Ok, I am now an architecture student with some industrial design and model making training. A while back there was some talk about new Miyata handles being built out of “Ultra High Molecular Weight (UHMW) polyethylene” now available through unicycle.com. I have been drawing plans for a new trials specific air saddle and am looking to go into production of a working prototype. To be short about it, I am looking for the e-mail address of the person/any person who is familiar with such materials as this UHMW polyethylene or any possible better materials I may use to build this prototype. Beyond such contact information I feel it is best to keep this thread private.
It is quite any easy thing to google and there a re lots of suppliers.
Without knowing what your application is it is hard to say if this is the best material.
- It is easy to machine. Good for low volume production
- Good abrasion resistance
- Low UV resistance. Not ideal for outdoor applications
You might want to look at Nylon too. It is used in similar applications to polyethelene. There is a vast range depending on what qualities you want.
Not wishing to dampen your spirits but I doubt you will ever get rich out of unicycle products so you might not need all the cloak and dagger. Keeping any unique features out of the public domain will allow you patent tham but I doubt this would be cost effective.
The google search has been done. Hotbot actualy, to set in my ways to try these new fangaled things like google. The results were 100% science labs and reasurch facilitys displaying unltra technical specs and whatnot on the material. I know of a supplyer of commercial plastics in the boston area, I will make a call to them soon and see if they carry the stuff or could get it, but I wanted to reasurch it first.
My main concern is: I’m doing this by hand, my school can’t afford/has no need for a full machine shop. The model shop is limited to a band saw, drill press, half a dozen different sanders, and I have a dremel tool equipt with a snake, a heat gun, and several hand tools. I’ve worked in cintra (sintra?). A plastic used mainly for building models, it is not terribly structrualy strong but is very easy to work with. For this application, I want very strong, as little flex as possible, and the easy of construction can be waived. So long as its possible.
my questions: Is it physicaly possible to work with the stuff by hand, sanders, saws drills etc.
and, will the stuff heat bend. Will it be possible to construct it out of a roughly 1.5" sheet, then by heating with one or more heat guns, bend the material to the desired curve? The parts I antisipate bending will be rounghly 3/4" thick.
My hopes arnt shattered. I may try to have it produced and sold somewhere, but I’m not gonna try too hard, and if I do, it will be for personal pride and accomplishment and ask for very little of what is made from it. I’m 19, my daddy pays for my schooling and my life in school, I’m not looking to get ritch quick. Mainly I see a flaw in the products available so I’m out to build myself something better. My current saddle is almost compleatly homemade also, from a semcycle seat frame. It’s just the way I do things.
I love the ultimate wheel by the way.
You should be able to work it with hand tools. It will drill and saw fairly easily. It should sand pretty well too. The biggest problem is if you try and over-do it with the power tools (Especially sanding) then it will start to melt. This will result in a poor surface finish.
If you take it slowly and work different areas so you don’t let one part get too hot you should be fine.
It will start to get flexible at a fairly cool temperature (100 deg C ish, get the specs off the 'net) so you might get some result with a heat gun although it will be very hard to get good results (It might take several goes). You could try putting a lump in an oven until it softens. It will be too hot to hold so forming it could be difficult. Maybe you could make a wooden form. The thicker the lump the harder it will be to get the shape you want. Again, you will want to heat it slowly so you don’t get hot-spots.
Go to www.mcmaster.com and search for “uhmw”. They have a very complete selection of the various forms UHMW is available in and what it costs. They also have some technical sheets that are available on-line.
I’ve been buying UHMW by the pallet load lately. It’s used extensively in the food equipment business because it’s inexpensive, tough and USDA compliant for direct food contact (ideal for unicycle parts eh?). I’ve seen cases when stainless steel and UHMW are rubbing, the UHMW will wear out the stainless.
I wouldn’t say that it’s easy to work with though. You can drill and saw pretty well but sanding it is tough. Cutting it on machine tools such as a lathe or milling machine requires a dead sharp tool to get a good finish. Sanding or filing seems to just create a very rough and hairy surface. I’ve never had any reason to heat and bend UHMW so I can’t say how well that would work.
Awsome. The McMaster site is better then anything I could have hoped for, I was expecting to have to buy it localy in 4x8’ sheets for 200$ plus. At 20$/sheet, thats cheap enough, and it seems promising enough that I’ll take my chances with the sanding and the heating. I think if a controled enough procedure is used I should be able to bend it smoothly enough. Thanks everybody very much. I’ll keep checking in for more posts, and I’ll check in to tell everybody how it goes.
