Blade slippage tip (or a no no?)

[savethebeer]

Doing some scrolling yesterday on 4mm BB using my ex 21. Got into more intricate sections so I changed to a smaller pre-used blade. Suddenly the blade was slipping from the top clamp far too often to be funny. Although I say pre-used, it is not bent or dull and when working it is perfectly fine.

Step 1 was to sand the top shank of the blade. No improvement.

Step 2 was to rotate the set screw [on the rear of the blade clamp] just in case grooves had been worn. The set screw was unmarked with damage but the blade slipped out just as much as before.

Step 3 today [same piece] was to actually tighten the set screw, after tightening the thumb screw, and then flip the tension lever. Suddenly I'm in the sweet shop and flying along. [that is the candy store to most of you].

I'm very aware of the dangers of stripping the threads on the head so I'm being very gentle on the set screw, using a hex key with a T handle for leverage, but its the barest turn of the set screw up against the thumb screw that does the trick for me. When I've finished this piece and go back to using a slightly bigger blade I'll see if the slippage continues. So on the whole I will use this method again if required.

Bob

 

[JTTHECLOCKMAN]

Is always a good idea to sand the ends of the setscrew and also the thumbscrew once in a while because they do get slick and shinny from metal on metal contact. You can completely take them out or run some sandpaper through the slot where the blade goes.

[CharleyL]

Length wise sanding won't solve your problem. Cross wise sanding should help, but it's a lot more difficult to do. You want the sanding scratches for an edge to catch the grip, not make tiny rails for the grip to slide along. Use a sharpening stone and rub the end of the blade across it to make the cross wise scratches. Don't pull the blade lengthwise.

The ends of the set screws get worn. A slight turn of the screw will give you fresh edges to bit into the blade. Look closely at the working end of the set screw and you will see a ring shaped ridge. With a magnifying glass, you will likely also see that this ridge is no longer sharp where the blade has worn it off. Turning the screw will give you a fresh sharp ridge again. After you do this repeatedly it will be time to replace the set screw with a new one. Use blue Locktite on the set screw threads to keep it from turning on it's own. Use only the blue Locktite, never another color or you won't ever be able to turn or remove the set screw again. The blue holds it in position, but lets you change the position when you need to.

Charley

 

Edited March 3, 2019 by CharleyL

[heppnerguy]

CharleyL, you always amaze me with your wisdom and great descriptive explanations. I always find them worth my time to read, I have a file on my HD that is totaled, "instructional" where I often copy and paste information like you often provide so I can refer back to them as needed

Dick

heppnerguy 

[JTTHECLOCKMAN]

I would hit the screws on the grinder before I chuck them. 

[NC Scroller]

I would not use a grinder as it will remove to much material and hard to maintain a flat.  You just want to touch it up.  I would opt for a small flat file or even a medium grain sharpening stone.

[JTTHECLOCKMAN]

1 hour ago, NC Scroller said:

I would not use a grinder as it will remove to much material and hard to maintain a flat.  You just want to touch it up.  I would opt for a small flat file or even a medium grain sharpening stone.

I do it all the time and never had a problem. It is called light touch. If you have a belt sander you can do it on that too. File could round over the bolt just as well. 

[kmmcrafts]

I drill appropriate sized hole in a piece of scrap 1/4" or 1/8" BBply.. drill the hole just the right size so the screws will actually thread into the wood.. thread both or all four as I do into the wood put a couple strips of wood on each end of the plywood high enough to keep the screws off the table and run my orbital sander  with 100 - 150 grit paper and sand all the screws at once.. you only want to dress a minimal amount so screw the screws in the wood just about flat with the wood.. just enough to touch the sander.. Works great for me.. You could use the belt sander too in this manor.. but screwing the screws into the wood helps hold the tiny things and also helps in holding them flat so you do not round over the edges etc.. 

[JTTHECLOCKMAN]

A little trick I do when sharpening tools on a grinder is to use a sharpie and color the end. Then lightly hit the edges and look to see if my grinding is at the right angle. I flatten screws of all sizes on a belt sander.

[teachnlearn]

SD Good has a set of videos on this subject. Can't take any credit for his knowledge or generous teaching other than direct you to a set Rick, RJF

https://www.youtube.com/results?search_query=sd+good+scroll+saw+blade+slip

[Norm Fengstad]

I had this problem on the Dewalt 788 done the sanding, changing position etc each helped for a while but it kept progressively getting worse till I changed out the clamps for new ones. Went to the Pegas clamp as it was only a few dollars more, shipping was cheaper and quicker, so far quite satisfied. 

