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Kickback prevention: Crosscut sled vs riving knife

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Forum topic by pandamonium54 posted 03-14-2015 07:14 AM 2243 views 0 times favorited 16 replies Add to Favorites Watch
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pandamonium54

10 posts in 1139 days


03-14-2015 07:14 AM

I’m still restoring a Delta 34-441, and I haven’t cut anything with it until I figure out a plan to protect against kickback (and maybe dust collection). Got some inspiration to figure out a riving knife plan, but it looks like it will be more expensive than a new saw if I were to get it fabbed. I don’t own the tools or have the skills to do it myself. So I’m trying to find a substitute…

Can a crosscut sled theoretically work as well as a riving knife in preventing kickback? I’m picturing a regular sled design with a clamp built into the front rail. I just don’t see how the saw can generate enough kickback to throw a whole crosscut sled around, plus the clamp should force the wood to track with the miter slots nicely. Ideas?


16 replies so far

View MrUnix's profile

MrUnix

4233 posts in 1664 days


#1 posted 03-14-2015 07:30 AM

There is very little danger of a kickback when cross-cutting.. with a sled or even when using a miter gauge for that matter. I think you are being overly paranoid.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View Bill7255's profile

Bill7255

354 posts in 1750 days


#2 posted 03-14-2015 10:56 AM

Agree with Brad. You can also look at the micro jig splitter for ripping. Not quite as good as a riving knife, but a whole lot better than nothing.

-- Bill R

View BorkBob's profile

BorkBob

124 posts in 2158 days


#3 posted 03-14-2015 02:22 PM

Kickback is caused by the “rear” teeth of the saw blade grabbing and throwing the work piece. The “missile” can be the primary piece, the off-cut or both. A riving knife or splitter provides a barrier near the “rear” teeth.

A cross cut sled will hold the primary piece in place but it’s possible for the off cut to be thrown if not secured. One of the advantages of a riving knife is that it can be used in conjunction with a cross cut sled. Factory splitters must be removed if the sled straddles the saw blade.

I applaud your safety consciousness.

-- Please Pray for Our Troops / Semper Fi / Bob Ross / www.theborkstore.com

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MrUnix

4233 posts in 1664 days


#4 posted 03-14-2015 02:35 PM

A cross cut sled will hold the primary piece in place but it’s possible for the off cut to be thrown if not secured.

Gotta disagree… there is nothing to bind the off cut against the blade for it to be thrown.. it might be kicked out of the way a little bit, if at all, but it isn’t going to come flying at you anything like you would experience when using the fence and ripping the stock. Matthias (woodgears.ca) even tried an experiment where he free-handed a cross cut, trying to force it to kick back, and didn’t have very good success:

http://woodgears.ca/table_saw/kickback.html

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View Rick M's profile

Rick M

7923 posts in 1845 days


#5 posted 03-14-2015 08:43 PM

You might as well give up and buy a newer saw. Many people have tried to retrofit those Deltas with a riving knife but it can’t be done without extensive reengineering, as you discovered, it’s cheaper to buy a new saw. Incidentally I’ve owned a Delta contractor for 15-ish years and haven’t used the blade guard or splitter most of that time and I’ve never had a kick back. Don’t cut wet wood, don’t stand behind the blade, and focus on what you are doing. And to echo the above comments, the riving knife is of no benefit when cross cutting. I have had pieces fly back while crosscutting but because there was a split inside the wood and the offcut separated into two or more pieces, a riving knife is of no value in that situation.

-- http://thewoodknack.blogspot.com/

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bondogaposis

4035 posts in 1817 days


#6 posted 03-14-2015 08:51 PM

A couple of tips for preventing kick back. Make or buy a splitter, they work great. Use feather boards. Don’t rip short stock, my rule, nothing shorter than 12”. Never use the rip fence in conjunction w/ the miter gauge on through cuts. That is one advantage of a sled, you have to take the rip fence off to use it.

-- Bondo Gaposis

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TimberMagic

114 posts in 644 days


#7 posted 03-14-2015 09:28 PM

Regardless of whether you add a riving knife, or maybe a splitter, I highly recommend a GRR-Ripper push block. I’d suggest watching their video. The legs are adjustable, it incorporates a movable, removable sacrificial push “plate”,. By design the blade passes though a “tunnel” formed by the block and its legs, making it very safe since your hand is not expsoed to the blade. Each one comes with a variety of add-ons to make it usable on just about any piece of material you plan to cut. I bought a specially priced “2-pack” that included some extras free of charge. Using two blocks allows you to use it on longer boards where you can use a hand-over-hand feeding style to make sure one of the blocks is always engaged with the piece of wood being cut.

-- Lee

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REO

889 posts in 1539 days


#8 posted 03-14-2015 09:34 PM

good explanation Rick and Brad!

View Rick M's profile

Rick M

7923 posts in 1845 days


#9 posted 03-14-2015 09:35 PM

+1 on the Grrripper. I thought they were probably a gimmick but bought one on sale and love it.

-- http://thewoodknack.blogspot.com/

View pandamonium54's profile

pandamonium54

10 posts in 1139 days


#10 posted 03-16-2015 04:09 AM

I saw the Grr ripper in a few youtube videos by the guy’s son… they look well engineered, but I never liked how close your hands got to the blade. I guess the main thing I’m picturing is that notorious kickback video where the guy used a regular push block. Even with the extra 3” or so of clearance on those things, if I were pushing down right over the blade, no amount of reaction time would be useful. I’d rather use a combination of push stick, feather boards, sled, etc.

I looked into the MJ splitter, and I was giving it serious consideration until I saw its price. I’d be in for $70 for a little guitar tab sized splitter adapter.

