Scrollsaw maintenance

[greybeard]

No monster surprises here! - all part of my scrolling learning curve!! But this may be of interest.......

Earlier this week I had the opportunity to check out my recent s/h acquisition, a single speed Hegner. It just so happens that my M-in-law lives about 10 miles from the Hegner UK base, so I took the chance and turned up unannounced - at Hegners I mean!

And what a friendly helpful bunch of folk they were. They put my mind at rest about whether the level of vibration was good/bad/terminal (as mentioned in an earlier post - I was concerned!) - "very good" - phew!
And then gave me a "do this" verbal checklist for maintenance and general usage, which I'll do my best to reproduce....
1 - it's the two pivot points that are critical to smooth running. Keep them clean (ok, as clean as possible!) (another old toothbrush job), and oil with a light oil from time to time - 3-in-1 is fine/good
2 - check the alignment from time to time - the sawblade should be squarely in the middle of the slit. You'll need to loosen the allen bolts under the base and move bits as appropriate to adjust the positioning
3 - blade tension - from the first tension adjuster 'engagement', one and a half turns should be just about spot on (I've also been told that that is represented by C above middle C when one plucks the blade!)
4 - the screw adjuster above the topblade clamp is just to stop the whole thing flying out in moments of excitement - it should be sufficiently clear of the clamp to allow the clamp to rock and lift slightly (not screwed down fairly tight like mine was!)

That's it!, just thought I'd pass them on.

 

[Gill]

Handy hints - thanks . We don't discuss saw maintenance as often as perhaps we should.

It's nice to know that I'm looking after my Hegners properly. I've heard that a drop of oil on the pivot points after every ten hours use is a good idea, but that didn't come from Hegner so I've no idea how valid it is. I suspect you don't need to oil the machine quite so frequently as that, but I still like to get the oil can out every few weeks.

4 - the screw adjuster above the topblade clamp is just to stop the whole thing flying out in moments of excitement - it should be sufficiently clear of the clamp to allow the clamp to rock and lift slightly (not screwed down fairly tight like mine was!)

This surprises me. I had dreadful problems with the top of my blades bending when I operated my saw with the top clamp loose. It made piercing work practically impossible. I mentioned this to a Hegner rep (his name was Roger, for what it's worth) at a woodworking show some years ago and he said that tightening up the top clamp would overcome this problem. I tightened up the clamp as suggested and I've never had a problem with bendy blades since. As I said, that was quite a few years ago when Hegner attended woodwork shows, so my saw's had quite a bit of use in this configuration. Doesn't seem to have done it any harm, though.

Gill

 

[alanjm]

I also run my Hegner with the top clamp tightened up, have done for well over 6 odd years and there does not appear to be any detremental effect on the saw. I was interessted in the vertical blade alignment element as I did not know you could adjust that. Have you ever had to adjust this Gill. One of the only problems I have had that took me ages to resolve was the blade breaking just at the pivot point in the bottom blade clamp mainly on size 5 or less blades. I still have this problem but not as frequently, I think it was caused by tightening the blade too much. From experience it is wise to be careful with the oil can as it is fatal if you get oil on the tensioning screw.

Rgds
alanjm

 

[Gill]

I never knew that either, Alan. I should imagine that if the vertical blade alignment element was out, you'd get some sideway bending of the blade at the point where it enters the clamps. It's not a problem I've ever had. Forward bending, perhaps, but that was rectified by screwing down the top clamp as I mentioned earlier. I've looked at my saw and the suggestion that the clamps should be allowed to move makes sense - screwing them down acts against the very minor backwards/forwards motion that you get with parallel scroll saw arms. Yet there's no doubt in my mind that the saw performs better when the top clamp is screwed down; strangely, I've never had problems with blades bending in the bottom clamp which can't be screwed down.

In fact, now that I've had a chance to look at my saw, I'm a bit puzzled by the suggestion about checking vertical blade alignment. The blade alignment is dependent on the position of the arms and both swinging arms are mounted on the main frame. So far as I can see, it isn't possible to make adjustments to the base and even if you could, it would make no difference to the blade alignment.

