Accuracy and the MFS as a Squaring Jig

H

Hotwheels

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Jan 23, 2007
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I have had some difficulties in the past with getting exactly 90' cuts using the saw, rail, and MFT. After reading Mr. Works MFS guide, I decided to try this. I bought the MFS700 and the 1000mm profiles that arrived last week. I am again having troubles with getting a square cut and for the life of me I can't see the source of error. I am hoping a fellow user may have some suggestions for problem solving. Here is what I did, using pages 13-16 or so of Mr. Work's guide as my reference.

1) put together the MFS 700, checked the diagonals (~915.8) and then the corners using a 12" Starrett combination square.
2) Mounted the 1000mm profile to the MFT, slid the profile and the assembled MFS 700 under the guide rail and used a block of wood to reference the edge of the MFS to the rubber edge of the guide rail. I used a quick clamp on the MFS to lock it down.
3) I aligned the 1000mm profile to the edge of the MFS and then locked that down using two FSZ clamps. This should mean the profile is now square to the MFS which is square to the edge of the guide rail.
4) I loosened the quick clamp and then calibrated the MFS to the profile as Mr. Works suggests on Page 15 of his manual. I used an Incra "t" ruler to align the marks on the profile and the MFS.
5) I set a cut for 10mm by sliding the MFS back from the edge of the guide rail and then using the clamping element to keep it in place. I did note that after checking the alignment after clamping there was some slight error, so I readjusted then re-clamped to ensure the cut was 10mm as indicated on the MFS and profile markings.
6) I took a 3/4" piece of cherry plywood scrap (~18X8) and placed it against the MFS and then clamped it down using FSZ clamps to ensure that it was firm against the MFS and would not move with the cut.
7) I made an initial trim cut on the piece, then made three successive cuts to get three test pieces.
"8"- I took a Mitutyo digital/imperial caliper and measured the markings on the MFS and profile as a means to calibrate the caliper to the scales on those pieces. The caliper measured 10.01 mm.
9) I then measured the three test pieces by marking a fixed distance at each end (start of cut and end of cut).
10) Here are the results where start means the "start" of the cut and "end" means the end of the cut.

a) Start 10.98mm
b) End  10.18mm
c) Diff=.8mm

e) Start=10.88mm
f) End = 10.06mm
g) Diff=.78mm

h)Start= 11.0mm
I) End = 10.01mm
J Diff= .99 mm

On page 18 of Mr. Work's MFS manual, after describing making 2mm wide cuts, he says "I find it easy with this setup to rapidly make repeat rips to get a bunch of narrow strips and can't measure any difference in width from one end to the other or from one strip to another."

Either I am doing something wrong or there is some other problem. Any suggestions?

Thanks,
John

ps -- did some rereading and I am going to the garage for some adjustments and retesting.....
 
I think this was a stupid error I repeated umteen times: when I made the "trim cut" I just forgot the flip the piece. When I did this and then made the cut, the start and end cuts were 10.04 and 10.09. That is still a difference, so I will try to find where in the setup that error is introduced.
 
I will just make this my MFS Blog as a record of my efforts to make this work or not.

Today I decided to redo the entire setup to check for errors. The steps were as follows:
1) check the MFS for square -- it was as square as I could tell with the tools I have.
2) Put the guide rail down and then align the MFS to the guide rail.
3) Clamp the MFS in place then clamp the 1000mm profile to the MFT.
4) Align the 1000mm profile to the MFS and then clamp the profile to the MFT.
5) Unclamp the MFS and then use a straight edge to align the guide rail to the MFS -- this should establish the zero point.
6) Align the 30mm scales on the MFS and the 1000mm profile to establish the "zero point" for measuring cuts from the edge of the mft.
7) Unclamp the MFT and slide a 1/2 pience of plywood under the rail and make a straight edge using the 1000mm profile as the "fence."
8) Reposition the MFS so that it registers a 10mm cut.
9) NOW FLIP the piece so that the stright edge is against the MFS acting as a fence.
10) Clamp the 1/2 plywood to the mft so that the cut edge is flush against the MFS.
11) Make 5 cuts.
Here are the results with the "start" and "end measurements:

1. start 10.44 end 10.05
2. start 10.58 end 10.08
3. start 10.58 end 10.01
4. start 10.44 end 10.14
5. sart 10.51  end 10.12

The difference between the "start" and "end" measurements suggests something is not square.  I need a glass of wine. I am going to try some more cuts tomorrow after another reset of all components.

