Crosscut Sled Sustained Accuracy

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talonzme
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Crosscut Sled Sustained Accuracy

Post by talonzme »

I am going to build a cross-cut sled for my ShopSmith Mark V. It is stock without any of the upgraded saw tables etc. Given that the headstock and blade are separate from the saw table and the guides that the sled will use how do you keep the accuracy of the sled when converting back to tablesaw mode on the shopsmith?
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dusty
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Re: Crosscut Sled Sustained Accuracy

Post by dusty »

Is this a rhetorical question or do you have a specific issue?

Slide the carriage and headstock together so that they both contact the rubber bumper. Remove the table insert and lower the table to about 3 inch blade exposure. The blade should be near the center of the table cutout when the quill is fully retracted. Tighten all of the locks (tile, quill, carriage, height, headstock). This gives you the standard positioning of the blade to the table and should be very repeatable.

When you have done this AND performed a "complete table alignment" if your setup is not correct - return here with your questions.
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garys
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Re: Crosscut Sled Sustained Accuracy

Post by garys »

It should stay as accurate as you originally build it. If you start with error on the build of your sled, that error will be repeated each time you use it. If you get it accurate when built, that accuracy will be repeated in future use.
This is woodworking, not metal machine work. You don't need accuracy to .0000001 inch.
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dusty
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Re: Crosscut Sled Sustained Accuracy

Post by dusty »

garys wrote: Thu Jan 07, 2021 7:27 am It should stay as accurate as you originally build it. If you start with error on the build of your sled, that error will be repeated each time you use it. If you get it accurate when built, that accuracy will be repeated in future use.
This is woodworking, not metal machine work. You don't need accuracy to .0000001 inch.
Agreed! For the work that the vast majority of us do, precision to within 1/64" (0.016") borders on over kill.
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Erik
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Re: Crosscut Sled Sustained Accuracy

Post by Erik »

If you build a cross cut sled I can highly recommend Nick Ferry's design. You can find it on the web. I built one a couple of years ago and wonder how I ever did anything without it. If you install T-track and clamps (like Nick does) then you can safely cut small pieces too. I always reach for the sled rather than my miter gauge when doing cross cuts.

As for the accuracy, like garys and dusty said, if you build it accurately and your machine is properly aligned it will always deliver that accuracy (because the sled is linked to the miter tracks). I think you will get a lot of use out of it. The cross cut sled and tapering jig are two of my most used jigs.
2018 0930 TS Cross-cut Sled - Nick Ferry Design.jpeg
2018 0930 TS Cross-cut Sled - Nick Ferry Design.jpeg (99.52 KiB) Viewed 1964 times
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Re: Crosscut Sled Sustained Accuracy

Post by JPG »

The repeatability of the 'rubber bumper' has always concerned me. I have far greater faith in the repeatability of the M5 plastic ring. I think having a ring on both way tubes would be more accurate. As mentioned, as accurate as it needs to be for what we are doing. Rigorous consisent seating of the saw arbor on the quill shaft etc. is necessary.
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garys
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Re: Crosscut Sled Sustained Accuracy

Post by garys »

I use the thin 500 rubber ring on my 510 instead of the wide one. That allows me to adjust the blade position myself instead of relying on the ring. This way, the rubber ring doesn't affect position of the head or the table.
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Re: Crosscut Sled Sustained Accuracy

Post by JPG »

i.e. It becomes redundant. Why not just leave it off?
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Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
garys
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Re: Crosscut Sled Sustained Accuracy

Post by garys »

If you leave it off completely, you don't have the thin one acting as a bumper between the headstock and the table. Do you want to bang things up or cushion them?
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Re: Crosscut Sled Sustained Accuracy

Post by RFGuy »

Unless the OP replies again on this thread to clarify, I don't know that their question was 100% clear. My interpretation of their question is with regards to the sawblade placement relative to the miter bar slots. Some Shopsmith owners rely on the rubber bump for carriage alignment and others don't. I use mine, but even so I can see 1-2mm of slop easy. It is enough that over time my ZCI insert becomes just an insert, i.e. not zero clearance any more and has to be replaced. This is despite trying to align the carriage perfectly every time so the sawblade is centered in the ZCI. So, I am assuming it is this horizontal alignment that the OP was asking about. Am I the only one having ZCI issues due to my inability to keep perfect spacing of headstock <-> carriage?

Keep in mind that crosscut sleds can be used for many functions, e.g. some set them up to do box/finger joints, etc. so maintaining a good alignment between headstock (sawblade) and carriage (miter bar slots) can be important for some repetitive cuts, etc.
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