Speetol Tap Grinding Jig

[peak4Participant @peak4]

A Sunday evening query for you all.
Has anyone ever come across a Speetol jig for sharpening taps; well I say sharpening, it looks like it's for adding the tapers and grinding the relief on the cutting edges.
I'm trying to work out how to set it up, as it was designed to be used, rather than just guessing; my Google fu seems to have failed on this one.

A well used wooden box contains a set of guides engraved for BSW from ¼" down, and BA from 0 -12.

This also contains a baseplate, with holes labelled 1st, 2nd, & 3rd, each with an adjacent slot, presumably for each of the three normal tapers in a set of taps.
There is also a rectangular cutout with a couple of arrows, which I guess are to point to the corner of a grinding wheel.
I'm not sure if the idea is to grind on the corner, or on the wide cutting face, or what shaped wheel it's been designed for use with. It looks to present the tap at an angle to the rectangular cutout, so I'm guessing the plan is to use the corner of a wheel. Maybe the arrows point to the point in space where the corner of a wheel should be aligned at centre height.
The actual end of the tap protrudes beyond the plate, which would make sense, as it's above centre height, so that part of the wheel would be further away. I guess i could play with a few different diameter wheels to see if that looks likely.

There is also the actual business part, with a sliding rod, and chuck, which fastens in each of the three holes. There is a cam which engages in the relevant slot in the plate which, when the ball ended lever is moved, swings the whole assembly about a pivot point concentric with the round holes.

The very right hand corner of the box contains a little Tee handled bolt which forms the pivot point as well as attaching the arm to the baseplate. Seen here assembled with a ¼" BSF tap and its associated guide bush

There is an adjustable guide and 3+4 legged indexing collar, which slides the main bar and chuck back and forth as it is rotated. The knife edge guide is adjustable for right and left handed taps.
There doesn't seem to be any way to index the orientation of the tap in the chuck; no detent to point to, or set, the cutting edge of a flute or anything like that.
This also seems odd as it's one of those chuck that rotates the jaws as it's tightened, unlike a keyed chuck.

And finally a plan view showing the ball ended handle, which rotates the eccentric in the slot.
That in turn swings the whole arm about the chosen pivot hole; 1st, 2nd, or 3rd.
There are no stops for the ball ended handle, to limit the angle of the arc, and thus the cut.
Swinging the handle of course, will alter the angle as well as the cut, which i find a bit odd.

Has anyone ever seen one, or even better have some instructions?
I assume it must be intended to bolt onto a T&C grinder or similar, using the hole above the trademark stamp. I can't quite visualise at what angle, or height, it's intended to present the tap to the grinding wheel.

Thanks in anticipation

Bill

 

Edited By peak4 on 27/01/2020 00:09:41

[peak4Participant @peak4]

[Clive FosterParticipant @clivefoster55965]

Bill

It may be worth looking at the instructions for the Clarkson Drill and Tap Grinding Attachment, find a copy here **LINK** .

Seems to me that your device uses the same sort of setting concept and generates similar moves to grind the tap lead.

Hafta say I'm not entierly clear on exactly how the Clarkson device is used and I've actually got one. Must try someday when I'm feeling patient.

Clive

[SteviegtrParticipant @steviegtr]

Nothing beats the human eye.

[not done it yetParticipant @notdoneityet]

Posted by Steviegtr on 27/01/2020 00:53:40:

Nothing beats the human eye.

Yes, and using them to read the instructions is often a last resort.

Clearly, in this instance, he has already been using his eyes – and engaging the little grey cells – but would appreciate some extra assistance from someone who actually knows…

[BazParticipant @baz89810]

Looks very much like the forerunner of the Clarkson drill and tap grinder. The three positions on the baseplate would give taper, second and plug angles, the protractor thing sets the relief angle and the thing wilt four pegs is for four flute taps, you may have a two and three peg one somewhere. If you send me a PM i will send you a copy of the Clarkson booklet, can’t get pics to work on here.

[Anonymous]

When I used my Clarkson tap grinder I think I set the tap orientation by eye so that the cutting edge was more or less on the horizontal plane along with the tap axis. I don't think it's that critical. Not a great picture but this shows the general arrangement:

Andrew

[peak4Participant @peak4]

Thanks for the replies thus far folks; I do have the Clarkson instructions, but whilst similar in idea, this does seem to differ a bit in the setting up. For instance, there are no stops on the swing handle to limit the cut.

I have a Clarkson grinder to mount it on, but I'd be guessing even about wheel height.

Also it seem to be designed for taps down to 10BA or 1/16" BSW, both of which I could make a complete hash of without instructions. (Typo above when I said 12BA)

Off out now to try and work out how to change a sidelight bulb in a Peugeot Expert.

Cheers

Bill

[Author]

Posts