Shopsmith Forums

I am drilling large circles (holes) with a new 2 1/2" in Forstner bit. Depth of cut is 1/4". SS running at 650 RPM's. I find I am getting belt slip even though I have tighten the best has much as I am comfortable with. Any suggestions on how best to proceed?

You may need a Powerpro . Lower rpm's would be ideal for that diameter.

In desperation you might try some paraffin or beeswax on the cutting edges (refreshing frequently).

Good luck,
Chris

I have a PP--so a lower RPM than 650?

Your rpms are ok for softwood, but perhaps too high for hardwood, per this article.
https://www.woodcraft.com/blog_entries/ ... n-use-care
My solution was to purchase a SS speed reducer, but I wanted it to turn large heavy blanks on the lathe, as well as large drill bits.

Good reference thank you. Yes cutting Walnut end grain. Will try a lower RPM, down around 550 RPM

The slower the better. I guess your powerpro will slow down to 250 ish. I’ve read complaints about new Forstner bits being dull out of the box, there are articles online for how to sharpen “better than new”.

I have tried slower RPM's down to 250RPM's. Tried wax. Still get belt slippage as depth of cut progresses--going very slowly to avoid this. Best approach I have found is first drill 1 1/4" to desired depth, then follow-up with 2 1/2" bit to finish the cut.

The sharpness and quality of the bit is very important when you get into those sizes. Cutting end grain makes that even more important.

Any time drilling with large bits it is easier/safer/quicker to drill smaller size and work up to final dimension.

Works on metal drilling as well. Final size should be removing very little material.

Wondering about using a decent quality set of hole saws to remove a lot of meat before final drilling?


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