[Karl S]

2 hours ago, Norm Fengstad said:

I had this problem on the Dewalt 788 done the sanding, changing position etc each helped for a while but it kept progressively getting worse till I changed out the clamps for new ones. Went to the Pegas clamp as it was only a few dollars more, shipping was cheaper and quicker, so far quite satisfied. 

Did you know that you can change out the contact end on your D/W/ clamps? The end swivels to avoid bending the blade, and you just pull the end out and replace it. It has a tiny "o" ring holding it in place. The ends are available from D/W/.

[savethebeer]

Thanks for all the tips and tricks. it turns out that this issue was to do with the one blade for some reason. This particular blade had not slipped much before [many of my blades slip at first fitting, till I've fined tuned the height of the top arm, which usually takes one or two adjustments only].  Changed it for a different blade yesterday and no more slippage. 

The circular ridge is still very visible on my end of my set screw, and does not look worn. I will probably just crosswise sand the shank in future, but tightening the set screw works also.

Bob 

[kmmcrafts]

7 hours ago, savethebeer said:

Thanks for all the tips and tricks. it turns out that this issue was to do with the one blade for some reason. This particular blade had not slipped much before [many of my blades slip at first fitting, till I've fined tuned the height of the top arm, which usually takes one or two adjustments only].  Changed it for a different blade yesterday and no more slippage. 

The circular ridge is still very visible on my end of my set screw, and does not look worn. I will probably just crosswise sand the shank in future, but tightening the set screw works also.

Bob 

You should never have to adjust that knob at the back of the saw for adjusting blade tension.. If that is what you're talking about... though it does move on its own some times..  That is only used to make the upper arm level or parallel with the table.. 

[wombatie]

I have also used rubbing alcohol on the set screw and wiped it on an old piece of cloth, that removed any unwanted oil left behind by a blade.

Marg

[Jim McDonald]

As my old DW788 screws were aging (since replaced by Pegas), I would put a piece of sandpaper on a marble tile and then sand the ends flat using that set up.  Seemed to get me an extra few months before I did eventually buy a new set of screws.  When It was time for another set, that's when I upgraded the clamps.

[savethebeer]

On 3/6/2019 at 11:11 AM, kmmcrafts said:

You should never have to adjust that knob at the back of the saw for adjusting blade tension.. If that is what you're talking about... though it does move on its own some times..  That is only used to make the upper arm level or parallel with the table.. 

I only use that knob with a newly fitted blade. It's to do with the blade not sitting in the bottom clamp exactly the same position that the previous blade did. The new blade could be 2mm too high or too low so the top arm needs adjusting.

[CharleyL]

On a DeWalt 788, and quite likely many other similar design scroll saws made since the 788 was released, you don't want to grind the end of the blade holding set screws flat. That is opposite of what is needed.

Look closely at the end of one of these set screws as they come from DeWalt, or haven't already been ground flat, by using a magnifying glass. You will see a conical shaped ridge (kind of like a miniature dead volcano) with a dimple in it's center. This circular ridge point is what holds the blades from slipping. Grind or file it off flat and you loose the benefit of it completely. Set screws, even stainless set screws are cheap. Don't file or grind them. Turn them slightly or replace them with the same style set screw. Even at the big box store you can replace both the upper and lower blade set screws for less than $1.00. Get yourself some Blue Locktite to hold their settings, and you will be good for another 5+ years of cutting with no blade slips. The thumb screw opposite the set screw does have a flat end, and it's a swivel, so it doesn't turn at the tip, as you tighten it. This thumb screw and it's opposing set screw, are the keys to getting a good grip on the blade. Don't sharpen them or grind them flat  or modify them in any way.

Something else that these set screws do besides holding the blade -

Changing the set screw position of only one set screw will move that end of the saw blade left or right a tiny bit. Run your saw very slow and get your face down close to the table and look straight at the teeth of the blade. Vary the blade speed while watching it. If you notice that the blade is moving slightly sideways during it's stroke, or you see a blurring of the blade in your vision of it, you need to adjust the upper or lower  set screw to make the blade move straight up and down with no sideways shift to it. If you can vary the speed from it's slowest speed gradually up and it doesn't shift sideways as it moves, you are good to go. If you can see a side to side blur at any lower speed setting, these set screws are not positioned correctly. The saw will do a much better job when it is set and adjusted correctly. You can also adjust both of these set screws the same amount if you find that the blade is not positioned in the center of the table hole.

