SE-76 and skewed Plane Iron

[kennyk]

Hi all, just registered here.

I've recently taken delivery of a T-7 in a school for sharpening all the chisels, plane blades etc.   However I'm having issues with it when using the SE-76.  I simply cannot get a straight bevel on my own Clifton Plane iron (the Plane is a No.7 Jointer) .  when looking at the blade front on (bevel towards me), the right hand side is always shorter  than the left.  I've tried a number of times to true the stone but that hasn't made any difference to the results.    the difference along the length is over 1mm ( around 1/32").

My observations so far: 
1.  there is play on the universal support leg that does NOT have the micro adjust, meaning that it is possible to knock the support out of parallel to the stone when adjusting the height after trueing the stone. I've tried truing after setting the support in all three possible 'positions' - first locking with pressure on the micro-adjust leg, then locking with pressure on the other leg, and finally with pressure on both legs, but all yield the same result.  which would you recommend as being the most consistent for acceptable results?

2.  with a 2" square on the front edge of the SE-76, the protruding blade is not square to the front edge of the jig.  is this critical or a red herring?

I re-ground a primary bevel using an ageing Viceroy Sharpedge flatstone grinder (just fitted with a new wheel) and even with play in the tool-holder due to wear on the height adjustment thread, I'm getting more accurate bevels, although there is a slight skew the other way.  So midway through the process it's hard to determine how bad the skew is going to be, as the edge looks convex.

I'm now starting to lose patience with the thing as I've got somewhere in the region of 200 chisels and 100 plane blades to sharpen for the various classrooms in the department!

Can anyone point me in the right direction?

[Jeff Farris]

Alignment of the tool in the jig is only half the job. It is also critical that you keep your pressure equal on both sides of the blade and monitor your work as you go. Keep a small try square close at hand and check the tool frequently. If you find it drifting away from perpendicular, move the short side off the grindstone, focusing the cutting on the long side. Using this method, you can also introduce a crown to the iron, if desired.

[Herman Trivilino]

1.  there is play on the universal support leg that does NOT have the micro adjust, meaning that it is possible to knock the support out of parallel to the stone when adjusting the height after trueing the stone. I've tried truing after setting the support in all three possible 'positions' - first locking with pressure on the micro-adjust leg, then locking with pressure on the other leg, and finally with pressure on both legs, but all yield the same result.  which would you recommend as being the most consistent for acceptable results?

I don't put pressure on either leg.  I just tighten the two set screws after adjusting the height.

[RobinW]

Hello kennyk

You are not alone. If you can find my posts started Feb 20, 2012, you will see I have been up the same learning curve.

The following link should take you there

http://forum.tormek.com/index.php?topic=1366.0

You will see that like a bicycle wheel a small angular difference at the hub (in either plane) translates to a large distance or offset at the rim.

I spent a lot of time trying to ascertain whether the edge inside the SE-76 against which the plane iron butts was at 90 degrees to the front face, as using a square on the front face (not dressed after casting) was the source of the problem.

The best advice I can give you after all my experience, is to use a felt tip marker on the bevel to be ground, keep checking it to see how the grind is going, and don't press too heavy.Keep trying.

[Ken S]

Kenny, welcome to the forum.  With as many blades as you have to maintain, you will soon become one of our most active members.

I looked at my support bar (T7).  I don't notice the play you mention.  Two thoughts occurred to me:     1)  Have you checked the tips of the screws used to secure the support bar to make sure they are flat and do not have a burr?  Not a likely problem, but one which is easily ruled out or corrected with a file if necessary.

2)  Have you checked that the support bar is parallel with the wheel?  This is easily done with a pair of inside calipers.  It's probably best to protect the caliper surface with a piece of paper over the wheel surface.

Have you checked the register edge of the SE-76 with your small square to verify that it is perpendicular with the edge of the jig? Not having the blade square with the front edge of the jig doesn't set well.

I agree with the other advice offered. one thing I might add, and it is just a personal preference:  I like to keep the distances of the support bar to the wheel and the blade projection as short as practical, especially with chisels and plane blades ground without camber. Shorter distances seem to admit less chance of error.  This may be an old wives' tale, but I believe it.

I only lengthen the distances when I need to add camber to a plane blade.

