Bouncing Wood

[Waka]

My Hegner has a cutting capacity of 2", yesterday I was cutting some wood 1 2/3" thick and for some reason it was bouncing all over the place. Yes the blade was in the right way round.

The other question is, when doing an internal cut, how do you ensure the blade is at right angles to the table?

 

[CHJ]

Not a scroller myself but sounds as though you are not clearing the wood dust from the gullets and the blade is binding, got no idea how you improve the dust removal with a blade that does not travel completely through the work piece though, other than using one with a courser kerf and feed slower.

On the blade alignment in thick stock that is hiding blade, can only suggest that you ensure the access hole is drilled at right angles on a pillar drill and use the hole (or at least its wall if it's significantly bigger diameter than the blade) to align the blade.

 

[mac1012]

sometimes if the wood is not completley flat the wood can jump about a bit a firmer grip might help pushing down on the area being cut to make sure that bit is flat will minimise vibration are you using a reverse tooth blade ? if so sometimes that can lift the work piece

to ensure blade at right angle to table i use a try square and align by placing parralell with blade and alter with table tilt mine is never on zero alway about half a degree out

mark

 

[mac1012]

Another thought is it the work piece that vibrating or the machine ? if the machine vibrating will transfer to work pice if bad

if machine vibrating not under load and work piece not flat then you have right conditions for work piece to jump a lot

mark

 

[Chippygeoff]

HI Waka. The wood you are cutting is quite thick so you need very good blade tension, a high speed and a slow feed rate. Do not push the wood, let it go at its own pace, As I said, the wood is very thick so it is bound to be slow, especially if it is a hardwood like ash or oak. Cover the pattern with clear packing tape, this will help a lot. Take turns and tight corners slowly to allow the blade to stay in perfect alignment. As was mentioned, if the wood is a bit warped this will cause the wood to bounce but it is more likely that when drilling the entry holes for internal cuts you have not sanded the holes off on the back, these little bits of wood that stick out can also cause the wood to bounce.

 

[Clockie]

Cutting thick wood on an Hegner is a all ways an uncomfortable experience in my book, and the closer you get to the theoretical maximum capacity the more difficult it becomes. The cutting action of the Hegner is almost vertical, for thinner woods this is ideal but the down side is when cutting thick wood. I would reiterate what has been said with the added comments that your choice of blade becomes a major factor, not so much the manufacture but the type. I have cut 2" elm on an Hegner but it was slow. I would suggest a double skip tooth or something similar about No. 9 or more likely No. 12. If you are using a standard blade or scroll reverse then you are going to have issues. Due to the thickness of the wood there will be some upward pressure and concentration will be vital. Cut about a centimeter then ease back a little to allow saw to clear. When I cut thick wood the blade will not back out of the cut all the way, due to packed sawdust in the cut.
You will also need good tension, being fairly heavy blades they should take it. It's going to be a slow old job. Best of luck.
Just as an aside, for cutting thick wood I think you would be hard pressed to find a better saw than a Diamond. I know one cutter all he cuts is in excess to 2" oak and the Diamond cope with it easily. noisily , but easily. Its a different cutting action.

 

[Gill]

Not a scroller myself but sounds as though you are not clearing the wood dust from the gullets and the blade is binding, got no idea how you improve the dust removal with a blade that does not travel completely through the work piece though, other than using one with a courser kerf and feed slower.

That's perceptive, especially coming from a non-scroller . I've come to the conclusion that it doesn't matter what the saw manufacturer states to be the saw's cutting capacity, what really matters is its stroke length. If you are cutting wood thicker than twice the stroke length then the blade does not have an opportunity to clear the saw dust it has produced at the point of cut in the middle of the workpiece. That doesn't mean you shouldn't cut wood any thicker than twice the stroke length - just be prepared for problems with swarf clearance. A skip tooth blade can help here.

Difficulty in clearing swarf shouldn't make the wood bounce, though. Using a blade with reverse teeth might, so that's another point to consider.

Insofar as blade alignment is concerned, if the blade is properly aligned at the start of the cut and properly aligned at the end of the cut, then it should be properly aligned in between . So check the alignment at the start and end of the cut. If the cut is still out of alignment it is likely that you're having sawdust clearance problems. If that happens to me I usually slow the speed of the saw down and 'nibble' cut, allowing the blade to bite the wood briefly and then backing off to allow sawdust to clear. This also helps to prevent the blade from getting too hot and extends its longevity considerably.

 

[Gill]

By the way, a quick method of checking blade alignment is to take a square block of wood, cut into it a little way to make a groove, then flip the block of wood upside down and present it to the blade again. If the blade is square to the table it will fit into the groove that you've just cut. If you have doubts about how square your block of wood is, cut a groove then put the wood behind your blade without flipping it over and see if it will fit. This second method is less accurate than the first because it doesn't account for the kerf of the blade, but it's still not a bad way to check.

 

[Waka]

Thanks for all the tips and advice. In light of what's been said I'll have another try tomorrow, I will get it right, get it right. This is a lot harder than throwing wood through my table, band and SCM saws, but more fun.
I'll let you know how I get on.

 

[Geoffrey]

Waka as Gill says and dont forget you can alter the stroke Length on Hegners and Axy 18 Machines
From 10mm to 20mm its easy see handbook. dont run at high speed . :idea:

Geoff

 

[boysie39]

I wonder if the moisture content of the timber affects cutting at all . I would imagine that it has to have as the blade kerf is so fine . Just a thought .

 

[Dangermouse]

What type of wood was it. Could it have been from a rubber tree ? :shock: :roll:

 

[Waka]

Well I had another go this morning on a piece of oak that was and still is 1 1/2" thick. I used a number 9 blade That came with the saw, took things very slow as recommended by you good folks, and hay presto the light came on and it went perfectly.

The things I was doing wrong are all listed in the thread.
Wrong blade,
Not enough tension,
Trying to force the wood through.

Still need a lot of practice, but the good news is with the help from the forum it's really stating to come together.

Thanks guys and girls, really is appreciated.