I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks

"buck" writes:

I am looking to build a crosscut sled for my table saw and want to buy
some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.

Just give proper consideration to thermal expansion for either plastic or
metal.

Tough to beat white oak or hard maple for this application.

HTH

Lew

I gotta agree with Lew. Nuthin wrong with oak for runners. I have 3
of the fancy incra ones, they are nice, but really, I do just fine
with white oak. Even have one with red oak, I think becuase I had
some sitting around that was already the right size. it works too.

I tried poly runners once, they squeezed out so much when I screwed
them on, they were un- useable.


-Dan V.


On Wed, 26 Jan 2005 02:58:34 GMT, "Lew Hodgett"
wrote:


"buck" writes:

I am looking to build a crosscut sled for my table saw and want to buy
some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.

Just give proper consideration to thermal expansion for either plastic or
metal.

Tough to beat white oak or hard maple for this application.

HTH

Lew

buck wrote:
I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks



Your local woodworking store? Lee Valley sells UHMW which fits.
www.metalsupermarkets.com might be in your area. ebay (search for
aluminium or aluminum, or UHMW)

I use MDF with an edge of scrap arborite for smooth running. It may be
a few thousandth's wider than .750, but a belt sander, plane, router, or
jointer will fix that.

Dan Valleskey valleskey at comcast dot net wrote in
:


I gotta agree with Lew. Nuthin wrong with oak for runners. I have 3
of the fancy incra ones, they are nice, but really, I do just fine
with white oak. Even have one with red oak, I think becuase I had
some sitting around that was already the right size. it works too.

I tried poly runners once, they squeezed out so much when I screwed
them on, they were un- useable.


Lew and Dan are right. The oak and/or maple beat the metal ones hands
down.

But, if you're not convinced, you can buy the Delta miter guides at
Rockler, like I did. Then you can remove them, put them on the shelf,
replace them with oak, and wish you had the $20 back that you spent on
them. Like I did.

It's not like they are more convenient. The great thing about wood is
being able to put the screws in from through the sled top, and not having
to hit a threaded hole, blind.

Gets you back to woodworking much more quickly.

Patriarch

I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but
looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks

I would think waxed hard maple would wear better than aluminum or plastic. I
got a 3ft sample of 4" wide 3/4" maple flooring for $2 and it'll provide
enough runners for a years worth of jigs and sleds.

I just built one with UHMW runners from Lee Valley. They was a little
play in them when I set them in the miter slots of my Delta Contractor
saw, but once they were screwed to the sled base, I had a nice fit.

FYI, they were selling these all over the place at the Indy woodworking
show this past weekend, so if there's one coming to your area soon, you
might pick them up there. Otherwise, hard to beat Lee Valley.

I almost bought the metal bars at Rockler, but was easier to drill and
screw down into the UHMW from above. Word of caution - screw once in
each end first, don't draw lines on the sled base of where the miter
slot should be and screw between the lines. YOu could miss the rail and
have the screw ding the miter slot. DAMHIKT...

buck wrote:
I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks

Never had a problem w/ UHMW.
Got a load from a buddy of mine and been using it w/ no problems.

Check ebay for some - should be able to get it pretty cheap.

OR just maple or oak scraps.

"buck" wrote in message
ervers.com...
I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but
looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks

I'm afriad I have to be the voice of decent. I've tried oak, maple and
other hardwoods. They work great to begin with but if you make them to have
a good, tight fit, I discovered that weather does have an effect and they
weren't always smooth over time. I also tried the UHMV thing and found the
same thing as the others. Once they were screwed, they splayed out making
it difficult to get a good fit. I reamed out the hole and got a workable
solution but I found a better way. Incra makes slot runners that have built
in slop adjusters. You will spend about $20 on an 18" one but it was well
worth it to me. It was adjusted to fit tight and it slides like butter
regardless of the weather. It aslo has the holes predrilled - for something
I use so much like a crosscut sled, the $20.00 was dirt cheap.

