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Failed table saw sled

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Forum topic by mskovs posted 11-15-2016 01:44 PM 990 views 0 times favorited 15 replies Add to Favorites Watch
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mskovs

3 posts in 390 days


11-15-2016 01:44 PM

Topic tags/keywords: jig

Hi there.

My first sled was a failure and migth need so help too figure out what went wrong.
The hardwood (oak) runners is loose at the front of the saw and binds at the end. Even if I turn them arround. I suspect that this is in issue with the cheap cabinet saw that I migth not be able too solve?

After my initial cut in the base I can still hear the blade rubbing against the plywood. is that too be expected?


15 replies so far

View Lazyman's profile

Lazyman

1493 posts in 1220 days


#1 posted 11-15-2016 02:20 PM

Did you have problems right away or after some time passed? When cutting hardwood runners, it is important to select a board with very straight grain that runs almost straight from end to end, especially with oak. If not, the grains can move ever so slightly after the cut. You also need to make sure the board is flat with no twist, cupping or warping to begin with. It also helps if you cut them so they look like they are quarter sawn where the grain is vertical across the narrow dimension when viewed from the end. I like to use maple for for my runners because they have very fine, closed grain that is less prone to warping.

You may be able to tune the runners with some sandpaper to make the sled usable. Take a sharpie or orther marker and mark along the sides of the runners. Put the sled on the table, blade retracted, and slide it back and forth to get some wear on the runners. You should be a able to see where the marker is rubbing or smearing and use some sandpaper to sneak up on a better fit.

The rubbing of the blade you describe sounds more like a problem with the blade not being perfectly flat or the blade is not tuned to be parallel to the miter slots or is not set at 90°. Does the blade appear to wobble as it slows to a stop? After you use the sled for a while, it will eventually wear the grove wider. But if the blade is not perfectly tuned, it will make it difficult to cut perfect runners too.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View HokieKen's profile

HokieKen

4503 posts in 971 days


#2 posted 11-15-2016 02:52 PM

Your problem sounds like the miter slots are worn. The good news is that it’s easily fixed.

Here’s the trick… you don’t need your runners to contact both sides of both slots. If your runners both “hug” the inside of the slot they ride in, then your sled will have no slop. You can leave 1/16” clearance or so to allow for expansion of the runners and still run true. Same thing if both runners contact only the outside of their slots.

My saw has worn slots as well. So I used a caliper to measure at different places to determine which sides were most parallel. On mine, it turned out that the outer edges were parallel and the inside of one of the slots was worn. So my runners ride on the outer edges of the slots and don’t contact the inner edges at all.

If you don’t have parallelism on either the outer or inner edges of the slots, then you’ve got a problem…

Good luck!

-- Kenny, SW VA, Go Hokies!!!

View Michael Murphy's profile

Michael Murphy

452 posts in 2838 days


#3 posted 11-15-2016 02:58 PM

I always use aluminum runners.Still workable with carbide tools for cutting and normal tools to drill and shape. You can buy 3/4 wide material to fit the slot. You can dimple the sides with a center punch to get it tighter if necessary and they never warp. The two primary ones I use are one made to be alsways 45 degrees and another that has adjustable fences. Latley they have been set to 22.5 for 8 sides. Making ocatagonal frame snd routing them round.

-- Michael Murphy, Woodland, CA.

View GR8HUNTER's profile

GR8HUNTER

2947 posts in 545 days


#4 posted 11-15-2016 03:02 PM

Your problem sounds like the miter slots are worn. The good news is that it’s easily fixed.
Here’s the trick… you don’t need your runners to contact both sides of both slots. If your runners both “hug” the inside of the slot they ride in, then your sled will have no slop. You can leave 1/16” clearance or so to allow for expansion of the runners and still run true. Same thing if both runners contact only the outside of their slots.

If you don’t have parallelism on either the outer or inner edges of the slots, then you’ve got a problem…

^^^^^^^^DITTO^^^^^^^^^^^^^^Kenny^^^^^^^^^^^^^^^^^^^^^^

-- Tony Reinholds,Pa. REMEMBER TO ALWAYS HAVE FUN

View HorizontalMike's profile

HorizontalMike

7649 posts in 2746 days


#5 posted 11-15-2016 03:12 PM

PICTURES OR IT DID NOT HAPPEN! Can’t really help without seeing it. Sounds like to me that the hardwood pieces at the front and rear, are probably NOT tall enough to prevent flexing. Remember that you need plenty of space(wood support) ABOVE the blade cut in order to hold both halves steady and in proper position/alignment.

Here’s mine:
http://lumberjocks.com/projects/57667

-- HorizontalMike -- "Woodpeckers understand..."

View Redoak49's profile

Redoak49

2887 posts in 1821 days


#6 posted 11-15-2016 03:57 PM

I use the Incra miter slider. When the sled gets worn out, I move it to the next sled.

