Steamboat

I didn't remove the two bolts holding the fixed jaw insert. I figured that IF and when I ever need to change the jaw insert I might give it a try. There is always the chance that the bolts might break, in which case you'd probably have to drill them out. You might be able to lightly dress the jaw insert in place if you want a nice straight edge, but for most purposes, I think it's probably OK as is, unless it's loose. If you want to try to remove the bolts, I'd suggest beginning with a very long soak in some rust-buster type penetrating oil/fluid, and you might consider trying an impact wrench on a very low torque setting (well below the amount of torque that could twist and break the bolts). Heating the jaw insert might help, but be careful not to overheat the insert. I don't know what particular steel/alloy the insert is made of, so I can't offer guidelines as to a safe temperature range that would not have a negative effect on the insert. Al (Steamboat)

Yeah, it looks like the same model, and it appears to be in good condition. Glad the diagrams were useful to you. I've been busy with tons of other projects lately, so I haven't posted to the forum for a while, but I'm hoping to get back to some blacksmithing projects soon and start posting again. Cheers, Al (Steamboat)

I have a selection of spiral-point and spiral-flute carbide and HSS taps that I use with my Bridgeport mill, and occasionally with my lathe. I, too, like the chip control they offer, and the spiral-flute taps are nice for ejecting chips when tapping blind holes. Al (Steamboat)

Jennifer, that is a lot of good advice. I totally agree that there are manufacturers who will apply titanium nitride and similar coatings on just about any kind of steel, whether it's taps, dies, drills, cutting tools, etc., since the coating creates the "impression" for marketing purposes that the tools are high quality, whether they really are or not. That said, if you're going to be working with "sticky" or "gummy" metals, such as stainless steel, etc., the coating can be very helpful, but one should always make sure that the substrate is a quality alloy (HSS or better for taps and dies). I've bought a lot of very nice used taps and dies over the years in virtually new condition, but I rarely buy used drill bits unless I know the seller and I'm sure of what I'm buying. As I mentioned earlier, I inspect used taps and dies carefully with a high-power loupe to check for wear and damage, as well as to have a closer look at the finish/machining quality, and I buy them cheaply enough that if I get a lemon once in a while, I just toss it, and I'm typically only out a buck or two. Like you, I have a lot of odd sizes of taps and dies, since several of my past restoration projects have involved antiquated fastener types and sizes that are no longer in vogue. On a somewhat related topic, regarding drill bits (for drilling metals, rather than masonry, etc.), I seldom buy anything other than brand-new cobalt-steel bits (usually with a titanium nitride or titanium aluminum nitride coating), with some exceptions, such as solid tungsten carbide end mills, bits, and other cutting tools for my mill or lathe, although solid carbide tools can be very fussy about how they are used, since it's easy to break or chip them if the work is not secured properly or if the feed and other factors are not set up correctly. I hardly ever bother with standard HSS steel drill bits any more. Cobalt drill bits are still subject to wear, of course, and occasionally need to be re-sharpened, but I don't have to re-sharpen cobalt bits as often as ordinary HSS bits, since they maintain their edge quality longer when drilling harder metals. Al (Steamboat)

Regarding space station construction, you might want to have a look at this: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120002584.pdf Al (Steamboat)

I totally agree that good tap wrenches and die stocks (die holders) are important. If space around the rod to be threaded is adequate, I prefer straight-handle tap wrenches over T-handles. And remember that you can get die stocks that have adjustable guides, which can really help a lot to start and maintain your threads in proper alignment with the rod being threaded. Al (Steamboat)

