I have some taps that will need some work before they’ll be cutting wood threads again:
I’ve never had to sharpen a tap before… Here’s what’s been suggested to me so far, from separate sources:
- Cut some threads in pine and load them with valve griding compound. Run the tap in and out a few times, reloading with more compound. This should polish things up nicely. Normal rust removal process on the shanks.
- Use a triangular file along the threads. Disadvantage is that the thread cutting profile might be changed.
- Touch up the cutting faces (the “flutes”) with a conical stone in a Dremel.
Also, I’d rather not chew the shanks up with a crescent wrench or a regular tap handle from a tap & die set. Maybe some oblong handles? Here’s an end view:
I’d like to make something a little more “period”, and I was wondering if anybody has seen (or has a picture of) a wooden-handled tap? (NB: the left one is stamped with “IV”, and the right one has holes in both ends as if it were turned on a metal lathe. Purty!)
Can anyone confirm that they’re mortised square to the grain, as opposed to diagonally?
TIA, HT gurus!
—————
/dev
Replies
The cutting face along the flutes looks pretty flat. As such, I'd think a bench stone might be a safer approach. I'd do that before cleaning the v-section of the threads.
Since the force on the handle will be a twisting action, square to the grain makes more sense to me. The handle might also be reinforced with hoops near the mortise or wire-wound for greater strength.
Just thinking out loud here, since I haven't actually done it either.
slash,
I'd suggest working on the flutes, and just lightly clean the threads themselves. Depending on the size, handles might be based on those of gimlets, or turnscrews, or augers.
Do you have the screwboxes (dies) to go with these?
Ray
> Do you have the screwboxes (dies) to go with these?
Yep, I think they look pretty clean. I feel more comfortable fettling the cutters, too.
View Image---------------
/dev
Regarding the sharpness of the "V" - it seems to me that for wooden threads in general, a rounded or squared thread tip would be stronger than a sharp V. Ultimately, however, the profile of the tap needs to match, or at least fit within, the profile of the corresponding die. Having a sharp V created by the cutting tool in the thread box, for example, would create a male thread with a higher profile compared to a rounded-over female thread created by the worn tap, thus resulting in fit problems.
Ralph,
Ah, but the outside diameter of the screw blank- the dowel, as it were- if slightly smaller than the full diameter acceptable by the "v" cut by the die's cutter, will yield a flat topped screw thread, that will fit inside the tapped out hole. Truth to tell, the sharp tips of fully cut threads will crumble off in the making, most likely...
It can be a fussy job setting one of these up just right. Esp if the last one to use it was a jack-leg.
Ray
Ray,
A jack-leg? A jack leg? Hey, I resemble that remark...
But seriously, where did you come up with that expression? I've only heard it a couple of times, and wondered where it originates. Any ideas?
ZoltonIf you see a possum running around in here, kill it. It's not a pet. - Jackie Moon
Zolton,
I grew up hearing that term applied to those with less than high standards of workmanship. I don't know, but if I had to guess, I'd say it is a reference to the way a male dog anoints whatever he comes near...
Old Jack gets a hard time wherever he goes. Jack leg, jack of all trades (master of none) jack-plane, jack knife.
Ray
Ray,
I just looked this up in an online dictionary and came up with this:
Main Entry:
jack·leg View Image
Pronunciation:
ˈjak-ˌleg, -ˌlâg
Function:
adjective
Etymology:
1jack + -leg (as in blackleg)
Date:
1850
1 a: characterized by unscrupulousness, dishonesty, or lack of professional standards <a jackleg lawyer> b: lacking skill or training : amateur <a jackleg carpenter>2: designed as a temporary expedient : makeshift
— jackleg noun
So, a somewhat insulting thing to call someone, eh?
ZoltonIf you see a possum running around in here, kill it. It's not a pet. - Jackie Moon
Zolton,
I've never heard it used as a compliment, that's for sure. But I've seen some work that would be complimentary to call jack-leg.
Ray
> But seriously, where did you come up with that expression?
This site references the Oxford English Dictionary, which seems to say that it is derived from the name of French knife-maker, Jacques de Lieges, whose knives were perhaps used by "hack" carpenters. Sounds like they were the original wood butchers. :)
As far as the rehab goes... I applied medium & fine stones to the flutes, and touched up the threads with a fine triangular stone. It seems to cut pretty well in 3/4-thick poplar. Next, I cut some threads on some dowel stock and tried 'em out. It was a little tight, so I compared the tap to the threads from the screwbox...
