Author Topic: straight edge blues  (Read 461 times)

Offline emlclcy

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straight edge blues
« on: July 29, 2020, 10:25:10 am »
 i have a T8 and an svh-320 planer blade jig. My planer blades are 10" x 3/4" so fit the jig well. I can true the wheel with the diamond attachment and grind a good edge on the blade BUT if i place the sharpened edge on a surface plate it is not flat. The strip of ptfe tape on the jig was bumpy and uneven so i removed that but still cannot get a straight edge.
any ideas?
regards
carl

Offline RickKrung

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Re: straight edge blues
« Reply #1 on: July 30, 2020, 03:08:08 pm »
I cannot help, as I have never worked a planer blade, so I'll just be following this one.  I have the planer blade jig, but my planer uses "disposable" blades which are too narrow to sharpen.  I didn't realize this when I bought the jig.  Disappointed. 

Have you checked flatness of the jig surfaces themselves?  Seems crazy as these are extruded pieces, but maybe...

I checked the plastic strip on my jig.  It also has some small bumps and is not completely flat and smooth.  Not sure of the sizes available, but I think Tormek sells a "sliding surface" adhesive backed plastic material.  If they don't offer something long enough, I'm sure something is out there.  I know I bought some for the scissors jig.  I have some in tape form but I cannot find my roll right now.  Here is a source of different types of tape: McMaster-Carr.

Another thought is that the USB bar can flex a bit towards the unsupported end.  Not sure if that would result in the type of non-flat edge you are experiencing.  From looking at the Tormek video, I think it should be possible to rig some sort of support for the free end. 

Like said above, I'll be following this.  But there are not many users of these jigs, so I'm not sure how much help there will be.  Probably best if you contact Tormek support: support@tormek.se

Rick
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

Offline Ken S

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Re: straight edge blues
« Reply #2 on: July 31, 2020, 03:07:44 am »
Carl,
Like Rick, I discovered that my lunch box planer used disposable blades after I purchased the SVH-320 planer blade jig.

When you place the blade on a straight edge, does the center area of the blade sag or is it proud of the sides? Does the shape of the second blade match the first blade?

Have you tried taking a lighter cut? One pass, compared to the original cut, should indicate if this is the problem. The cut line should either be the same or more straight.

This is the first post I remember with the grind not being straight. Keep us posted. We will get to the bottom of this mystery!

Ken

Offline emlclcy

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Re: straight edge blues
« Reply #3 on: July 31, 2020, 11:47:44 am »
i have a milling machine and ran a dial gauge along both the sliding extrusion and the fixed steel part and they are both not exactly flat so maybe the combination of two errors and the blade at a shallow angle will cause this error. i'm going to take a very light cut off both parts where the plastic strip was glued and try again
regards
carl

Offline emlclcy

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Re: straight edge blues
« Reply #4 on: July 31, 2020, 12:03:32 pm »
too narrow to sharpen
if you had a narrow strip to pack out the blade, is there enough material on the blade to clamp it?
If there is you could get metalsupermarket to guillotine a thin strip of aluminium. The shop nearest me - i'm assuming you are in the uk, charge 50p/cut and the metal would be pennies

Offline RickKrung

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Re: straight edge blues
« Reply #5 on: July 31, 2020, 02:51:30 pm »
i have a milling machine and ran a dial gauge along both the sliding extrusion and the fixed steel part and they are both not exactly flat so maybe the combination of two errors and the blade at a shallow angle will cause this error. i'm going to take a very light cut off both parts where the plastic strip was glued and try again
regards
carl

Good move.  I'll have to check my jig similarly.  I have a small knee mill, but it is straight and flat.  And a plethora of indicators. 

Thinking off the top of my head, without actually looking at the planer jig, about a setup for this operation, I believe I would try to use the guide bar holes as the reference surface/planes, rather than the exterior jig material/surfaces.  I'm thinking, put a long 12mm bar through the USB holes and rest the ends on "Vee" blocks.  That setup would benefit by being aligned straight with the table axis (front to back - "Y").  The Vee blocks should align it in the vertical axis ("Z").  Then block the leading edge up level. 

Just some thoughts.  I really enjoy figuring out jigging/fixturing/setups.  I was once asked to teach a jig and fixture class by my woodworking mentor, a patternmaker, as part of the woodworking courses he teaches through the local community college. 

I'd be interested in hearing about and seeing photo of the setup you come up with.  And the results, of course, on how it rectifies the problem you encountered. 

Rick
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.