Rip Saw Kick-Back Prevention
Pondering how to prevent a recurrence of a rip-saw accident that sent the off-cut flying and crushed a finger. December 14, 2009
Question
About a week ago I was ripping to width a bunk of colored beech when a cut off piece back fired and literally crushed my finger. It shattered my joint and fractured it in five other places. I had to have emergency surgery where they put five screws in my finger and they are hoping that I will be able to get partial use out of the finger in a few years. I was wondering if anyone has ran into an encounter of sorts where an off-rip backfired and if so, if you found a way to prevent it. The odd thing is that there are two anti-kickback devices on the machine but it still managed to get by them. I would appreciate any help or ideas because this accident has our whole shop concerned about what happened and how to fix it. I appreciate your time.
Forum Responses
(Dust Collection and Safety Equipment Forum)
From contributor F:
Can you give us some more details? How far above the material was the blade raised? Was there a riving knife/splitter being used? What are your anti-kickback devices? Were you getting a decent cut? It all goes back to blade problems. Which part of the board kicked back?
From the original questioner:
The blade is set to cut right through the material. I am not sure if you are familiar with a rip saw but you send it through and it is on a conveyer that puts a straight edge on it. There is actually a groove on the conveyer for the blade to go into so there is a clean cut through the wood. There is no splitter but there is pressure on it. The anti-kickback devices are a row of fingers that are angled to let the board go through but not come back. The first set of them actually touch the conveyer and the second are probably 3/8" off the conveyer. The blade was just recently switched out for a sharp one so we were getting a great cut. It was the off rip that kicked back it was probably a 1/2" thick.
From contributor M:
I have never had a kick back like that before personally. I have used Madison 202 ripsaws for many years ripping up to 3" thick stock. On occasion rips do get stuck in the fingers, but the next piece gets it out. It is an old rule that you never ever stand behind the board when ripping. A long time ago at my family’s factory a man was killed from a kickback so it can happen unless you are careful. Always listen to the ripping you can hear when there is a lot of stress in the wood which in my opinion is the most likely time for kickbacks.
On a foot note I think the ripsaw is the safest and fastest way to get a glue joint edge on boards, so tell the shop not to worry but to respect the machine like all woodworking equipment and they will be fine.
From contributor U:
The anti kickback fingers could be damaged or not moving freely at the pivot. I've had the ones on a old regular sliding bed saw slip off the side of an off cut, due to wear, defeating their purpose and putting the off-cut into the side of the blade. On an inline rip they're usually more of a curtain of fingers therefore they might be catching on each other if they're damaged, or stuck in an up position. As contributor M said don't stand behind the material being ripped.
From contributor F:
One thing you could change if you want to eliminate the off-rip all together would be to add a hogger head. It basically chews up the off-rip into dust collector compatible pieces as it is ripped by the blade. There are many types available from carbide tipped up to insert tools. Many people find this a good way of eliminating having to handle scrap pieces as well.
From contributor F:
One thing you may also take a look at is the anti-kickback pawls. Often they are so dull or even rounded over they don't grab stock well enough to prevent kickback. The last shop I worked at took them off and ground the tips so there was a sharp edge. It’s better for catching the wood I would think.
From the original questioner:
I appreciate the responses. The weird thing was I was not standing behind it, I was standing to the side getting ready to put in another piece when it happened. If I were standing behind it I would say I deserved it. Thanks again and if you have any other responses that would be a great help while I try to figure out what happened.
From contributor E:
I was just reading the manual for our ripsaw the other day, while looking for some other repair information, and noticed that there is a warning about small off-rips falling down along-side the blade where there is no pressure from the top rollers. If your blade insert is worn, and allows the piece to drop down a little, or tilt, it just might be small enough, or at the right angle to get kicked back between the fingers. I am not sure there is a solution to this, except being very careful when taking narrow rips off of boards.