View Image
Is it just me, or do I have a 5 TPI screwbox and a 5.5 TPI Tap? :(
Measuring the thread spacing inside the thread box seems to confirm the difference, but it's hard to be sure. Can bad screwbox technique change the thread spacing? ---------------
/dev
That tap and the thread box which made the dowel thread are not "an item"...Philip Marcou
Fascinating! Thanks for passing along this information on the etymology of the word jack-leg. You've educated me on this subject, and now I can - and will! - deploy this insult in the most effective way...
Very interesting..
Zolton
If you see a possum running around in here, kill it. It's not a pet. - Jackie Moon
slash,
If they are a pair, the threads in the box's "outfeed" side were made with the mating tap; thus the screw must emerge as a perfect match for the tapped hole, in the box as well as in the project the tap was used on. Variances in set up of the screw box will involve the height of the vee cutter in the box relative to the starting of the outfeed thread, resulting in binding, if it is too high or low; or in depth of cut, resulting in too-shallow threads (wide flats on tops of thread, binding in the outfeed) or too deep a cut (screw threads breaking or crumbling, and too loose a fit in the tapped hole, which will lead to stripping of threads.) Old boxes will often have a bolt with a hook or overhanging head to secure the position of the vee, but the forces involved sometimes require that paper or wooden shims be placed under, over, beside or behind the cutter to make it fast, and prevent its twisting or rotating out of its ideal position.
The diameter, and consistancy of diameter over the length of the screw blank is obviously a factor too.
Ray
PS-- with the tap, and a sample box as a reference, it is a fun project to make your own screw box that does match. More of a challenge (for a woodworker, that is) to make a tap that matches a n old box!
A dremel tool with a grinding bit is very aggressive. It'd be pretty easy to take off way more metal than you intend, but the advice to sharpen the flute as opposed to the threads is accurate. My suggestion would be to get the set of 1000-grit japanese waterstone slips that Woodcraft sells. They're pretty cheap, and the 1000-grit abrasive should do a pretty quick job of removing rust and sharpening the arris. If you need to remove a good bit of metal, you could supplement the waterstones with either a diamond hone or one of the ceramic round files that Woodcraft sells.
I do have an old tap handle - the form is as you'd expect, a 6" long cylinder of wood (probably hickory) with a square, tapered, mortised hole in the center. A ring of (probably) wrought iron encircles the handle at the mortised hole location.
I've no idea how old this tap handle is, but judging from the patina of the wood and the condition of the wrought iron reinforcement, I'm betting it's at least 100+ years. It's tough to tell, though - I've some coachmaker's tools that are certifiably from 1836 that look like they are early 20th century vintage because they were nearly unused and stored in a dry place, and some molding planes that are definitely early 20th century vintage that appear to be early 19th century tools because of hard use and storage in a barn.
Ok, I'll use sharpening stones. The smallest one needs the most work -- note the rounded-over thread peaks. I'm not sure I can resist using the Dremel for that one. sigh.
> A ring encircles the handle at the mortised hole location.
Ah. I was wondering what keeps that tap from working its way through the handle if it's not bolstered and/or tapered. I assumed I should use a stopped mortise.
Does that mean the tap seats through a hole in the ring? Fascinating.
Thanks!---------------
/dev
The method of using valve grinding compound is for honing the edge. Alot of old time carpenters had a piece of solid beech pretapped and would use that along with a brace and the compound to hone the edge back on and to clean unwanted resin out of the grooves.
> The smallest one needs the most work -- note the rounded-over thread peaksActually I think the rounding is mostly a result of the tool being tapered. The full diameter one looks pretty sharp. I can't see that compound in a "properly" threaded piece of wood (even if you could make such a thing) would help other than making the tool duller and shinier. If you work the flute, you should be able to get a sharp edge that should work decently. Unless you have above-average skill with a dremel, I wouldn't go freehanding with one.If there's rust, I'd start with electrolysis or a brass wheel to clean it up.Pete
Maybe I've got an antique honey-dipper instead of a tap:
View Image
;) You're right, though. The largest is probably "sharp enough," the mid-size needs a touch up, and this one is, well... no threat to St. Roy. :D---------------
/dev
"Does that mean the tap seats through a hole in the ring? Fascinating."