My collection of taps and dies is such a mish-mash as far as manufacturers go that I really don't have any favorite maker that stands tall above the others. That reflects the way that I usually buy those tools, which I would call "semi-haphazard." I visit used tool stores, flea markets, pawn shops, garage sales, surplus outfits, etc., quite often, and if I run across tools that interest me, and if the price is right, I buy them. Obviously, high-speed steel will outperform the cheaper carbon steel threading tools over time, and titanium nitride and other coatings will further enhance their performance (as will proper thread-cutting oil). And there are a number of exotic "cantaffordium" alloys out there as well. Good quality taps and dies are not cheap when new, but you might be surprised how easy it is to pick up good used ones for half a song and a dance. Here's my simple approach: I keep a small 14X loupe (magnifier) in my truck's glove box, which I use to check the edges and surfaces of any kind of used or old-stock cutting tool that I'm considering. I avoid anything with dinged, chipped, or rounded/worn cutting edges. The magnifier also lets me have a better look at the tool's finish quality, because a high-quality finish "tends" to suggest better quality tools (not always, but often). Buying good used threading dies is usually easier than buying good used taps, not because there are more dies around, but because the critical edges and surfaces of dies are more protected against dings from being stored improperly or from being dropped on hard surfaces. Taps tend to get banged up more because of their exposed critical areas. They might look OK at a glance, but often a magnified view will show small, but significant defects. I've gotten a bunch of very nice taps and dies for a few bucks each, and sometimes cheaper. One minor problem is that when I run across some interesting tools I can't always remember what size(s) I may have been looking for, so I often end up with duplicates. A notebook would be a good idea. If you need a particular size right away and can't wait, at least splurge for a high-speed steel tool and threading oil, and then build up the rest of your collection over time. It won't take long before you have a massive set of these things. Just remember to store them with some protection around them. Glad to be of some service. As to experience, I had a few years of professional fabrication and machine shop experience back in my college days, but no matter what various paths my career may have followed over the decades, I've always enjoyed designing, building, restoring, or modifying things for all of my adult life and most of my misspent youth. I'm also a lifelong tool junkie. Al (Steamboat)

I noted the smiley face, so I won't take that comment verbatim , but seriously, even in a "fab shop," I would consider any work to be unacceptable that was cut or fitted so poorly that it would require extra weld fill to make up for the sloppiness...but that's just me. And there are other operations that take place in a fab shop that require higher levels of accuracy in measurements than most welding operations. Otherwise, I agree with you. I find that a line made by a sharpened flat soapstone stick can be "relatively" thin (say about 1/32" to 1/16" thick) which is certainly adequate to serve as a guideline for hand-held welding and plasma (or oxy) cutting operations. I have a pretty steady hand, but even when following a straightedge with my plasma cutter, I probably waver more than 1/16" at times. Other fabbing operations, however, like shearing, for example, usually require more accuracy, in which case I use more accurate marking methods. As I already alluded to, I would not attempt to use a soapstone stick for precise layout work. One needs something that will produce a very thin line and produce that line consistently. For more precision, I often use layout fluid and a diamond-tipped or carbide-tipped scribe. Having different colors of layout fluid is also recommended, since you can choose a color that contrasts best with the metal surface color. You can get an 8-ounce bottle of layout fluid for about 10 or 12 USD, which will make a lot of markups. And of course, when going beyond what most people would consider the fab-up stage of a project and getting into subsequent high-precision operations, my machinist measuring tools come into play (micrometers, dial gauges, gauge blocks, digital readouts on my vertical mill and lathe, etc.). I don't have CNC on those machines, but since most of my projects are one-off personal projects, I don't consider it to be much of a handicap. This is marginally off the taps-and-dies topic, but I guess it ties in insofar as marking accurately for drilling, tapping, etc. Cheers, Al (Steamboat)

There is a lot of high-quality tooling coming out of Poland, and I've found that the pricing is generally pretty decent. Vaughn, I think that as you collect more taps and dies, you'll probably be using them more often. There is a tendency to use other means of fastening things when one doesn't have the capability to cut the thread sizes needed for specific jobs, but having a full set of taps and dies gives you more options. As to soapstone markers, they aren't much good for precision work, but I often use a flat soapstone stick (in a holder) for markups for welding. Soapstone has a high melting point, and the whitish lines show up pretty well through a darkened welding lens. I frequently draw a soapstone line parallel to the planned weld so that I can see a bit farther ahead when laying a bead, with the line acting like a guide. It's also good for indicating start and stop points, stitch welds, plasma cutting guidelines, etc. One drawback in some situations is that the soapstone line rubs off easily, but that usually isn't a problem for me. On stainless, I often use a black marker instead. Al (Steamboat)

That was a very good introductory video, Vaughn. Good imagery, classic narration, and very clearly spoken, unlike a lot of newer videos. Pretty much all of the information is still applicable today, although there are some newer materials and surface treatments that have come along since then. Hmm. Al (Steamboat)