More to come.
 
John,

The variations you describe may indicate you have lost track of the play in the guidrail at the near end where the fingers slip into the groove under the guiderail.

Try this;

1. Make sure your guiderail is preloaded at the near end so there is no play when you push the guiderail to the left.
2. Make sure your MFS is square.

3. Push your MFS up against the left side of the guiderail, not the splinterguard which is too subjective, while making sure the fingers at the near end are still bearing against the left side of the guiderail groove.

4. Clamp the MFS in this postion. To remove all doubt use two clamps. Best to do this with 1000mm rail already installed with clamps loose so you are close to the right position.

5. Align 1000mm rail to MFS and clamp from below.

6. Set MFS under guiderail to cut width desired.

7. Check results.
 
Hello Greg,
Thanks for the feedback. This morning I did some additional cuts using a piece of MDF about 18" long.

1) I have been preloading the guide rail, but that is a good reminder.

2) I did recheck for square on the MFS and it is close as I can possibly get it by measuring the diagonal  and then checking corners with the machinist square. The measurement seems to correspond with what Jerry Work says it should be.

3) Last night I pushed the MFS against the left side of the guide rail and that makes more sense to me. But, today I did use the splinter guard as suggested by JW. You are right it is more subjective.

4) I did use two clamps today to make sure there is no movement in the MFS.

5) Yes.

6) The cuts I made today had the following measurements.

1. start 10.50 end 10.35
2. start 10.49 end 10.30
3. start 10.55 end 10.22
4. start 10.47 end 10.22

averaging the start and end cuts and then subtracting the difference there is about a .23mm or .009" difference. This is a better result, but it is still not the difference that I interpret JW as indicating.

Guess I will give this a rest, but I thought the MFS would be the route to a very square cut. Although this is likely to be operator error, for the life of me I am not seeing where the error is being generated.

Any more thoughts would be appreciated....

Thanks,
John
 
I am coming in late on this so please excuse if I missed something. When I get into a quandry like this, I try to reduce the number variables. For one, I would place two clamps on the MDF workpiece so that they stay against the fence. Then I would go about the squaring of the guide rail using a large square between guide rail and fence...assuming the guide rail is in its"locked" position. Then make the cut.
 
Well your best difference before was .3 and now that is your worst. You are headed in the right direction. All deviations are in the same direction so I would guess that your MFS square is not perfectly square and I'll bet it is about .009" out-of-square. The rest is probably variation derived from technique.

If you have an indicator on some form of base that you could slide along the guiderail, against the rib/not against the splinterguard, you could extend the MFS beyond the splinterguard and check it for parallel to the rail by running the indicator along the MFS. Ultimately, if you are using the MFS for a stop/fence combination this is what you want on the money.
 
Thanks John & Greg,

I spent a couple more hours on this without much progress. Unfortunately I do not have a large square, just a 12" Starrett that I use as my reference. More and more I seem to have a need for a larger square, so I may invest in one of Ed Bennett's 18" squares. My understanding is that the ENCO square has changed and it now less desirable than older models. Mr, Bennett's tools seem to have the accuracy that ensures a known starting point.

I did check and recheck2 and then readjust the MFS to the best of my ability to resolve squareness by placing the Starrett on each corner and adjusting things flush. It may still be operator error, but if so, then it is just beyond my ability to establish the corners so that I get a truly square MFS.

I will try to rig up my TS-Aligner tool to measure as you suggest Greg, or I may just pack up the MFS and send it back so my blood pressure will return to normal.

Thanks again for the suggestions.

