Drilling Holes in a Plastic Gauge Cluster Crystal?

OK, so I am planning on replacing the gauge cluster that is currently in my Blazer with an "updated" "custom OEM" version that has a clock and a trip meter. I already have all the parts to do this. I just finished replacing all the bulbs in the new cluster, too. For the 5 display bulbs I used amber colored LED's and for the 7 other bulbs I just used some new incandescent ones.

Anyway, I am going to have to use a hole saw and drill to cut a hole out in the back of the white plastic housing for the clock. This shouldn't be a problem.

The real issue I think I'll be running into here is gonna be with the crystal. I gave up trying to find one with BOTH of the holes for the clock and trip meter, so I ordered a new one without any holes at all and decided to just "make my own" holes. The problem I need advice on is how to properly mark where the holes go and how to make the holes. I thought about using a soldering iron to melt them, maybe?

As for marking where they go, I have one crystal with a hole in it already for the trip meter. I just figured I would lay the crystal with the trip meter hole on top of the new crystal and use the hole to mark the other crystal where I need to drill. That should be OK. The real problem will be locating where to put the hole for the stem used to set the clock.

Any advice on how to mark the clock hole and how to drill both of these holes in the plastic crystal will be greatly appreciated. I don't want to screw up this new crystal.

Thanks!

@bigcountry78 might have some insight. He swapped in @buckets clock in his 78 k10.

I don't understand what "crystal" means here. Do you mean the clear plastic in front of all the gages? That is generally called the "lens", IIRC.

I cut a lot of acrylic at work, so here is my main advice: get some other thin acrylic fom like HDepot, cut it into two pieces and sandwich the thing you are cutting between them. clamp it together pretty well, then drill through all three.

The backer prevents blow-out on the back, and the front cover keeps the lens material from getting torn up on saw/tooth/blade entry. Between two pieces of any matl, it has nowhere to go so can't tear or jitter or skate or walk or do the Watusi or shatter, or suddenly spin out and slash your hand really badly because it's now become a sawblade itself. Etc.

You could use anything smooth for the backer, but acrylic front helps you see to align it. Don't make the front sheet too thin, 1/4 is what I would use.

BRetty

Vbb199 said:

@bigcountry78 might have some insight. He swapped in @buckets clock in his 78 k10.

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Yea, measure like 7 times, drill once. Don’t do what I did. I got lazy when I first put it in, and the clock ended up at an angle. So the hole I drilled was way off, then I had to keep reaming it out, resulting in the mess you see here. As for making the actual hole, all I used was my drill and the correct size bit. I took my time, and I didn’t have any issues with cracking or splintering. Now, my truck is a driver, not a show truck. So depending on your level of detail needed, you may want to do it differently.

As far as actually fitting the clock into the cluster, if yours is like mine, then there is a thick plastic tube in that spot or an idiot light that was never there in my case. As I found out, that entire plastic tube has to be dremeled out for it to fit properly. I had to open the back of the cluster up for the wires as well. I used a dremel for that too, just don’t damage the printed circuit on the back. Also, don’t do this in your house, as it’ll make the whole place reak of this funky burnt plastic smell that souses don’t really care for. Ask me how I know. Anyway, once the clock is in place, I just held the lens over the stem, lined the rest of it up over the cluster as best as I could, and marked and drilled. After all this mess, and the mess I made, I ended up with a lens that already had the clock stem hole in the correct spot. I got it from a member here so I didn’t have to look at this mess everyday. I hope this has helped some.





This is what I finally ended up with.

bigcountry78 said:

Yea, measure like 7 times, drill once. Don’t do what I did. I got lazy when I first put it in, and the clock ended up at an angle. So the hole I drilled was way off, then I had to keep reaming it out, resulting in the mess you see here. As for making the actual hole, all I used was my drill and the correct size bit. I took my time, and I didn’t have any issues with cracking or splintering. Now, my truck is a driver, not a show truck. So depending on your level of detail needed, you may want to do it differently.

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I just got a brand new CRYSTAL (AKA: "Lens") from LMC. This gauge cluster CRYSTAL (AKA: "Lens") needs 2X holes drilled in it - one for the clock, one for the trip meter. Like I said earlier, I think that marking and drilling the trip meter hole shouldn't be an issue. I'm just gonna lay the old one with the trip meter stem hole down on top of the new one and cram the tip of a Sharpie marker through the old hole to mark where to drill the new one. Marking where to drill the hole for the clock stem is what has me worried. I don't wanna knock your handy work or anything, but I would like it to be just a tad bit cleaner than what you ended up with there LOL. I don't have a "show truck" either but I'm gonna try to make the hole precise enough so that the clock doesn't end up crooked and so that I can use one of these rubber grommets I found at Lowe's to fit around the stems.