Don


"buck" wrote in message
ervers.com...
I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but
looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks

"buck" wrote in message
ervers.com...
I am looking to build a crosscut sled for my table saw and want to buy
some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but
looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks


Cutoff has the white UHMW, works fine. Miter sled has leftover mdf-filled
Pergo-type flooring on it, also fine. I'm in a basement, and the climate is
cold, so wood doesn't work as well for me. The EMC gets up 15% in the
summer, 4% in winter. Don't waste your money on the adjustable aluminum.
Or if you care to, pay the postage and I'll ship you one that is on my
circle-cutting jig, so I can replace it with one of the others.

First time you get some moisture together with that oak strip you forgot and
left on the saw and your iron top, you'll regret it.

Casting a vote for metal!

I found some cold-rolled steel stock at a local farm store where they had
some miscellaneous welding supplies. I think it was about six dollars for a
four foot stick. I also understand quite a few local welding shops would
carry similar items.

I've tried aluminum and found it wanting. I had four hard-set miters made,
two 45's and two 90s, left and right, made of aluminum runners and aluminum
angle metal. They operated fine, no apparent degradation through
temperature changes. But I'm not the friendliest user so one of the runners
got a little bent out of shape! Most likely wouldn't have that problem on a
sled though. But given time, I'm sure I could find a way to bung that up
too!



"buck" wrote in message
ervers.com...
I am looking to build a crosscut sled for my table saw and want to buy
some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but
looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks

On Tue, 25 Jan 2005 22:26:08 -0500, Dan Valleskey valleskey at
comcast dot net wrote:

I tried poly runners once, they squeezed out so much when I screwed
them on, they were un- useable.

HDPE is OK, but UHMW or Teflon is trading a little hoped-for
slipperiness for far too much loss in mechanical stability.

"Andy Dingley" wrote in message
...
On Tue, 25 Jan 2005 22:26:08 -0500, Dan Valleskey valleskey at
comcast dot net wrote:

I tried poly runners once, they squeezed out so much when I screwed
them on, they were un- useable.

HDPE is OK, but UHMW or Teflon is trading a little hoped-for
slipperiness for far too much loss in mechanical stability.


Well, if you do it properly - no. Counterbore, spread the load with the
proper fastener.

The aluminum ones have elaborate but inadequate means built in to do squeeze
the sides, and it's considered an advantage.

On Wed, 26 Jan 2005 06:50:00 -0600, "D. J. Dorn"
wrote:

I'm afriad I have to be the voice of decent. I've tried oak, maple and
other hardwoods. They work great to begin with but if you make them to have
a good, tight fit, I discovered that weather does have an effect and they
weren't always smooth over time. I also tried the UHMV thing and found the
same thing as the others. Once they were screwed, they splayed out making
it difficult to get a good fit.

FWIW, I have used UHMW and I have used my brad nailer to attach pieces to
my MDF sleds. No spreading. When I have used screws, I have made an
over-deep tapers for the flatheads and sneak up the tightening on the
screws. I have actually found that by tightening/loosening the screws I
can adjust the fit, as needed. -- Igor

In article rs.com,
buck wrote:
I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks



The 3/4 X 3/8 bar stock is a little difficult to find, but a home
center like Home Depot or a good hardware store will usually stock 3/4
X 1/4 which I find works just as well.
--

Larry Wasserman Baltimore, Maryland

Lawrence Wasserman wrote:
In article rs.com,
buck wrote:

I am looking to build a crosscut sled for my table saw and want to buy some
metal or plastic Miter Bars/Miter Sliders. Any good sources for these.
Also, could these be made from some aluminum stock. Looking to fit the
standard 3/4" X 3/8" slot. I know you can make these from wood but looking
for metal or plastic. Not interested in the expensive Incra ones.
-Thanks




The 3/4 X 3/8 bar stock is a little difficult to find, but a home
center like Home Depot or a good hardware store will usually stock 3/4
X 1/4 which I find works just as well.
And you can buy a 3 foot piece for a lot less money than a commercial
miter bar.

In article , John wrote:
Lawrence Wasserman wrote:
The 3/4 X 3/8 bar stock is a little difficult to find, but a home
center like Home Depot or a good hardware store will usually stock 3/4
X 1/4 which I find works just as well.
And you can buy a 3 foot piece for a lot less money than a commercial
miter bar.

