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Flooring MC and milling tolerances

Started by jrdwyer, March 25, 2006, 02:18:48 PM

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jrdwyer

I am new to working with wood products and have a few questions for some of the experienced people here.

This past Fall I purchased and installed 500 sf of R&Q unfinished red oak in my home. It turned out beautiful with the Waterlox satin finish and we are very happy with the overall results.

My questions concern the milling tolerances typically allowed or followed by those who make flooring. Would a flooring manufacturer allow width deviations as great as 1/32" in some of the finished product? I was under the assumptions that .005" would be the norm with today's modern moulding machines. I do know that some of the larger sawmills that I sell timber to maintain .005" on the thickness tolerance of the green lumber they produce.

A second question I have concerns the MC variability of flooring. Most hardwood flooring companies advertise 6-8% MC for their finished product. What range of moisture content would be considered normal in a given batch of flooring. In my case, I had lots of planks in the 8-10% range with lesser amounts in the 6-8%  and 10-12% range. I culled around 10 boards above 12% MC. I used a new Wagner MMC 205 to check the MC during site acclimation.

Thanks in advance.

HORSELOGGER

If you are very happy with the  overall  results, why be concerned about the other issues after the fact? I am not a flooring factory, but a custom shop, making a lot of flooring. I run a 1990 Weinig 5 head moulder... 5 thou, Dont know, wouldnt measure to that degree of tolerance. 3 1/4 is 3 1/4 no?  If the floor fits together and has no gaps between boards , I run the pile and watch for snipes when end trimming after the moulder.  The moisture content swing is probably not that unusual in a r & q floor, as some quarter sawn boards dont give up the last few points as easy as flat sawn. Any shrinking and swelling should not result in gaps in the floor, one of the features of a rift and quarter floor. If you picked out the high pieces, and are happy with the floor, be happy 8)
Heritage Horselogging & Lumber Co.
"Surgical removal of standing timber, Leaving a Heritage of timber for tommorow. "

beenthere

I suspect the tolerances when moulding the flooring were pretty close to the .005 you speak of. However, with increase in MC (lumberyard warehousing the flooring in winter temps and high relative humidity) since mfg., the sizes won't stay put. I'm guessing the size you speak of was over, not under specs?
The 1/32" you speak of seems a bit high, however, with increase in MC of 7% (from 6 - 13), red oak can swell 0.024" and add the 0.005 tolerance, gets to 0.029 which is pretty close to the 1/32" (being 0.031).  MC of wood stored in the cold (say 30°F and 90% relative humidity) will try to reach equilibrium of 21% MC.  Not knowing the history of the wood flooring since it was machined, can't say much about what it's size was when manufactured. I've been in flooring mills, and the machining was a pretty important phase but knives wear and sizes get bigger as that happens. Just not sure if this would account for the oversize, or if it was storage. Either way, the size cold be affected.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

jrdwyer

I am just trying to learn what is considered normal for hardwood flooring. Why would I want to know this? Well, the next time I purchase hardwood flooring, it will come in handy. Maybe someday I will get out of the forestry end of things and into flooring. I have many interests besides trees.

One of the biggest pains when installing hardwood floors is having to spot check milling quality. In my case, it was planks 1/32" under the stated widths. I ended up pulling some out and installed others due to time deadlines and not having enough replacement product immediately available ( I purchased 10% over).  After spending several years reading the hardwood flooring forums on other internet sites, this issue always comes up with both the DIY crowd and with installation professionals.

So, from what both of you have said,  it could be a combination of plank shrinkage and knife wear that would lead to 1/32" under on widths? The shrinkage could be caused by not getting the flooring blank MC low enough prior to milling and then it shrunk in the warehouse.

In my area, R&Q flooring is not locally available and it is more of a special order.  I went with a medium to large flooring company located outside my area for the planks.  They advertise having the latest Weinig moulders, etc. They sold the product directly to me and it was shipped by LTL carrier.  As an observation, there seems to be a market void in many areas for locally procured (retail/warehouse or manufacturer) speciality hardwood flooring.

As I've gotten older and mellower, I've learned to live with much less than perfection. Our hardwood floor is very beautiful and I'm glad that I had the time to take on the project. It's nice that the wood (in a general sense) came from red oak trees that I mark and measure all the time.

HORSELOGGER

Okay, JR DWyer.. ;D  I came in from doing TSI work in my own woods for lunch, read your post and fired off a quick reply, which, on rereading seems to dismiss your questions, and for that I am sorry.  One thought I do have is on the size diferences... When a pile of rough lumber is preped for the moulder, all the blanks are ripped to the same size, usually a 1/4 inch over the desired finish size, so for a 3 1/4 floor, plus a 1/4 for the tongue plus a 1/4 for the moulder to have a little something to clean up, makes a 3 3/4 blank. When setting the infeed fence, or straightening fence on a weinig, you would set that to take 1/8 off plus make the groove profile on the right or inside head. Rift and quartered wood loves to side bend, and will still do so some after being ripped from a wider board to be made into flooring. As that piece makes its way through the machine, it can be less than fully profiled on one side or the other. I like to feed those  "ears " out to make sure I get a full groove profile, as a partial tongue is easier to see when grading out the floor after moulding. It takes an extremely expensive machine with hydraulic hold overs to push warp out of wood, probably out of the financial reach of small to medium floor shops.
Heritage Horselogging & Lumber Co.
"Surgical removal of standing timber, Leaving a Heritage of timber for tommorow. "

beenthere

Quote from: jrdwyer on March 25, 2006, 05:46:34 PM.......So, from what both of you have said,  it could be a combination of plank shrinkage and knife wear that would lead to 1/32" under on widths? The shrinkage could be caused by not getting the flooring blank MC low enough prior to milling and then it shrunk in the warehouse...............

I was assuming you were getting 1/32" oversize;  not under,   and higher MC; not lower.
If moulded at 6% and the flooring picks up moisture, it will swell (get larger). If the knives wear during moulding, it will become oversized. 
::) ???   
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

HORSELOGGER

Also, if the fence is not set quite right after the inside head, the flooring can be slightly undersized. (dont ask me how I know this)  If an occasional piece is undersize, the blanks may not have been quite plump enough.


Beenthere, when you coming horselogging???
Heritage Horselogging & Lumber Co.
"Surgical removal of standing timber, Leaving a Heritage of timber for tommorow. "

FeltzE

I really have to watch as we rip the lumber, occasionally we get a bowed piece and rip a straight board out and don't notice the board may be a little under width. Then run the lumber through the logosol and my helper stacks everything together, not really paying attention to QA issues. Occasionally resulting in a board with under width ends or middle.

I only run short orders of a few hundred sq ft of lumber at a time to around 1500 sq ft. I don't think it's knife wear I think it may be machine set up issues, if you are running stock from two different runs or two different machines the set up could be out a little. I ask my customers to keep runs together, as we do change setups for people often running 2 considerably different widths of flooring to maximize use of stock and minimize waste.

If I am selling flooring ... the only guarantee I give is that we will provide enough to cover the desired sq footage, at the agreed price, that way the customer can have a little more choice over defects in the floor as we don't cull all the defects out at the chop saw. If they call and need more I provide it at no charge providing it's a reasonable request.

Eric

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