Gill

 

[greybeard]

Following on the comments above, I thought I'd better double-check to try and make sure that the information I'd re-presented was accurate!

Regarding the loose/tight securing of the upper blade clamp, the original Hegner "Instruction book" states......
Lock the upper clamp by means of the knurled pressure screw (.....to hold position etc when a blade is released and fed through a workpiece, and then re-secured....)
Loosen the knurled pressure screw (a quarter rotation only!) (exclamation mark in the I/book) so that the clamp can oscillate freely (boldened in the Instruction book)
Give tension to the blade

This is the only reference I could find to the upper clamp and pressure screw partnership, and this was in the middle of the section of cleverer stuff than I can do so I hadn't previously read it properly!
But it does seem to bear out the advice I was given.

As for the vertical blade alignment, I think that maybe I didn't explain it very clearly. The Hegner chap noticed that the table was a tad out of alignment with the blade (or, conversely, that the blade was a tad out of proper alignment with the table I suppose. I'm not to too clear which one is considered to be out of line from an engineering perspective), i.e. that the blade was slightly to the left (looking at it from the front) of where it should've been in the slot. But vertically as vertical as it should be.
His recommendation to bring it back in line was as I described since all component parts are bolted to the base in one way or another.
I had a fiddle - actually I had several, and in all honesty I'm not convinced that I managed to change the relative geometry, although I think it might be a bit better! One of those jobs where at least three hands are needed, and four would probably be even better!

Hope this presents a clearer picture.

 

[Gill]

You're quite right - the instruction manual does say to loosen pressure screw on the upper blade clamp in the way you describe. However, it doesn't make sense to me. If you loosen the screw by a quarter of a turn, the clamp will not have space to oscillate freely; you have to loosen it much more, several complete turns. As I tried to say earlier (but not using the much more descriptive words of the manual ) , when I operated my saw with the screw loosened so as to allow the clamp to oscillate freely, the blades bent so dramatically that they were useless for piercing work. They were so bent that I couldn't even insert them into pilot holes I had drilled in my workpieces. Fully tightening the screw cured this problem.

It's strange. The Hegner, like most modern saws, uses a cutting action whereby the arms move parallel to each other as opposed to the old-fashioned 'C' frame type of saw in which both arms just oscillated on a single pivot point. The rocking action of the 'C' frame tended to produce a cut which wasn't vertical - it was only slightly out but nevertheless it was inaccurate. Logically, a saw with parallel arms should have a slight back and forth pendulum motion as it cuts. The blade will always remain vertical, but it will only cut when the arms are parallel with the table and the blade is at its furthest point of travel. In order for the blade to remain vertical, it must be free to move back and forth (or oscillate, as the Hegner manual describes it) at the point where it pivots on the arms. Indeed, Diamond saws have a blade clamping system whereby the blade clamps swing on a pin at the end of each arm which gives them the freedom to move back and forth. Anyone who's used a Diamond will be aware of this idiosyncratic motion, especially if they rotate the blade holders through 90 degrees and try sawing sideways!

Yet if you allow the upper clamps on the Hegner to oscillate freely, the blade bends. It's counter-intuitive, but that's what happens. Restricting this oscillation stops the blade from bending and incidentally makes blade changing much faster. Looking at my DW788 I see its blade clamps are not designed to have a slight pendulum motion either. Common sense suggests that if the blades are not free to swing, there's got to be some some give in the system elsewhere. You'd expect the blades to bend at the clamps if they're not free to oscillate but they actually bend more if they're free. I can't figure it out.

Greybeard, have you tried using your saw with the top clamp screwed down? If not, you might be surprised at how much longer your blades last. It doesn't seem to adversely affect either the performance or the longevity of the saw, as both Alan and I will testify - and the anecdotal Roger from Hegner .

Gill

 

[greybeard]

Hi Gill

Apologies for the delay in responding - my day job demands have been rather too pressing recently to let me get to the shed, let alone sit and play.

I follow your logic re the top clamp, I will give it a go, and let you know the results, but it may be a while yet!

cheers