LumberJocks

What the heck should I do here, pretty peeved....should I be

  • Advertise with us

« back to Jigs & Fixtures forum

Forum topic by TDog77 posted 870 days ago 2679 views 1 time favorited 44 replies Add to Favorites Watch
View TDog77's profile

TDog77

125 posts in 980 days


870 days ago

I spent the whole day working on my sled today and after lunch I milled down the Ultra high density plastic, dadoed the bottom of the sled to capture the runner and then I pre drilled holes and had it perfectly sized for the miter slots on the table saw; however when I screwed it in from the bottom (by hand with only a little pressure) at each and every screw hole there was a slight bulge so I spent the next 4 hours shaving sanding etc. on the runners to just hit that point where it would slide without binding but now I can feel ever so tiny of a wiggle when the sled is pushed all the way forward where the blade wold be passing under the rear fence. When I say a tiny amount of wiggle I am putting my hands on either side of the sled and push back and forth I end up getting .002 of movement left to right. I have a hard time accepting this as I am a complete perfectionist but my wife said I am chasing something Ill never get. I am thinking of running and picking up some hardwood in the morning and making some good old wood runners and redoing it. What do you think?


44 replies so far

View Sawkerf's profile

Sawkerf

1730 posts in 1696 days


#1 posted 870 days ago

That’s pretty insignificant. This is woodworking, not tool and die machining. Try some paste wax on the runner, sled and saw table. It’s ok if it’s a bit stiff – it will wear in eventually.

-- Adversity doesn't build character...................it reveals it.

View TopamaxSurvivor's profile

TopamaxSurvivor

14721 posts in 2303 days


#2 posted 870 days ago

Tighten those screws another 1/2 turn if it bothers you. I know the feeling. In the big picture, it doesn’t matter, but it still bugs yoiu ;-( I like wood runners glued on. They stay put where I clamped them on top the saw ;-)

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View doughan's profile

doughan

96 posts in 1218 days


#3 posted 870 days ago

take up faceting

View RandyM68's profile

RandyM68

693 posts in 945 days


#4 posted 870 days ago

You’d probably better just throw it away and start over. You’ll never be able to live with all that slop, you’ll make more scrap than good parts. But seriously, two thou doesn’t mean anything unless you are going for a press fit on a bearing or something important. You can make new runners, but chances are, they will be just a little off, too. If they fit perfectly, and are made out of wood, they will lock up in the slot when the humidity goes up, and wiggle just a little when it goes down. I have that problem with my oak runners, and was thinking of using plastic. Maybe, if you counter sink the holes just right, it won’t swell when you tighten it, but I’ll bet it does. I’ve machined a lot of plastic on a mill. It is almost impossible to get perfection with a $200,000 CNC. That stuff moves all over the place, when you machine it, and when you screw it down. The only way that you might get it perfect, is if you make the runner over-sized, screw it in place, and trim it to fit. Good luck.

-- I can explain it to you, but I can't understand it for you. I'm sorry,thanks.

View TDog77's profile

TDog77

125 posts in 980 days


#5 posted 870 days ago

Tightened up the screws in a pattern and it took up some so then I added a few strategic ones and bam it is just about perfect.

Thanks Topamax, I did not think those little screws would put up with the stress of trying to compress it more but they have held out pretty good and the few extras was all that it took.

Judging by the comments if it does get a tiny out of whack in the future maybe I won’t fret soo much. I just like to have my equipment and jigs just about perfect so that I am the only one to blame when things don’t come out instead of chasing down equipment errors.

View a1Jim's profile

a1Jim

112011 posts in 2204 days


#6 posted 870 days ago

I’ve made some runners out of rolled steel and filled it to fit. You could try adding a little epoxy on the loose end and sand to fit or try putting a thin strip of the metal type duct tape on the loose end and see if it’s the right size to cure the problem.

