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Bandsaw table insert failure.
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=28068		 Page 1 of 2
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 9:10 am ]
Post subject:  Bandsaw table insert failure.
I know this has been touched upon here on the forum before but after last night I am compelled to bring it up again.

The insert on my Rikon (plastic) decided to cave in last night whilst resawing some headstock overlays from some of my new Brazilian Rosewood stock. Lots of noise and some damage. The blade (a 3/4 tooth 3/8th's Tri-master) took out a portion of the fence, bent the door of the guide post, broke the viewing glass (plastic), and quite possibly ruined the blade. It's bent in some ways I've never seen a bandsaw blade bend. I've had this blade lengthened so it's already got two weld joints in it.

The real reason for posting is to get ideas on a zero clearance insert. I can make them but don't like to (they never fit perfectly for me).

Thanks,
Chris
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 9:48 am ]
Post subject:  Re: Bandsaw table insert failure.
I'll go get pics right now...but I'm definitely in the running for the aluminum.
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 10:29 am ]
Post subject:  Re: Bandsaw table insert failure.
Getting photos of the blade was really hard and I'm not sure you are going to be able to see it. It's bent on every axis. I posted thumbs rather than full size images. Keeps everyone from having to scroll left and right to read the post. Just click.

Image

Image

Image


Here's the guide post door. I've already bent it back. Plastic viewing shield is gone.
Image


And here's the fence. Not to bad now that I've looked at it this morning. File the nibs off and
I might not ever know it happened. Last night I had blurry vision from high blood pressure.
Image

I threw the insert (3 pieces) away last night. I'm up for funding on this project. I may make some sort of temporary insert in the meantime. Google doesn't show anything for an aftermarket insert.


Chris
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 11:51 am ]
Post subject:  Re: Bandsaw table insert failure.
verhoevenc wrote:
FREAKY! The SAME thing happened to me two days ago! I just made a new, and better, maple one that's even more zeroy. That said, mine didn't do the same damage, but it IS VERY dangerous. If you are resawing something small it likes to tilt that forward which sends you hand towards the blade. All the damage mine did was take out the plastic insert, and lose me about 1.5" worth of teeth on my woodmaster CT.
Chris


I'll get a hold of Iturra on Tuesday and see what he says about the blade. If I can get this fixed with no more than 2 weld joints I'll do it. Anything over 2 weld joints and the blade starts acting funny, lower quality of cut, etc. I've put the CT back on the saw since I WASN'T FINISHED!!!! gaah gaah [headinwall] [headinwall] pfft pfft

Chris I'm curious about how you made your insert.

Chris
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 12:36 pm ]
Post subject:  Re: Bandsaw table insert failure.
Todd Stock wrote:
Most factory inserts are set up to handle 45 deg tilt of table...just like tablesaw inserts. A run of phenolic or aluminum inserts would be good. FWIW, slot to the back is usually safer.



Todd I don't think a zero clearance insert is still 'zero clearance' if you mill the insert to accomodate a 45 degree tilt. I may be wrong about that though. Agree with slotting to the rear of blade. They are easy enough to pop out when changing anyway.
Author:  Darrel Friesen [ Sun Jul 04, 2010 1:40 pm ]
Post subject:  Re: Bandsaw table insert failure.
I bought a 4 pack of the UMHW inserts at a woodworking show. I cut the zero clearance slot and put it to the back as per Todd. Three years and I still haven't had to replace it. Like Filippo, I never change the angle of my table, perhaps because I've never had a reason to. I'm still not entirely clear on what happened here? Looks like the insert tipped and a chain of damage events then happened?
Author:  Stuart Gort [ Sun Jul 04, 2010 1:54 pm ]
Post subject:  Re: Bandsaw table insert failure.
That would be a very simple aluminum project except for one thing. The saws aren't made nearly accurate enough to have the blade track in the exact same position from machine to machine. So making one for mine may not fit yours, especially if you need to kick into the 45 degree position unless the slot was made fairly wide.

If using wood....I'd make it fit fairly loosely into the hole, epoxy two studs into the bottom, and make a small clamping bar that would clamp it to the underside of the table. It would never fly off if done that way. Using wingnuts you could have something that was fairly quick to dissemble which would make having two of them more viable. One for 90 degrees and one for 45 degrees....or whatever.

I'd also make the plug .05" or so higher than the table and just use a router to bring the plug flush to the table.
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 2:00 pm ]
Post subject:  Re: Bandsaw table insert failure.
Darrel Friesen wrote:
I bought a 4 pack of the UMHW inserts at a woodworking show. I cut the zero clearance slot and put it to the back as per Todd. Three years and I still haven't had to replace it. Like Filippo, I never change the angle of my table, perhaps because I've never had a reason to. I'm still not entirely clear on what happened here? Looks like the insert tipped and a chain of damage events then happened?


The insert collapsed. That removed any support the wood may have had.....the blade grabbed the piece of wood and tried to pull it through the hole and caused the end (of the wood) I'm holding to launch to the moon...guide post cover stops it but pays the price. Blade deflects all over the place cuz all that energy has to go somewhere. It takes out the looking glass (plastic) and nibbles on the fence a little. I'm sticking to my story....and keeping all my fingers.

