- Joined
- Mar 7, 2018
- Messages
- 42
Is the title says it has been awhile. I am always reading and keeping up various places. Finally purchased a full 20x40 bed mill, Gt27 lathe, hobber, and many other pieces of equipment and now we can machine the column and bed for linear blocks without worry of inaccuracies. Anyways I have a question and perhaps I’m feeling a little cheap after all the money in parts and equipment I’ve spent. So the pm833 cnc conversion is finally underway but I need the last few pieces. I’m debating between 7075 block for a saddle and z axis spaced to head but the more I think about it I feel like I should coin up and go for cast block from McMaCarr. Only availability is gray cast in these sizes. I can machine it on the bed mill then send it out for heat treat and surfacing. Otherwise it’s aluminum machined. Yes accuracy matters especially when I’m being spoiled with .0001 accuracy on the bed mill. Originally I made drive belt pulleys and decided to integrate a 10000rpm bt30 spindle I purchased that is enroute from overseas and uses a 5m timing belt so we will hob one here for the spindle from 4130. The pair of cast blocks will cost $600 so it’s not a cheap venture but in comparison to several thousand spent on screws, AC servos, etc... I also plan to extend the Y, and add cross supports to the column and base. I’d like to stick the head out further but with blocks and a 2.5” maximum thickness for the cast I only gain 1/2”. I’d like to go 1.5” beyond factory. I would also like to buy the cast stand for the pm727. Heck the mill base would be great too and save me headache extending but the cost to performance benefits I’m not sure are there presuming it’s even available. I’m using hgr30cc blocks on the column and hgr25HA on the base axis’s. Of course the dovetails are being machined off and no worries they’re worn after 1.5 years where either scraping and turcite or linear rails were needed. Rather not deal with stick slip any way. Perhaps someone has a better source for cast plate and block. I did consider a solid block for the mill base but the weight of the block alone was around 2,000lbs so I think we will just epoxy granite fill it for now. Yes I’d love that weight but handling it around the shop without a forklift would be a pain. If anyone had had positive results using aluminum for a saddle and head extension let me know. I feel like it’s bound for inaccuracies and other issues where cast would supersede the downfalls. Look forward to your suggestions and any projects you may have underway that I could see.