-- http://artisticwoodstudio.com Custom furniture

View Loren's profile

Loren

7400 posts in 2275 days


#7 posted 870 days ago

You can tap holes in the sides of your runners and put a set screw. You
could probably tune it out with 1 tapped set screw if you correctly
identify where the most slop is occurring. There are other ways to
shim or make a runner bulge too. Look at commercial models to
get some ideas. I think there is a kit with set screws and phenolic
plugs available… but generally meant for miter gauges. I think it might
be a Woodhaven product.

That said, wood neither accepts nor demands the precision metal
machining does.

-- http://lawoodworking.com

View crank49's profile

crank49

3371 posts in 1598 days


#8 posted 870 days ago

If you want perfection, make the whole sled out of cast iron next time.

Seriously though, did you use flat head screws in counter sunk holes? i.e. angled bottom on the head.
If so, that is the basis of the design of some jigs to be adjustable; exactly like you just found.
Plastic is very good at a physical attribute called “plastic deformation”. Wonder where they got that name?

One way to reduce this effect is to counter bore (flat bottom) holes and use a pan head or flat washer head screw.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View TDog77's profile

TDog77

125 posts in 980 days


#9 posted 870 days ago

I think the part that bugs me about the plastic is it is pretty hit or miss as far as how much smaller you should cut it then the total width of the miter slot since you don’t really know how much it is going to deform once screwed. I could not really believe how much it bulged with very little pressure. I initially cut it about .002 less width then the slot and that is ENTIRELY too tight for a plastic runner unless you want to do a lot of fitting. So what would I cut to next time….don’t know but it would be a fair amount less. Now that I do have it about perfect I am pleased to have something on there that will stay the same regardless of weather.

View Bertha's profile

Bertha

12951 posts in 1320 days


#10 posted 870 days ago

I was thinking like A1. Buy a spark plug gap tool, cut it up, drill a small hole for the epoxy to collect, and glue a shim on each side. Good luck!
Edit: you could also strip off the runners and buy some Incra ones.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View Gene Howe's profile

Gene Howe

5518 posts in 2056 days


#11 posted 870 days ago

Just a thought….yeah, I get one every several weeks…I wonder if gluing in a wood or phenolic block or dowel, then counter sinking a hole through that, would work. Don’t use much UHMW so not sure about the glue to use.
To save the hassles, I just buy metal sliders.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View Fuzzy's profile

Fuzzy

289 posts in 2615 days


#12 posted 870 days ago

Wait until the weather warms up a bit more … the fit will be very tight … next winter, it will have gobs of slop. That is the major drawback to UHMW … it moves with temperature changes … and it moves a LOT. I have bunches of it that I picked up where I worked as scrap … the only place I use it is where I need to reduce friction AND the application requires zero precision.

As for gluing shims to it … forget about it … there is only one adhesive that will truly bond to UHMW, and it’s very $$$$. Even with that, it’s only really good for sticking two pieces of UHMW together … anything else has a different thermal expansion coefficient, and the constant flexing eventually will break the bond.

I’ve com to using LEXAN (also old scraps from work) ... not as slippery, but much more stable … and it wears like iron.

-- - dabbling in sarcasm is foolish … if you’re not proficient at it, you end up looking stupid … ... ...

View shipwright's profile

shipwright

4901 posts in 1425 days


#13 posted 869 days ago

Were you using countersunk heads? If you want to fasten UHMW and not have it deform you would have better luck with pan head screws in flat bottomed counterbores. If that is what you did…............. never mind :-)

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View TDog77's profile

TDog77

125 posts in 980 days


#14 posted 869 days ago

Yes I used bugle type heads, however even flat bottom heads would still deform it to some degree although I agree it would be less.

Fuzzy, could you take a pic of your lexan system?

View ajosephg's profile

ajosephg

1850 posts in 2188 days


#15 posted 869 days ago

How did you measure that alleged 0.002?

-- Joe

showing 1 through 15 of 44 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase