MFT and Guide Rail Alignment

[Qwas]

Qwas, please do keep the ideas coming.  Building on one another's ideas is how we all advance.

Dave R.

That's why I like the FOG. And the comments and questions on this thread has helped me tremendously with advancing this idea. I love to see others building on my ideas and adapting it to fit their needs.

I like a simplistic approach to my mods but I don't expect others to build the same. Their needs are different and their mod should look different. But we can all learn by seeing what others have done.

 

[Qwas]

Here is another idea for a fence. Might be great for field use.

Use a large speed square to act as a fence for parallel cuts. The lip on the speed square rests on the MDF edge. You can use the front edge or the back edge. If you have concerns about the square being out of square, use the square to align the guide rail. The speed square can slide on the table's edge to move the workpiece to the cutting mark.
[attachthumb=1]

You can do the same with a framing square.
[attachthumb=2]

You could also use a drafting T-Square although it is designed for light work. You could make your own T-Square and use thinner stock for the head so it will slide in between the table top and the guide rail clamp. Use the bench dogs to align the fence portion of it. This T-Square could also work on the left side of the table.
[attachthumb=3]

Any of these squares could be held against bench dogs in a vertical row to act as a fence for crosscuts. And the speed square could be used for 45 degree miters (although bench dogs in a diagonal row would probably be more accurate).

 

[mhch]

Corwin's comments in this thread led me to make the following experiment
using a home made fence installed on the MFT side extrusion. The idea is
to use both a hole aligned guide rail and a MFT top side aligned fence to make
square cuts. Accuracy measurements are given at the end of my post.

This fence is made of a plywood base, the MFT fence itself, and another
piece of wood.

- the base is 30mm wide, 8mm thick and extends along the MFT side. Its right
  side runs under the guide rail between the MFT top and the hinge bracket.
  A small notch in it is needed to accomodate the hinge bracket hook sliding on
  the extrusion.

- To the left of the guide rail, the MFT fence or an Incra incremental
  track is screwed/bolted on this base, aligned with the MFT top side.

- The other piece of wood covers the right side of the base, thick enough
  to be 2mm above the MFT top, exactly aligned with the MFT fence, so
  that it provides an "under-rail thin fence', very useful to rest
  those workpieces just as large as the rail or to cut narrow strips
  on the right side of the blade.

  [attachimg=1]

A cut is made in this under-rail thin fence using the guided saw.
thus exactly aligned with the cut running in the MFT top along the
rail splinter guard. It is used to measure cut length on both side
of the blade in order to adjust the fence stop accordingly.

[attachimg=2]

I used the 5-sided-cut method to measure the accuracy of this setup,
on a 24" square piece of wood. Here are the pics of the final measurements,
first the A side, 1.743"

[attachimg=3]

Then the B side, 1.753"

[attachimg=4]

The difference is 0.01", so a 0.0025" squareness is achieved for
a 24" long piece without any special effort.

 

[Corwin]

Great post!  If you are happy with your setup, you will surely like what I will attempt to illustrate very soon -- hope to begin shooting this weekend.  

For some time I had attached a mounting board that spanned across not only the entire width of the 1080, but extended on either side, providing for a longer fence on the left side and also allowing for a fence to the right of the cut.  This certainly stiffened the table combination, but one problem I did notice in attaching items to the top or sides of the MFT's profiles is that the profiles do no sit exactly square with the tops of any of my tables.   Anyway, rather than mount to the profiles, I took to mounting to a sub-base that extended beyond the back of the fence where I bolted it through the MFT's existing holes.  Also, like you I used the base that ran past the guide rail area as backup to the back edge of a cut.  In my case, I added sub fences on either side where the inner facing edges were back beveled -- this allows me to cut a length of material (same thickness as sub fence) that is wide enough to span the gap and with bevels down the length of its sides I end up with stock from which I can cut slices the size I need.  Easy to cut as needed, or have a few for your typical thickness material.  If you look closely at one of the photos in my gallery, there is a shot showing a silly miter gauge example that sits on top of a large ripping jig with that fence in the background.  I'm sure many think this a problem, but in my ignorance I have always used a backer board or sliding jig, so I do not have any cut lines across  the surfaces on my MFTs.  Just started out that way and never stopped.  Once someone commented that covering the holes was bad, so I ran into the shop to check -- but all was fine, the MFT was still alive and well and showed no signs of turning blue.

Now with Steve's thread on the accuracy of the hole spacing, everything is much much simpler -- and the fence can now be mounted/unmounted at will.  You could even take it on the road, as it really is not fragile and is far shorter that the guide rail you will most likely be transporting.  Its own little case could be constructed if you are prone to toss your tools in the back of the pickup.  And, all you need to get started is two lengths of the track and two stops.  Why two?  Well, there are a few ways to use these as story sticks.  You may later elect to get additional tracks and stops, but with just two sets, you can get a lot accomplished.  Not only on the MFT, but also on jigs for cutting table usage.  All the MFT setups can be done without the hole pattern advantage, but that feature does hasten the setup process.