I wonder, though, about the tolerances. The Incra miter bars are machined
straight to pretty tight tolerance. How close to straight is the bar stock at
Home Cheapo?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.

On Thu, 27 Jan 2005 12:21:32 GMT, (Doug Miller)
wrote:

snip snip .
And you can buy a 3 foot piece for a lot less money than a commercial
miter bar.

I wonder, though, about the tolerances. The Incra miter bars are machined
straight to pretty tight tolerance. How close to straight is the bar stock at
Home Cheapo?

=============================
You do NOT need a perfertly straight piece ...just one that sets
firmly in the slot with no slop... I always had to take out a file and
file the bar a little here and there to get the fit the way I like
it.. not a big problem...

Bob Griffiths...

In article ,
Doug Miller wrote:
In article , John
wrote:
Lawrence Wasserman wrote:
The 3/4 X 3/8 bar stock is a little difficult to find, but a home
center like Home Depot or a good hardware store will usually stock 3/4
X 1/4 which I find works just as well.
And you can buy a 3 foot piece for a lot less money than a commercial
miter bar.

I wonder, though, about the tolerances. The Incra miter bars are machined
straight to pretty tight tolerance. How close to straight is the bar stock at
Home Cheapo?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)


I've bought a few lengths of cold-rolled 3/4 X 1/4 over the years and
I've never had one that wouldn't fit in the table saw slot. That's
straight enough for me.


--

Larry Wasserman Baltimore, Maryland

"Bob G." wrote in message
...
I wonder, though, about the tolerances. The Incra miter bars are machined
straight to pretty tight tolerance. How close to straight is the bar
stock at
Home Cheapo?

=============================
You do NOT need a perfertly straight piece ...just one that sets
firmly in the slot with no slop... I always had to take out a file and
file the bar a little here and there to get the fit the way I like
it.. not a big problem...


Well, not necessarily. What fit snugly may not even be in the groove after
the first four inches of travel. So you need a straight edge. That's the
downfall of these fore and aft adjusting aluminum jobbies. tight goes to
flop pretty quickly.

On Wed, 26 Jan 2005 13:41:39 -0500, WoofWoof
wrote:

Doug Miller wrote:


Is there really a significant difference in thermal expansion rates for
plastic or aluminum vs. cast iron? Granted, the bar will get wider as it warms
up, but so will the slot. Does it *really* make a difference?

And what about expansion or shrinkage driven by changes in moisture content?
That's gotta be at least an order of magnitude greater than any thermal
changes in dimension, and obviously does not affect plastic or aluminum.

I doubt that thermal expansion is a significant factor over the likely
temperature range. Expansion/contraction due to humidity changes can be
a far more significant problem with wood.

I do see significant thermal expansion in the rails of my table saw.
it's enough that I can't trust the scale on my biesemeyer. now, that's
a lot more metal than a miter bar, but it's real. OTOH, the baltic
birch ply sliders on my sleds don't give me any problems with humidity
changes.




However, if you use a typical sled construction technique employing both
mitre-slots with a wood sled the dimensional changes in the sled itself
(due to humidity changes) cause much more trouble than the sliders by
grossly changing the distance between sliders. Particularly as the
sliders are usually constructed of relatively stable hardwood and
sealed/waxed whereas the sled usually isn't.

If you live in a climate that is dry as a bone in Winter and humid as
all get out in Summer it can be a serious problem.

One with experience (I built my sled in Winter - it's unusable in
Summer). (:-)

s wrote:
On Wed, 26 Jan 2005 13:41:39 -0500, WoofWoof
wrote:


Doug Miller wrote:



Is there really a significant difference in thermal expansion rates for
plastic or aluminum vs. cast iron? Granted, the bar will get wider as it warms
up, but so will the slot. Does it *really* make a difference?

And what about expansion or shrinkage driven by changes in moisture content?
That's gotta be at least an order of magnitude greater than any thermal
changes in dimension, and obviously does not affect plastic or aluminum.

I doubt that thermal expansion is a significant factor over the likely
temperature range. Expansion/contraction due to humidity changes can be
a far more significant problem with wood.


