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Installing a DRO on a Hartford Bridgeport Clone.
- Thread starter Susquatch
- Start date
Former Member
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Scary isn't it and a real eye opener. Gives a whole new mean to I'm Ironman.....
Been a while since I posted progress on this project. It's tax time so that's my priority right now....... FWIW, farm taxes are unbelievably complex. I think those CRA folks know how easy it is to play games on the farm so they want everything broken out so they can track you and find ways to catch you. They make your life miserable at tax time.
Anyway....... as of today here is where I am on the mill DRO project. This takes into account all the stuff you guys have posted here as well as what I have seen on other posts you folks have done on your own mills:
I've pretty much decided to mount my X, Y, and Z (knee only) scales flush to the moving part with a gaurd. Although I really like the inherent dirt advantages of mounting them upside down, reading about jitter and vibration has convinced me to go for maximum rigidity instead with a separately mounted cover (not directly connected to the scale) sort of like @thestelster did. I like what everyone said about using thin sheet metal for the cover. If need be, I could even put a rubber bead seal into it.
I spent ages trying to find a way to use all the factory brackets for the sensors and then I had this very vivid dream that I had a mill! In fact two mills right now!
When I look at the brackets on @thestelster install, all I can say is "WOW"! Those mounts are built like a brick Shi# house! Same goes for most of @CWelkie s X-axis. So I'm now planning to mount the scale directly to the table and machine my own mounts for my read sensor out of solid bar to attach to the saddle. With a custom mounting bracket I don't need to worry about complexity or rigidity. These concerns will be minimal with a solid one-piece bracket. About all I lose is some adjustability - done carefully, that should not matter.
Note that the factory mounting holes for the read head are slotted to provide about 1.4 mm (55 thou) of adjustment to the scale/head spacing - maybe a wee bit more if I remove the shank threads on the screws which I would only do if necessary. Shims might be more effective.
The precise dimensions can be developed as the install progresses. But in general, my current thinking for the X-Axis sensor mount looks like this:
This is a side view looking down the length of the x-axis. It's not really obvious from the drawing, but the bracket will have side ears on it for the bracket to saddle screws.
Unless somebody provides any comments that make me rethink this or doubt myself, I plan to order the bar stock for the read head brackets later today sometime.
The shield is just bent sheet metal as suggested by @Darren & @Brent H. Cheap, easy, and effective in my mind. I don't have a brake or I'd make my own but siding flashing should be easy to find. I have not looked but I bet they already make that stuff with a Z bend in it. If not, I'll make standoffs like @thestelster did. But I'll prolly make a rubber lip seal instead of plywood.
By mounting the sensor next to the table joint there is lots of room under it for a future way cover. I like @thestelster's cover the way it probably once was. In my mind's eye I see heavy duck canvas - like a heavy tarp. But I'm also on the lookout for a treadmill belt at the dump. We don't have garbage pickup here so I go to the dump once a week anyway. So far nothing there.
But first things first. Get some bar and make a read head bracket. Nice break from doing taxes.
Anyway....... as of today here is where I am on the mill DRO project. This takes into account all the stuff you guys have posted here as well as what I have seen on other posts you folks have done on your own mills:
I've pretty much decided to mount my X, Y, and Z (knee only) scales flush to the moving part with a gaurd. Although I really like the inherent dirt advantages of mounting them upside down, reading about jitter and vibration has convinced me to go for maximum rigidity instead with a separately mounted cover (not directly connected to the scale) sort of like @thestelster did. I like what everyone said about using thin sheet metal for the cover. If need be, I could even put a rubber bead seal into it.
I spent ages trying to find a way to use all the factory brackets for the sensors and then I had this very vivid dream that I had a mill! In fact two mills right now!
When I look at the brackets on @thestelster install, all I can say is "WOW"! Those mounts are built like a brick Shi# house! Same goes for most of @CWelkie s X-axis. So I'm now planning to mount the scale directly to the table and machine my own mounts for my read sensor out of solid bar to attach to the saddle. With a custom mounting bracket I don't need to worry about complexity or rigidity. These concerns will be minimal with a solid one-piece bracket. About all I lose is some adjustability - done carefully, that should not matter.
Note that the factory mounting holes for the read head are slotted to provide about 1.4 mm (55 thou) of adjustment to the scale/head spacing - maybe a wee bit more if I remove the shank threads on the screws which I would only do if necessary. Shims might be more effective.
