I am also looking for good belts for my Unisaw. I ordered Gates Premium AX24 belts. They are a cog belt which is suppose to be good on transferring power. Cog belst also are suppose to work well on small pulleys. I assume using the low setting on your drill press you are on the largest and smallest pulley so a cog belt may help. I don't have my belts. They will be here on Thursday.

That being said. I have an old Atlas drill press and I run a link belt on it. Single belt. With my 1125 rpm motor on the low setting I was able to drill through 8 or 10 inches of oak without slipping. I can't remember but there is a thread on this forum about it. Too bad my 1125rpm 1/2hp motor burned out. I am looking for a motor.

 

I was just going to suggest that link belts might be a solution. However, this is a heavy duty industrial grade tool. They may not be heavy duty enough or the best choice. I'll defer to more seasoned VOE.

My second thought is, like Lee's (Coxhaus) Unisaw the drill press may need to have the pulleys replaced. Another possibility is to use belt dressing on the belts to increase the coefficient of friction on the existing pulleys.

Finally, all belts are not created equal. I would stick with OEM recommendations or the higher quality manufacturers. All things being equal, it will probably just be a one time purchase on replacements.

 

look to Gates or Springfield belts....
the slippage may be that on speed changes the belt tension drops..
the
the Continental belt are too stiff or aren't fully seated in the pulleys..
the belts are smidgen too long....

 

pulley belt calculator