and the female at that pitch.
SS joint collar threads are offered from Atlas in 5/8x11 & 5/8x18, no 14.

http://www.cuestik.com/store/product.asp?DEPARTMENT_ID=85&ITEM_ID=5756

You'll notice there is also a 3/4x16 but that's for the thin-wall collar.
Since you mentioned a 5/8 tenon I'd assume you're using one of the first 2 collars.

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Hey KJ, how goes it?

I think he made his own collar.

Kelly

fugdbdt said:

I just now got around to trying my milling bits from Hightower.
Beautiful threads but i cant seem to make the male and female match.
5/8 x 14 tpi is what i was trying for but i would settle for anything in
that range. My tennon size was .625 an my hole size was about .562.
Id say my male thread depth was about .070 and the female was about
.100 deep. What am i doin wrong? Any advice? thanx

Click to expand...

I would suggest either making your hole a little larger then cutting threads deeper or make the tenon smaller and do the same. Trying to hold too tight of a fit is usually not a good thing for gluing on collars. Drop the hole size by .010" and the tenon size by .010" and cut until the threads are almost sharp on top on both pieces and they will probably fit.

When machining threads, any method, the fit is determined by the pitch diameter od the mating parts, not so much by major and minor diameters.

Live threading

fugdbdt said:

I will try that Chris ... also what tpi works best with 5/8ths.

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I am not trying to answer for Chris but I do have a tip for you. Use a common
course thread such as 5/8-11 and purchase a nut and a matching bolt at your
local hardware store. Then you can figure out if it is the male or female threads that are giving you trouble so you can adjust accordingly. Good luck.

Though I am not Chris, there is nothing wrong with 5/8" -18 for your application, IMO.

Kelly

> Having never used a mill for cutting threads but taught how to use single point cutters for external AND internal threads to make parts match,I'm gonna guess this info I'm about to pass on will work the same.

If faced with the same dilemma,the first thing I'd want to figure out is exactly how tight I'd want the 2 parts to fit.

Let's say I chose to cut the male part first,and for the sake of commitment I choose 5/8-18.

I'd cut to .627 and give myself just a hair to sand and deburr back to a true .625.

To calculate single depth for a 60 degree thread form,you divide .6495 by the number of threads per inch.

.6495/18=.036.

Multiply x 2=.072 for total thread depth.

.625-.072=.553. This is the minor diameter.

Now that the numbers have been established for the male part,I'd decide how much room to allow for glue.

Using a tap to cut threads in ANY material is based on a long established standard of 75% thread engagement.

Using internal threads with either a single-point or milling cutter can be used to achieve close to 100% thread engagement,if you really want to split hairs.

Doing so however leaves no room for glue expansion or even room for the glue itself.

The proper calculation for internal threading goes like this.

.541 divided by TPI. .541/18=.030 single depth,then x 2 for double depth.

.625-.060=.565. That is the size hole you would bore out before starting the internal threads,if you wanted to make it so tight you didn't have room for glue. From there it would just be personal preference or perhaps anomalies with the threads themselves.

I was taught that with metal,.002 under on your major,and .002 under on the thread depth gives you a 100% guarantee that a premade nut will fit the screw you just made,provided you are willing to accept 75% thread engagement. Maybe I'm wrong but it seems like 75-80% will be just fine once you use good glue.

If it were me,I'd try boring the hole to .585. Tommy D.

Any thread will work. I like the 14 thread pretty well as it has more grab than the 18 and is easier to cut than 10 or 11. But the down side with a non standard thread is you can't buy a bolt and nut to test with as has already been mentioned. If you cut until you have sharp threads with the diameters we discussed you should be fine with 14 thread.

I'm not saying It's a better way to go, because It could be a very subjective matter, but If Using a standard 18tpi collar such as the 1 in KJ's link, Then It really doesn't take as much to get a snug enough fit with a acme tenon as one might think, and the smaller the OD on the tenon the easier the fit will be. I'm only using this as an example, but If the threads are good, then the tips don't need to be that deep to get something that can actually be clamped down tight without stripping the treads, so if the tenon only needs to be slightly under sized to make a good fit, then It would be plenty good enough to get the job done. How undersized You go can reduce surface contact though, and depending on how much that could create more of a void for glue then You may want, so Might want to draw a hard line on just how small is acceptable to the individual, because that's an area that can be very subjective, but technically speaking It will still work. If your able to cut both parts to acme then that may be even better, but It's possible to run into similar problems, and still have to either decrease the male or increase the female for the correct feeling fit. Once You figure out something you can live with though, don't do like I often do and not write it down, make sure to log them, and also Log in the materials that You used. Believe It will save you from having to figure It out again. Just about every size or thread pitch I use, I try to custom fit everything that way. I don't want a sloppy fit, but at the same time I don't want them so tight that It creates some kind of internal pressure, and/or creates a dry socket.

Greg

BarenbruggeCues said:

I'll give a few hints on live cutting threads in wood. Some things that apply to cutting them in metal do not apply to cutting them in wood. If you're cutting both the male and female in wood you will be much farther ahead of curve if you think acme style. Learn how to set up and chase them to accomplish this style of thread. They'll be much more forgiving than any V pointed style threads when mating the two parts in wood.

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WORD!
Not even close.