I do see significant thermal expansion in the rails of my table saw.
it's enough that I can't trust the scale on my biesemeyer. now, that's
a lot more metal than a miter bar, but it's real. OTOH, the baltic
birch ply sliders on my sleds don't give me any problems with humidity
changes.

Well, to be fair the thread was on mitre bars and I was commenting on
the expansion of the significant (3/4") dimension but lets see:

The thermal expansion coefficients:

steel is ~ .000006 in/in/degF
aluminum ~ .000012 in/in/degF
UHMW ~ .00011 in/in/degF
wood ~ .000003 in/in/degF (cross-grain) **

(** I found several references for this suprisingly small value for wood
- less than steel. It seems to confirm that the major problem with wood
rails would be humidity rather than thermal expansion).

So for a 3/4" mitre bar over a 30 degF temp. range the expansion would be:

steel = .000135" (.000006 x 30 x .75)
aluminum = .00027"
UHMW = .0025"
wood = .00007"

For a cast-iron/steel table, the diferential expansion of the bar to
slot would be:

steel = 0"
aluminum = .000135"
UHMW = .0024"
wood = .000065"

For an aluminum table, the differential expansion would be:

steel = .000135"
aluminum = 0"
UHMW = .0022"
wood = .0002

Over this temperature range, I would suggest that only UHMW *might*
(just barely) be noticeably affected by thermal expansion/contraction.
(I still feel that humidity would be the controlling factor for wood. I
don't offhand have any hygroscopic data for UHWW ... some plastics -
nylon for instance - absorb a fair amount of water and can swell
noticeably with humidity changes).

As far as your front rail goes, assuming it's ... what, 4 ft long? The
expansion in that case (over the same temperature range) would be:

steel rail = .0086"
aluminum rail = .017"

I assume the scale is thin and bonded to the rail so the rail would
control the expansion. I'm not familiar with the Biesemeyer so I don't
know the material for sure but the expansion is almost 20 thou for
aluminum (but over the total length ... proportionally less for shorter
distances). Whether that's a problem in your work, only you can say.
(I think, in my case, my innate lack of craftsmanship would swamp it (:-) ).

Doug Miller wrote:
In article , John wrote:

Lawrence Wasserman wrote:

The 3/4 X 3/8 bar stock is a little difficult to find, but a home
center like Home Depot or a good hardware store will usually stock 3/4
X 1/4 which I find works just as well.

And you can buy a 3 foot piece for a lot less money than a commercial
miter bar.


I wonder, though, about the tolerances. The Incra miter bars are machined
straight to pretty tight tolerance. How close to straight is the bar stock at
Home Cheapo?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.


If it fits in the groove, it is obvious straight enough. If
it doesn't fit(has a bend) whack it till it does, then it
will be straight enough.

On Thu, 27 Jan 2005 20:26:36 -0500, WoofWoof
wrote:

wrote:
On Wed, 26 Jan 2005 13:41:39 -0500, WoofWoof
wrote:


Doug Miller wrote:



Is there really a significant difference in thermal expansion rates for
plastic or aluminum vs. cast iron? Granted, the bar will get wider as it warms
up, but so will the slot. Does it *really* make a difference?

And what about expansion or shrinkage driven by changes in moisture content?
That's gotta be at least an order of magnitude greater than any thermal
changes in dimension, and obviously does not affect plastic or aluminum.

I doubt that thermal expansion is a significant factor over the likely
temperature range. Expansion/contraction due to humidity changes can be
a far more significant problem with wood.


I do see significant thermal expansion in the rails of my table saw.
it's enough that I can't trust the scale on my biesemeyer. now, that's
a lot more metal than a miter bar, but it's real. OTOH, the baltic
birch ply sliders on my sleds don't give me any problems with humidity
changes.

Well, to be fair the thread was on mitre bars and I was commenting on
the expansion of the significant (3/4") dimension but lets see:

The thermal expansion coefficients:

steel is ~ .000006 in/in/degF
aluminum ~ .000012 in/in/degF
UHMW ~ .00011 in/in/degF
wood ~ .000003 in/in/degF (cross-grain) **

(** I found several references for this suprisingly small value for wood
- less than steel. It seems to confirm that the major problem with wood
rails would be humidity rather than thermal expansion).

