Jointer knife-setting jig (and a question...)

[bkhop]

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[drewa]

First thing, Check your outfeed jounter bed. It should only be .002-3 below the blades. That is what Jim McCann and Nick have said in the past. That is where I would check first.

We'll keep checking in as you troubleshot this problem.

Drew

[bkhop]

.............

[dusty]

In conjunction with the new jig, you might want to read through this thread. It contains a number of different viewpoints regarding the proper height of the outfeed table with respect to the blades.

There is a lot of discussion here. Some of it is not applicable because of your new/improved fixture but some of it (regarding blade height) is. Hope this helps.

Once again, I learned the old ways and have honed my skills to a personally acceptable level and I AM NOT GOING TO CHANGE. The "olde dog" syndrome applies here.

http://www.shopsmith.net/forums/showthr ... ht=outfeed

[Ed in Tampa]

I'm reluctant to say anything here since I was deeply involved in the other thread. My way of setting jointer knifes is to use the commercial jig called Magna Set.

It is two bars of steel with three magnets inset in each bar, the bars are connected by two steel rods that allow one of the bars to slide closer or further away from the other.

To use the jig you place the bars on the Jointer and with one set of jointer knifes at the highest point scribe a slight line on the jointer bed even with an existing mark on the jig.

Now remove the knifes and sharpen or change them but once you insert them you again line up the scribed mark with the mark on the jig and tighten the gibs down locking the blades in place.

After doing this I was taught to hand crank the blades backward while holding a honing block flat on the table if the blades were equally polished I was done. If not I tweaked the outfeed table (on adj outfeed table machines) until the blades were equally polished. We then made a test cut checking for any grooves, snipe or anything that would cause a less than perfect cut. We then rechecked the fence and began using the jointer.

I have since bought a homeowner version of the Magna set (I believe from Shopsmith) for $45. While I haven't used it (yet) it looks like the commercial one I was trained on. I checked both bar and as best I can tell they are ground perfectly flat and when pushed together they are in the same plane there is no offset I can see.
Ed

[Bruce]

I also constructed the jig from the sawdust session and have had the same problem with snipe. So after setting the knives with the jig, I double-checked them with the straightedge like PTWWFE describes. The knives did not even contact the straightedge. I don't know if I built the jig wrong or what. I do have a question for all who made the jig. How did you get the hole drilled for the 4 1/2 inch bolt? I used the horizontal boring position and couldn't get the entry and exit holes to come out at the same relative position. Does the drill press do a more accurate job?

[dusty]

Ed in Tampa,

Is this the Magna-Set that you have? If it is, when you have used it successfully would you please post details of your efforts. I have recently discovered that I have one. I found it amongst my horde of things I couldn't do without, still wrapped in its original cellophane wrapper. So far, it hasn't helped improve alignment. Documentation that came with it promises successful adjustment in just minutes.

http://www.woodcraft.com/family.aspx?FamilyID=908

Earlier in this thread, there was some discussion about height of the outfeed table with respect to cutter blade. Use of the Magna-Set would imply that the blades should be the same height as the outfeed table (+/- .002"). This seems consistent with what others have reported.

[charlese]

...Once again, I learned the old ways and have honed my skills to a personally acceptable level and I AM NOT GOING TO CHANGE. The "olde dog" syndrome applies here.

Does your new find mean you are in fact going to change?

[Ed in Tampa]

Ed in Tampa,

Is this the Magna-Set that you have? If it is, when you have used it successfully would you please post details of your efforts. I have recently discovered that I have one. I found it amongst my horde of things I couldn't do without, still wrapped in its original cellophane wrapper. So far, it hasn't helped improve alignment. Documentation that came with it promises successful adjustment in just minutes.

http://www.woodcraft.com/family.aspx?FamilyID=908

Earlier in this thread, there was some discussion about height of the outfeed table with respect to cutter blade. Use of the Magna-Set would imply that the blades should be the same height as the outfeed table (+/- .002"). This seems consistent with what others have reported.

Dusty
That link is it. I used something identical to this when I was shown how to sharpen and adjust jointer and planner knives. I thought the instructor had built his jig but years later I saw the one Shopsmith offered it and I bought one.

As I previously reported I was instructed to adjust the blades perfectly even with the out feed table (although the outfeed table was adjustable and we did sometimes tweak it after the initial adjustment).

I can understand setting them slightly proud of the table surface as Nick explained to compensate for spring back.
As the wood is being cut there would be a certain amount of compression of the wood at the cut line at the instant the blade is at it's highest and making the cut. The wood would then immdiately spring back and end up slighly lower than the blade. If the blade was exactly even with the table this spring back could cause the wood which is lower than the blade at this point to snag on the table.

However I think the problem is declaring that spring back to be "X" thickness. I would suspect that each wood would react differently and the only way to compensate for this would be to set the blade slightly proud of the table. Then the question becomes how much is slightly proud, I would think it would be somewhere between 0 and 0+.

My way of thinking about things is to toss the dial indicator. From watching old tool makers use dial indicators I learned they often spent more time insuring the measuring point never changed than they did actually measuring.

Everytime I pick up the dial indicator to measure something on my SS I find that hand pressure, a slight location change, and my poor rigging of the dial indicator introduced more error than I want to figure out how to remove.

Think about it, the wood fiber fuzz on the bottom of the jig could introduce as much as .001 error depending on which way you moved the jig last. Then consider the effects of varying hand pressure holding the jig, dust, location of the jig on the bed, and etc. When your measuring in .001 you must have a reference point (standard) that is uneffected by any changes at all.

I think the Power Tool Wood Working for Everyone book probably comes the closest to the correct slightly proud measurement by insuring the blades rub a test piece of wood.

While I haven't used "my" Magna Set guage, I have no doubt it will work as well as the one I used before. And yes it sets the blades height to be even with the outfeed table as best I can determine.

Frankly I would think a better way to adjust the table should you really want an .002 difference would be to use the magna set (or something similar) set up on the infeed table that is adjusted EXACTLY .002 above the outfeed and the adjustment is left there until the measurement is finished. That way the infeed table reference would never change, it would be polished metal to polished metal and little or no chance of introducing an variation in the reference point (standard).
Ed

[dusty]

No, charlese. I will probably not change the procedure that I am now using. It is sort of antiquated in that it uses none of these new fangled contraptions but it works and I am comfortable with the results.

ed, I checked my equipment data base and found that I bought that magna-set in the mid-eighties and have never used it. Probably what happened is I bought it, set it aside when the equipment was new and didn't need adjustment, forgot I had it and learned the procedure I now use when I did need it.

It does result in the outfeed table being the same height. I double checked that with the dial indicator. My blades are .001" higher that the table which accounts for the creep that I adjust for the old fashion way.