A couple days ago I was testing narrow cuts to the right of the saw.  These were made across two joined MFTs -- about a 58" cut.  The setup was put together quickly and my initial results were interesting as one end of the resulting pieces was typically 0.010" off -- disappointed that I didn't have better results, I checked along the length and found all but one end to be within 0.002" or so.  But that end...  I am thinking that it is either something in my method, or that after the piece is free as the last bit gets cut it might move slightly into the blade.  I think someone else had discussed this kind of result.

Sorry for the rambling...

 

[mhch]

I' m aware of the possible misalignment between side extrusions and table top, this is
why I built some sloppyness in the bolts I used to secure the fence to the extrusion,
i.e. the holes through the sub-base and under-guide wood piece are a bit larger
that what a M8 bolt would normally need.

This sloppyness allows me to make sure that both MFT & under guide fences exactly rest
  against the table top, when I screw the bolts. The base thickness is also choosen to
be smaller than the visible table side, so it's easy to make the fence resting against
the top, thus aligned.

One problem is that the new MFT.3side extrusion exhibits a V-shaped upper side
and so special V-nuts, likely available as spare parts, will be needed to attach
my home made fence. The other way will be to attach it to the lower side T track
of the new profile, but it might be less convenient.

 

[Michael Kellough]

....one end of the resulting pieces was typically 0.010" off....

Which end?

 

[Qwas]

I' m aware of the possible misalignment between side extrusions and table top, and the
holes in the sub-base and under-guide wood piece are a bit larger than what a M8 bolt
needs,

This sloppyness allows me to adjust the home made fence when securing it with
M8 and starred plastic bolts (one of them is visible in my pics), making sure
  that both MFT & under guide fences exactly rest against the table top,
  This is why the base thickness is choosen to be smaller than the visible table side.

One problem is that the new MFT.3side extrusion exhibits a V-shaped upper side
and so special V-nuts, likely available as spare parts, will be needed to attach
my home made fence. The other way will be to attach it to the lower side T track
of the new profile, but it might be less convenient.

Nice fence with great results! Can't argue with success.

I wouldn't worry too much about the MFT/3 until it is available and has users. We can master it then.

Corwin, I seen your fence in your picture gallery numbers 20 and 21. Looks interesting. Can't wait to see the pictures.

 

[Corwin]

....one end of the resulting pieces was typically 0.010" off....

Which end?

I think the end of the cut was the problem.  Not positive, as I often flipped end for end for a quick check.  If the problem is in fact only at the end of the cut, then I have some ideas on that...  on these cuts, I ran the trailing edge of the blade past the last of the material being cut.  Since the saws are set with a toe in attitude, they therefore have a heel out condition that may contribute the problem.  As the saw first cuts completely through the material the piece on the right is set loose and soon after as the trailing portion of the blade comes along the blade may pull the loose piece in towards the blade somewhat.  

I would think it better in most cases to have the waste on the right, but in this case I was just trying the setup that I had, well, just set up.  I am, however, always interested in why an operation fails to provide the desired results -- so, if you have an answer, I'm all ears.  Or no, maybe that should be all eyes?  ....Sorry.

 

[Michael Kellough]

....one end of the resulting pieces was typically 0.010" off....

Which end?

I think the end of the cut was the problem.  Not positive, as I often flipped end for end for a quick check.  If the problem is in fact only at the end of the cut, then I have some ideas on that...  on these cuts, I ran the trailing edge of the blade past the last of the material being cut.  Since the saws are set with a toe in attitude, they therefore have a heel out condition that may contribute the problem.  As the saw first cuts completely through the material the piece on the right is set loose and soon after as the trailing portion of the blade comes along the blade may pull the loose piece in towards the blade somewhat.  

I would think it better in most cases to have the waste on the right, but in this case I was just trying the setup that I had, well, just set up.  I am, however, always interested in why an operation fails to provide the desired results -- so, if you have an answer, I'm all ears.  Or no, maybe that should be all eyes?  ....Sorry.

When cutting on the MFT I've noticed a problem at the end of the cut (on the piece under the guide rail) when the fence is set as far back as possible, in the last row of holes. At first I thought it might be happening if the saw didn't travel completely off the wood but as you did I made sure to run completely past the wood and still get a little snipe-like overcut. On closer examination the snipe appears to be mainly on the upper surface of the wood. I'm pretty sure the cause is a slight tilting of the far end of the guide rail to the left since the foam is completely conpressed by the hinge bracket clamp. When I move the fence forward (away from the hinge bracket) there is little or no snipe. It might be worthwhile to add a shim to compensate for the foam compression.

