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Re: Milling a helix

Posted: Wed Jun 06, 2018 9:16 am
by Richard_W
I take it you don't have a fourth axis for your CNC mill?

If you have a horizontal head for your Bridgeport? You could turn the horizontal head to the desired helix angle of your worm. Cincinnati mills had an adapter for their horizontal mills which allow them to cut a spiral on a plain mill. I used one once way back when, but not to spiral mill with. At the time I didn't know what it was I was looking at. But worked for the task at hand.

Richard W.

Re: Milling a helix

Posted: Wed Jun 06, 2018 10:13 am
by Dave_C
Picture a large kitchen bread-dough blender, but for sand. Usually wider than deep, with slow moving mixing blades.
Many variations of design are possible. Even a cement mixer can work nicely.
~RN
Thanks,

That was pretty much what I found on the Internet when I did a search for said item.

Dave C.

Re: Milling a helix

Posted: Wed Jun 06, 2018 4:02 pm
by Harold_V
GlennW wrote:
Wed Jun 06, 2018 6:48 am
Harold_V wrote:
Wed Jun 06, 2018 3:49 am
Setting the angle is the real challenge, as marks on machines are not accurate enough to be reliable.
Sweeping an accurately positioned sine plate or bar with a DTI in the spindle should be plenty accurate. No?
Sigh! If only I had one! I have the gauge blocks, and I have what amounts to a kit sign plate and bar, but nothing that's finished. I've managed to survive years without them, although I often wonder how.

Things get real testy when working with angles due to the possibility of compounding. The ram of the machine must be dead perpendicular to the table, otherwise as the head is tilted, the resulting angle is no longer the one you desire. I'll have to start by squaring the turret, then set the angle and inspect the results, trusting my vernier protractor, or my comparator. What I'll shoot for is a match to the gear, which displays minor wear. As the part is not intended to be interchangeable with other parts, so long as it matches the mating part, all should be good, and matching the existing condition of the gear should yield the greatest worm/gear life, as they won't have to "seat". That's why I'm not concerned about the angle on the opposing flank---it, in theory, won't ever make contact, and if it does, it won't be under any load.

Thanks for your thoughts, Glenn.

H

Re: Milling a helix

Posted: Wed Jun 06, 2018 4:05 pm
by GlennW
I can send you either one if you need to use it for this project.

Re: Milling a helix

Posted: Wed Jun 06, 2018 4:50 pm
by RONALD
FYI Simpson Mullers:

Here is what a typical portable Simpson Muller looks like. The little guy trying to push it, while the Instructors gab, today, is approaching 60! Did he go for a career in metal casting?

Today, there are no more shops at the school but that Simpson 5HP Proratable Muller sits in my backyard foundry. In the second photo is a Simpson Lab Muller, a little smaller, but great for batches of less than 25 pounds, behind it is that bigger one.

If Harold lived a lot closer he might be able to use one.

Re: Milling a helix

Posted: Wed Jun 06, 2018 8:54 pm
by NP317
That Simpson muller is the same one I had in my Univ. of Washington foundry classroom.
I had to laugh when I saw the person trying to push that heavy muller. The lift handles (one of them, anyway) are on the opposite side!
Simply lift and move.

Guess you gotta start learning somewhere...
~RN

Re: Milling a helix

Posted: Wed Jun 06, 2018 9:44 pm
by Patio
Google search on Muller pictures.
https://www.google.com/search?q=sand+mu ... jw8frxXrKM:
Harold's Muller is in many pieces at the moment. His uses wheels.

Re: Milling a helix

Posted: Thu Jun 07, 2018 1:41 am
by Harold_V
Richard_W wrote:
Wed Jun 06, 2018 9:16 am
I take it you don't have a fourth axis for your CNC mill?
Correct. Wish I did, but the cost can't be justified when my use of the mill is very sporadic. Now if I was using it for gain, that'd be another matter! :wink:
If you have a horizontal head for your Bridgeport? You could turn the horizontal head to the desired helix angle of your worm.
Thanks for that, Richard. I do have a horizontal head, and I must confess the thought never entered my mind, but the cost of the side cutter would make the project virtually prohibitive. I'd do it if that was my only resort, but I had planned on building this attachment for many years, and was the chief reason I purchased the huge assortment of gears I own. I'll be able to machine the worm with end mills, which are relatively inexpensive in the scheme of things, and certainly useful for other projects, unlike the special side cutter I'd have to purchase, assuming one would be available. I say this because I know the gear and worm were built expressly for the muller. They are not standard in any way.

H

Re: Milling a helix

Posted: Thu Jun 07, 2018 1:47 am
by Harold_V
GlennW wrote:
Wed Jun 06, 2018 4:05 pm
I can send you either one if you need to use it for this project.
You're a trusted and valued friend, Glenn, but I'm pretty sure I can deal with this simply by making the first setting by the marks on the machine. Once I start machining, I'll be able to determine the angle in regards to how it relates to the gear, which is my objective. Making final adjustments will then be relatively easy. Thanks so much for your thoughtfulness, though. It means a great deal to me.

H

Re: Milling a helix

Posted: Thu Jun 07, 2018 1:51 am
by Harold_V
NP317 wrote:
Wed Jun 06, 2018 8:54 pm
I had to laugh when I saw the person trying to push that heavy muller.
Indeed!
I have no idea what mine weighs, but I know that the two wheels, alone, run right at 200 pounds. Keep in mind, mine is powered by a smaller motor (1½ horse).

Simpson built machines that were intended to go the distance. Corners were not cut. I've worked on several pieces of machinery in my many years, and I'd place Simpson pretty much at the top where quality of construction is concerned.

H

Re: Milling a helix

Posted: Thu Jun 07, 2018 1:57 am
by Harold_V
Patio wrote:
Wed Jun 06, 2018 9:44 pm
Google search on Muller pictures.
https://www.google.com/search?q=sand+mu ... jw8frxXrKM:
Harold's Muller is in many pieces at the moment. His uses wheels.
Yeah, what Patio said, and I didn't take any pictures of the sad looking critter before I started dismantling. I do have several I've taken along the way, for use as a reference if need be.

I didn't consider that some folks aren't familiar with a muller, and they vary widely in design and how they work internally. It doesn't resemble either of the two Ron owns, although they all accomplish the same task. When mine is finally finished, I'll post a picture or two, so you can get an idea of what it looks like, for those who have an interest. I'll probably post at least one picture I took while dismantling, so you can get an idea of what I started with. It looked like hell.

H

Re: Milling a helix

Posted: Thu Jun 07, 2018 1:06 pm
by f350ca
You mentioned cutting the worm on a lathe. My Summit will cut 1/4 tpi, 4 inch pitch, slowest speed 20 rpm would give a carriage speed of 1 1/3 inches per second. I've never used that setting. Would you use a single point cutter or some sort of milling attachment. Square thread form is the only thing I've run across with close to that pitch. Guessing anything using it would be multiple start.

Greg