Bldsmth and Farmall seem to be right on track. You have what looks like one end of a flexible coupling on the shaft. The other two pieces of the coupling are missing. Those would have included a similar metal piece to go on the end of a driving shaft (such as a motor shaft or a jackshaft) and a rubber/elastomeric intermediate cross-shaped piece called a "spider." Flexible couplings can often tolerate slight shaft misalignment and reduce vibration and shock transmission. It's a pretty large blower, but potentially useful. Al (Steamboat)

Thanks for the comments, Jim. I've seen photos of the accessory jaws with the half-round grooves, but I don't have any of those...just the flat jaws. Fortunately, my vise already closes tightly without having to add a shim or jaw liners, and I've set up the foot pedal so it rises on its own to a comfortable height. The jaws close completely when the pedal is pushed down within about one inch of the base, so I have a little extra travel available that will allow for future wear. I gained some extra travel when I replaced the worn pivot bolts. I think that I may already have a milling cutter that closely matches the profile of the teeth cast into the body of the vise, so it's just a matter of finding time for yet another project to make an upsetting block/stop. Cheers, Al (Steamboat)

Yep, I agree that a properly-fitted/machined counterbore would definitely be a good way to avoid shear and bending forces at the the relief cut, which is the principal stress riser location in a shoulder bolt. When torqued to produce the correct stretch in the bolt (or to specs for the bolt material, size, threads, etc.) and engineered for the intended use and load, it's an excellent approach. Al (Steamboat)

Glad you liked the vise setup. As you said, it could be redesigned slightly (larger bore through the arm and through one hinge cheek) to accommodate a shoulder bolt where the shoulder would tighten against one hinge cheek and leave a bit of space under the head of the bolt to avoid squeezing the hinge and breaking it. The teeth are there to engage an adjustable block (which is missing) that could be used for upsetting the end of a piece of stock at some set depth below the top of the vise, or it could be simply used as a general-purpose adjustable depth stop. It's my observation that the block is usually missing on these old foot vises. I've seen a couple with the block intact, and I might eventually see if I can machine one to match the teeth. It would be a handy time saver when doing repeat operations, such as adding a bend or twist at the same location when making up a series of bars. Al (Steamboat)

From the photo you included of the tapered taps, it appears that they are tapered continuously along the full length of the cutting threads. You might have a closer look to see if there might be a very short section at the large end of the threads where there is no taper. However, at this point I am assuming that they are tapered all the way, and if so, there are a number of possibilities as to their type and purpose, but I cannot give you a definitive answer. I did find some information in Handbook of Small Tools, by Eric Oberg, 1908, which you might find useful. There is a 40-page chapter on "taper taps," which describes a number of tapered taps, such as: "Pipe Taps" "Taper Boiler Taps" "Patch Bolt Taps" "Mud and Wash Out Taps" "Blacksmith's Taper taps" (A few other types of tapered taps are described as well.) It's possible that your taps don't specifically fit any of these categories, but it's a start. Here's the link: https://books.google.com/books?id=nplKAAAAMAAJ&pg=PA257&lpg=PA257&dq=blacksmith+tapered+taps&source=bl&ots=S6IaJIlAwp&sig=yZ8Ho9E8xddezQvYpdTNP-Mszmc&hl=en&sa=X&ved=2ahUKEwjese-XtbzeAhWig-AKHchOAQQQ6AEwAXoECAgQAQ#v=onepage&q=taper taps in general&f=false Al (Steamboat)