I originally bought the used saw to save money. ($250 for a rusty Delta 34-441 with 30” unifence with TS stand, no mobile base, missing 30” wing +/- some accessories, and an Incra Jig Ultra.) I’ve been tallying my restoration expenses in an excel file, and I’m in for about $640 so far (including the $250). I have yet to use the saw to cut anything because I want to reassemble this thing one time, properly. If I could recover $250 for the thing, I’d give serious consideration to dumping it for a new Sawstop Jobsite. I’ve sunk at least 100 man-hours in this project and I don’t have a whole lot to show for it.

Knowing what I know now, I should have bit the bullet and bought new to begin with. I’d probably be $2k lighter than I am now, but instead of drawing up plans for tool maintenance/tweaking/etc, I could be drawing up plans for the pieces that I could use on a day-to-day basis.

Hell I spent the other night reading about tapping threads into cast iron and doing acrylic “welds” to see if I could fab my own sawblade shroud and riving knife.

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MrUnix

4233 posts in 1664 days


#11 posted 03-16-2015 04:24 AM

I’ve been tallying my restoration expenses in an excel file, and I’m in for about $640 so far (including the $250).

Hate to say it, but you obviously are doing something very, very wrong, or really have no idea what you are doing to have sunk that much into a restoration. What in the hell have you been spending all that much money on? If the thing ran, a good cleaning, paint, new belt and bearings should not have run you more than about $50. A mobile base is like $30 at HF, and the missing extension wing can be made yourself for another $20 or less depending on what you have around the shop.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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pandamonium54

10 posts in 1139 days


#12 posted 03-16-2015 04:54 AM

$26 PALS, $56 Machined pulleys, $25 for bearings, $30 to get a machine shop to pull the old bearings, $66 Rockler Mobile base, $18 for mobile base lumber, $15 for a new power switch (the saw’s switch was rigged so that I couldn’t detach the motor), $100 on T9/scotchbrite pads/WD40/Battery charger/sacrificial rebar/other electrolysis supplies, $26 for some new hardware, $50 for primer/paint/brushes/mineral spirits/paint stripper. (Never again will I use paint stripper…)

Biggest mistake might have been choosing this particular saw. If I had spent more time reading up on Incra and comparing pictures, I would have learned that it was an older router fence. But I wasn’t sure if another local was going to jump on it.

Only other thing I can think of is that I wasn’t patient enough with electrolysis and thought that I could get away with stripping the paint off the underside of the table. Added a god-awful lot of man hours and a second round of electrolysis to just clear out the stripper residue.

I don’t think I made many more mistakes than that. I figured a lot of my expenses are because I’m starting off. So instead of getting cleaning supplies piecemeal as I need them, I’m having to buy them all at once on the front end. Before this, I owned a drill, some bits, a jigsaw, a walmart “homeowners tool set”, and a Kreg jig.

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MrUnix

4233 posts in 1664 days


#13 posted 03-16-2015 05:25 AM

Biggest mistake might have been choosing this particular saw.

LOL – while it does sound like you paid way too much for it to begin with, that was just your first mistake of many IMHO. Most of what you spent was either completely unnecessary or way too much, and some of what you paid for could have been obtained for free pretty easily.

There is a huge pool of people who could have offered real hands on guidance and advice out there, and could have saved you a lot of grief and money along the way. It appears like you didn’t tap into that resource, which is unfortunate. And that may well be your biggest mistake.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View rwe2156's profile

rwe2156

2198 posts in 946 days


#14 posted 03-16-2015 10:47 AM

1. The only way to get kick back on a crosscut is get the cutoff caught between blade and fence. Its only happened to me like twice in 25 years and both times it involved me ripping thin stock and not minding my p’s and q’s regarding blade height. It also involved me getting it right in the groin…...one time so bad it broke the skin.

2. Don’t waste your time/money trying to fab a riving knife. The Miicrojig works great and is a whole lot easier to remove when plowing a groove.

3. For the price of 1 Grrrper I can make 20 years worth of push sticks. Plus all that fiddling.

Remember: The most important piece of safety equipment in the shop is between your ears.

4. For dust collection, you can close in the bottom and fabricate a port. I would stay away from over the blade DC I don’t think its worth the cost for the benefit. If you’re getting into stuff like MDF, you should be wearing a respirator no matter how good your DC is. There are videos out there on this.

5. MOST important: once you get the saw up and running, you must do a complete alignment check on both the blade and the fence. There are plenty of videos out there about this.

Panda, you’re learning a valuable lesson about buying used equipment and although I agree with Brad in FL (but perhaps a bit more gently) that you’re investment will be more then the saw is worth, still you’re gaining experience and just like the rest of us, experience is not free. But in the end you will have a saw the you know YOU put together and it should last for many, many years.

Finally, keep in mind what you’ve got here is a basic 1 1/2 hp contractors saw with a decent fence. Since you’re getting into this depth of restore, you might consider upgrading to a 2HP motor. Also, going with thin kerf blades is a power boost.

If you’re just starting out, it would be great if you found an experienced woodworker you can buddy up with to who can advise you on stuff like this. If there’s a Woodcraft store around, you can find out about local ww clubs.

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

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firefighterontheside

13503 posts in 1322 days


#15 posted 03-16-2015 12:48 PM

A crosscut sled won’t do anything for you when ripping. You will still need to either have a riving knife, splitter or get along without it. I have nothing on my grizzly saw. It’s too old to have a riving knife and I won’t use the splitter or blade guard. Too inefficient. I crosscut all narrow stuff with my miter saw and anything say 8” or wider with the sled.

-- Bill M. "People change, walnut doesn't" by Gene.

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