Problems milling sycamore

[Ilnumero]

I have been milling some sycamore and keep getting staining on the boards. The top of the board is fine but the underside has clumps of sawdust sticking to the board. This sawdust is very light purple in colour and when I brush it off it leaves a stain on the board.

 

I have tried brushing it off immediately the board comes off the cant but it is already marked. It seem that the water lubricant on the band may be causing this as the water is principally running on the top of the band, the bit in contact with the underside of the board being cut.

 

I tried cutting without the water but the boards are still marked, although slightly less.

 

I have plenty of set on the teeth so I don't think the body of the band is rubbing on the board.

 

Any ideas as to the cause of this staining?

[agg221]

The staining will be a reaction between the iron in the band and tannin in the wood - classic purple/blue staining. This indicates that the band is rubbing. It may be that the band is running not quite in line with the cut, ie slightly twisted. Is it all along the cut or does it start part way down? If it's all along the cut it is more likely to be in the mill set-up, if part way down it may be the wood moving around due to release of stresses as the board comes off.

 

If it's the wood moving, it may be worth taking the first cut up the middle of the log - this will take most of the stress out and minimise further movement.

 

The stain doesn't go deep as there is no iron present on the board surface to carry it deeper. You can either ignore it as it will sand/plane out when the boards are finished, or if you need it gone then oxalic acid solution will take it off. Be careful handling this as it is a poison.

 

Alec

[muttley9050]

The staining will be a reaction between the iron in the band and tannin in the wood - classic purple/blue staining. This indicates that the band is rubbing. It may be that the band is running not quite in line with the cut, ie slightly twisted. Is it all along the cut or does it start part way down? If it's all along the cut it is more likely to be in the mill set-up, if part way down it may be the wood moving around due to release of stresses as the board comes off.

 

If it's the wood moving, it may be worth taking the first cut up the middle of the log - this will take most of the stress out and minimise further movement.

 

The stain doesn't go deep as there is no iron present on the board surface to carry it deeper. You can either ignore it as it will sand/plane out when the boards are finished, or if you need it gone then oxalic acid solution will take it off. Be careful handling this as it is a poison.

 

Alec

 

Interesting Alec.

Will this solution take all ferrous metalsstaining off wood . Like the big blue marks in milled oak containing metal.

Cheers

James

[agg221]

Interesting Alec.

Will this solution take all ferrous metalsstaining off wood . Like the big blue marks in milled oak containing metal.

Cheers

James

 

Hi James, it will take all ferrous staining off a surface, but it doesn't penetrate very easily, so unfortunately it won't take it right out through a nail stain. I've never tried it to see what the surface looks like if you treat this type of stain though so it might be worth trying.

 

For what it's worth, if you don't want to buy oxalic acid, boiling up some rhubarb leaves is a good source.

 

Alec

[muttley9050]

Hi James, it will take all ferrous staining off a surface, but it doesn't penetrate very easily, so unfortunately it won't take it right out through a nail stain. I've never tried it to see what the surface looks like if you treat this type of stain though so it might be worth trying.

 

For what it's worth, if you don't want to buy oxalic acid, boiling up some rhubarb leaves is a good source.

 

Alec

 

Thanks. Will give it a go soon.

[Ilnumero]

Hi agg, thanks for that.

 

I have checked the blade and there's no contact between the wood and the body of the blade, just at the points of the teeth. I'm using a ripper blade and there's plenty of set on the teeth so good clearance.

 

I am familiar with tannin staining but I would have thought that the blade wasn't in contact with the wood long enough to actually stain it. It seems to be where the sawdust is collecting that the stain occurs.

 

I'm doing some more today and will try some other methods. I'm also going to try dry sawing some. Will report later.

[Big J]

Use diesel as the blade lubricant rather than water. Water is messy, doesn't lubricate well and reacting with the steel of the blade stains the wood. Also, you use very, very little diesel by comparison - get weeks and weeks of cutting out of about 5 litres of red.

[richy_B]

Use diesel as the blade lubricant rather than water. Water is messy, doesn't lubricate well and reacting with the steel of the blade stains the wood. Also, you use very, very little diesel by comparison - get weeks and weeks of cutting out of about 5 litres of red.

 

 

Daft question but does the red dye leave any trace?

[Lazurus]

Oxalic acid is brilliant stuff, I use it a lot on pale woods which have stains, patios, and on the fiberglass on my boat as it doesn't damage the gelcoat. It even removes rust marks on the boat which to have polished out or to buy a "trade" cleaner costa a fortune. Cheap as chips on E*ay.........

[youcallthatbig]

or you could try this:

Plantoil - Home Page,

 

not cheap but with a 20:1 mix with water works out about £7.00+ vat for 20 litres of mixed solution, which lasts a days full milling with high flow ,cutting sycamore you would use less , and somewhat kinder to the environment than diesel if out on site, one down side is freezing of lube system unless antifreeze added in sub zero temps.