Filippo I don't use my saw in that manner either (angled cutting) so I don't think I'd need anything like that.

Chris I'm out in the shop today making another insert, but waaaaaaaaay more complicated than what you describe. Wish I'd read your post first. I'm measuring with dial calipers and calculating depth and radius and the tangent of the moon in February...... laughing6-hehe What I'm doing will work certainly but I went all the way to Saturn and back to do it.

[headinwall]

Darrel I'm not sure which inserts you speak of. This is an 18" Rikon and I THINK the insert diameter is considerably larger. If it's the same diameter of a standard 14" insert I'm gonna be really twisted. You'll likely read about me in the newspaper.

Chris
Author:  Stuart Gort [ Sun Jul 04, 2010 2:53 pm ]
Post subject:  Re: Bandsaw table insert failure.
Yeah...I really wasn't thinking zero clearance but if I made one I'd make it a lot tighter than the factory does. Maybe .05 - .075" on each side of the blade.

Also....if I made one...I'd make it out of aluminum so the stud holes would be threaded and it could never crack.

UMHW is nice stuff for sliding but the reason to make something other than a factory plug is to guarantee that it won't come out and cut things that were rather left uncut. My design objective would be to fasten it to the table and UMHW is a bit hard to work with when it comes to attaching fasteners. It could be done with countersunk machine screws through the plug, through the clamping bar....but aluminum would be easier.

Yeah....I'd want it laminated with at least two perpendicular plies if wood. One might consider phenolic as well. Phenolic has some pretty nice homogenious properties and would machine easier than metal, be stronger than wood, and be a little bit slicker than either wood or metal. Acrylic would work too. Epoxy sticks well to phenolic and acrylic so you wouldn't have to tap the holes for the mounting studs....just glue the studs in place.
Author:  Darrel Friesen [ Sun Jul 04, 2010 3:11 pm ]
Post subject:  Re: Bandsaw table insert failure.
Chris, mine are for a 17" General and about 3/8" thick. I just checked and they are nylon, not UHMW. They fit snugly and seem very strong to me. They are made by Workbench Design. 1-888-994-2836
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 3:42 pm ]
Post subject:  Re: Bandsaw table insert failure.
Thanks for that information Darrel I'll check it out.

Stuart I didn't consider making something that attaches the insert from the bottom of the table....but will. I've got almost .050" clearance between the inside side of the blade and the ledge of the insert. I think this will be adequate as I've yet to resaw anything that wasn't .100 or thicker. I cut headstock overlays at about .110 and that's about as thin as it gets.

In the meantime I've spent a better portion of the day making an insert and here is what I've come up with. This will get me through until we figure out what the next insert will be.

I used a scrap of quartersawn white oak I had laying around in the shop. Broke out the dial calipers and went to work. Used a circle cutter on the drill press to do the milling. I've got several other 'bits' I've made for different things that came in handy here. Once I had it rough fit to the table I just used a random orbit sander on the entire table to flush the insert. The table needed to be done anyway.

Dimensions were:
2.746" for large outside diameter
2.430" for inset diameter
.600" total thickness (didn't need to be this thick but I really wanted this overbuilt)
.197" thickness for outside lip that sits flush to the table top

These numbers probably aren't dead on but they worked and the fit is good.

Here are some pics (click for larger view).

Image

Image

Image

Image

Image
Author:  SteveSmith [ Sun Jul 04, 2010 4:05 pm ]
Post subject:  Re: Bandsaw table insert failure.
Chris aka Sniggly wrote:
... I'm measuring with dial calipers and calculating depth and radius and the tangent of the moon in February...... laughing6-hehe What I'm doing will work certainly but I went all the way to Saturn and back to do it. ...
Chris


I'd like a nickle for every time I've been to Saturn :roll:

Delrin would be a good material. Machines and takes fasteners well. Bettern than UHMW or nylon.
Author:  Tom Armstrong [ Sun Jul 04, 2010 4:37 pm ]
Post subject:  Re: Bandsaw table insert failure.
Chris,

This is deja vu all over again. Approx 3 years ago while re-sawing coco for sides with my Rikon 18" using a trimaster blade the same thing happened to me. It necessitated a trip for me to the ER. I replaced the broken plastic (POS) insert with a homemade 1/4 inch aluminum......no more issues. I think the insert took me all of 15 minutes to cut out and fit.

Glad you weren't hurt.

Tom Armstrong
Author:  Chris aka Sniggly [ Sun Jul 04, 2010 5:18 pm ]
Post subject:  Re: Bandsaw table insert failure.
Tom - When I was writing this I culdn't get the idea out of my head that I read a similiar story here on the OLF. It was you. Sorry about ER visit but glad you're still kicking. Funny that I too was using a Trimaster.....well maybe not funny.
Author:  Bobc [ Sun Jul 04, 2010 8:43 pm ]
Post subject:  Re: Bandsaw table insert failure.
Same thing happened to my Laguna about 6 mo. ago. Luckily everything just stopped dead. The Laguna insert is square and rests on 4 adjusting screws so I made a new one out of 3/4" plywood. Works great.
Author:  GregG [ Sun Jul 04, 2010 11:07 pm ]
Post subject:  Re: Bandsaw table insert failure.
Yeah, same thing happened to me on my saw, I made a new one out of a mahogany block with 4 adjustable screws on the bottom corners, never had a problem since.