My Blazer originally came from the factory with a good bit of options for its day, and I think that adding the OEM clock and speedo w/trip meter to the gauge cluster would be a cool way to add a couple more. From my understanding, these mechanical speedometers with the trip meters were kinda rare, as most like them were electronic rather than the mechanical variety. I think they were only available in '88 according to all I have been able to gather from old forum posts here and a few other places. Here is a pic of the gauge cluster I'll be using. I'm going to just go ahead and order a new printed circuit for it, as well as new contact clips that snap into the back of the cluster housing. I've already put all new bulbs and sockets in it - 5 amber LED's for the display and 7 regular incandescent bulbs for the blinkers and such.



This newer model gauge cluster has several small differences from the '85 in my vehicle now.

• It has a trip meter
• The fuel gauge has "E, 1/2, and F" instead of the 3 circles with varying degrees of white shading them in
• The blue high-beam indicator light is one big blue circle rather than the two smaller circles
• The voltage meter has a block of white paint on the far right rather than orange paint

bigcountry78 said:

As far as actually fitting the clock into the cluster, if yours is like mine, then there is a thick plastic tube in that spot or an idiot light that was never there in my case. As I found out, that entire plastic tube has to be dremeled out for it to fit properly. I had to open the back of the cluster up for the wires as well. I used a dremel for that too, just don’t damage the printed circuit on the back. Also, don’t do this in your house, as it’ll make the whole place reak of this funky burnt plastic smell that souses don’t really care for. Ask me how I know. Anyway, once the clock is in place, I just held the lens over the stem, lined the rest of it up over the cluster as best as I could, and marked and drilled. After all this mess, and the mess I made, I ended up with a lens that already had the clock stem hole in the correct spot. I got it from a member here so I didn’t have to look at this mess everyday. I hope this has helped some.

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The space in my cluster housing on the bottom left corner appears to be pretty open on the inside - like the clock was meant to go there but just wasn't installed. I don't know how much material I'll have to remove from the inner part, but the back I was just going to cut out the diameter of the back of the clock with a hole saw. Hopefully the clock will just fit right in there snug, but if not, I've got my trusty Dremel Tool at the ready.

And yes - I appreciate any and all advice I get here. Thanks!

bigcountry78 said:

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This is what I finally ended up with.

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Looks good! You have the same type of clock as me - the "QUARTZ" variety. There was an earlier one that looked a little different and had the stem in a different spot. This is the one I ordered off eBay quite some time ago and it STILL hasn't gotten here yet. I know there has been inclement weather in Texas but this is getting ridiculous. The thing was supposed to have been here on the 22nd of last month.

I did this to my truck. The clock fit in just fine. Like factory. After you get your clock installed, lay the lens over the top of the bezel and insert tooth pick or something similar into each fastener hole to line everything up and use your sharpie to mark where the clock stem is. just make sure to remove the knob off of the stem prior. The clock wiring just plugs into the upper left hand side of the fuse block for power and the ground hooks up on the ground plug above your master brake pedal.

crpntr78 said:

I did this to my truck. The clock fit in just fine. Like factory. After you get your clock installed, lay the lens over the top of the bezel and insert tooth pick or something similar into each fastener hole to line everything up and use your sharpie to mark where the clock stem is. just make sure to remove the knob off of the stem prior. The clock wiring just plugs into the upper left hand side of the fuse block for power and the ground hooks up on the ground plug above your master brake pedal.

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Thank you. The toothpick idea is excellent and should help out a lot. And thanks for letting me know where the clock plugs into. I was wondering where that was.

If ya mess up I got one I'm not gonna use that has the clock hole with the rubber grommet. No hole for trip tho.

82sbshortbed said:

If ya mess up I got one I'm not gonna use that has the clock hole with the rubber grommet. No hole for trip tho.

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Well, I should have 2 extra used OEM LENSES after this project is complete barring any major eff ups. If you wanna get rid of that clock hole I could probably help you out.

There are special drill bits used to drill plastic that prevent cracking and blow out. They are used to install aircraft windows.

The way I did this when I found a junkyard clock was I cut out a small section of clear plastic and used it as a template. I put it right ontop of mine and the bumps put it in the right spot. If you pay shipping its yours.



For drilling it out I used a hand drill and small files.

On the tan plastic housing (the bit all the gauges screw into) I again made a bunch of holes and then used a small file to connect them and punch out a space for the connector. I then glued in a post I took from another cluster and up it in for the clock to screw into. I'll try and get a picture of this for you if you want.

@just_some_guy,

Now I want you to do all that drilling on top of your wifes fine table I see, and use that chrystal dish to hold it up to! Ha, ha, And have her come in while you're doing it. Then we'll be seeing an obituary instead of a finished job.