So for a 3/4" mitre bar over a 30 degF temp. range the expansion would be:

steel = .000135" (.000006 x 30 x .75)
aluminum = .00027"
UHMW = .0025"
wood = .00007"

For a cast-iron/steel table, the diferential expansion of the bar to
slot would be:

steel = 0"
aluminum = .000135"
UHMW = .0024"
wood = .000065"

For an aluminum table, the differential expansion would be:

steel = .000135"
aluminum = 0"
UHMW = .0022"
wood = .0002

Over this temperature range, I would suggest that only UHMW *might*
(just barely) be noticeably affected by thermal expansion/contraction.
(I still feel that humidity would be the controlling factor for wood. I
don't offhand have any hygroscopic data for UHWW ... some plastics -
nylon for instance - absorb a fair amount of water and can swell
noticeably with humidity changes).

As far as your front rail goes, assuming it's ... what, 4 ft long? The
expansion in that case (over the same temperature range) would be:

steel rail = .0086"
aluminum rail = .017"

I assume the scale is thin and bonded to the rail so the rail would
control the expansion. I'm not familiar with the Biesemeyer so I don't
know the material for sure but the expansion is almost 20 thou for
aluminum (but over the total length ... proportionally less for shorter
distances). Whether that's a problem in your work, only you can say.
(I think, in my case, my innate lack of craftsmanship would swamp it (:-) ).



the rail is about 6' long. and I live in Arizona. I'll figure the
shop temp varies close to 100 degrees from a cold day in the winter to
a hot day in the summer. that would result in a total variance of
..043, or about 3/64".

I'm definitely seeing more than that, so there's probably something
else going on. for instance, right now it's reading about 1/16" short
in the 36" range. it's not particularly cold weather right now- brisk,
but nice.


hey, and thanks for digging up those numbers.

You do NOT need a perfertly straight piece ...just one that sets
firmly in the slot with no slop... I always had to take out a file and
file the bar a little here and there to get the fit the way I like
it.. not a big problem...


Well, not necessarily. What fit snugly may not even be in the groove after
the first four inches of travel. So you need a straight edge. That's the
downfall of these fore and aft adjusting aluminum jobbies. tight goes to
flop pretty quickly.

======================
No I have to differ with you on the need for an absolute straight
edge...BUT I do agree with you on the adjustable "jobbies" since they
generally only have a few "adjustable" points on the bar that are in
contact with the sides of the miter slot.....

It is not at all hard to fit bar stock to fit the miter slot snug the
ENTIRE lenght of the miter slot...

Bob Griffiths

s wrote:

the rail is about 6' long. and I live in Arizona. I'll figure the
shop temp varies close to 100 degrees from a cold day in the winter to
a hot day in the summer. that would result in a total variance of
.043, or about 3/64".

Is that all? My shop temperature in the mountains of Virginia varies by
about 120 degrees from the lowest low to the highest high, as measured by
the thermometer inside the shop. (Not by ambient air temps.) A lot of
this is because it gets hotter than my thermometer can actually tell me in
the summer. I've gone out there on a 20 degree day and seen it 55 inside
the shop, just from solar heating. I really need air conditioning, but I'm
not going to get it.

--
Michael McIntyre ---- Silvan
Linux fanatic, and certified Geek; registered Linux user #243621
http://www.geocities.com/Paris/Rue/5407/
http://rosegarden.sourceforge.net/tutorial/

"Bob G." wrote in message
...

You do NOT need a perfertly straight piece ...just one that sets
firmly in the slot with no slop... I always had to take out a file and
file the bar a little here and there to get the fit the way I like
it.. not a big problem...


Well, not necessarily. What fit snugly may not even be in the groove
after
the first four inches of travel. So you need a straight edge. That's
the
downfall of these fore and aft adjusting aluminum jobbies. tight goes to
flop pretty quickly.

======================
No I have to differ with you on the need for an absolute straight
edge...BUT I do agree with you on the adjustable "jobbies" since they
generally only have a few "adjustable" points on the bar that are in
contact with the sides of the miter slot.....




It is not at all hard to fit bar stock to fit the miter slot snug the
ENTIRE lenght of the miter slot...


