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What is the way to put these holes in the right place?

They are on sloping faces

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Ian P08/10/2019 18:06:39
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20191008_172533.jpgI have made one of these but I need to make several more.

The two end faces are at 45 degrees and have to fit closely between other faces on an existing manufactured product which has clearance holes for the three tapped holes in each end.

I can set the part up to mill and drill/tap each end but I am stuck knowing how to position them accurately. The sloping face is just over 21mm wide but the holes need to be offset slightly but its hard to measure to an edge which is not at right angles.

Ian P

Michael Gilligan08/10/2019 18:18:48
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Can you tolerate a scribed line [or a maybe a reamed hole] on what is pictured as the top surface ?

... if so, just use that as a reference datum and pretend the mill is a jig-borer.

[ no need for any further marking-out ]

MichaelG.

mechman4808/10/2019 18:28:22
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Do you have a set of stepped odd leg calipers? one leg is stepped at 90* the other has a scribing point fitted, if so then all you need to do is set your measurements & placing the stepped leg along the 45* edge & scribe along the 45* face at whatever your measurement needs to be, if you get my drift, many have used an older digital vernier to the same effect., I have.

George.

JasonB08/10/2019 18:35:30
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With the work held at 45deg, machine the end then touch the acute angled edge with an edge finder and move the mill in by the required amount

Edited By JasonB on 08/10/2019 18:35:41

Ian P08/10/2019 19:06:23
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Michael, there has to be other holes anyway and a central one used as a reference when I set the part at 45 degrees on the mill table make good sense.

George, I was hoping to use a method that did not involve marking out as that just adds another two chances of variability creeping in (marking in the first place and following the marks in the second)

Jason, I basically use the acute edge as a reference but (whilst this part does not need micron precision) my concern was whether any machining burr would extend the edge and if so whether to remove it. I now think that if I use a new cutter and take a very fine finishing cut on the face there would be no perceptible burr. I have had an edge finder for years but this will be the first time I've used it!

Ian

JasonB08/10/2019 19:16:56
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If you make the cut so that the material is being cut in from the edge rather than cut out over it the burr should be minimal, and even if taken off with a stroke of a fine file will only make a thou or two difference which is less than you are likely to get eyeballing a scribed line.

not done it yet08/10/2019 19:17:09
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Any reason why you cannot drill and tap the holes before machining the ends to 45 degrees?

JasonB08/10/2019 19:24:54
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You could always make up something like this which would then give a vertical edge to touch off against, two slitting saw cuts across a bit of say 1" wide material should do.

Clive Foster08/10/2019 19:31:49
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Probably faster to go the long way round and make up a jig to hold the plates exactly right then use the mill axis scales to co-ordinate drill the holes.

I'd be thinking in terms of clamping them in an L shape channel set at the right angle. Once you have the co-ordinates figured for the first one everything else repeats.

Model Engineer and Home Shop Workshop types have too much of a savings / economy mentality when it comes to materials. Objectively sacrificing a bit of metal to do the job just like that beats the pants out of messing around for a day with knife'n fork methods. One day I'll convince myself (don't hold your breath, haven't managed in 50 odd years so far).

Ian P08/10/2019 19:33:42
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Posted by not done it yet on 08/10/2019 19:17:09:

Any reason why you cannot drill and tap the holes before machining the ends to 45 degrees?

The tapped holes are normal to the angle face.

Ian P

Martin Connelly08/10/2019 19:39:29
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Dovetails are measured with cylinders to avoid problems like this. Do you have any silver steel or other ground rod that could be used against the angled face to allow more accurate measurement?

Martin C

not done it yet08/10/2019 19:39:48
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Posted by Ian P on 08/10/2019 19:33:42:
Posted by not done it yet on 08/10/2019 19:17:09:

Any reason why you cannot drill and tap the holes before machining the ends to 45 degrees?

The tapped holes are normal to the angle face.

Ian P

Make a jig?

JasonB08/10/2019 19:41:17
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Don't need to go wasting metal making L shaped jigs when you have a pair of Uncle Ketans blockswink

photo 142.jpg

Or the little jig I mentioned above

45deg.jpg

Ian P08/10/2019 19:42:06
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Posted by JasonB on 08/10/2019 19:16:56:

If you make the cut so that the material is being cut in from the edge rather than cut out over it the burr should be minimal, and even if taken off with a stroke of a fine file will only make a thou or two difference which is less than you are likely to get eyeballing a scribed line.

I agree, a few though does not matter here but I wondered what the correct method of dimensioning this part would be if it was drawn for someone to manufacture.

I like you woodworking jig idea, on reflection I have made and used jigs like that previously but it slipped my mind for these parts.

Ian P

Ian P08/10/2019 19:48:31
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Posted by JasonB on 08/10/2019 19:41:17:

Don't need to go wasting metal making L shaped jigs when you have a pair of Uncle Ketans blockswink

Or the little jig I mentioned above

45deg.jpg

Now there's the basis for a new product from Ketan.

If the block is precision ground to a 25mm cube (say) and the convergence of the two faces at 45 degrees is exactly on centre, then we have a 'Balamy Blocks'

I can think of other uses for the Balamy Blocks too.

Ian P

Ian P08/10/2019 19:51:45
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Posted by Martin Connelly on 08/10/2019 19:39:29:

Dovetails are measured with cylinders to avoid problems like this. Do you have any silver steel or other ground rod that could be used against the angled face to allow more accurate measurement?

Martin C

Trouble with rods etc is that its fiddly holding everything in place, Balamy Blocks solve that.

Ian P

JasonB08/10/2019 20:04:14
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Rods also need to fit into a Vee to be of any use.

MK2 JBBlock. 20 x 20 would make it easier to just knock 10mm off the indicated edge, hole will clear a burr thrown up in either direction.

jbblock.jpg

Ian P08/10/2019 20:22:27
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20mm cube and a name change, but I've just realised what the reason is!

Its to get round paying royaltieswink

Ian P

JasonB08/10/2019 20:29:40
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what do you think of the deluxe block, acute & obtuse angles and a vertical face directly above the corner for the mathmatically challenged who can't add/subtract 10 or those who work in imperial.

jbblock3.jpg

It's not your royalties I'm worried about, it's Ketan's cut that's the problemdevil

Ian P08/10/2019 20:56:55
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Jason

Your latest design incorporates some of the things I was thinking of, however putting them all in one block reduces sales and potential profit, far better to market a set of JBB's

Ian P

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