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Pair of compasses, to hold a pencil?

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TominDales

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Did you know that if you use any trammel with a pencil (sharpened with a pencil sharpener) the diameter can be kept precise by mounting the pencil at the same angle as the sharpener.
As the pencil lead wears down the inside/outside edge of the line stays true.
Cheers Andy
Brilliant build, Pencil leads wear done fast if working on large rough wood, this is a good idea. I found I have to keep sharpening them...
 

Jacob

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Brilliant build, Pencil leads wear done fast if working on large rough wood, this is a good idea. I found I have to keep sharpening them...
Veritas probably make a pencil sharpener with brass knobs on and adjustable bevel angles.
 

schnapps95

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Hello,
Regarding the big compasses you are trying to acquire. Some 25 years ago, I altered these to be compasses. They were originally engineers' scribers. You can see the large one, close up, holding a pencil. The wider out you go the more angle you need on the pencil, as you can see by the photos. These are 18" long and you can see how wide they will go. You might need some bigger ones for your 16" radius. There are six men in the workshop and these are used regularly, above that we then use trammells, but obviousl;y for smaller things compasses are much handier.

Incidently, my son, who is a teacher, suggested trying suppliers of school drawing instruments as they still use compasses for whole class instruction. He sent a link to one that he still use at his work place and which can be purchased here: https://www.ypo.co.uk/product/detail/stationery/whiteboard-equipment/711772 though he isn't sure how big it actually goes.

Hope this is of some use to you.

Stan
 

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TominDales

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Rorschach

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Looks like a nice tape for measuring inside cupboards as well as drawing arcs. another £10 blown at Amazon. Thanks
They are superb tapes. Takes you a little while to learn how to use it effectively, there is a knack to it, but once sorted I am able to confidently measure internal dimensions to mm accuracy. I definitely recommend measuring a few times though, internals are more tricky than externals so the old measure twice should be measure four times lol.
 

TominDales

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They are superb tapes. Takes you a little while to learn how to use it effectively, there is a knack to it, but once sorted I am able to confidently measure internal dimensions to mm accuracy. I definitely recommend measuring a few times though, internals are more tricky than externals so the old measure twice should be measure four times lol.
yep, I recently added a rail to a cupboard and despite adding the 5cm to the pocket Stanley 31-026 - layed box to clip, it came out 5mm too long despite pulling the tape tight. I think there is always some slack in an internal measurement? I chickened-out and slowly cut the rail back 1mm at a time until it fit. Could not get the internal measurement to agree with the pole length.
Red fellow arrived this am so will give it a go. Most reviews say its their go to measure, but that the spring is prone to breakage over time. I'll see how it fairs in our household....
 

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yep, I recently added a rail to a cupboard and despite adding the 5cm to the pocket Stanley 31-026 - layed box to clip, it came out 5mm too long despite pulling the tape tight. I think there is always some slack in an internal measurement? I chickened-out and slowly cut the rail back 1mm at a time until it fit. Could not get the internal measurement to agree with the pole length.
Red fellow arrived this am so will give it a go. Most reviews say its their go to measure, but that the spring is prone to breakage over time. I'll see how it fairs in our household....
Had mine for about 2 years I think, no problems with the spring but I only use it when needed (i.e. for internals). It's not my everyday measure.
 

JoshD

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Not exactly what the OP was after---only 13" and doesn't take a pencil--- but just bought these trammel dividers. Just made something where I wanted 24 holes exactly 100mm apart along a line, so that total line is 2300+/-1mm. Doing this with dividers to give precisely equal hole spacing requires setting dividers to 100+/-0.04mm or thereabouts. Did it with regular trammel, but thought fine adjustment screw nice to have.
PXL_20210303_052632279.jpg
 

Jacob

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Not exactly what the OP was after---only 13" and doesn't take a pencil--- but just bought these trammel dividers. Just made something where I wanted 24 holes exactly 100mm apart along a line, so that total line is 2300+/-1mm. Doing this with dividers to give precisely equal hole spacing requires setting dividers to 100+/-0.04mm or thereabouts. Did it with regular trammel, but thought fine adjustment screw nice to have.View attachment 104970
Doing it with dividers is easier than you think. That's why the are called "dividers". It's a lost art perhaps. If you google "why are they called dividers" you get only partial answer.

Say you want to divide by 3 between two points: you set the dividers as near as you can judge and then mark out the points from one end to the other. If there is an error you reset the dividers to reduce/increase by a third of the error as near as you can judge and try again. If there is still an error you divide that again. Incremental correction of a smaller and smaller error.
If the division was by 5 you adjust the error by a fifth and so on.
In your case you'd use larger dividers and divide your 2.3m by, say, 6 (depending on size of dividers) then divide each of these by 4.
Sounds tedious but once you've got it it's fast and very accurate. Several sizes of divider can help
 
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JoshD

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Doing it with dividers is easier than you think. That's why the are called "dividers". It's a lost art perhaps. If you google "why are they called dividers" you get only partial answer.

Say you want to divide by 3 between two points: you set the dividers as near as you can judge and then mark out the points from one end to the other. If there is an error you reset the dividers to reduce/increase by a third of the error as near as you can judge and try again. If there is still an error you divide that again. Incremental correction of a smaller and smaller error.
If the division was by 5 you adjust the error by a fifth and so on.
In your case you'd use larger dividers and divide your 2.3m by, say, 6 (depending on size of dividers) then divide each of these by 4.
Sounds tedious but once you've got it it's fast and very accurate. Several sizes of divider can help
Thanks, yes agree it makes sense to subdivide into first say 6 then 4---but helps if you have two sets of dividers (if you're doing multiple boards) hence recent purchase! FWIW I found my traditional spring dividers (10" Kinex) had too much play to be useful here; nor are they big enough to do 1/6 of 2400 ie 400mm. Trammel dividers have much less play than my traditional dividers, although fine adjustment is fiddly without fine adjustment screw. I found I had to be careful using iterative approach you describe because even tiny holes from the divider pins can cause deflection when you try and insert dividers nearby.
 

Jacob

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......I found I had to be careful using iterative approach you describe because even tiny holes from the divider pins can cause deflection when you try and insert dividers nearby.
You have to do the repeat along a fresh parallel line to avoid the pinholes already made.
Subdividing (6x4) also distributes any error or it may all accumulate on the last stride - you do a 16 step stair riser with 0.5mm error and find that the top step is 8mm different, but 0.5mm per step is nothing if shared out, say 4x4 if you have some long dividers.
That's one advantage of the offset line (plus T square) method - less precise than a straight line with dividers, but the larger random errors distributed.
 
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TheUnicorn

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nice technique here, possibly a bit more rouch and ready than you are looking for?
 
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