A TC18 is rated for a 6 foot BH, so you would be 1 step above the rated size. I have a Woods 750 on my TC33. I can't say if you would have problems with it on the TC18 or not.
I have a TC 29 with a woods 750 bh. Use the machine with BH most of the time since 1999. I think the TC18 may be a little light for the 750. I would be afraid of breaking something on the TC 18.