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I don't think you're wrong.Originally Posted by Jim Koepke
I got confused because the Chris Swarz article seemed to be about the Skew Rabbet plane,
but the string seems to be talking about the small plow plane.
It doesn't make any difference, because the depth stop design is the same.
I have the Skew Rabbets (gloat-both of them), but I lust after the small plow, I just haven't justified it yet.
Last edited by lowell holmes; 10-13-2015 at 1:52 PM. Reason: sp
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I have the Small Plow Plane, and initially had a sometimes problem with depth stop slippage. I then roughed the depth stop shaft with 180 grit sandpaper and never had the problem again.
Member
Wrap a little teflon tape (the kind for plumbing) around the threads and it will hold much better. Have done this at work on a threaded knob that would not stay in place, works very well.
[OP]
Member
Robin Lee said to me at Handworks 2015 in Amana, Iowa that the reason they don't slot the screws at the factory is because people would over tighten them, and snap the threaded portion from the head. For those considering cutting your own slot, I'd venture to guess that if you're smart enough to read this post is smart enough not to over-tighten to the point of breakage. There's a BIG sweet-spot between "WILL NOT SLIP" and "SNAP". Think about it: When's the last time you snapped off a light bulb due to your unbridled brute force?
Consistent with what others have said, Robin Lee mentioned that a fix is in the works. He didn't divulge any secrets, but i would guess that it may be a steel screw pressed into a 'pretty' knurled brass head like the one shown below. I don't think even a Neanderthal could snap a #10 steel screw with just a screwdriver.
bullet_knob_sm.jpg
I agree with Derek and the other commenters that the screwdriver (e.g. shop-made slotted head) is the safest way to tighten the existing brass screw with the least risk of breaking it. In other words, if you're up against an insufficiently strong screw as we are, using a screwdriver is a better idea than a strap wrench if your goal is to reduce risk of breakage for a given level of resistance to stop slipping.
More physics:
I think it's a good idea to lubricate the brass threads too. The screw's tensile load creates force between the stop and the plane body, which creates stiction/friction, preventing stop slippage. With this in mind, the more easily the screw can twist in its threaded hole, the more the screw's finite strength can serve the purpose of tensile load, and the less it will be taxed by torsion (e.g. forces caused by resistance to twisting forces under load). In other words a screw over-tightened to the point of breaking be at higher tension when it snaps if the screw had been lubricated than if unlubricated.
This also means that in the SAME way that others have had success with FENCE slippage by 'roughing up' the fence rods, there MAY be some benefit in roughing up the interface between the depth stop and the body/tracks which it rides in. This would presumably create more friction for a given amount of screw tension. Perhaps this would totally negate any need for a slotted head. :-)
Personally, I'm very happy to have my screw slotted. If I break that brass screw, I'll eat my own hat, then buy everyone here on this forum a beer.
Last edited by Karl Fife; 10-14-2015 at 2:20 AM.
Member
It's not necessarily the easiest issue to sort out, and a mechanical engineer would likely concede that getting it right is as much a matter of practical trial, error and experience as it is the simple application of some calculation/formula or similar.
The trick has to be to get everything balanced - to come up with a knob that comfortably applies enough torque to provide the required clamping force - without overdoing it to cause damage to the clamped item or breaking the screw. Spanners and wrenches as well as being inconvenient risk over tightening.
I'm not a big fan of the classic knurled finger knob either - while they tend to be the default choice because everybody doing turned parts has a knurling attachment as you guys have said they tend to be a bit slippery and to invite reaching for a pliers or vise grips.
The screwdriver slot sounds a reasonable balance. Another option might possibly to head for a tooling supplier like these guys, and select a few appropriate metal knobs with a grippier/lumpier and/or possibly slightly larger head, but they won't be as pretty or compact: https://www.berger-tools.co.uk/Stand..._Screws__Nuts/
There's reasonable choice available, including brass and plastic tipped ones. Brass would be the aesthetic choice, and even without a two piece/steel stud it can be very strong stuff (similar to steel) - but a lot depends on the grade and the temper, and there's typically not many choices of stock knob available in it from the likes of tooling supply houses.
The standard brasses typically used for furniture knobs and the like may (my memory is hazy) be chosen more for free machining and ease of e.g. casting/forming than strength - while stuff like the right grade of aluminium or managanese bronze is strong (similar to mild steel) but harder to handle. Not necessarily the same colour either...
