For those that remember, the D15 I'm running was a barn find from across the road. Sat there for 20 years before I took it on. Less known was it was also hooked to a JD 450 pull type sickle bar mower for all those years too. Now have that out and am attempting to revive it too. I have some experience with that type of mower as I ran one mowing hay with them when I was a kid. 

Anyway, fixed both flat tires, greased it up, hooked it up to the D15 and gave it a whirl. It actually worked. Condition of sickle (they call it a knife) is marginal. Needs to be sharpened at minimum, but also concluded it needed all new guards, some of which bent pretty far from hitting something. Looked like maybe half might have been the originals, then 3 or 4 other miss matched brands. They all have two things in common.......flat worn out and sickle sections rested on the ledgers as they are supposed to. 

Turns out the ledgers can all be replaced, and started with that plan, except you can't buy those and if you could, cost as much as new guards. Aftermarket guards show up in parts books, but iffy supply and if you could find them almost as much as actual JD, so JD it was. Ordered 33 of them and not cheap. Have now put them on and all of them also have two things in common.......they are all new and none of them fit right. There is a gap of as much as 3/16 of an inch between guard ledger and sickle sections and those two have to touch to work right. I see no way to adjust these to fit. 

Anybody familiar with these at all?

Old guard that fits perfect.

New correct guard that doesn't fit at all.........

Those guards are made of malleable iron and can be bent to close the gap to the section.  There is a special tool that you use for that ; works sort of like a special anvil,  and once it is placed properly you hit the section with a hammer to bend it.

https://www.google.com/search?client=firefox-b-d&q=adjusting+sickle+mower+guards+to+align+them#fpstate=ive&vld=cid:32c8a956,vid:fKu0B8ZhczE,st:0" rel="nofollow - https://www.google.com/search?client=firefox-b-d&q=adjusting+sickle+mower+guards+to+align+them#fpstate=ive&vld=cid:32c8a956,vid:fKu0B8ZhczE,st:0

Was looking at the wear plates and hold downs and likely all would benefit from replacement. But something else is wrong with those guards. They bolt up at an entirely different angle. And they are made heavy enough there is not bending of them. Not like the New Holland guards shown in the video (which btw was one of most informative and annoying videos ever. More google ads imbedded than video content). 

And this sickle knife uses rivets. Not enough room under the hold downs for the bolt on sections to pass under. I have the special V shaped grinder wheel used to grind these. No need to replace them all the time. The underserrated sections can be sharpened many times. Do not have the rivets however. I asked JD and don't think they had them either. 

And do have a copy of owner's manual and parts book. Parts number for the guards is right. Both in the book and on the guards. 

I found that All States Ag Parts has a guard that fits JD 350 and replaces same parts number. Have one ordered to see if they are a match for new or old. 

For most mowing tasks, these days there are better options. Disc mowers, brush hogs, etc. For hay, even the old but related New Holland Haybine is better. But for some things......they do come in handy. 

  Yes, you can replace the bolt in sections without removing the knife, but if you have everything in good working order the biggest problem of pulling a knife is to be sure all your fingers are not in the way.