Advanced machining help?

I am sorry if the title is not very informative but I did not know what else to put. My machining career has consisted mostly of automotive applications. I either modify existing parts or make spacers, bushings, brackets etc. I have never had to machine any sort of complex part before. There in lies my question and problem. I know all of the basic machining skills and I own a 13x40 Southbend, a 9x36 Bridgeport and most of the tooling that I think I could ever need so equipment is not holding me back. I just don't know how a seasoned machinist would go about turning raw material into the final product. What I am looking for is a video, book or some thing that could show me a few examples or teach me how to analyze a drawing and know what to do first. The part that set me on this quest was actually a hobby of mine. I have been into remote controlled vehicles since I was very young and a few years ago I got into RC rock crawling. When that segment of the RC hobby started you needed to make your parts because there was no market for them and there for no suppliers. I was on another forum when I came across a set of custom knuckles made from aluminum. I would like to make myself a set but after I true up the block, what would I do next? I contacted the gentleman that made these and he is using a CNC Bridgeport. While I would love to have CNC capability, it is not a luxury that I can afford at this time. Here is a link to the forum I mentioned.
http://www.rccrawler.com/forum/showthread.php?t=190739&page=3
Any help and input would be greatly appreciated.
Steve

Can you snag a copy of those pictures? I don't want to register on their forum to have a look at what you want to build, but are knuckles U-joint components or what?

What you are describing is how you tell the difference from a machinist and tool maker from a machine operator. Figuring out how to hold a part and in which order to perform the operations is almost a gift. I've seen a lot of people that can't do this. It certainly helps if you can think in 3-D.
JR

Knuckles are basically the part that holds the front axle and allow the front wheel to pivot (steer).. I couldn't see the pics either, don't want to register just to see them. To do the parts, you will be doing the same thing as the guy on the CNC machine did, but without circ. interp. steps; you'll need to bore or ream instead. Ask him nicely for his order of operations and perhaps he'll help you out. (Unless he's selling the parts, then he might not be willing to give out that info). I made a set of front and rear knuckles/kingpins for my R/C car when I was in high school shop on a manual Bridgeport, so it's not impossible.

The normal method of training people to do what you want to learn is via a set of graded step by step exercises whereby you simultaneously pick up both machining skills and drawing interpretation skills. Starting with simple obvious stuff and ending with fairly complex things. Goes best with supervision and a bit of pressure to keep you working. Not that practical outside a school type environment tho'.

As you have basic skills two fairly obvious options are:-

1) If you can think in 3D use the artist approach to creating a sculpture "carve away all the bits that don't look like the sculpture you have in mind". The machinist version is to consider the starting block of metal and figure out how it has to be held to cut any single feature from that block. Having got that straight its not too hard to figure out an order of operations which lets you cut the features before chopping off the bit you need to hold it by whilst doing the cutting or align it with when setting up for the cut. Usually several choices, best to pick the one which minimises the number of re-alignments and re-grips. As you are used to making / modifying single, simple, parts your experience should click in part way through and an acceptable method will fall into place. Most of the time there is nothing much to choose between several reasonable ways of doing the job. When there is the issue is usually holding without distortion, finish on a given feature or keeping alignment.

2) If you can't think in 3D you need to hunt up some apprentice / school shop project books and dive in at the highest level you can understand. Regrettably there are no reasonably modern exercise sets for the home shop guy in your position. The only reasonably modern one I'm aware of is probably a bit too low level for you.

Another way would be to read some of the details how to descriptions accompanying magazine published plan and project series. Major drawback here is that much of the descriptions seem to concentrate on how to skate round equipment lacks and deficiencies.

If you don't get sorted fairly soon PM me and I'll find you some PDF's of course project type material.

Sorry about the pictures, I didn't check the post again until today. Here they are.
Steve

STJ7780 said:

Sorry about the pictures, I didn't check the post again until today. Here they are.
Steve

Click to expand...

Do you have a rotary table? This, I think, will be indispensable, and a boring head for the mill will be highly desirable.

Steve,

If Mr Kineteks won't give you a copy of the drawings you will have to make some yourself. Can you make your own set of drawings?

The photos you posted give all the hints (to me anyhow) on how he went about making them. The first photo with the three partially finished parts in a row shows you a lot.

With your lathe and mill and a rotary table you should be able to make similar parts that look at least as good as his.

One book that can give you a lot of hints is "Machine Shop Trade Secrets" available at:
http://www.proshoppublishing.com/

The Users Tips on that site are mostly from PM members.

A good website on techniques that are well illustrated and explained is Frank Ford's site:
http://www.frets.com/HomeShopTech/hstpages.html

-DU-

+1 on "Machine Shop Trade Secrets". One tip from that book that bears directly on the parts you want to make, that's been echoed to me by a few of my best teachers:

For complex parts with lots of features, start by making any holes first, while your stock material still has six flat sides. This makes them easier to locate, and they can then be used to easily locate any features concentric to them. I see alot of such features on your knuckles.

After making holes, proceed to the cuts that remove the least material next. The idea is to keep the part in block form for as long as you can to maintain its rigidity and ease of clamping.

E book called advanced machine work

i got a hard copy and its pretty good stuff.

http://www.metalwebnews.org/ftp/advanced-machine-work.pdf

The fellas here are right, if the parts to tricky for you now, put it aside and work on a couple of simpler things, reading some and learning some as you go.

in a couple weeks or months of tinkering on something else, it wont seem so tricky.

Everyone learns gradually

if you had a good square block to begin with, and were pretty handy with tool makers buttons, you could do a great deal of that shape on a lathe.