Seems to define a straight edge, or is your slot curved?

"Doug Miller" wrote in message
news

It is in fact "obvious" that this is not correct. Suppose the miter slot
is
0.750" wide, and the bar is 0.740" wide with a 0.009" bow in it. The bar
will
fit in the slot, and fit snugly at that -- as long as both ends of the bar
are
in the slot. At both the start and end of a cut, though, when only one end
of
the bar is in the slot, there will be considerable slop in the fit, and
hence
slop in the cut.


Well, there would be up to .009" variation in the cut. Surely suitable for
woodworking. Nothing that a light sanding or a very light pass with a plane
couldn't handle. I'm not arguing in favor or slop, I'm just suggesting that
we might be too focused on precision that is beyond that which the tools
we're using give on a good day, especially in light of the material we're
working with.
--

-Mike-

In article , "George" george@least wrote:

Not to mention - returning to the requirement only of a straight edge - if
the slot is 0.75 and the _straight_ bar(s) 0.25, perfect cuts can be made
by riding the straight edge against one side of the miter groove. A firm
set can be made by attaching another in the other channel, so both ride
either the inside or outside portion of the grooves.

But only if they're straight (or reasonably close to it). And so we come back
to my original question: how tight are the tolerances on the bar stock that
comes from Home Cheapo? I'm quite certain that they're not as close to dead
straight as the precision-machined miter bars from Incra, but how close are
they?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.

In article , "Mike Marlow" wrote:
I'm not arguing in favor or slop, I'm just suggesting that
we might be too focused on precision that is beyond that which the tools
we're using give on a good day, especially in light of the material we're
working with.

A point well taken... but it still seems to me that it's important to know
just what sort of tolerances we're dealing with, before recommending use of
off-the-shelf bar stock from Home Cheapo. Incra miter bars are machined to a
degree of precision that I'm sure we can all agree is more than sufficient for
woodworking. But how close is the home-center bar stock?

To take what is probably a more realistic example than the one I presented
previously, suppose that a nominal 3/4" bar measures 0.748" actual width. If
your miter slot is 0.750", that bar had better be _no_more_ than 0.002" out
from dead straight, across its entire length, or it's going to wedge in the
slot before it gets all the way through.

And, of course, if that nominal 3/4" off-the-shelf bar from the home center is
actually 0.751", it isn't going to fit at all, even if it's dead straight.

So... are the tolerances that good on the home-center bar stock? Personally, I
have my doubts, after having purchased 3/4" aluminum angle from HD that
turned out to be almost 0.020" out of straight over 24 inches. It's hard for
me to imagine that the bar stock is an order of magnitude better.

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WoofWoof wrote:
Doug Miller wrote:

So... are the tolerances that good on the home-center bar stock?
Personally, I have my doubts, after having purchased 3/4" aluminum
angle from HD that turned out to be almost 0.020" out of straight over
24 inches. It's hard for me to imagine that the bar stock is an order
of magnitude better.


... er actually it might well be. Al angle is extruded ... the extrusion
process often leads to a fair amount of bow. Steel bar stock is usually
cold-rolled and the straightness is pretty good.
Simple test
try first half or third in front of miter slot
try full length in slot
try rear third or half toward rear of slot
If bar fits in all three cases and has minimal slop it is good enough to use
Steel bar stock I bought passed this without difficulty. I am now using
the bar in a circle jig for the bandsaw.
John

On Fri, 28 Jan 2005 20:33:12 GMT, (Doug Miller)
wrote:
..

But only if they're straight (or reasonably close to it). And so we come back
to my original question: how tight are the tolerances on the bar stock that
comes from Home Cheapo? I'm quite certain that they're not as close to dead
straight as the precision-machined miter bars from Incra, but how close are
they?
==================
I am not about to argue (hate to loose) that Home Depots' bar stock
has anywhere near the tolerances of a bar made by Incra ...

BUT the simple fact is that I have never had any problems fitting Home
Depots' or other hardware store bar stock to any of the slots on my
Tablesaws or other machines... Thay may not be perfectly straight but
getting a slop free fit is not hard to do... I can not recall a
single screwed up cut in close to 40 years of woodworking that I
could blame on a sled or jig that used a cheap piece of bar stock to
ride on...That is not to say that I did not have to "work" the bar
stock to make it fit....

