# Backlapping and Bedknife Adjustment



## ahartzell (May 18, 2017)

In some of my previous posts, I had been noticing the yard quality slipping. After scalp and sanding, it was looking great. Lush, dark green...but it seems as though it has gotten a little thinner, lighter green, uneven, and some scalping going on (despite not changing the HOC).

I cut the lawn monday and when I looked at the grass wednesday, the tips were brown and frayed. I decided to backlap the reel and adjust bed knife. The manual isn't really great on adjusting bed knife if it isn't already pretty close (i.e. what if bed knife is 20 clicks off on one side?). So I loosened it about 10-12 clicks on both sides resulting in no contact and a free spinning reel. I then retightened each a click or two until I had slight contact.

Next, I applied ************ compound, removed side cover, and........realized I didn't have the correct tools to backlap with a drill. So I ended up doing it manually the best I could.

After I finished ************ and cleaning the compound off, I did the paper test. It was like a hot knife through butter. Before the paper test was ok - it would cut the paper pretty clean but it took some reel momentum and was hit and miss.

I'm not sure if it was a reel sharpening issue, a bed knife issue, or both. I say this because I loosened the bed knife 10-12 clicks but when I retightened it I only had to click 5-6 times to get light contact...thinking maybe it was too close and ripping the grass?

Either way, I cut today and while it still looks a little off (due to not putting down PGR, behind on frequency, etc.) the actual quality of cut is a lot better.


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## Redtenchu (Jan 28, 2017)

If the reel to bedknife is too tight there will be stress on the bearings, belts, chains, sprockets, reel and bedknife. The reel and bedknife would've taken the most damage/wear from this. A new bedknife and some proper backlapping can make a big difference. Can you post some pictures of the bedknife?


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## ahartzell (May 18, 2017)

Redtenchu said:


> If the reel to bedknife is too tight there will be stress on the bearings, belts, chains, sprockets, reel and bedknife. The reel and bedknife would've taken the most damage/wear from this. A new bedknife and some proper backlapping can make a big difference. Can you post some pictures of the bedknife?


 Will when I get a chance. I'm sure the bed knife is in need of replacement. Looks like the edges are "thicker" than the middle (aka worn down in middle from being too tight). For now it's decent...but I definitely backed off 8-10 clicks and only needed 4-6 to get it in light contact


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## ahartzell (May 18, 2017)

Redtenchu said:


> If the reel to bedknife is too tight there will be stress on the bearings, belts, chains, sprockets, reel and bedknife. The reel and bedknife would've taken the most damage/wear from this. A new bedknife and some proper backlapping can make a big difference. Can you post some pictures of the bedknife?


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## Redtenchu (Jan 28, 2017)

Bedknife looks to be worn on the left (operator position). You should face the bedknife and backlap again. Make sure all future adjustments are made from the reels leading edge (right side).

I'd recommend replacing the bedknife before next spring. uneven wear of the Bedknife could lead to coning of the reel.

Here is a simple way to face the bedknife without any expensive tools. Just a file.

https://youtu.be/-oGAwe_g_PY


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## ahartzell (May 18, 2017)

Redtenchu said:


> Bedknife looks to be worn on the left (operator position). You should face the bedknife and backlap again. Make sure all future adjustments are made from the reels leading edge (right side).
> 
> I'd recommend replacing the bedknife before next spring. uneven wear of the Bedknife could lead to coning of the reel.
> 
> Here is a simple way to face the bedknife without any expensive tools. Just a file.


So is this a good/correct order?
(1) Back off reel from bedknife
(2) Face the bed knife
(3) Re-engage reel to bedknife starting at leading edge
(4) Backlap reel
(5) Paper test
(6) Adjust HOC

My only issue is if I adjust bedknife clearance (steps 1-3) how do I know it's even? Like I can adjust leading edge until light contact but hard to tell when other side is even.

Also it's frustrating that dealer told me it was backlapped and that bedknife had >50% life left :x


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## Ware (Jan 28, 2017)

ahartzell said:


> ...Also it's frustrating that dealer told me it was backlapped and that bedknife had >50% life left :x


Ever talk to a used car salesman? :lol:


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## Redtenchu (Jan 28, 2017)

Making small adjustments is the key. When moving the bedknife away from the reel, only use 3-4 "clicks" on each alternating side until the contact is gone. Face the Bedknife. Then use 2-3 clicks on the leading edge, then the trailing edge and rotate the reeel to check for contact, repeat. When you first hear contact, use a piece of paper to gauge each side. You want the same resistance (pinch) on each side.

_Example: If the leading edge is jamming or cutting with the paper between the bedknife and reel, but the trailing edge is only folding the paper over, you need to move the trailing edge 2 clicks in. _

Once you get a good even feeling using paper with and maybe a little cutting in some spots, tighten the reel to bedknife 2 more clicks on each side and backlap. Check the clearance again after cleaning the compound off and adjust back off if needed.


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## Pete1313 (May 3, 2017)

Great advice Red! :thumbsup:

I use a .002" feeler gauge instead of paper to check clearance. I get it where both sides are .002" and then go 2 clicks tighter on both ends(each click on a JD QA5 head is .0005") to get light contact(~.001" clearance) and then check to see if it cuts paper.

Question on facing the knife. I have been facing after I backlap, and notice you recommend facing before backlapping. Is before preferred over after?


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## Ware (Jan 28, 2017)

Pete1313 said:


> Great advice Red! :thumbsup:
> 
> I use a .002" feeler gauge instead of paper to check clearance. I get it where both sides are .002" and then go 2 clicks tighter on both ends(each click on a JD QA5 head is .0005") to get light contact(~.001" clearance) and then check to see if it cuts paper.
> 
> Question on facing the knife. I have been facing after I backlap, and notice you recommend facing before backlapping. Is before preferred over after?


Great advice on using the .002" feeler and then making two .0005" clicks. I think most feeler sets only go down to about .0015".

I bought a package of these just for giggles once, but usually just adjust down until I pinch a strip of paper.

On the facing, I've done it both ways, but I assume the thought is if facing created any burs along the edge of the bedknife, backlapping would remove them.


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## Spammage (Apr 30, 2017)

Ware said:


> On the facing, I've done it both ways, but I assume the thought is if facing created any burs along the edge of the bedknife, backlapping would remove them.


+1 -- I've noticed that if you face after then you will have contact and dull the surfaces quicker than if you backlap after facing.


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## Redtenchu (Jan 28, 2017)

I see what you guys mean and in normal maintenance I also lightly face my bedknife after backlapping (not before) to remove metal burrs. I felt the bedknife pictured above was in poor shape and really needs extra work. I should've added a step to lightly face the bedknife again after backlapping.


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## Pete1313 (May 3, 2017)

Good points made. I have been facing after and like Red mentioned, it was lightly to keep the edge and remove any burr. It is more to keep the edge then try and restore it in my situation. So little material is removed. I might still switch to before backlapping though, as that argument makes sense also.

For those that face their knives, how often are you guys facing? Small touch up every backlap? Every other backlap?


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## dfw_pilot (Jan 28, 2017)

I suppose I face my bedknife each time I look at it?


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## Spammage (Apr 30, 2017)

dfw_pilot said:


> I suppose I face my bedknife each time I look at it?


 :lol: With my zoysia, I will hit the face lightly every couple cuts and give a more thorough facing along with backlapping about once a month.


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