Sorry, Vaughn. I have a 'tenon-cy' to get carried away sometimes. Getting back to the "threading thread," I have a few suggestions that I find useful: First of all, I use thread cutting oil, which helps cut cleaner threads and makes the dies and taps last longer. It seems to help reduce the effort as well. I really can't say which cutting oil is "best," because I really don't know. I've used several different brands successfully. Just make sure that the cutting oil is recommended for your application and follow the instructions and safety guidelines. While I'm threading a rod, about once every three or four new threads, I unscrew the die, brush off the swarf with an old toothbrush, and then screw the die back on and continue to cut more threads, repeating this until I'm finished. A little patience usually pays off. Preventing the swarf from building up will help make cleaner cuts and help prevent flakes from getting wedged between the die and the threads. I use a similar approach when using a tap to thread a hole. If it's a blind (closed) hole, you'll have to figure out how to get the swarf out after the tapping is done. I usually use a liquid aerosol cleaner with a long, thin plastic tube attachment. Be sure to follow the instructions and safety warnings when using aerosol cleaners and solvents. If you leave cutting oil in the hole it can affect torque readings, threadlocker effectiveness, etc. I'd like to echo Kozzy's comment about buying quality taps and dies. I don't have a specific brand to recommend, but at the minimum, get "high-speed steel" rather than "carbon steel." They're pricier, but in the long term they're more economical because when used properly, they should far outlast the cheaper ones. If you want even greater longevity and better threading characteristics, you could buy high-speed steel taps and dies with titanium nitride coating, which is especially recommended if you're threading stainless steel, which can be challenging to thread. Make sure that your cutting oil is recommended for stainless steel, and go slowly when threading stainless. It's still no cakewalk to thread stainless, but that should help. There are a lot of other coatings available, but titanium nitride is the most common. If you want to thread a rod that has mill scale or forge scale on it, remove the scale right down to clean metal before threading. Your dies will last a lot longer and you'll get cleaner threads. There are high-performance tap and die materials available, such as cobalt steel for threading hardened steel, and special taps and dies for threading titanium, etc., but for most purposes high-speed steel (preferably with a titanium nitride coating or similar) will work great and last a long time when treated nicely. Taps and dies for use with mills and lathes and other machinery bring up a whole new list of possible options too lengthy to mention here. Also remember that there are different "chamfers" of taps, which refers to the number of tapered (or incomplete) threads at the starting end of the tap. The most typical are "taper" (or "starting"), "plug," and "bottoming," but there are other names and variations on these. The taper tap makes it easier to start tapping a hole and helps you align the tap within the hole. The plug tap is good for most general-purpose tapping, and the bottoming tap has full-diameter cutting threads just about all the way to the starting end or "front" of the tap, which lets you cut threads almost all the way to the bottom of a closed or "blind" hole. I think that a bottoming tap should only be used when necessary, since in my experience I think it produces a slightly rougher thread finish and requires more torque than the other chamfers. When I need to use a bottoming tap, I first tap the hole as far as I can with a plug tap and then just use the bottoming tap for cutting the last few threads at the bottom of the hole. Getting your taps and dies started in correct alignment is perhaps the most challenging thing about threading. Some die handles (aka, wrenches) have built-in adjustable centering guides to help start the die straight. To make a simple jig for starting taps in holes, use your drill press to drill a nice straight hole through a 1"-thick piece of hardwood and clamp the wood flat on the surface of the object to be tapped, with the hole in the wood directly over the hole that you want to tap. The hole in the wood serves as a guide to start the tap straight. This general idea can sometimes be used in conjunction with a threading die as well. There are a LOT of other ways to get the tap or die started in proper alignment, but I'll leave those to your imagination. I also recommend buying adjustable dies that allow you to make minor adjustments to the thread diameter to produce the kind of fit that you want in the female threads of a nut or threaded hole. I could also mention that there are special taps and dies for reconditioning threads that are a bit rusty or slightly damaged. You may hear terms like chasing, repairing, rethreading, restoring, etc. and there are a lot of variants among these dies, which I won't go into here. Just remember that these can't perform miracles. If the threads are too damaged, replacement may be the best or safest option. Also, be SURE to clean debris out of the threads before using a thread reconditioning tap or die. I'm sure I've forgotten to mention a few things, but that might give you a couple of useful ideas, and I hope that we're back on topic now. Al (Steamboat)

I started collecting Old House Journal maybe a year or two before I published an article in one of their 2013 issues. I do have some Fine Homebuilding issues that go back quite a bit further than that. Hmmm. Taps and dies. That sounds familiar. Topics do tend to "evolve" around here...happens a lot. I'm perfectly happy going back to the taps and dies "thread" though. Al (Steamboat)

I don't think my old issues go back that far, but I'll see what I can find online. It could be an interesting read. Thanks. Al (Steamboat)