 

[Corwin]

Thanks Michael, I'll check that out next time.  Glad you pointed me in this other direction, as I might otherwise have spent far too long looking in the wrong place.  Sometimes trying to find a tool I was just using goes like that too.  

 

[Qwas]

I have completed my manual on this method and it can be downloaded from here. You will need to right click on the PDF picture to start the download.

The link seems to have some problems. If you have problems try clicking "Gallery" in the menu below the FOG banner. Go to the Qwas gallery and it is the PDF file. You will need to right click to download.

There is nothing new in the manual, it's just easier to understand than this thread and maybe has some better pictures.

I'm going to start a new thread for comments on the manual.

Thanks everyone.

 

[Qwas]

If anyone is interested in getting some 20 mm PVC pipe to use as bench dogs or to hold a jig on your table, please see my new post here.

 

[Qwas]

I decided it was time to get back to making some dust while waiting on our pvc pipe to arrive.  I'm (slowly) working on making new kitchen cabinets and was turning some scrap pieces into some drawer sides. I wanted my cuts to be parallel first and then make my right angle side cuts.

I used my fence that has pegs going into holes parallel to the guide rail and decided to grab a caliper and measure the distance from the top end of the fence to the left side of the guide rail. Next I measured the distance from the bottom end of the fence to the left side of the guide rail. My fence is 24 inches long and after making 50-75 cuts since aligning the rail, I found the guide rail was off by 30/1000 of inch (3/4 mm) over the 2 feet.

So, I loosened the bottom of the guide rail and, with the use of the caliper, I was able to align it within 3/1000 of an inch (1/10 mm). I could have done better but it is only drawer sides so I was happy with that.

I found it best to keep a board under the guide rail while "tweaking" it. That gives some resistance while you tap the rail to move it left or right.

By using a caliper I'm able to verify the alignment and pretty much guarantee my cut. And once I know the guide rail is aligned for parallel cuts, I know the crosscuts will be dead on.

By using a caliper, you can put your fence, or bench dogs, into a vertical row and move (slide) your guide rail to achieve the exact length you need.

 

[mhch]

Very good point to remember

I found that the simplest and most squareness-guaranteed way to install the guide rail
to make sure its left side rests against pegs installed in MFT holes (PVC pipe
sections in my case), while adjusting the position of the top and bottom
hinge brackets.

Just resting the rail left side against pegs results into the kerf line running
across other MFT holes, which I did not like. so I used a 3/4" shim (a narrow
piece of MDF installed vertically on its side) in order to move the rail to
the right and to have the kerf line where I prefer it to be

Better verify the guide rail alignment often, and to make sure that the guide rail
is well resting on the pin located on the bottom hinge bracket.
That is very easy to overlook when doing a lot of cuts.

When very accurate cuts are needed, one can use pegs inserted in
horizontal holes and others in vertical holes, so that fence AND rail
each rest against a reference WHILE cutting. This requires the workpiece not to be too big.

 

[Qwas]

Just resting the rail left side against pegs results into the kerf line running
across other MFT holes, which I did not like. so I used a 3/4" shim (a narrow
piece of MDF installed vertically on its side) in order to move the rail to
the right and to have the kerf line where I prefer it to be

Better verify the guide rail alignment often, and to make sure that the guide rail
is well resting on the pin located on the bottom hinge bracket.
That is very easy to overlook when doing a lot of cuts.

Very good point to bring out. You don't want to be cutting in the middle of holes because you might get some tear out. Use shims if that happens. I use some scrap metal pieces as shims but anything you can trust as being square is fine.

 

[Qwas]

When very accurate cuts are needed, one can use pegs inserted in
horizontal holes and others in vertical holes, so that fence AND rail
each rest against a reference WHILE cutting. This requires the workpiece not to be too big.

Another good point. Once the pvc pipe gets here, and gets distributed, I will have to try that. A couple 3 inch pieces of pvc pipe installed in holes at the top and bottom of the rail. The 3/4 inch shim could be attached to the pipe by running a screw through the pipe on the opposite side from the shim.

Then every time the rail comes down on the work piece, the alignment is quickly verified.

Nice idea!

 

[mhch]

a 2 cent idea, further to the idea of screwing the shim to the peg.

What about using the screw to micro-adjust the shim position, thus the rail ?
Would that speed up the process of making very accurate cuts ?

Details need be worked out, and since the kerf line would move, then
a sacrificial piece of thin MDF could be used under the workpiece.

 

[Qwas]

The screw could be used as a micro adjust. If it's just a couple of thousands of an inch, I would worry about the kerf. If it's more than that that, the micro adjust could be put on the fence to preserve the kerf line.

Personally, I don't worry too much about the kerf in the table and I have several on there now. Sometimes it is easier to move the rail than moving everything else.