Ok, I have very little understanding of what exactly machining is, except that I understand what it does. So, I was looking through the McMaster.com site, found a section on milling cutters, which claim to be used to cut metal. About what I was expecting. So, I did a search for “milling machines” what came up looked very much like the large drill press in my schools model shop, but with a nifty stand. will a large drill press really take the type of forces involved in cutting rather then drilling. Is this what people commonly use for this type of project? Are all large drill presses also known as milling machines, if not is it possible that mine is? Should I go out and buy some sort of bit and just use the press??
what confuses me is, I had always assumed that machining involved some level of computerized/automated prosses taking out the sence of the human touch/error.
A milling machine is similar to a drill press but different in very important ways. First of all, consider the three dimensional axis system: say you are sitting at a desk holding a pencil perfectly vertical with the tip of the pencil pointing down and several inches away from a piece of paper taped to the top of the desk. If you want to draw a straight line left to right you would first move the pencil down to where the tip touches the paper. This would be a Z axis move. Then, while you are holding the pencil perfectly still but pressed against the paper, a couple of friends slide the desk from left to right drawing a line on the paper in the process. That would be an X axis move. Moving the desk toward or away from you is a Y axis move.
That’s basically how a milling machine works. The part that is to be machined is fixed to a table that can move horizontally in both the X and Y directions while the spindle that holds the cutting tool can move in the Z direction.
Now consider a drill press. It’s designed for one purpose and that’s to move a drill bit in the Z axis only. There’s no mechanism that will allow a controlled movement of the work piece or the drill bit in the X or Y axiis. Additionally, by design a drill press can’t handle the side loads that are generated with X and/or Y axis moves.
A drill bit is designed to cut only on the tip. The tip of a drill bit is tapered to make it more self centering. A cutting tool on the other hand - or “end mill” as they are commonly called - can cut not only on the end but also from the side. An important difference is that the end of an end mill is usually flat making it not ideal for drilling holes. The flat end won’t self center and would rather wander thus producing a larger and/or not round hole.
Now, having just said all that, here’s how you CAN use a drill press for milling! A drill press spindle will stand some side loading - just not much or alot of it. You can “chuck up” an end mill in the drill press chuck. But what about the X axis and Y axis moves? Go to the McMaster site again and search for “cross slide table”. A cross slide table is a two piece contraption where the lower part can be fixed to a rigid base (a drill press table for instance) and the upper part can be moved in the X and Y axiis by means of “lead screws” with handles on the ends of the screws. There’s a handle for the X axis and another for the Y axis. The handles have graduation marks usually in .001". Turning a handle moves the upper part of the cross slide table by however many graduation marks (or .001") you want. Which handle you turn determines whether it’s an X move or a Y move.
As an aside - McMaster Carr certainly isn’t the only place to find this kind of stuff. I wouldn’t be surprised if there aren’t several cross slide tables for sale on ebay at any given time. Another source is www.grizzly.com. Go there and search for “slide table”. They have inexpensive Chinese machine tools that are adequate. Another source is www.harborfreight.com. Search for “cross slide” and you’ll see a selection of inexpensive cross slide vices that might work well for small projects.
I’ve seen drill presses set-up like this. A gun smith I know has a drill press with a cross slide table. He added an external bronze bushing that runs on the drill press chuck to take care of the side loads. He’s used it for years that way but only on small gun parts.
The milling machine you saw on the McMaster Carr site is called a mill/drill. It’s a heavy duty drill press with large bearings in the spindle to handle the side loads generated by X and Y axis moves. It also has a cross slide table built in to the base. I’ve owned one and it worked fine. After getting involved in a “real” machine shop I sold it to another gun smith.
Yikes! Computerized machine tools are only now becoming main stream. They have been around for many years but only in the last 10 years or so have they been inexpensive enough for little shops to afford. I was born and raised in a machine shop completely devoid of any kind of automated equipment. In fact the mills and lathes were so profoundly worn out that SERIOUS human touch and skill were required to produce a decent part.
Hope this helps …
(longwinded) Steve Howard
Wow. That was exactly the type of responce I was praying for, but deffenetly did not expect to get. Thank you very much.
I’ve checked it out a little. ebay has nothing this week. it looks like I can get a vice based one for like 50$ which is within my price range. Is it nessisary? are there forces which make control difficult enoug that such a thing would be nessisary, even with the polyetheline stuff rather then metal? anything I should know about the end mills? types that would be better for plastics?
I have used my drill press to machine machine plastic parts. I have a drill vise with x and y feed screws bolted to the table, and use wood router bits with the spindle speed set as high as it will go (about 5000 rpm) would love to have a computerized milling machine, that will provably never happen though.