spot weld tool & bits recommendation

[911 tweaks]

I have been using the Blair barrel type bits w/ the center spring tip...I am tired of only getting 1/2 to maybe 3 spot welds before a tip breaks off the cutter & the bt is trash...
Can you guys suggest what has worked for you & what bits worked the best...
shopping black friday is tomorrow & I want to buy a nice tol & bits that works well & fast and is worth the money...I know I am talking hundreds here...but if it is NOT a pos, I think it will be worht it in saving time...drill bits walking away from where i am trying to drill out a spot weld, ect...
thx in advance for your help here...bob

[911 tweaks]

anyone have plans they can share for building a 911 car rotisure...?
I have seen cars using them but I cannot find a thread w/ how to make and what is needed for materials to make one...
I need to make one for a 911...I dont think I want to make the 6 sided cage type...I am leaniing twds the one that attaches to f & r bumper points...has engine stand type round chucks at f & r of car and some some attachment bar running the length of the car near the ground to tie the front stand & the rear stand together...
Also, I am concerned about maintaining structural correctness & integrity of the tub so as not to make a crab after I am done with panel replacements...so...how do I ensure the tub is well secured to a solid structure...??
IDEA: put tub on a 4 wheel dolly where suspension points on tub attach car to dolly, THEN, raise dolly & car up in air & attach dolly to torisure to enable me to roatate car & ensure the tub stays square & not twisting or messing up any area of the car... especially after a panel is removed awaiting a new panel to be installed...
You all get my point & concerns(S), I hope...what do you all think...??
thx in advance fr your help...bob

[962porsche]

I have found you need many different types of spot weld cutters on any one car .
the reason why the center pin is braking could be from many reasons .
the 1st is lube . take the set screw out of the back and put a dab of white grease were the pin spins on the cutter housing .
make sure the pin will spin freely .
when your cutting the spot weld use a cutting oil to lube the cutter . thing like wd40 are not cutting oils .
drill a dimple using a 1/8 " drill bit to center the cutter before you start to cut the weld .
do not move the drill when your cutting the weld hold the drill straight and even with the panel if you don't as the cutter is cutting the weld the cutter will catch and spin and snap the center pin .
you should be going thru about 3 to 6 rotabroach cutters to 1 pin .

[mreid]

I gave up on spot cutters years ago. I use a regular twist bit and drill all the way through the panel. Then when I weld in the new panel, I plug weld using the hole in the panel still on the car. In cases where I can't get to the back of the panel, I still use the twist bit, but drill just enough to break through the top layer. Sometimes I need a panel knife, but you often need one with the spot cutter anyway.

[911 tweaks]

thx guys for your insight...
what about the drill bits that are cobalt coated? but have a center point...?? would this be the easiest and fastest & most cost effective way to drill out the welds...??
I understand that the actual weld matal is harder that the panel metal, so, I need a stronger than hss drill bits...so what do you all recommend...??

[962porsche]

dripping out spot weld with a drill bit you use to drill holes thru metal is in no way the right way to go .
I could list the many reasons as to way that is so but just don't do that !

you do know you have to use a drill made for drilling metal and not the run of the mill drills made for drilling things like wood when it comes to using spot weld cutters .
the regular old drills spin at to high of a speed for spot weld cutters to work . they will over heat the cutters and drake from that . you run of the mill drills spin at about 1000 RPM's were drills made for drilling metals spin at about 500 RPM's .
it tells you at what speed your drill has to spin right on the package I would bet .

check out the blair solid carbide cutters or check out summit sum-900138 or 900139 .
but even with that type of cutter you will still need a drill that spins at the right speed for the bit your using .

[911 tweaks]

thx 962...I sent u a pm from the other post I have running on building a rotisure...please reply today if you can...thx, bob

[cary]

I use RotaCut. The same as the Rotabroach.
http://www.hougen.com/downloads/sheetmetal_catalog.pdf

I'm restoring a 914 basket case.
I have a cup of cutting that I continually dip the cutter into.
Dip, Drill, Clean with blow gun, dip, drill, etc.
Dipping into oil makes all the difference in the world.