Thread: Adustable Parallel !

Hi Guys,

Following some notes and info from Bob about adjustable parallels, I decided to have a go at making one from some gauge plate that I have that has been sitting unused in its wrapper for well over 30 years. It is 3/4" of an inch by 5/16" inches, (19.3 mm X 8.04 mm) for those that want metric measurements. The wrapper also has details printed on it for hardening and tempering it. There are a few speckles of rust on it but nothing that would cause a problem. Quite surprising after all this time.

Adjustable Parallel.png
This is the drawing of the proposed parallel. Two of these are needed. I've used 8 degrees as the slope angle which should allow for about 55 mm extension. A groove of 3 mm has been used to hold the two parts together. I'll take some pictures later.

Hi Barron, looks an interesting project to be put in my projects to do file. Thanks for the diagrams. Have you thought of a method to fix the parallels once they are set to size? It appears to be a tougue & groove design to locate the 2 parts and allow them to slide. Interested to hear your thoughts if they are to be used as job supports whilst machining. cheers

Hi Ian,

Thankyou for your comments,

I had originally thought about simply using a 3 X 3 mm square piece of brass bar to align the two pieces, a spot of super glue or Locktite to secure it in one half. Particularly since I hadn't considered that the maximum hight would only be about 30 mm with the material I have.

The other possibility would be a fine dovetail, not that I have the ability to cut one that small !

Any thoughts about this ?

.I think they could be handy. At the very lest look pretty flash with all the other stuff.
Do they some times have a gib arrangement?
aaron

Hi Aaron, Guys,

Originally Posted by azzrock

.I think they could be handy. At the very lest look pretty flash with all the other stuff.
Do they some times have a gib arrangement?
aaron

To be honest, I don't know. Maybe Bob will chime in and answer that question. Also he will be able to say how they are locked together, assuming that they are.

At the moment I'm going to stick with the original plan and use a square brass bar !

The set that I have use either one or two small screws to lock the 2 halves together.

I have a set of Starrett 154-A that use a dovetail with a slight angle to connect the 2 halves. I presume that all sizes would use a similar design.

Adjustable Parallel (2).JPG

Adjustable Parallel 2.JPG

those pictures clear things up a bit

Hi Lex, Guys,

Yes it does ! Thanks for those pictures. I had not thought of that method of clamping. Simple and obvious when its pointed out.

Hi Guys,

I've done some work preparing for the making of an Adjustable Parallel.

I mentioned that I had some gauge plate that is 3/4" of an inch by 5/16" inches, (19.3 mm X 8.04 mm) and 18" inches long. So using my newly refurbished bandsaw, I cut two pieces off approximately 90 mm long. Over length so that I could clean up the ends by milling them flat.

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I was surprised that the cut ends were as square as I could measure and both pieces within a thou of each other in length. I know that I took care to set up the bandsaw properly, but didn't expect this kind of performance.

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This is a picture of the wrapper that the gauge plate came in showing the hardening instructions printed on it.

Now I don't have an angle plate to set the angle of the work pieces in the mill vise, so I made one from a scrap of chipboard very slightly thinner than both pieces of gauge plate when held together.

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First I took a cut to ensure that I had a flat edge square to the end of the bit of chipboard.

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Then I set the saw to about 8.5 degrees. It specified 8 degrees on the drawing but it isn't critical.

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I took a cut so that I could check the angle was correct. I then cut off a piece 30 mm wide so that it would raise the two pieces of gauge plate to the correct hight in the mill vise.

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As a double check I used my angle gauge to check that when the two pieces of plate were set in the vise they were at the right angle and high enough to cut without hitting the vise top. I marked the wooden angle and cut off the excess then used the vise stop to set the position.

At this moment that is as far as I've got. I'll post more later as I progress.

Hi Guys,

I've not been upto much today ! I got around to thinking, why spend ages milling the waste material off the workpiece to produce the angle that I want the parallel to be, why not just saw it off !