Assuming most of the chisel blades will be ground at the same angle, I definitely recommend standardizing on the bar to wheel and blade projection distances.

From your post, you seem to know what you are about.  I trust the frustrations will be short lived and that you will soon be having a satisfactory experience with your Tormek.

Best wishes,

( the other) Ken

[kennyk]

Hi again all, thanks for the welcome.

I just want to clarify my findings regarding the tool support:  The legs are of a smaller diameter than the mounting holes in the top of the T-7, to the extent that when using the micro adjust it is very easy to set the support out of square, which is where I suspect at least some of my difficulties are arising.

If I loosen the locking screws on the tool support and allow it to rest on the micro-adust, there is play on the other leg in the mounting hole. To exaggerate this, if I put pressure on the outer overhang of the support above the grinding wheel it is highly possible to lock the support squint, or for that matter if I put pressure above the micro-adjust leg.    I'm wondering if this play is within specification.  To clarify, there is no play when the support is locked with the two screws.

It's possible that I've trued the wheel using the truing tool with the support squint as described above.  However it should be possible to replicate the squint  accurately (for want of a better word) every time when locking the support, I think.  Although since I have no way of truing the wheel and leaving the support untouched before sharpening a plane blade, it's difficult to rule this line of enquiry either in or out.

Any comments or thoughts would be appreciated.

[Jeff Farris]

Kenny,

You're uncovering all the reasons that it is so often repeated here that a square grind is not guaranteed without careful attention by the operator. The issues you raised, jig alignment and Universal Support alignment, combine with inaccuracies in the tool dimensions, inconsistencies in both the stone and the tool, inconsistencies in pressure from dominant hand to the other, and several other little twinks one way or the other to make it critical that you set the tool up as carefully as possible....but then grind to square by checking to a try square and adjusting where you grind.

[Herman Trivilino]

I just want to clarify my findings regarding the tool support:  The legs are of a smaller diameter than the mounting holes in the top of the T-7, to the extent that when using the micro adjust it is very easy to set the support out of square, which is where I suspect at least some of my difficulties are arising.

I just took some measurements.  I have the US inserted about half way into the supports and resting on the micro-adjuster.  I can rock it to the left before locking in place, or rock it to the right before locking it in place.  The height of the free end of the US differs by about 1/32 inch (a bit less than 1 mm) when I do this. 

Let's do a little math.  The US has a length of 12 inches (about 300 mm).  Assuming it pivots at the other end, the tip moves through an angle of 1 mm/300 mm =  0.0033 rad, which is only 0.2 degrees.  Across a one-inch chisel that'd be 0.0033 inches, which is ten times smaller than 1/32 inch!  You'll couldn't see that with a try square.

By far, the out-of-square distance is due mostly to the difference in the amount of force applied to each side of the chisel, provided the grindstone has been properly prepared.

By the way, the best time to true up an out-of-square chisel is just after you've trued the grindstone.  The surface of the grindstone is coarsest then, too coarse in fact for finer work like sharpening kitchen knives.

[kennyk]

I've just measured the gap at the outer edge of the wheel with the US touching the inner edge. 15 thou or 0.4mm is the gap if the leg without the micro-adjust is pressed and locked with the screws first.   

over a 2 3/8 blade width, I'd be surprised if a misalignment of the US wasn't at least partly responsible for the skew I've been experiencing.

(Presumably it would be possible to true the wheel with the US misaligned as well and induce the same gap on the inner edge  by not pressing down on the leg when adjusting the support, thus reversing the direction of the skew.)

Another area where I'm unsure if I'm getting things right is the clamping of the blade in the SE-76.  Can anyone explain a simple way of ensuring that I've not over-tightened one side and inadvertantly bent the jig, which I've read about somewhere.

[Rob]

With the alignment of the US and the wheel.  As along as when you true the wheel you apply roughly the same pressure as you would with the square edge jig then you should eradicate that part of the problem.  The thing with the support bar is it only needs to be parallel to the wheel, even it they both skew equally, as long as they're parallel the skew wont affect the grinding.  In other words if the bar bends ever so slightly during trueing because of you leaning on it with downward pressure and that skew gets transferred to the wheel, it doesn't matter so long as the the wheel is parallel to the bar at the end of truing.

