Heads Up

[Steve Clardy]

Here is a shot of a Country style arched rail pattern made by CMT. This pattern is a very dangerous pattern to route. Note the red arrow on the pattern. The router bit turns fast enough that it actually creates a suction on this part of the pattern. When this happens, it will actually suck the pattern and wood rail into the cutter. And if you are not prepared, you will loose the rail and possibly a finger.
The first time I ran these patterns, I did not have the attached handles on them. [I made them out of closet rod stock and attached them with a dry wall screw.] The pattern was simply braded down to the rail, which the instructions call for.
There was not enough control or space to grip it tightly, safely, so I added the handles.
I usually route the right end lightly first.
Then start at the left side, lightly routing till you get to where the red arrow is.
Pull back and start at the left end again, going full depth all the way to the right end. That way the bit is buried into the curve where it is so dangerous.
I have fought these patterns on three sets of cabinet doors and finally got comfortable running them.
I tore the hide off one finger the first time it caught and slung the pattern and rail across the shop.
Steve

[Dave Arbuckle]

Yikes! Have you notified CMT?

I have an older set of CMT arch guides (mine are white), they not only instructed the use of a handle but included it. It looks like the handle on a jointer pushblock.

Sounds to me like someone dropped the ball somewhere along the line.

Dave

[Steve Clardy]

Originally posted by Dave Arbuckle
Yikes! Have you notified CMT?

I have an older set of CMT arch guides (mine are white), they not only instructed the use of a handle but included it. It looks like the handle on a jointer pushblock.

Sounds to me like someone dropped the ball somewhere along the line.

Dave

Dave, I haven't let them know about this problem, but when I first received the patterns, they were real rough cut at the curves. I contacted them, they sent out another set, same problem. They then referred me to Mark Sommerfield, which his secretary required me to send them in for analayis. I could not send them as I was using them. After several phone calls, emails, Mark never did contact me to correct the problem. I finally gave in and sanded them smooth to make them usable.
[ And I always though a template pattern was to be smooth]. Guess I went to the wrong school?
Anyway, if anyone has these patterns, be careful with them.
Steve

[Lee Schierer]

The problem you are encountering is pretty common. As you start up the curve from where the red arrow is, the cutter tip is hitting directly on the end of the grain. The grain catches the cutter edge and bang, it will knock the part right out of your hands. I had the same problem with some lamp bases I template routed. Broke two before I wised up and climb cut the area. In your case, you want to climb cut from the right side of the template as photographed toward the red arrow. Once you get past the red arrow, you can and should switch to the far left side and cut the other way.

Be careful climb cutting, the router will try to run away from you. I would suggest removing the bulk of the material with a jig saw or bandsaw first, then clean up the remainder with the router.

This is not a design flaw with your templates. It is a function of wood grain.

[Steve Clardy]

Originally posted by Lee Schierer
The problem you are encountering is pretty common. As you start up the curve from where the red arrow is, the cutter tip is hitting directly on the end of the grain. The grain catches the cutter edge and bang, it will knock the part right out of your hands. I had the same problem with some lamp bases I template routed. Broke two before I wised up and climb cut the area. In your case, you want to climb cut from the right side of the template as photographed toward the red arrow. Once you get past the red arrow, you can and should switch to the far left side and cut the other way.

Be careful climb cutting, the router will try to run away from you. I would suggest removing the bulk of the material with a jig saw or bandsaw first, then clean up the remainder with the router.

This is not a design flaw with your templates. It is a function of wood grain.

Lee. Have you ran these patterns?
First, let me say there is no waste removal when I am running this template. I have already in advance bandsaw cut to remove waste, flush trim with flush trim bit to smooth to pattern.
I tried the climb cutting. This is a no-no on this application. When you are engaging end grain in a curve like this, and climb cutting, it's bad news also. I tried that.
I start just slightly PAST the red arrow, going to the right, about 1/3 depth. This to to prevent wood blowout.
Then, second stage, start from the left, engage wood about half the depth of the cutter. Follow the pattern TILL you get to the second curve, pull it back away from the cutter. Then, start back at the left side again, full depth all the way to the end. When you reach that second curve, the bit is buried completely, and it cannot jump or catch. There is no way for it to grab then, as you have control by the two handles, and most of the material ia already removed.
I guess maybe I did not quite explain the main problem here.
There is nothing provided to hang on to this template safely, and most of all, no instructions. Instructions are especially important on new tools, patterns, machinery, etc.
As Dave said, someone dropped the ball on these patterns.
There is that suction problem in the last curve that PULLS the work piece in to the bit. And if you are paying attention fully when coming to this curve, problems arise.
I am not above climb cutting when necessary, but not on this application.
Steve

[jack duren]

im assuming these cmt bits cut face down like the amana line? how thick is the pattern you show in the picture? this isnt uncommon on shapers. on a triple cut crown you can lose 10% of your pieces due to "blowing" out the material in that portion of the profile.

because shapers allow up to cut the crowns face up we can see whats going on but often burn just a few as we go.

sems best bet is a few extra light passes towards the end should help....jack

[Lee Schierer]

Originally posted by Steve Clardy

I start just slightly PAST the red arrow, going to the right, about 1/3 depth. This to to prevent wood blowout.
Then, second stage, start from the left, engage wood about half the depth of the cutter. Follow the pattern TILL you get to the second curve, pull it back away from the cutter. Then, start back at the left side again, full depth all the way to the end. When you reach that second curve, the bit is buried completely, and it cannot jump or catch. There is no way for it to grab then, as you have control by the two handles, and most of the material ia already removed.


Steve, you're right, I was looking at the bit the wrong way. I was still right on the nature of the problem though. It is undercutting the grain and you are bound to get tear out. You will need to sneak up on the final dimension with many light cuts since you are always going to be routing into the grain ends on that one side. Since that is a pattern following bit, can you get a different size bearing for it and make a pass that is slighly less than full depth, then change to the full depth bearing and make one final pass as a smoothing cut.

Your handle addition looks like it will give you better control.