Kevin Olson

Here's where I bought the Pin High back-lapping grit I've been using:
https://shop.jescoproducts.com/pinhigh-lapping-for-homeowners/1-lb-220-grit-pinhigh/


Jesco manufactures lapidary compounds, also, but Pin High is their gel-carrier back-lapping compound brand, in several grain sizes.

As I'm writing this, they do not show a price for the 1 lb tubs ("call for price"), but the 5 lb tubs are $28.50 (USD).  I seem to recall it was 7 or 8 USD each for the 120 and 220 grit  tubs I bought from the a few years ago, plus some nominal shipping charge.

California Trimmer, a manufacturer of powered walk-behind self-propelled reel mowers - including an electric model -  also sells 1 lb tubs of 80 grit:
https://caltrimmer.com/products/h0906f-backlapping-compound-jar-80g-all-models

 
 

That is a steep price - about the same as the 5 lb tub from Pin High (Jesco).  But, a little goes a long way, in my experience, so it might be another viable source.

R Scott wrote:The old order Amish near my old house used reel mowers, they had a guy that specialized in sharpening and repair. He had jig/machine that would keep the angle right and grinder even to get it true.

No Amish are close to me (more's the pity - I might be able to learn a thing or two about timber framing by helping on a project).  We do have a community of Mennonites not too far from here, but they are of a fairly modernized sort, and fully mechanized - probably less likely to be using reel mowers (but I am, so who knows).  Maybe not as quite modernized as is my Mennonite sister (who has an M Div., worked for Duke's Theology department and was a Mennonite pastor), but fairly much technologically modern, smart phones and all; I think I still have one of the guy's cell numbers in my phone, from when they helped clean up after a flood, a few years ago.  I guess I could check with them.  If nothing else they may know who does have the gear to grind a reel true.

Jeremy VanGelder wrote:Valve grinding grit, you say? I've never sharpened my reel mower because I didn't want to buy compounds just for that purpose. But I think we have some valve-grinding grit around. Thanks for the tip!

Yeah, it's basically the same thing - silicon carbide grit, per the Pin High Safety Data Sheet.  Clover compound (a brand name, for those unacquainted) is in some sort of grease carrier.  That might work, too, but seems messier.   I don't know what the carrier gel in this Pin High stuff is; the safety sheet wasn't very specific, but I'd guess some sort of vegetable gum or starch, maybe psilium or guar or xanthan gum.

That being said, I haven't actually tried loose grit, just the Pin High stuff.

Rather than clutter up this thread with the blow-by-blow of my back-lapping procedure, I made a new thread describing my process, here:
https://permies.com/t/373628/lapping-sharpening-fashioned-reel-mower#3777003

Anyway, that's how I keep an old reel mower cutting sweetly.

I haven't messed with any "modern" mowers, so I don't know how applicable this might be to something that's a mere 50 years old!  However, I am happy to try to answer any questions you may have.

I mowed until about 10:20PM, after which it was getting too dusky to see what I was doing (we're getting on toward the solstice, so the evening light lasts fairly long, though not like truly high latitudes).  After I hung out a load of wash this morning I took a photo of the results.  Not too bad, though I missed a few blades here and there.  This is a "mixed pasture" lawn - various grasses, clover, yarrow and the ubiquitous dandelions.

Now, flip the mower over, so that the wheels are still on the ground, but the gauge roller is up the air.  Push the mower around "a bunch".  I push it on the street, up and down my short town block - probably 500-600 feet, or a couple of hundred meters.  It should be difficult to push at first, but not impossible, but become progressively easier.  The sound will change, too.  I don't have a good photo of the pushing part of the operation.

Then, you can wash or wipe off the grit, and return the reel drive to the correct direction by removing the wheels, flipping the ratchet pawls back over, and putting the pinions back on the proper sides.  A dab of grease on the gear teeth - I like the black moly stuff, but use what you have, some being better than none - before you bolt the wheels back on is a good idea.

Unfortunately, I managed to snap the "ears" off not one but two of the bed knife adjuster screws in the process, so I'll need to either cut new straight blade drive slots with a Dremel cutoff wheel or hacksaw blade, or replace them with (extra fine pitch) new screws (still TBD).

Now apply the lapping grit to the edges of the reel and to the bed knife.  I bought two small tubs - 120 grit and 220 grit - from Pin High, a golf course supply company.  I don't think I've ever needed to use the 120 grit stuff, though.  Basically, this is silicon carbide valve grinding grit in a water-based gel carrier.  I apply it with a cheap chip brush.

So, put the whole mess back together, and snug up the square nuts on the carriage bolts.

You'll also need to adjust the bed knife so that it contacts the reel firmly, but not too firmly, since you want the reel to be able to still rotate.  You'll get the hang of it once you overshoot too much one way or the other a couple of times.  My bed knife adjustment has a pair of opposed set screws on either end, which rock the bed knife on a pivot.  Slack one off a fraction of a turn and snug the other to adjust the clearance of the knife relative to the reel.

Here's what the pawls on my machine look like (grimy fingers and all!).