Yep. The square hole is cut through both sides of the ring (and the handle). Since it's tapered, the force of using it further seats it into the ring and handle.
That idea of using valve grinding compound is an old myth It actually rounds over the cutting edge and if repeated enough times thoroughly destroys the tool' Same thing occurs, when by following that old wives tale to sharpen a pair of scissors by cutting a sheet of sandpaper. A definite (NO NO)
Using a brass (or bronze) wire wheel attached to a grinder or electric drill to remove any heavy rust is the first thing recommended. (BY ME)
Followed by using a medium diamond coated hone, file the tapered forward (Starting) edge to produce a sharp leading edge at the same time filing off the tailing edge to provide a slight clearance angle similar to the original edge.
Next, along the flutes, run the hone along the several tooth edges to create a new sharp edge along the row of teeth across all the cutting edge of the teeth abutting the grooves' To simplify the procedure, First coat all the surfaces with red or blue magic marker to better check your process and not file extra material again.. When the teeth feel sharp stop filing. Steinmetz.
> ...file the tapered forward (Starting) edge to produce a sharp > leading edge at the same time filing off the tailing edge to > provide a slight clearance angle similar to the original edge. OK, correct me if I'm wrong: I think you're saying to file carfully along the threads, just enough to get flat "channels" at the cutting face and without making the cutting face narrower than the rest of the tap thread behind it...
> Next, along the flutes, run the hone along the several tooth edges > to create a new sharp edge along the row of teeth across all the > cutting edge of the teeth abutting the grooves.
...and then make a flat cutting face in the flutes. Hopefully, where the flat channel meets the flat face, I now have a cutting edge.Thanks,
/dev
> OK, correct me if I'm wrong: I think you're saying to file carfully along the threads, just enough to get flat "channels" at the cutting face and without making the cutting face narrower than the rest of the tap thread behind it...
I don't think it's possible to file the threads without making the cutting face narrower than the thread. I think you're going to want to cut the flute area back to create the sharp edge.
Pete
I think you understand what I tried to explain . Every cutting tool (be it a drill bit, or a lathe cutting bit,) in order to remove metal, has to have its cutting point or edge protruding more promenently from it's tailing edge The tailing edge is always less promenent and usually tapers back even more to reduce drag and allow clearance for the leading edge to do it's job When the cutting edge wears, it becomes blunt and the tool rides upon the cut back clearance which cannot cut.
The starting edge of most taps are chamfered to allow the tool to enter the hole easily and remain centered while gradually digging in to cut full threads.
The flutes are used to provide more than one row of cutting edges contacting the work. Also, the flutes can capture the scraps of material removed by the cutting edges. After penetrating the hole a few revolutions, this material (Whether wood or metal) bunches up and can 'sieze up' the tool. That's why it's a good idea to back up turning a half turn, then proceed to tap a few more turns. The tap stays sharp longer and the debris is removed. In no case, file off any of the circumference of the tap, but just hone the length of the flutes to create all new sharp edges. Just a few strokes is all you need .Steinmetz.
Edited 8/18/2008 1:21 pm ET by Steinmetz
Try to find a local engineering shop with a tool and cutter grinder who will regrind your taps at the corect angles it should not be expensive.
Regards from Melbourne
You can make it fool proof but not idiot proof
Old post .. I have read all the replys. Most seem reasonable.
Old metal worker so I think the (wood Taps) may not apply. However, it is still made out of metal..
I would forget all about the rust in general. I could be all wet in my thinking, but I would do nothing to them (at first) but get some old skid wood. Usually some old wood that will take anything up to a point..
Check for nails etc.. NO NOT go near them.. Drill a bunch of holes sized for the tap to cut.. Cutting oil would be perfect but any automotive oil will do in a pinch. If you have a brace... Chuck the bit up the best you can (no fit? use wooden wedges to fit) and HAND drive the bits in the drilled holes. Use plenty of oil... Use a new hole for the next threading operation. Somebody said pine? I would think you want to stick with some old knurly hard wood!
Your arms will be very tired unless you do this every day!..
Hard to tell, but you pictures suggest surface rust.
I'd bet you will see improvements in the thread cut in every new hole as you back out the tap!
And the tap teeth a bit more pretty!
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