I'm sure that whoever was building the chairs came up with a technique for the "bulbous tenon" type joint that worked, and as you said, it could easily have been a self-regulating effect of their drilling equipment and technique (and the type of wood) that achieved what I had suggested with regard to dimensional compensation for expansion and shrinkage effects in the joint. Antique chairs (and many reproduction chairs) are likely to have been built using some combination of slow-speed and hand-held tools. An asymmetrical result from drilling or turning wood can be much more pronounced when using a low-speed hand-held drill as opposed to drilling wood clamped securely to a drill press table or mill table, or when turning wood on a low-speed wood lathe with hand-held turning tools vs. (at the other extreme) a high-speed CNC wood lathe. When using hand-held tools and low cutting speeds, the cutting edge paths can be significantly influenced by wood grain characteristics. I experience it all the time when working with woods like southern yellow pine, with its surprisingly hard slow-growth layers. I get pretty uniform results when drilling SYP with a hand-held drill if I use a freshly-sharpened bit and the optimum cutting edge speed for that particular bit, but if I want even better results, I will take the extra step of clamping the SYP in a drill press or using a portable jig/press to secure the wood relative to the drill, in which case I almost always get nice straight, round holes. Of course, the type of drill bit can also make a difference. Al (Steamboat)

Yes, "stretchers" would be the traditional term for the cross brace in a wooden chair...couldn't think of that last night for some reason (CRS syndrome, maybe?). The spoon-drill-and-round-tenon wood joining method you mentioned (I can't think of a name for it) is not one that I've dealt with, but quite interesting. I can see that it would require some precise fitting, as moisture-related shrinkage and expansion produces relatively small dimensional changes in such a small-diameter joint. The smaller the joint, the smaller the dimensional changes, and the more precision is required. The actual dimensional change will vary with the nature of the wood, of course, but I think the general idea still applies. Also, the moisture-related dimensional changes relative to the grain will be generally be greatest tangentially, moderate radially, and minimal along the grain (longitudinally), which I think would need to be allowed for in such a joint. Since you said the tenon would be "turned round," I assume that it would be spherical, in which case one potential pitfall that pops into my mind is that when the mortise wood (in this case a chair leg) shrinks and the spherical tenon expands, it could exert force not only along the grain of the chair leg, but across the grain as well, so if not done correctly it has the potential to split the chair leg. A good deal of experimenting and/or a long tradition of closely-followed practices would probably minimize that possibility, but it's still a consideration in my mind. I have never attempted that particular type of joint, but my guess is that to do it successfully without risking split chair legs, one might make the tenon slightly aspherical to allow a bit of extra space to accommodate the fact that the chair leg will shrink more across the grain (tangential/radial shrinkage) than along the grain. I'm also thinking that by experimenting and measuring the actual dimensional changes in the dried-out tenon as it regains moisture, there could be a favored orientation of the tenon relative to the chair leg, so that if, for example, the diameter of the tenon shows greater expansion in one direction, it could be oriented so that the direction of greater expansion is aligned along the grain of the chair leg instead of across the grain. Maybe some combination of those approaches would work best...just a guess. An obvious advantage of using wedged tenon joints is that you can direct virtually all of the wedging pressure along the grain instead of across the grain, which can produce very tight joints and pretty much eliminate the chance of splitting. Well, maybe not all of this wood-related stuff crosses directly over to metalworking, but I'm always discovering different ways in which seemingly distinct skill and experience sets overlap and contribute to each other in a symbiotic manner. Getting back to the tap-and-die topic. I have a set of antique sliding-block-type dies like the ones that duckcreekforge posted, and I have found them useful on a few occasions, since there is more adjustment capability than in a split-type round die, although mine are not exactly what you would call high-precision dies, so I don't use them for any critical application. Al (Steamboat)

