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I like the hood design on that Slik 14" on eBay. I don't know if that was stock or not but it looks like it would be fairly easy to replicate for most any model of boxed-in based drop saw.

IMHO the best tool for pre-shaping/prepping rocks for tumbling would be the Rock Rascal model "T" outfitted with a coarse grit diamond wheel (60 or 8o grit).

After having recommended the MK-225 Hot Dog Blade on this thread three years ago I feel I should let anyone researching 10" blades know that I am no longer as enthusiastic. Today I received two new MK-225 Hot Dog blades (ordered through Home Depot but the order was drop shipped from MK Diamond Products in Torrance, CA). The quality of these blades appear to have dropped from what they were 3+ years ago. Both blades I received today are cupped. They appear to have gotten cupped during the arbor hole boring/stamping/? process. And both have very little kerf and what kerf they do have feels uneven.

They will probably still be okay for trimming slabs but being cupped may be an issue if trying to slab. I may be able to flatten them a little by laying them on the milled flat iron surface of my table saw and tapping them with a wooden block and hammer. Using this method I've been able to straighten older softer steel lapidary blades that have gotten cupped. Not sure if it will work on the MK-225 steel core or not.

My older MK-225 blade still has some use left in it so it will probably be a while before I try using these new ones. When I do, if there is a noticeable difference in how they perform when trimming slabs then I will do a follow up post.

Have you checked to make sure that your wheels are balanced. Out of balanced wheels or a slightly misaligned arbor can cause enough vibration to contribute to cabs breaking along natural fractures or falling off the dop.

That said Larsonite is often not very solid material and is notorious for falling apart when slabbing and cabbing.

I only slab, cab and facet so don't have any experience polishing large bookend surfaces. I had a couple of dot discs many years ago. It's been so long that I don't remember much about using them other than I only liked them for rough grinding but as best as I remember they wore out pretty fast compared to standard laps.

As for your stated purposes of doing the backs of cabs I think that they are fine for that. And probably would work well for smaller faced specimen surfaces too. But for bookend size flat surfaces I'm not so sure. I would think that using flat lap discs of any kind for the sanding and pre-polishing size grits on bookend sized surfaces would be very time consuming and tedious. Plus could get expensive when using dot discs. I would be inclined to find another method of processing those larger flat surfaces.

That said I know I still didn't answer your question about grit successions. Back in the early to mid 1970s when man made industrial diamonds were still under patent and expensive, the coarser grits were really costly. So when cabbing using diamond instead of SC, many of us started off preforming and shaping with a less expensive 180 grit as our coarse wheel followed by a 360 grit for final shaping before sanding. Then from the 360 plated wheel to 600 sanding belt or resin disc. Then to 1200 pre-polish and depending on the material may next go to a 3000 pre-polish. Then to an oxide polish or if only using diamond then 8k to 14k to 50k polish. Today many people start out with 80 grit plated wheels and then go to a 220 grit wheel before going to sanding.

Faceting small faces follows a different succession. It used to be common that cutters would rough out the stone with a 260 grit plated lap and then jump to a 1200 plated lap for most materials. Some materials like corundum would undercut on 1200 so the next step after 260 would be reduced to 600. Then 3K on a copper or tin lap for a pre-polish. But nowadays many faceters don't want to risk sub surface damage to their material so the coarsest grit they will use for roughing is 360. Then on to 600 or 1200 or depending on the material may even skip the 1200 and go to 3k or 8k pre-polish. I know that all of this doesn't directly address your situation but I included it to illustrate how broad the gaps can be depending on materials and applications. And how narrow for others.

To reiterate, I think the dot disc will work fine for you for doing the backs of cabs and smaller polished faced specimens. But I have real doubts about them working well on larger surfaces - especially in the mid range to fine grits. For the former, choosing three of the given grit options you state are available to you, I would be inclined to try [60] 120-325-600 then to diamond belts on expando drums for anything finer. And if you find the 120-325 to be too large of a jump then you can always add a 220 into the line-up later.

Many years ago I saw a unit with the same type double end arbor that had burned out. And the owner had removed all of the winding and electrical guts from the motor and cut a large square hole in the back of the motor. He added a pulley to the center of the arbor shaft and ran a v-belt though the square hole he had cut in the back of the motor housing to a 1/3hp continuous duty/general purpose motor so that he could continue to use his cabbing unit without having to replace the more expensive double ended arbor motor. He essentially turned his double ended arbor motor into a functioning arbor similar to the Lortone ProMax unit except the belt and motor were to the rear rather than on top.

Larsonite can have a habit of separating at seams. So I wouldn't try any drilling or "controlled breaking" techniques unless you don't mind turning a portion of it into tumbling rough. Over the course of time as I found myself with a nice piece of rough too large for my saws at any given time, If I couldn't find someone to slice it for me for a reasonable trade then I usually just hung onto it until I did have a saw large enough. Started out with a 6" saw 50 years ago and keep adding. Am up to 20" now but still have a few pieces too large for the 20" so am letting them sit and wait. (One of them a large piece of petrified palm has been waiting since 1980.) Good rough is too hard to come by to risk destroying and very little of it is worth damaging a saw/saw blade for, especially on larger saws.

We used to have a rule on this board...If there's no photos then it never happened!

They've dropped the price down to $850. The craftsman B&I GemMaker unit and the saw are going to need a little elbow grease and probably minor work but IMO the lowered price is fair. A 12" saw for slabbing and trimming, the old Crown cabbing unit for cab shaping and sanding, and after removing the faceting head the old B&I GemMaker units are great for polishing with oxides on flat discs with felt, suede, or canvas. So as Hummingbird stated, this would be an okay starter package for someone wanting to get into lapidary on the cheap.

The B&I faceting heads are a 1940s hobby oriented design and only came with a 32 index so are limited to very simple cutting designs. Their arbors have step pulleys for changing speeds. So if one has the patience of Jobe they can buy the laps needed and facet with it too!

The B&I faceting heads still turn up from time to time but the dop stick sets for them are very difficult to find. Also the B&I faceting heads had paper and/or foil printed indexes on the protractor and faceting gear which are usually in poor shape but with a little help from CAD software can be replaced with new PC printed ones.