Boring head would help immensly

Bear in mind his first photo shows a CNC setup. This would only be doable in a conventional mill if you can get your hands on a hollow end mill of some sort, in the right size. Even then, hard to get a nice size and finish on the cylindrical stub, especially on aluminium, where the escaping swarf will abrade the stub.

You'd be better to mount a vice on a rotary table and make a cut like his, using a conventional end mill and cranking the table round.

Similar to the way you'd separate the large cylindrical diameter from the block, except in this case you'd have to hang it out the end of the vice, and probably contrive some extra clamping.
Or - You might consider making them in pairs, siamesed back-to-back, and just separating them at the end, so you've got more to hang onto on that side block (the one which ends up being discarded). This way, a vice might provide enough clamping.

There's lots of ways to tackle it, and nothing will be wrong if you can make it work. If you wanted, you could do a dry run with a chunk of acetal or other suitable easily machined material (even MDF laminated into a block, if you don't mind getting the dust all over your machine - not the best for bearings and such, though....) to prove the sequence. With more experience, you'll find you can do this in your head, perhaps with a few sketches for something tricky like this.
The main challenge is to preserve alignments, eg so the two short stub axles are truly in line. Ideally, this would be achieved by flipping it over and using the same two datum faces you used for the opposite stub. One can remain bearing against the fixed jaw of your vice; the other will have to flip to the other side of your spindle centre, but at the same distance. You could establish that distance using an edgefinder in both cases, and your dials or DRO.


You might also want to consider finishing the outside first, including the lever, then chucking in a 4 jaw in a lathe for truing up to complete the bore details. Especially if you don't have a boring head.

If you are using a boring head, I'd leave the clamping block intact until the bore details were complete.

Seek out qualified retired machinists for mentors or take classes if they are available. Books and such work well by themselves for a small minority, most learn best by a combination of books, classroom and structured increasingly difficult shop challenges guided by masters. Hands on, observation, seeing and doing a vast variety of machining is the only way to arm your quiver of arrows pointing to the best way to do a job.

Your part isn't difficult to produce with the manual machines you have but it could be high hurdle from where you are. You need a teacher. You can't learn machining by asking questions on a forum.

There are an infinite number of paths to a successful outcome, a few of them are better than all of the others. You showed a progression of operations by someone using CNC.

With manual machines that sequence is an option but isn't what would have been done before CNC. You're before CNC with minimal manual machines. We got into space without CNC, you can do as well with your machines.

Troup offers one approach, my manual approach would be entirely, totally different. So would every other opinion on how you might proceed.

All that does is spin your head around. Decide if making hobby parts is really important, you have the tools. You're near the bottom of the learning curve, that you want to learn is priceless.

David Utidjian said:

Steve,
If Mr Kineteks won't give you a copy of the drawings you will have to make some yourself. Can you make your own set of drawings?
-DU-

Click to expand...

I have experience in design and drawing so I am set. I am actually going to change his design some to fit my setup.

David Utidjian said:

The photos you posted give all the hints (to me anyhow) on how he went about making them. The first photo with the three partially finished parts in a row shows you a lot.
-DU-

Click to expand...

I thought the same thing, I am going to bore for the stub axles and bearings first while I still have good reference sides to the block.

hickstick_10 said:

Boring head would help immensly

Click to expand...

I have a 3 inch boring head and a good assortment of boring bars.

Troup said:

You'd be better to mount a vice on a rotary table and make a cut like his, using a conventional end mill and cranking the table round.

Click to expand...

I have mounted my vice on the rotary table before and it worked great. That idea would work perfect on the outside diameter of the knuckles.

Troup said:

The main challenge is to preserve alignments, eg so the two short stub axles are truly in line. Ideally, this would be achieved by flipping it over and using the same two datum faces you used for the opposite stub. One can remain bearing against the fixed jaw of your vice; the other will have to flip to the other side of your spindle centre, but at the same distance. You could establish that distance using an edgefinder in both cases, and your dials or DRO.

Click to expand...

From the first picture I think that would work best for me. I could flip it over and locate off of the opposite hole.

Troup said:

If you are using a boring head, I'd leave the clamping block intact until the bore details were complete.

Click to expand...

I have the boring head so that is the way I will machine them.

Thank you guys for all of the help. I have an 8 inch rotary table and a boring head so I should have what I need to get the job one. My thoughts were to true up the block, bore for the stub axle and bearings, then use the rotary table to mill the outside of the knuckles. From what I have read, I am on the right track hopefully. I am going to give it a shot here in the next week or so. Thanks again for all of the input.
Steve

My first inclination would be to do most of the work (main bore and stub axles) in a 4-jaw on the lathe.

Starting with a trued up rectangular block.
Blue up and layout all centers, diameters and radii on the surface plate.
Carefully punch all centers.
On the mill, drill all small holes through.
Small center holes for the main bore.
Using a pump center or long thin pointed drill rod in tailstock chuck and indicator center up one of the stub axle centers.
Turn stub axle.
Loosen only two jaws.
Flip part and check center of second stub axle as above.
Turn stub axle.
Flip part and center up main axle bore as above.
Bore.
Turn OD to level of stub axle bosses.
Pull partially finished part and turn a mandrel that will fit the main axle bore closely.
Mount mandrel and center in rotab.
Center rotab under spindle of mill.
Mount part (back side up) on mandrel and secure with SHCS and washer. Make sure it is TIGHT.
Use a milling cutter of correct radius for fillets.
Using one axis move rotab such that cutter will cut the correct OD.
Cut away exess from OD.
Cut away excess from steering arm using table axes.
(or something like that)

Lots of different ways to do it... thought of three others while writing the above. I just prefer to do round features on the lathe as much as possible.

-DU-