Another way is to make a narrow slot in the runner and counter sink it and then use a flat head 10-24 bolt. As you tighten the bolt the runner expands. I have done this and it works OK.

Personally, I find too much time is spent with wooden runners. A heavy plastic is better. For $18 on Amazon you can get the Incra miter slider.

View rwe2156's profile

rwe2156

2707 posts in 1313 days


#7 posted 11-15-2016 04:41 PM

Check for parallel slots first. If they are not parallel, you will haven an issue buidlng any kind of sled.

Make sure the runners are perfectly straight, attach with screws every 3”. Be aware that when screwing the runners on it is best to do it from the top because the tapered head tends to bulge the grain outwards.

When I build sleds, I put the runners in the slots, align the sled on top, then secure with screws without removing sled or runners.

You can usually see the rub marks and I use a plane blade as a scraper to fine tune the fit. Then a liberal coating of wax.

-- Everything is a prototype thats why its one of a kind!!

View mskovs's profile

mskovs

3 posts in 390 days


#8 posted 11-15-2016 10:33 PM

Thanks for all your replys.

The blade is in fact parallel too any of the runners. The slots are not worn. The saw is located in a community workshop and most users go for the sliding table. The saw is just a cheap china model where nothing really is in allignment.

I will try with non wood runners next time and will spend some time on alignment on the blade.

View HokieKen's profile

HokieKen

4503 posts in 971 days


#9 posted 11-16-2016 03:32 AM



Thanks for all your replys.

The blade is in fact parallel too any of the runners. The slots are not worn. The saw is located in a community workshop and most users go for the sliding table. The saw is just a cheap china model where nothing really is in allignment.

I will try with non wood runners next time and will spend some time on alignment on the blade.

- mskovs

I don’t understand. If the blade is parallel to “any of the runners” (I assume you mean slots), then how is “nothing really in alignment”?

-- Kenny, SW VA, Go Hokies!!!

View Carloz's profile

Carloz

952 posts in 424 days


#10 posted 11-16-2016 05:07 AM


Check for parallel slots first. If they are not parallel, you will haven an issue buidlng any kind of sleds.
- rwe2156

Are you so sure ? one runner is more than enough for a sled and parallel slot or not does not matter.

View rwe2156's profile

rwe2156

2707 posts in 1313 days


#11 posted 11-16-2016 03:06 PM


Check for parallel slots first. If they are not parallel, you will haven an issue buidlng any kind of sleds.
- rwe2156

Are you so sure ? one runner is more than enough for a sled and parallel slot or not does not matter.

- Carloz

You’re right!! I’m referring to large table sled with two runners.

-- Everything is a prototype thats why its one of a kind!!

View mskovs's profile

mskovs

3 posts in 390 days


#12 posted 11-16-2016 10:25 PM

Correct. The blade is not parallel to any of the two slots.
Well blade is not true 0 or 45 degress. sliding table is not true. That is caused by too many people messing with it. So I really need a sled to be consintent

View HorizontalMike's profile

HorizontalMike

7649 posts in 2746 days


#13 posted 11-17-2016 01:25 AM



Correct. The blade is not parallel to any of the two slots.
Well blade is not true 0 or 45 degress. sliding table is not true. That is caused by too many people messing with it. So I really need a sled to be consintent
- mskovs

Either adjust it, if you can, or get another saw… IMO. I am known for using store-bought washers and shims when needed…

-- HorizontalMike -- "Woodpeckers understand..."

View HokieKen's profile

HokieKen

4503 posts in 971 days


#14 posted 11-17-2016 04:18 AM



Correct. The blade is not parallel to any of the two slots.
Well blade is not true 0 or 45 degress. sliding table is not true. That is caused by too many people messing with it. So I really need a sled to be consintent

- mskovs

Unfortunately, if the saw isn’t consistently aligned properly your sled will never be reliable either.

-- Kenny, SW VA, Go Hokies!!!

View Lazyman's profile

Lazyman

1493 posts in 1220 days


#15 posted 11-17-2016 04:12 PM

Kenny is correct. You have to get the blade parallel to at least one miter slot, preferably the one most often used with the miter gauge, to have any chance of accuracy on the saw. Once you have the blade lined up with a slot, you should also adjust the fence so that it is aligned with the same slot. If the fence is not aligned with the slot and therefore the blade, this becomes a potential safety issue. Trying to rip with a fence that is out of alignment relative to the blade is just asking for a kickback and it will be next to impossible to rip cuts where the sides are parallel to each other. It sounds like this is community or classroom saw. Everyone would benefit from taking an hour or two trying to get the blade aligned properly for safety sake alone. Even a cheap saw can make decent cuts if it is properly tuned.

By the way, you mentioned that the blade is not true to 0 or 45. Don’t worry too much about what the tilt gauge says the angle is. You should always use a square to set and check the angle of the blade.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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