Anvil, you're pretty much on track regarding wedged blind wooden tenons. Here are some additional details: First, let me say that a "blind" wooden tenon is not necessarily always wedged, but without wedges the tenon would still need to be secured somehow, such as with wooden pegs, screws, glue, etc. In terms of wedged blind wooden tenons that don't depend on glue or fasteners, the most common secure type is often referred to as a "blind fox-wedged joint" or a "stopped fox-wedged joint," and to work well it requires high accuracy in joinery. Here's how it works (and your take on it is very close...just needs some details): A blind mortise is cut into the wood with a taper, so that the mortise gets wider as it goes deeper into the wood. The tenon is straight, but two narrow kerfs are cut into the tenon to receive wedges, typically fairly close to the edges of the tenon. The wedges are inserted a short distance into the kerfs, and then the tenon and wedges are inserted together into the mortise. When the wedges hit the bottom of the mortise and the tenon is pushed in farther, the wedges are pushed deeper into the kerfs, which spreads the edges of the tenon so that the tenon tightly fills the mortise. I published an article some years ago in Old House Journal dealing with restoration work, and this was one of the joint types that I discussed. I've restored a number of old wooden items with these joints, and they can be VERY difficult to take apart, sometimes requiring surgery. The Japanese have a special name for this joint. Check this link: http://www.aisf.or.jp/~jaanus/deta/j/jigokuhozo.htm That said, these joints do have the advantages of hiding the end of the tenon for a "clean" look while protecting the end-grain of the tenon from moisture incursion, which is good for exterior doors, since moisture penetrates wood most easily via the end-grain. However, when used in doors, this kind of joint typically cannot be tightened if the joint loosens due to wood shrinkage, since the construction of the door usually prevents a tenon from being pushed farther into its mortise. In other situations, however, the joint can sometimes be tightened. For example, in the case of straight (or relatively straight) round dowels such as those that are often used as cross-braces between chair legs, the dowels can sometimes be forced in farther to tighten the joint if the wood has shrunk (assuming that the tenon has not bottomed-out in the mortise), although this means that the chair legs will end up closer together, which might loosen or damage other joints, depending on how far the legs are moved. I prefer not to use wedged blind tenons in my own built-from-scratch woodworking projects. I much prefer through-tenon joints where I can access the wedges for future tightening/adjustments. That's probably more than you wanted to know about these joints, but there you go. Al (Steamboat)

Thanks! Glad to hear the positive feedback on the logo design(s) from you folks. Al (Steamboat)

You might also search for "ripper shank," which would provide more shank shapes and curvatures. Also note that the replacement teeth for either scarifier or ripper shanks are also available in sharply pointed shapes for easier soil penetration. https://www.google.com/search?rlz=1C1CHBD_enUS725US725&biw=2048&bih=1000&tbm=isch&sa=1&ei=_S3bW--8CMqy5gLljoK4Aw&q=ripper+shank&oq=ripper+shank&gs_l=img.3..0i67j0l4j0i5i30l5.16161.18075..18395...0.0..0.83.894.12......1....1..gws-wiz-img.....0.JN7EE6e8jmA#imgrc=_ Al (Steamboat)

Do you want to build a long-lasting implement? If so, then I think you should consider building one where the "wear parts" can be replaced. The concern that I have with your design is that the points of the tines might quickly become blunt or bent from hitting stones. You could maintain them as they wear by using hard-facing welding rod, but I think it's easier and cheaper to maintain tines that use very inexpensive replacement teeth/tips that can be replaced in minutes, as I have done on my own equipment. The implement that you are designing looks a lot like what I would call a "land clearing rake" or "land clearance rake," like the one in this linked document. Note the replaceable teeth. https://www.craigattachments.com/pdf/excavator/specialty/land-clearing-rake-info-sheet.pdf However, to save money, you "might" consider building an implement that is more like what I would call a "scarifier rake," which uses adjustable and replaceable "scarifier shanks" with replaceable teeth/tips. Here is a photo of one that is made to fit a three-point hitch, but you could probably build something similar that would connect to an excavator boom in place of the bucket, or possibly to the bucket as an attachment. You could space the scarifier shanks closer together, depending on your needs. https://cdn3.volusion.com/wf72e.9ho5t/v/vspfiles/photos/LS-SCARIFIER-3.jpg?1457341521 Note that scarifier shanks are available in different shapes and curvatures, some of which might more closely match the curvature in your proposed design. If you do an Internet image search for "scarifier shank," you'll get a lot of results. https://www.google.com/search?q=scarifier+shank&num=30&rlz=1C1CHBD_enUS725US725&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjszYC8zrPeAhUSneAKHcHVC8oQ_AUIDygC&biw=2048&bih=1039 Scarifier shanks are quite inexpensive and typically might cost roughly 20 US dollars each or less (plus shipping) and the replaceable tips/teeth usually only cost 5 or 6 US dollars each. You can shop around to find the best prices on either OEM or aftermarket parts. In addition to the scarifier shanks in the above link, which have holes in them for the height adjustment pin, there are also shanks with notches in the edge for the height adjustment. These also have replaceable tips/teeth. I hope that gives you some ideas. Al (Steamboat)

True. Portability for field use is yet another factor that could promote the use of interchangeable accessories for a workbench/workstation, so as to avoid having to lug around too many workstations. Al (Steamboat)