John
 
John,

Just a heads up about Starrett...  About four weeks ago, I was cutting some 2X4 for a tub deck (drop in tub) on my MFT using my TS55.  But they weren't square!  :o  So, I looked at the TS55 and the guide rail on the MFT.  And tried a bunch of other things.  Then...

I realized that I was always checking "square" using my Starrett 12" combo square.  I mean REALLY...  It's a STARRETT.  It must be perfect!!!

Nope!  It turns out that my Starrett is some what inacurate.  It depends on where I set it.  I tried unlocking, moving, and then locking it in multiple positions.  When compared to some engineering squares that I have, sometimes it's very close to square and sometimes not. 

I've since gotten two Incra "Guaranteed Squares" - one 5" and one 7" that I now use all the time.  Here's a review on Benchmark.  The bad news is that the overall quality isn't what I'd like to see.  Fit and finish is good, but not excellent.  That said, they are very accurate, light, and easy to use.  Now my cuts are much better.

I no longer use a Starrett combo square for a reference.  If absolute squareness is a requirement, you might want to check out a precision square.  My Incras are good and the Starrett "Master Precision Squares" look even better (.0001" every 6").  Of course there is the small matter of price.  My 7" Incra cost $60 at Woodcraft and the 6" Starrett Master Precision Square is $200!  Of course if you want to "go for the gold", you can get the Starrett 20-24.  It has a 24" blade and a 12" beam.  Such a deal at $1,000!!!  ;D

Regards,

Dan.
 
I hate to admit this, but Woodpecker's home site is the site I've been using for a home page for far too long.  Since I didn't want to miss out on anything, this seemed like a good idea.  Problem is, with all these neat products on special every so often, it can get hard to resist...

I have longed for one of those nice, expensive squares.  Then Woodpecker's offered their 12? Precision Triangle last week -- so, I bit.  I think this will work rather nicely on the MFTs once it arrives.

When you don't have an accurate square, why not test the squareness of your fence with a large scrap using the 5-cut method.  Once it is right you will have your fence set and have a nice square to use next time.

Corwin
 
Corwin said:
I hate to admit this, but Woodpecker's home site is the site I've been using for a home page for far too long.  Since I didn't want to miss out on anything, this seemed like a good idea.  Problem is, with all these neat products on special every so often, it can get hard to resist...

I have longed for one of those nice, expensive squares.  Then Woodpecker's offered their 12? Precision Triangle last week -- so, I bit.  I think this will work rather nicely on the MFTs once it arrives.

When you don't have an accurate square, why not test the squareness of your fence with a large scrap using the 5-cut method.  Once it is right you will have your fence set and have a nice square to use next time.

Corwin
Click to expand...

Hi,

        I also have several of the Woodpecker squares. All very nice and while not cheap they are reasonable for what you get.  I have the 12" speed (carpenters) square, a 4.5" ? and 6" precision that come in a set and also the 24" T Square. The T square is excellent to mark sheet goods  for guide rail placement. It really improved my accuracy. By marking through the small holes it greatly cuts down on slightly misplaced marks along a ruled edge.
      They make a couple of 18" also which might be great for MFT use.

Seth
 
John,

Don't know if this will help, but here's an observation:

Your results not only indicate out-of-square, but an inconsistent amount of out of square.  That suggests to me that something is moving during the cuts, or certainly between one cut and another.  have you looked at/eliminated all possible sources of movement?

Dave
 
Dave,

The inconsistency also bothers me since I clamped the MDF test piece using two clamps and I also used two clamps to hold down the MFS. It seems unlikely that the work piece or the MFS was moving. I have two MFTs connected and the floor is not level, so that may introduce some vibration during a cut. If that is not the answer, then the next logical source of the inconsistency --- other than measurement error -- seems to be the saw.

I did disassemble the MFS and reassemble it in better light and working conditions where it was easier to see the relationship of the square blade to the MFS. This was done 3 times checking square each time using the Starrett 12" and also a Brown & Sharpe 8" square. Using feeler gauges on the corners, I simply could not make all corners completely square. A .003 gauge fit between the square blade and the MFS. This became frustrating and it is just time to move on. The MFS was delivered a couple weeks ago, so the hope is I can exchange it and start fresh.

