Thursday, September 16, 2010

There Really Should Be Something Between a Vertical Mill & A Chop Saw

What I mean, is something that does coarse cutting--but not as coarse as a chop saw. 

I started to switch over a few months ago from making the ScopeRoller assemblies entirely of acetal, to using aluminum tubing, with an acetal insert threaded to accept the caster.  Part of the manufacturing process that I use for making the acetal insert involves cutting diagonal slices off of a piece of acetal rod.  This is fine as long as you have six or seven inches or more of acetal rod to hang on to--but when you get down to the last three or four inches--you really don't want your fingers that close to the blade! 

I've come up with several fixtures for holding pieces that are already machined, and have threaded holes in them because of that, in position on the chop saw.  But what to do about a small piece that is not already machined?  Round stuff isn't real easy to clamp in place, especially when it is so short.  It would be really nice if there was a way to do roughly what a vertical mill does--but fast, and maybe not so accurate.  Something measured in tenths of an inch accuracy, instead of thousandths--but without power to make big cuts.

I have a band saw, but I confess that I seem to break blades a bit too often to feel confident in it.  If the blade is taut enough to not be waving all over the workpiece, kaching!  Broken blade.

12 comments:

Epsilon Given said...

A piece of advice from someone who has read a couple of books on machining, and who has taken an introductory class (so take my advice for what it's worth :-) would be to make some sort of tool that would extend the pipe, and allow it to be held in place. I'm currently imagining some sort of clamp specially machined for the right diameter of the pipe.

Of course, this is probably easier said than done, and you may have even tried a solution or two, and have already found it impractical.

Even so, one of the things that fascinates me about machining is the "cultural" aspect of "if you need a tool, machine it". It made me realize that the thing that sets humans apart from other animals that use tools is that we'll make tools to make tools...as opposed to picking up a rock to open shellfish, or grab a stick to pick up ants.

Kirk Parker said...

"Round stuff isn't real easy to clamp in place"

I assume some kind of collet is infeasible/too expensive?

Rorschach said...

Band saw is the tool you are looking for. If the blade is wavering too much, you need to look at the blade guides and make sure they are set properly. You also should be looking at the quality of the blade you are buying. Cheap quality blades or saws could be your problem, or it could be poor adjustment. A properly set up and running bandsaw is very accurate.

Alchemyst said...

Good points above. You need a jig. Bore a hole into a piece of Al so that your acetal is a slip fit, slice the Al in half and voila a jig that can be easily clamped in a vise. If necessary mill the end of the jig to the angle you're cutting and you can also drill through the sides for alignment pins. Finally, sounds as if you need either a better band saw (I don't mean super expensive either)or you need to spend some time setting yours up properly. Cutting plastic is easy - you should hardly ever break a blade.

Mauser said...

Is that a power hacksaw/metal-cutting bandsaw?

The clamping jig sounds like a good idea anyway.

Clayton Cramer said...

It is actually a woodworking bandsaw. I switched to a fairly large blade (measured front to rear, not width)--and it seemed to have more problems with cutting plastic without deviation than the smaller blade. I went back to the smaller blade, because that's all I had, and it seems to work much better.

Clayton Cramer said...

Good suggestions all. Something that is an obstacle is that I am basically using up the existing inventory of wheels to fill orders, and when those are done...it's over. I don't want the suit risk, and I don't have the time. I confess that the whole suit thing has really depressed me.

Mauser said...

I really think you should get over this lawsuit gunshyness. At least for the ScopeRoller. You run more risk in being sued over a traffic accident.

Epsilon Given said...

I have to agree with Mauser, for his reasoning, and for a second one: if we all stopped doing any work that is potentially prone to lawsuits, nothing will get done!

Although, if you do limit your reasons to "I don't have the time", that's a perfectly valid reason in and of itself; don't be afraid, though, to start things up again, if you get some time later on.

Clayton Cramer said...

If I get sued for a traffic accident, I have an insurance company that will defend me and resolve the problem. (Well, I suppose if I had an accident that caused a nuclear weapon to be set off, it might exceed my liability limits.) The problem is that I can't figure out what clever suit will get filed against me for ScopeRoller.

It might not even be clever--it could even be very stupid, and I would still need to spend thousands of dollars to make it go away. If I were making piles of money at ScopeRoller, it would be worth taking some risk. But this isn't that spectacularly profitable that it justifies the risk. As lawyers get more desperate for income, more of these suits are going to happen.

Mauser said...

I think, however, that you are far overestimating the risk.

But if you're really worried, look into a rider on your homeowner's insurance for home business liability.

Or include some product disclaimer with the scoperoller.

Clayton Cramer said...

I repeat: I am not worried about the product liability. The most that is likely to happen is a failure of a unit causes a telescope and mount to fall over. That might be (for the some of the high end units) a few thousand dollars, unlikely to happen, and unlikely that it would lead to a lawsuit.

What concerns me is something completely out of left field--a lawsuit that would be completely bogus--but so expensive to defend that it would destroy all my profits, and then some. I suppose that I could look for some sort of general business liability coverage. Homeowners covers libel, defamation, slander, workmen injured on the job, that sort of thing, but not a general liability, and not copyright infringement, as I discovered when this silly suit appeared.