Also, when concentrating pressure on the tip of the bevel during sharpening, try NOT to lean too much on the support bar, instead concentrate finger pressure right over the edge of the blade.  At least that will minimise any skew that comes from play in the bar that is exaggerated by your weight on it.

On the question of the clamping pressure, my procedure is:  align the plane/chisel iron with the right hand edge of the jig and tighten to snug so it doesn't move.  Then I tighten the balancing screw till it feels tight enough and ovoid over tightening.  I am always very careful to keep the right hand edge aligned during the snugging up process.  But, as Jeff has said, its really important that YOU keep monitoring the squareness of the grind whilst its in progress because you'll NEVER get it square without this manual intervention.  I have one of those tiny weeny engineers squares that I offer to the emerging edge every minute or so.  That guides where I bias the finger pressure ie to the left or right of the back of the bevel.

[Jeff Farris]

Kenny,

The comments you are referring to are most likely directed at the previous model of the chisel jig. The newer model references from the flat side of the tool, thus greatly reducing the influence of clamping pressure.

That said, it's a good idea to visually inspect the clamping bar and the clamping base and see if they are parallel with each other.

But, it always comes back to monitoring and adjusting.

[Herman Trivilino]

I've just measured the gap at the outer edge of the wheel with the US touching the inner edge. 15 thou or 0.4mm is the gap if the leg without the micro-adjust is pressed and locked with the screws first.   

Are you tightening one of the set screws, applying the force, and then tightening the other set screw?  Just to be clear, that's not the right way to do it.

Another area where I'm unsure if I'm getting things right is the clamping of the blade in the SE-76.  Can anyone explain a simple way of ensuring that I've not over-tightened one side and inadvertantly bent the jig, which I've read about somewhere.

Do you have the newer SE-76 Square Edge Jig or the older SVH-60 Straight Edge Jig?  If you have the former it'll be clearly labeled as such on the jig itself. 

[kennyk]

I've just measured the gap at the outer edge of the wheel with the US touching the inner edge. 15 thou or 0.4mm is the gap if the leg without the micro-adjust is pressed and locked with the screws first.   

Are you tightening one of the set screws, applying the force, and then tightening the other set screw?  Just to be clear, that's not the right way to do it.

Another area where I'm unsure if I'm getting things right is the clamping of the blade in the SE-76.  Can anyone explain a simple way of ensuring that I've not over-tightened one side and inadvertantly bent the jig, which I've read about somewhere.

Do you have the newer SE-76 Square Edge Jig or the older SVH-60 Straight Edge Jig?  If you have the former it'll be clearly labeled as such on the jig itself.

Hi Herman

Not quite, it was more a simple way to exaggerate the aligment issue to find a way to overcome it. Although I've been applying pressure to the non micro adjustable leg and locking that first, then tightening the microadjust leg without applying further pressure just for the purposes of testing.    At the moment I'm just trying to find a procedure that will work for me given the sheer number of blades I've got piling up...

I have the SE-76 Jig.  The machine is brand new.



But I feel like I'm getting somewhere.  I re-ground the primary bevel of my Clifton Blade on the old Viceroy Sharpedge flatstone grinder, and managed to get an edge without a skew using the T-7.  However I'm unsure at the moment what I did differently... 

[Herman Trivilino]

However I'm unsure at the moment what I did differently... 

Practice is like that.  Our brains adapt.  There's even evidence to suggest that when we dream we are practicing the skills we learned that day.  So when when we wake up the next morning we have a new brain that's better able to proceed.

Decades ago I spent more than six years working as a carpenter, mostly building houses.  I can now go months without picking up a hammer, but when I do I find driving nails to be a completely natural action.  After a few nails the hammer becomes an extension of my arm and when it swings there's just something familiar about it that I find satisfying.  The nails just goes along for the ride.

[kennyk]

Just a further update;  I seem to be getting more consistent results now.   

I've come to the conclusion that the amount of finger pressure required to skew a blade is far less than I'd originally thought, unless anyone can give me evidence (anecdotal or otherwise) to the contrary. But by varying the pressure seems to be working.   

Out of interest, do most people put a very tiny (a few thousandths of an inch) curve on their plane blades by putting a bit of pressure at the outer corners of the blade?