Runaway Depth Using 1/4 Upcut Bit

[lshuck]

I have a PRS BT48 Standard using PW 2.015 and Sb 3.6.12.

On 3 occasions with 2 within the last 5 days when making a profile cut and after running through the first of several parts in the file the bit has started a decline and bored into the spoilboard.

All parts received the same parameters when specifying the tool path (.5 cut per pass with .47 as depth). The bit starts to dive on an inclined plane and in one case (still using an older Sb) I did not catch it in time and the bit broke. The second time with the updated Sb I caught it but it left the bit in the material.

I Thought I might not have tightened the bit enough but I used the same technique I always do.

After the first recent dive, I contact SB and Frank said he had not heard of that problem but recommended upgrading to the current Sb to 3.6.5. as a precautionary measure.

I checked the run file and could not see any instruction that would explain the diving and upgraded the Sb to3.6.5.

Then, today when cutting Sample LinkerLogs with a the updated Sb, a new bit and a new collet I had the same experience. I then redid the tool path and the second time it worked fine.

Any of you had this problem and if so what did you find to correct it? Or any ideas?

Les

[ken_rychlik]

First off switch to a down cut bit. Second if you use the up cut bit again, measure how much is sticking out of the router or spindle before the file and double check after. Then at least you will know for sure if it moved. Lastly you can jog over the part after the cut and set the z to one inch. Measure and see if it really is one inch.

Upcut bits are nothing but trouble on my machine. They pull the work up off of the table, they pull the bit out of the router, and they splinter up the surface of the work.

Kenneth

[gary_n]

I had a similar problem when cutting the Linker Logs for the grandkids. It turned out that my 1/4" collet was badly worn. After replacing it everything was fine. Be sure to blow out the collet with every bit change. I noticed that you changed to a new collet and that is good.

[erik_f]

com speed?

[lshuck]

Kenneth, Gary and Erik

I changed to a down bit yesterday and all went well w/o issues except, on my machine I had to increase the Cut Depth by .003 beyond what I was using on the UpCut bit. I put a piece of 1/4 MDF on top of the spoil board so that I could clear things w/o scarring the spoil board. I should have done this before but I just did not get around to it.

Thnx for the tip on blowing out the collet, I have not been doing that.

Erik: I am not familiar with the term com speed other than computer speed, so plz help me with the term.

Les

[loriny]

Go to utilities. Then Diagnostic tools. Then do the speed test. This will test the communication speed. fyi mine is usually 86% or so.
Lorin

[erik_f]

This^^^
SB says 70% in min communication speed. I can't seem to get mine above 76%, but I don't seem to have any problems. I had a 3D file running on a new PC and kept getting a "shift" in the carving...I checked the com speed and it was around 50%...SB uncludes a USB hub that I wasn't using...as soon as I plugged the hub in and then the bot to the hub my com speed went up to 76%...no problems since then.

[lshuck]

Lorin & Erick;

Thnx for the definition, comments as to where to locate and how to use as well as the "standard" that needs to be met. I will check it out and see what the performance level is.

Les