Greg
Author:  Mike OMelia [ Mon Jul 05, 2010 12:08 am ]
Post subject:  Bandsaw table insert failure.
Are u all resawing "against" the fence??
Author:  wbergman [ Mon Jul 05, 2010 6:01 am ]
Post subject:  Re: Bandsaw table insert failure.
I had a problem with the blade being displaced that was not really from the insert failing, but the insert got damaged in the process. The ball bearing wheels that hold the blade in position are on ecentrics. When you move them into place, you can move them from above the axis or below. If above, during use they can tighten onto the blade and push it out of position. In my case, a chip of wood was carried through with the blade and hit the wheel below the table, jamming it onto the blade and pushing the blade forward. So, now I only rotate the bearings from below.
Author:  Chris aka Sniggly [ Mon Jul 05, 2010 6:42 am ]
Post subject:  Re: Bandsaw table insert failure.
Mike O'Melia wrote:
Are u all resawing "against" the fence??


Won't speak for everyone else here but I do. I've seen other methods but have just gravitated towards this method. To be clear, if I am sawing for a .140 back piece, that piece originates from between the blade and the fence. I think that's what you mean. I can just pull the billet back towards the front of the blade, start over, and reproduce the exact same thing over and over and over again....till I run out of said billet. I can get as many cuts as I set up for.

Chris
Author:  Tom Armstrong [ Mon Jul 05, 2010 8:45 am ]
Post subject:  Re: Bandsaw table insert failure.
Mike,

I was definitely using a fence.

I still have some of the coco billet I was cutting when the accident happened and I cringe whenever I have occasion to cut a set from it.

Tom
Author:  Mike OMelia [ Mon Jul 05, 2010 9:29 am ]
Post subject:  Bandsaw table insert failure.
I can't imagine why a plastic insert could cause this. I have the standard aluminum one that came with my saw and I have hit it many times, hard too, gashed the thing.

This sounds too me like the blade was somehow pinched. That is why I asked. One thing I learned from watching Borsen videos was the use of a sacrificial backing, glued to the billet to keep it from warping.
Author:  Bobc [ Mon Jul 05, 2010 9:53 am ]
Post subject:  Re: Bandsaw table insert failure.
Mike on the laguna the insert is a square at least 3/4" thick. What I think happened but it was too fast to know for sure. I was slicing a 6" x 6" block into 1/8" slices for rosettes. I may not have had the piece flat on the table but at initial contact with the blade it grabbed the wood and slammed it down into the insert which in turn cracked in half weding the wood between the hole and the blade.
Scared the living s@#$ out of me but no injuries or damage other than the insert. The insert is already cut 1/2 way across it's width.
The new insert is 3/4" ply that I coated with CA
Author:  Chris aka Sniggly [ Mon Jul 05, 2010 12:58 pm ]
Post subject:  Re: Bandsaw table insert failure.
The short of it...in my case atleast - I think I wasn't paying as much attention as the task required. Pure and simple.
Author:  Mike OMelia [ Mon Jul 05, 2010 9:47 pm ]
Post subject:  Re: Bandsaw table insert failure.
Could this be a case where a "well made" insert was made a little too well? My stock Jet insert is perhaps 0.1" thick. All aluminum. It has been attacked several times (inadvertantly) by 1" blades with no repercussions (save a slightly mangled insert).

Yet, as I utter this words, I seek a piece of solid wood to knock on...

Mike
Author:  Chris aka Sniggly [ Mon Jul 05, 2010 10:13 pm ]
Post subject:  Re: Bandsaw table insert failure.
I can definitely say in the case of the Rikon insert that this is not a case of made 'too well'. I wish I had snapped a photo of that piece of brazilian sticking out of the hole in the table top. The insert collapsed inwards. The cause of that failure, now that I write this, I guess, could have been something other than the quality of the insert.

I really just feel as though I wasn't mentally situated before I began that run. I think I could have prevented this if I were more in tune with what I was doing. Admittedly, I was excited to see what this brazilian revealed because it was my first headstock overlay run. I've never seen anything like the first bookmatched set produced and got even more excited. When I started sending the wood back through the second time...that's when it happened.

I've had instances in the past (mostly in Cocobolo) where you start to push a billet through the blade and it suddenly, for no apparent reason, wants to lurch forward. This sudden increased feed rate shocks the band a little and it makes an insane noise. I try to avoid this situation by being extra aware of what the saw sounds like all the while adjusting feed rate accordingly. Some woods you can zip right through...some you have to watch like a hawk.

I've been over this in my head a 100 times cuz I don't want to experience this again. Plus, I don't want to ruin any more wood.

Chris
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