Thanks,
John

side note -- just to check my sanity, I cut four 2" wide pieces of MDF using my table saw and checked square using the same method applied to the MFS --- no problems.
 
ounds like a machining/manufacturing error in the MFS.  I'm sure Festool will exchange it without a problem.

Keep us posted on the final outcome.

Thanks for taking the time to post the details.

Dave
 
Dave,

I did one final check this morning, just for my sanity, although I changed a couple of variables at the same time.  I took my usual squaring jig -- a 2x3' piece of MDF squared on a sliding table saw -- and used it instead of the MFS. I followed the same procedures as aboveusing the squaring jig, but I did shim the table legs so the table is more level than before. I then made two test cuts with everything clamped down as before. 

I used a ruler marked to 1/64" and a magnifier and light to check the measurements. They were within a half a division (~1/128) from top to bottom. I then rechecked the cuts made yesterday with the MFS using the 1/64 rule and the cuts measured about 1/32+ difference from top to bottom or about the same as before.

I took the magnifier and looked at the edges of the MFS and there is one edge that has some burring --- when i put the MFS back in the shipping box I noticed a depression in the exterior that corresponds with where the out of square piece probably was. My guess this is the culprit.

Thanks for your comments and observations.

John
 
To continue the remarks on the Woodpeckers squares:  I got the 18" speed (carpenter) square.  Seehttp://www.woodpeck.com/speedsquare.html for a description.  I was tempted by the 24" t-square, but while the blade is long, the base is kind of short in comparison.  The 18" speed square solves this problem.

Tom
 
I have the 12" version of the Woodpecker speedsquare.  Quite frankly the quality level is not quite what I expected.  That said, it works very nicely for squaring wood against a guide rail for cross cuts.

Dan.
 
I ordered the Ed  Bennett 18" square today ... will report on its usefulness for working with the MFS/MFS.
 
I have yet to use my TS 55 and MFT to try to cut square panels, but that day is fast approaching.  One thing I did notice when resetting the toe-in of my saw (mine was delivered with toe-out instead of toe-in and Festool admitted to that error when I called them!) was there is "slop" or "play" in the hinge joint connecting the base of the saw to the motor et al. that move toward the base when the saw is plunged.  Festool claims this is normal, but it is a possible cause of inconsistent cuts.  You can test this on your own saw.  Placing the saw on a guide rail (with power disconnected).  Adjust the little wheel followers on the base of the saw to eliminate any side play between the grooves in the base of the saw and the raised rib on the guide rail.  Now, plunge the saw blade and apply a little inward, then a little outward sideways force through the handle of the saw, and note if there is any wiggling of the saw blade relative to the rubber edge of the guide rail.  There is on my saw, and you can hear a little mechanical noise due to the fitment of this hinge pin.  But even so, my TS 55 enabled me to make near perfect beveled cuts on all four edges of some new oak passage doors that I fitted to existing frames and hinges in my old house.  I could  not have done that with other tools - I am not a skilled or professional carpenter, and never before attempted such cuts.  The cut edges needed a little sanding, they were done before I realized I had toe-out instead of toe-in.  (Thank you, Rick Christopherson, for your manual !!)

What's the "Ed Bennett" square and how does it differ from others?  I need an accurate square and am currently thinking of buying one from Woodpeckers.  I wish they, too, had a showroom since they are located not far from where I work.  I much prefer to see and handle the tools I am considering, especially when they are expensive.

Late in 2007 I bought a Woodpecker's 18 inch carpenter's square.  I find it very useful for quickly resetting the fence and guide rail on my MFT, which I frequently remove completely including the stops to do other work.  I also find it useful for marking for cross cuts away from the MFT.  It can be used to help set a guide rail square across a wide sheet.  I've also found it useful in setting up the hole drilling jig when I need to drill several rows of holes located beyond the length of the side stops and the short LR 32 hole drilling guide rail. And its size also allows me to use it as a precision straight edge to help check alignment of the extension tables on my table saw and router table, and jointer.

Dave R.
 
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