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So that is exactly what I did. I cut a piece of chipboard scrap to the same length as the workpiece and then cut one edge at the 8 degrees that I required. Clamp the wooden guide in the bandsaw vise, then place the workpiece up against the wood, lower the bandsaw blade down onto the work and let it cut at the required angle. This picture is looking down onto the blade, so you can see how it worked out. The only thing holding the workpiece was the blade, the vise edges and me holding the workpiece against the wood. Yes I used a push stick !

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This is the result of cutting the two pieces. I've deburred them so that there are no sharp edges to cut your fingers on when handling.

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These two pictures show the workpiece and the off cuts above. There is only a thou between them, so they should clean up nicely by fly cutting. I could almost make a second smaller parallel out of the off cuts.

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I decided to test just how accurate the cuts were by placing them together.
Sorry about the camera shake in this picture. Artificial lighting and relatively long exposure. Using flash might have been better

Using the bandsaw was very much a test of just how good a cut could be made and using it was much quicker than milling.

I'll post more later.

Looking good!
Are you going to use a dovetail between them, or just stick with parallel?
I was thinking that since it only needs a slight angle the internal dovetail could be cut using a slitting saw. You'd end up with a slight angle in the root of the dovetail but that wouldn't be an issue as its not a bearing surface (and you'd be removing most of it when slitting for clamping anyway).

Steve

Hi Steve,

I think for the time being, I'm going to stick with just milling a slot in each half and using a piece of square brass rod to act as a guide between the two half’s. I can always slit one half and use a clamp screw as in the ones shown in the pictures earlier.

I really don't think that I have got the skill to cut a dovetail with the precision that would be required ! In fact I might struggle with getting a simple slot cut with the required accuracy.

To be honest I'd be grateful for any help or advice I can get !

I think you sell yourself short John
IMO from seeing your other work you've definitely got the skills to do it - although not having actually done it myself I might be underestimating how hard it is.

My thinking is that a parallel "tongue" is likely to be a pain in the backside to use, with the 2 pieces wanting to part company when you least want/expect it, and murphy's law says if you drop one half on the floor it will be the mating face or tongue that ends up with a ding in it. from that perspective I think its worthwhile pursuing a dovetail of some form.

For the female dovetail my thought was to use a slitting saw, angle the part a few degrees and slot it to the dovetail depth. Flip the part over and repeat to get the other face.
For the male, maybe use an end mill to rough out the initial angle on the main dovetail face, then square up the root and finish off using a flycutter and HSS tool ground to match the angle.

Like I said, I haven't done it - so that's just my thoughts on how I would approach it!

Edit: I'm assuming that the female part would also be slit for clamping like in the photo posted previously.

Steve

Hi Steve, Guys,

Steve thankyou for your reply and the vote of confidence.

I am only going to slit one side, but I do appreciate the risk of damage should it fall apart and land on the tiled floor ! So far I've only managed to damage my "Spot On" 0.0005 gauge and a 20 mm slot drill by dropping them. I don't know which upset me the most, probably the gauge, since it was given to me many years ago.

Anyway its about to be retired, since I've just ordered a new one.

Today’s efforts have gone into fly cutting the band sawed edges dead flat and square. I've also milled a slot down one of the pieces to accommodate a brass strip. I propose to super glue the brass strip into this slot.

My thoughts go like this...
I can if needed at a later time remove and replace the brass strip should it prove necessary. Since only one half of the parallel will need to be slit to allow a clamp screw to pull them together, machining a dovetail can be done at a later date and the brass strip replaced to accommodate it.

Now for today's pictures.

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I took two cuts across the sawn edges of 0.05 mm. You can see in the second and third pictures that a single cut wasn't quite enough to fully clean up the surfaces.

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The second 0.05mm cut almost did. I left it at that since most of that will disappear when milling the 3 mm wide slot

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Here I've just started to mill the slot in the first workpiece. I'm running the mill at 800 rpm and about 15 mm a minute traverse. The depth of cut is 1.5 mm. In the second picture you can see how I used the mill vise stop to set the wood angle so that the workpiece was above the vise top.

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I decided to take a picture of the cutter package sat in the slot just in case anybody wanted to know what Chinese cutter I used. One of Banggood's finest ! At a pound each, brilliant value !