Last edited by ian maybury; 10-14-2015 at 8:03 AM.
Member
I like Karl's picture of a steel shanked screw pressed into an oversize brass knurled head.
Teflon tape is a smart idea,too. Just make sure that none comes in contact with the steel shaft you are trying to prevent slippage of. But,that's obvious.
Member
I dunno, have you seen some of the cheap stuff being passed off as steel fasteners these days?
Got refunded by Grainger 'cause a box of ``steel'' screws they sent me weren't even as strong as the brass screws I'd bought them to pre-drive holes for --- fortunately, I found a small bag of American-made screws in the right size (and for a flathead driver) which I was able to use.
Member
Personally, I hope that there is more to the solution than just a screw that will take more torque. In my opinion the depth stop is inadequately designed for the task asked of it. I have two owned two of the LV plow planes in question and both were "iffy" about holding a setting, particularly the earlier of my two planes. To me, finger tight should be my end of the deal. Designing it to hold a setting is up to the maker. A screwdriver is ok with me if that works best, but I would not use one on the current brass knob.
Member
There are many different grades of steel screws. If you are ordering machinist types of screws,order grade #8.
[OP]
Member
Mike Brady said: >> A screwdriver is OK with me if that works best, but I would not use one on the current brass knob.
The reason I wrote the post is that It's perfectly acceptable to use the current brass knob as long as you're not John Steinbeck's "Lenny", always accidentally crushing bunnies to death with big, powerful steam shovel-ey hands. It's not a concern.
I'm sure that Veritas would indeed have returns on their hands if they'd put a big slot in the screw as I did, but only because people wouldn't think they needed to be careful.
Member
I would include the skewed rabbet plan in the problem also, it has the same issues.
Contributor
It is relevant to understand that the depth stops for the Skew Rabbet plane and the Small Plow plane are different in design. Consequently, the solution for each is actually different.
The Skew Rabbet looks like this ..
What you will see here is that the depth stop is clamped down with direct pressure from the head of the screw.
The Small Plow looks like this ...
Here the depth stop is held in place with a collar that is clamped to one side.
In the case of the Skew Rabbet, adding down force will aid in tensioning the depth stop shaft. However, in the case of the Small Plow, more down force will not add directly to tensioning the depth stop shaft. It only does this indirectly - the collar will end up with uneven pressure and the one side tightens and the other side does not. The shaft will be held more firmly, but it is unpredictable how well.
One answer for the Skew Rabbet is more downforce. Of course, this must not be seen in isolation - downforce simply causes more friction, which limits movement. Therefore rough the rod and rough the groove in which the rod goes, and then the added downforce will make more sense. The screw slot is not just to tighten the head, but also to loosen it!
With regard the Small Plow, I do have a solution, but I think that it is prudent to mention it to Lee Valley first before I air it here.
Regards from Perth
Derek
Last edited by Derek Cohen; 10-15-2015 at 1:38 AM.
[OP]
Member
Out of curiosity is that the very same #10-32 all brass thumbscrew on both the plow and the rabbet? If so, the screw seems like even more of an Achilles heel on the plow than it is on the rabbet.
Take a look at what Lie Nielsen is doing to hold the stop on their up-and-coming plow. The casting receives a steel stud, and the knurled brass knob is threaded onto the stud. I don't have an opinion about the choice, but it definitely solves the "soft brass screw" problem without having to make the pretty but expensive combination Steel + Brass "Frankenscrew" like the one I posted earlier. Even death-grip, bunny-killing "Lenny" couldn't strip 10-32 'soft' brass threads with a screwdriver, whereas snapping the screw would be... a snap :-). Should I have said "Rabbet-Killing Lenny"?
IMG_20150516_105727 (Large).jpg
Last edited by Karl Fife; 10-15-2015 at 1:47 AM. Reason: OCD
Contributor
Lie Nielsen is following the original design of the early Stanley Miller's patent plow plane. My recollection is the 'stud' is actually the threaded end of a rod threaded through the body for supporting the fence.Take a look at what Lie Nielsen is doing to hold the stop on their up-and-coming plow. The casting receives a steel stud, and the knurled brass knob is threaded onto the stud.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
[OP]
Member
That certainly is consistent with all of the pictures in the thread on this forum about the LN Miller Plow prototype,
http://www.sawmillcreek.org/showthre...sen-PLOW-PLANE
especially this picture:
IMG_20150516_105626 (Large).jpg
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