Odd clamping jig/workholder

This seems to be a post in need of a question, "why?". Takes me about

Stan

Ditto. Not only would a mill -- if you could use it properly -- be way more precision than is ever necessary to whack a grass stem in two, but if the blade is decently hardened at all you'd have to use some fancy extra-hard cutter and hold the work a lot closer to the cut than you're proposing.

Ignoring the more important issue (why???), are those turbulence slots wide enough to get a bolt through, to use for clamping? 6" of overhang is going to guarantee chatter -- possibly deathly to the milling tool -- regardless of the rigidity of the thing that's holding your springy piece of metal that far from where the cut is being attempted.

How about casting a zinc or lead (or solder!) bed for the blade, and clamping to that? Cast it over the back side of the blade, using a suitable method* to keep it from sticking, then mill its bottom side to the angle you want. Then use some sort of "reach over and push hard" clamp to hold the work.

You definitely want something that snubs the metal up tight to the working surface of the blade, or the darn thing will vibrate like a reed.

• Note that I don't know the best way to do this -- really wanting it to stick generally works quite effectively when I'm soldering, but that's hard to apply here.

I've made aluminum blocks with vee slots, and tapped in wedges, to clamp flat items in similar situations. If you can find a good flat surface on a mower blade, that'll work.

Otherwise, bore a couple of holes in inconspicuous places, and bolt the blade down to a block that's easy to clamp down (or hold in a vise). You'll want to whittle the block to get the angles just right. Don't use weak bolts.

Sorry, that doesn't make good sense. A quick grind with an angle grinder or a belt sander it a more appropriate fix. When I HAD grass, I alternated between two blades, I bought the spare on sale for $5.00. Now I just have flowers and river rock. I am planting a 8'x10' patch of grass for the little doggy to ruin, I'll just weed-whack it.

For that size, you could use scissors and a ruler.

Tim Wescott fired this volley in news:5bSdnS9GLcni_GDWnZ2dnUVZ snipped-for-privacy@web-ster.com:

To both of you. These are high tip speed blades for a commercial mower. The manufacturer _recommends_ milling them instead of grinding, and offers suggestions for cutter inserts -- which I have. The tool and the mill are already in my shop. I just need a way to hold the blades.

(and if you've ever looked, all commercial blades are milled, not ground)

LLoyd

"Buerste" fired this volley in news:htjou7$pha$ snipped-for-privacy@speranza.aioe.org:

Read my reply to the same above. The manufacturer recommends milling. I mow 6 acres of Bahaia a week. That's a set to sharpen every week.

LLoyd

Two angle vises with spacers for the irregular surfaces?

"Denis G." fired this volley in news: snipped-for-privacy@z17g2000vbd.googlegroups.com:

Now, that's a good idea. Cut away part of one to make room for the fins.

LLoyd

If that's the case then my suggestion to make a fixture specific to the blade is all the more sensible. Keep it on a nail on the wall behind the mill, and every week you can take it down and get the job done in quickly and efficiently.

Only you probably want to use something more wear-resistant than lead or zinc -- I was thinking you wanted this for a one-time deal; I hadn't imagined that there were mower blades that demanded being milled instead of ground free hand.

How big an angle plate do you have?

Gunner

Well, that changes everything! Tear out the grass and plant Pot.

Well, I have a 21" commercial Honda mower, and yes the blade edges were milled, but I clamp them with a bench vice and sharpen them with a BIG mill file. The file has no problem cutting the blade metal, which is quite soft, so the blades won't shatter when they hit a rock. Anyway, I would make a fixture out of a hardwood like Oak (for the damping) with metal clamps of some kind, and use an ordinary HSS cutter.

Joe Gwinn

Joseph Gwinn fired this volley in news: snipped-for-privacy@news.giganews.com:

The wood jig is a good idea for its vibration damping characteristics. Total rigidity isn't a really big deal, since finish isn't terribly important; just angle and balance. One thing they state as important as that there be no "camber" in the angle. It needs to be flat. Apparently (from other searches I've done) mower manufacturers work quite hard to optimize their blade edges for angle and lift.

But the HSS isn't the recommended MOSN PVD inserts recommended for this particular alloy. And I have them already...

LLoyd

I want to put mine on my surface grinder.

A mill - the blade is to hard for milling.

Sure someone can do it with the right horse power and process. Quarts rock/sand is what rounds them over. Quarts is harder than steel.

A mill should have sine bars and sine bar type wedges of all sorts of degrees.

Martin

Mart> I've got a tough-dog clamping job to do.

"Martin H. Eastburn" fired this volley in news:tekLn.141224$ snipped-for-privacy@en-nntp-16.dc.easynews.com:

Horse s*it, Martin. Lawnmower blades are deliberately made on the soft- temper side to prevent them from shattering upon hitting hard objects.

I don't get it: A whole bunch of "metal" guys telling me that a tool designed to hit concrete at 270MPH without breaking is also too hard to cut with ordinary milling bits...

Of all the crap (I _mean_ crap) I've gotten from this post, there have only been two constructive posts; both from guys who seldom post, but who obviously read before they do.

The rest of the "experts" have decided that 1) the manufacturers of mower blades don't know what they're doing, and 2) tools don't exist to mill medium temper carbon steel.

I guess it give me a perspective on the guys who respond vs. the guys who actually do metalwork.

LLoyd

I wonder how critical it really is, so long as both ends of the blade are the same, so the blade remains aerodynamically and kinetically balanced.

Which alloy is that? I expect that the Honda blades are 1018 or the like, judging from the feel while filing.

But I'm sure your inserts will work just fine.

Joe Gwinn

Lift wing turbulence slots are often a nuisance, aren't they!