How to enlarg holes in hardened 123 block?

stoneaxe · Apr 21, 2019

I have a couple of cheap Chinese 123 blocks with holes- half of them tapped to 3/8" and the other half through holes. One would imagine in some logical universe the through holes would accept a 3/8" bolt, but no- they are slightly smaller.
I want to use some existing tee nuts in the table and drop a bolt through, so I tried to drill one out- no go.
Is there some easy way to drill these out, or should I toss the POS and buy some that will work? I do not want to spend the time to set up on the mill, center every hole, and use an end mill. Will a straight flute carbide drill bit self center in the holes with no clamping?

I know this is stupid- I mean, one broken bit and it is the cost of some new blocks... But still, curious if it would work- I have drilled thousands of holes on the drill press without clamping to the table, just letting the entire vise and part float so the drill would self center- just have no idea if a carbide straight flute would do this.

Cole2534 · Apr 21, 2019

I imagine this is an errand in futility, but could you mount them to a lathe faceplate and either grind or bore them?

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PeteM · Apr 21, 2019

Hard to know how hard these are given the likely absence of much QA, but most 1-2-3 blocks are hard enough -- and with deep enough holes - that you'd likely go through $200 of carbide die drills to maybe get the holes on these $20 blocks larger. Just as likely chip the outer edges of the drills and give up. It's pretty tough duty to use just the outer lips of any bit on anything super and erratically hard.

It's really a job for grinding, once they've been hardened. Could test with a file, though, to see how hard they are, how deep the case, etc.

Assuming the threaded portion will pass (and if not, they really are a piece of crap), you might be able to quickly neck down some bolts or cap screws to fit.

Red James · Apr 21, 2019

Spend your time making tee-nuts with a 5/16 thread, or even 1/4. Washers are easy.

EPAIII · Apr 21, 2019

It is probably not worth the time if you are in a professional environment. Just get some 1-2-3s that are properly made. Even if you enlarge the holes in the imported blocks, you will find that the spacing of those holes is now very good and bolting them together will be problematic.

I think Suburban Tool has one such set. They will cost more than the imports but the holes will accept bolts and will line up nicely when you assemble the blocks.

PRECISION 1-2-3, SETUP & TRI-BLOCKS by Suburban Tool, Inc.

If you are going to enlarge those holes I think a carbide bit will be at great risk of fracture. I would suggest using the same technique that can be used for drilling a hole in glass. Get a brass tube of the desired diameter. File some notches in the end: leave about 50% of the original end and 50% in the notches. Mix up some abrasive and oil. Mount the brass tube in the drill press and dip the end in the abrasive mixture. Use that as an abrasive drill bit. Start with light pressure and increase as the cutting action begins. Refresh the abrasive-oil mixture as needed. Slow going, but a lot easier to control than any drill bit and the brass tube will not fracture like carbide will.

All the usual disclaimers: I have no relationship with Suburban Tool.

edwin dirnbeck · Apr 21, 2019

Use a cheap $2 masonry drill,60 rpm .Hold block in vise. Set stop on spindle so that you only go about .050 at a time. This will keep drill from catching and chipping.Be very careful when you break thru so that you don't pull the vise up. Edwin Dirnbeck

Billtodd · Apr 22, 2019

edwin dirnbeck said:
Use a cheap $2 masonry drill,60 rpm .Hold block in vise. Set stop on spindle so that you only go about .050 at a time. This will keep drill from catching and chipping.Be very careful when you break thru so that you don't pull the vise up. Edwin Dirnbeck

Similarly, you could try a 10mm diamond tile drill .

ErnieD · Apr 22, 2019

Is there a edm machine available ?

basalt · Apr 22, 2019

I had the same problem however I am retired and have lots of time. So, I made up inserts O.D.= 3/8-16 and I.D.=1/4-20.

Greg Menke · Apr 22, 2019

I have a similar pair, the bolts they included in the box don't even screw in... As blocks they're fine, but not woth modifying so I use them "beater" work with small thru bolts if fastening is needed. Good 123 blocks are not all that expensive- I have a set of Fims blocks that I really like and some a couple pairs of yardsale blocks.

A set of 2x4x6 blocks are occasionally handy, I went ebay on those to gamble on lightly used good quality blocks rather than the cheap imports. I don't need the big ones enough to justify new high quality units.

gbent · Apr 22, 2019

If the hole is only slightly smaller Chicago your screws.

Conrad Hoffman · Apr 22, 2019

Probably useless info to you, but this is where the honing machine excels.

Cole2534 · Apr 22, 2019

gbent said:
If the hole is only slightly smaller Chicago your screws.

Go on.....?

TeachMePlease · Apr 22, 2019

Cole2534 said:
Go on.....?

Probably the opposite of Pittsburghing a hole?

DMF_TomB · Apr 22, 2019

you can buy 1x2" precision ground flat stock thats not hardened. cut to any length you need.

cranium · Apr 22, 2019

Perhaps the guy who just bought the Moore jig grinder can fix these for you?

HuFlungDung · Apr 22, 2019

stoneaxe said:
I have a couple of cheap Chinese 123 blocks with holes- half of them tapped to 3/8" and the other half through holes. One would imagine in some logical universe the through holes would accept a 3/8" bolt, but no- they are slightly smaller.
I want to use some existing tee nuts in the table and drop a bolt through, so I tried to drill one out- no go.
Is there some easy way to drill these out, or should I toss the POS and buy some that will work? I do not want to spend the time to set up on the mill, center every hole, and use an end mill. Will a straight flute carbide drill bit self center in the holes with no clamping?

I know this is stupid- I mean, one broken bit and it is the cost of some new blocks... But still, curious if it would work- I have drilled thousands of holes on the drill press without clamping to the table, just letting the entire vise and part float so the drill would self center- just have no idea if a carbide straight flute would do this.

I'd probably use up some old beater endmills on a job like this. This is one reason I don't sell my old carbide, there is likely some salvage in scrapped cutters that makes the scrap of more value in my hands than a couple of dollars from a scrap man.

However, you do have to securely clamp and find each hole to use an endmill without immediately destroying it, and you'd have to wind up with the knee to control the feed.

But little grinding points for a die grinder are cheap and might do the job on a few holes. A carbide burr will probably also serve, but will likely not last very long as well.

DMF_TomB · Apr 22, 2019

many times you really dont need precision ground 1x2x3 blocks for much of anything. cold rolled steel even if .001 undersize is usually the same thickness if you cut from close to same part of bar. sure bar might be gentle wavy .0005" over 12 foot lengths
.
and if you bolt steel to table and machine or trim them they are then the same height cause you machined them same time. and of course .001" and .0012" (.03mm) and .0015" feeler gage stock comes in rolls you cut to length needed and is used to shim parts using a indicator

D.D.Machine · Apr 22, 2019

just use a old 3/8" carbide endmill ... free hand grind a 45* angle on the corner and use it to drill out the holes ... most 3/8" bolts are under size so a 3/8" hole would work good .

Cole2534 · Apr 22, 2019

cranium said:
Perhaps the guy who just bought the Moore jig grinder can fix these for you?

I haven't bought it yet.

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How to enlarg holes in hardened 123 block?

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