Now do this next test without the saw running, but while looking at the side of the blade. In this case there are no actual blade adjustments available, but there should be. Using a small machinist square positioned behind or in front of the blade and against the blade and looking from either side, there should be no increasing gap between the blade and edge of the square. For cutting really intricate work, like my 1" high 3D reindeer, the blade needs to travel as vertically as possible. I elongated the screw holes in the lower yellow blade arm of my saw, so the silver colored blade arm and mechanism could be moved about 1/32" further than the factory position. This corrected the problem. The blade is now perfectly vertical with respect to the table. Your saw blade might tilt slightly forward or back. Make your decision on which of the arm screw holes to elongate based on which end of the blade needs to move. I can't say that all of these saws are the same. You must check and adjust depending on your blade squareness test. It may require a different amount of hole elongation or you may need to do it to the upper arm instead of the lower.

An alternate fix that is not as easy to do it to raise the rear pivot of the table. This would likely require a different rear table mount/pivot. After studying this, I opted to elongate the holes in the lower yellow blade arm, but either way will correct the problem. A perfectly square to the table blade will not make as aggressive a cut, but it will allow much finer scroll sawing, and this was my goal for doing this.  

Charley

[Roberta Moreton]

On 3/7/2019 at 10:38 AM, savethebeer said:

I only use that knob with a newly fitted blade. It's to do with the blade not sitting in the bottom clamp exactly the same position that the previous blade did. The new blade could be 2mm too high or too low so the top arm needs adjusting.

I don’t understand. The blade can be adjusted by simply releasing the knob holding it,  then when the blade is straight, tighten the knob again. There is no reason the blade needs to be in a certain position up and down. Or am I missing something? 

[Woodrush]

On 3/7/2019 at 10:38 AM, savethebeer said:

I only use that knob with a newly fitted blade. It's to do with the blade not sitting in the bottom clamp exactly the same position that the previous blade did. The new blade could be 2mm too high or too low so the top arm needs adjusting.

Your top arm should be parallel with the table. Once you get that parallel,vthe you adjust the motor for your front to back blade movement. After that you should never touch the rear knob unless it move slightly like Kevin said. Put some pegas chucks on it. I hated the upper on the ex as I like to see the top of the blade when I'm installing it.

[OCtoolguy]

Yes, Pegas chucks for sure. When I mount a blade on my EX, I position the blade into the top clamp so that the top of the blade is just right at the top of the clamp. Then I install the blade into the bottom clamp. Once that's done, I loosen the top back up and pull down on the upper part of the mechanism to take any slack out of it and re-tighten the upper clamp. I hated the old EX upper clamp.

 

[ike]

iF NONE OF THE ABOVE SUGESTIONS WORK i WOULD GET A pEGAS BLADE HOLDER SYSTEM THE ALUMINUM IS HARDER AND HOLDS REAAL GOOD . i HAVE AUTHORITUS IN MY FINGERS AND i HAD TO USE A sTEVE gOOD TOOL TO TIGHTEN THE SCREW WITH THE PEGAS I DON'T .

ike

PS EXCCUSE THE SPELLING MINE IS THE WORSE.

[RangerJay]

Timely topic.

Have historically had the same trouble with blades eventually starting to slip out of the bottom clamp on my EX16 - when they start to slip I've sanded the ends using the same technique as KMMCRAFTS described except I use 80 grit paper - that technique seems to work OK until it doesn't - then - once I become frustrated enough I swap out the set screw and the end of the thumb screw for a new set - did that yesterday and expect to be back in business for the foreseeable future.  Never tried WOMBATIE's suggestion of wiping the ends of the screws with rubbing alcohol - that makes a lot of sense - next time I'll try that first. 

 

[barb.j.enders]

On 3/5/2019 at 3:27 PM, Karl S said:

Did you know that you can change out the contact end on your D/W/ clamps? The end swivels to avoid bending the blade, and you just pull the end out and replace it. It has a tiny "o" ring holding it in place. The ends are available from D/W/.

They are also available from King Canada, which were a lot cheaper than the DeWalt brand.  http://files.kingcanada.com/catalog/products/servicemanualxm/KXL-16 service manual.pdf.  However it did take awhile for the service center to get them in.

[danny]

Only a lil tiny remark on the subject.  Hegner parts Last a Long, long time and seem to no wear out.

Mine is a 1998 model and still Purrs like a kitten.  Blade holds Always.  Oh yea....Only use Flying Dutchman

and mainly only use the FDUR #1....  Just my 2 cents............................Danny  :+}