Just my opinion...

Bob Griffiths

Doug Miller wrote:

Thanks Doug, but it's obvious that you can't separate
different problems. Straightness has nothing to do with the
width being off. If the miter slot is .75 and the bar is
..74 it doesn't fit period whether or not it is straight.


Thanks yourself, George, but it's obvious that you're the one who has trouble
separating different problems. You said "if it fits in the groove it's
obvious[ly] straight enough." This is clearly false, as the example I provided
demonstrates: a 0.740 bar with a 0.009 bow "fits in the groove" as you said,
but it is very obviously not "straight enough".


Keep to the subject which is straightness.


You can't divorce straightness from proper fit.

Sure you can and you better. But I can divorce you!



OTOH, if fit is
a problem and it is only .74. whack it and soon it will be
..75. Don't you adjust your miter bar to fit?


Yeah -- but not by "whacking it until it fits".

The books I have read indicate that is a standard procedure
and certainly works for me. You whack it but rather
specifically you dimple it enough so that any looseness
disappears.


You might want to look at your sig.


Why? Is there something the matter with it?


It's about trolls.
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In article , "George E. Cawthon" wrote:
Doug Miller wrote:

Thanks Doug, but it's obvious that you can't separate
different problems. Straightness has nothing to do with the
width being off. If the miter slot is .75 and the bar is
..74 it doesn't fit period whether or not it is straight.

This is false too, by the way. A 0.740 bar *obviously* fits into a 0.750 slot,
and as long as it's straight it can be used to make straight cuts, by keeping
it in firm contact with one side of the slot throughout the cut. It makes no
difference that it's undersized.

Thanks yourself, George, but it's obvious that you're the one who has trouble
separating different problems. You said "if it fits in the groove it's
obvious[ly] straight enough." This is clearly false, as the example I
provided
demonstrates: a 0.740 bar with a 0.009 bow "fits in the groove" as you said,
but it is very obviously not "straight enough".

Keep to the subject which is straightness.

You can't divorce straightness from proper fit.

Sure you can and you better.

Do you really mean to suggest that straightness is irrelevant to proper fit?

But I can divorce you!

Ooooooh, are you going to killfile me? I'm trembling. Tell you what: let's KF
each other. Then I won't have to read your nonsense, and you can post nonsense
to your heart's content without having to worry about seeing me expose it for
what it is.

OTOH, if fit is
a problem and it is only .74. whack it and soon it will be
..75. Don't you adjust your miter bar to fit?

Yeah -- but not by "whacking it until it fits".

The books I have read indicate that is a standard procedure
and certainly works for me. You whack it but rather
specifically you dimple it enough so that any looseness
disappears.

As I have pointed out several times, a tight fit does not necessarily mean a
good fit. By simply "whacking it until it fits" you have *no* assurance that
the bar is straight, and thus *no* assurance of getting straight cuts.
Particularly if one is using your bizarre definition of "fits".

You might want to look at your sig.

Why? Is there something the matter with it?

It's about trolls.

And your point would be...? If you want me to add you to the list, George,
just come out and say so.

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Doug Miller (alphageek-at-milmac-dot-com)

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Doug Miller wrote:


This is false too, by the way. A 0.740 bar *obviously* fits into a 0.750 slot,
and as long as it's straight it can be used to make straight cuts, by keeping
it in firm contact with one side of the slot throughout the cut. It makes no
difference that it's undersized.

Yeah, you caught me, I should have said a "tight" fit. I
think most woodworkers would assume that tightness is
include in the idea of "fit.:" No one would say a board fit
in a rabbet if the rabbet was 1/8" greater than the
thickness of the board.



Do you really mean to suggest that straightness is irrelevant to proper fit?

Of course. If you have a groove in an arc and a piece of
metal in an arc fits the groove, what does straightness have
to do with the fit?

You can have a piece of metal crooked as hell, maybe a
little bend every 1/4-1/2 inch and it can still fit in a
groove with no discernable slop. Fit and straight are simply
two independent elements.


Ooooooh, are you going to killfile me? I'm trembling. Tell you what: let's KF
each other. Then I won't have to read your nonsense, and you can post nonsense
to your heart's content without having to worry about seeing me expose it for
what it is.

I don't kill file anyone.

As I have pointed out several times, a tight fit does not necessarily mean a
good fit. By simply "whacking it until it fits" you have *no* assurance that
the bar is straight, and thus *no* assurance of getting straight cuts.
Particularly if one is using your bizarre definition of "fits".

Huh? did you just switch sides?

It's about trolls.

And your point would be...? If you want me to add you to the list, George,
just come out and say so.

Ok, you need help to understand, it's about trolls. Who is
the troll, maybe you?


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Doug Miller (alphageek-at-milmac-dot-com)

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So... are the tolerances that good on the home-center bar stock?
Personally, I
have my doubts, after having purchased 3/4" aluminum angle from HD that
turned out to be almost 0.020" out of straight over 24 inches. It's hard
for
me to imagine that the bar stock is an order of magnitude better.

... er actually it might well be. Al angle is extruded ... the extrusion
process often leads to a fair amount of bow. Steel bar stock is usually
cold-rolled and the straightness is pretty good.


Can't speak for Home Depot bar stock, but I've got an old Ryerson book in front
of me that gives their width tolerance for cold finished low carbon steel bars
as +0, -.003" for .750" and under. Since that's their tolerance, most of their
stock is better than that. No straightness tolerances specified.

How much do you think your miter slot varies from end to end?

John Martin

Doug Miller wrote:


Ummm... I was starting to think you might be trolling, George, posting this
obvious nonsense and continuing to argue that it's correct, long after your
errors have been pointed out to you.

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Bye now teacher, you have a happy life.

You can have a piece of metal crooked as hell, maybe a
little bend every 1/4-1/2 inch and it can still fit in a
groove with no discernable slop. Fit and straight are simply
two independent elements.

That's simply false, as I have already illustrated at least once.

========================================
NO it is not false...
And that is why your illustration has been chalanged...

You can drill a 1/4 hole every 1/2 inch along both sides (on the
edges) of the miter bar and the damn thing will still fit and slid
without slop....The first and last inch may have slop...but that is
not a problem at all...

Bob Griffiths

In article , Bob G. wrote:


You can have a piece of metal crooked as hell, maybe a
little bend every 1/4-1/2 inch and it can still fit in a
groove with no discernable slop. Fit and straight are simply
two independent elements.

That's simply false, as I have already illustrated at least once.

========================================
NO it is not false...

Yes, it is. If the bar is not straight, it *cannot* fit properly into a
straight slot. And thus "fit" and "straight" are not independent.

And that is why your illustration has been chalanged...

I don't consider either the curved miter slots, or the zig-zag miter bars, of
George's fevered imagination to be a challenge to my illustration.

You can drill a 1/4 hole every 1/2 inch along both sides (on the
edges) of the miter bar and the damn thing will still fit and slid
without slop....The first and last inch may have slop...but that is
not a problem at all...

You're confusing straight with flat. If the bar is straight, and you drill a
bunch of holes along the edges, it's *still* straight. It just isn't flat any
more.

You can contrive as many bizarre situations as you want, it still won't change
the fact that a miter bar *must* be reasonably close to straight if you want
to get cuts that are likewise reasonably close to straight.


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Doug Miller (alphageek-at-milmac-dot-com)

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In article , (Lawrence Wasserman) wrote:

If the bar is .740 & the slot .750 there will be slop regardless of
whether the bar is straight or not.

True, but if it's straight it can be held firmly against one side of the miter
slot and achieve a straight cut despite being undersized.

At any rate, a piece of
cold-rolled 3/4 X 1/4 will be damn close to .750 IME and fit as
tightly as a factory miter gauge bar, for whatever that's worth.

Nobody ever questioned how close the Home Cheapo bar stock is to 0.750. The
question I raised was, how close is it to *straight*? The closer it is to the
exact width of the miter slot, the straighter it had better be, or it won't
fit, e.g. a bar 0.749" wide that's bowed 0.002" out of straight is going to
get wedged before it makes it halfway through the slot.

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