The precise dimensions can be developed as the install progresses. But in general, my current thinking for the X-Axis sensor mount looks like this:
This is a side view looking down the length of the x-axis. It's not really obvious from the drawing, but the bracket will have side ears on it for the bracket to saddle screws.
Unless somebody provides any comments that make me rethink this or doubt myself, I plan to order the bar stock for the read head brackets later today sometime.
The shield is just bent sheet metal as suggested by @Darren & @Brent H. Cheap, easy, and effective in my mind. I don't have a brake or I'd make my own but siding flashing should be easy to find. I have not looked but I bet they already make that stuff with a Z bend in it. If not, I'll make standoffs like @thestelster did. But I'll prolly make a rubber lip seal instead of plywood.
By mounting the sensor next to the table joint there is lots of room under it for a future way cover. I like @thestelster's cover the way it probably once was. In my mind's eye I see heavy duck canvas - like a heavy tarp. But I'm also on the lookout for a treadmill belt at the dump. We don't have garbage pickup here so I go to the dump once a week anyway. So far nothing there.
But first things first. Get some bar and make a read head bracket. Nice break from doing taxes.
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Got the bar but decided to mount the x scale first. What a HUMUNGOUS PIA!
Drilling for M5 screws into cast iron is a royal pia. Wow. Two drill bits later, only the scale is mounted and even that is only at the ends. No center support just yet.
I made an oak plate to align the drill and tap. Worked just fine (great might be a better word) for the tap, but nfg for the drill. Prolly should have made it in aluminium or brass but didn't want to waste that much metal.
Still have a lotta holes to drill and need new drills anyway. Not much else is gunna happen today. Any better suggestions for drilling small holes (M4) in cast iron?
PS, this is the table and saddle so no drill press - just a battery powered drill.
Drilling for M5 screws into cast iron is a royal pia. Wow. Two drill bits later, only the scale is mounted and even that is only at the ends. No center support just yet.
I made an oak plate to align the drill and tap. Worked just fine (great might be a better word) for the tap, but nfg for the drill. Prolly should have made it in aluminium or brass but didn't want to waste that much metal.
Still have a lotta holes to drill and need new drills anyway. Not much else is gunna happen today. Any better suggestions for drilling small holes (M4) in cast iron?
PS, this is the table and saddle so no drill press - just a battery powered drill.
I know cast iron can vary greatly in hardness/composition, but with all my Asian made machinery I was surprised how easy it drilled and tapped. Make sure you start with a good sharp bit and when you are already working with such a small size a pilot hole probably isn't worth it. Center punch it and it should drill okay if you have a decent bit. The cobalt bits work well on harder material like ss, so if it hardness that's giving you trouble you might try a cobalt bit.
I was actually surprised at how poorly it drilled. I've drilled cast iron before with no problems. Tried several different bits. Made no difference. They are history now. I'll try to get some cobalt drills tomorrow.
Never considered that. I have some diamond Dremel bits I could try first. But it drilled difficult no matter how deep I was.
Doubtful that it's anything special like Meehanite. It's a Hartford Clone of the Bridgeport Pulley Drive made in Taiwan.
Dabbler
ersatz engineer
If it is meehanite, you will have to buy a carbide drill. the cobalt ones wil work - for a shallow hole. Been there. burnt the drill bits. BTW just because they say 'cutting oil is not needed' you can cool the drill using 70% alcohol or WD40; if it is Meehanite, you will need the cooling.
Hmmmm, I think you are saying that the Hartford could be Meehanite after all, and even if not, it could be something similarly hard.
I think that changes my drill buying plans for today. Varco is the only place around here that has any hope of stocking carbide or high cobalt. If not, I might have to drive into Windsor hoping that KBC has some. At $2 a liter for diesel fuel right now, those will be expensive drill bits.... I better call ahead.....
is there a big M on the casting below the ram?
Sometimes cast iron can have hard spots/imputities that are a bitch to drill. I've had decent luck with cobalt bits from Napa.
At $2.25/L here, and 15 mins out of town, i'm not leaving my yard unless its an emergency.
Dabbler
ersatz engineer
I guess that 'delivery' is out of the question...
I will look for the M.
I bought some Cobalt drill bits today. No luck. They do drill but very very slowly and only seem to last for one hole.
Carbide is ordered for delivery on Thursday.
My truck is a 2500 mega cab with the big Cummins in it.
Ya, I wanted to go get them so I could get at least one scale installed and working. KBC didn't have stock so delivery it will be.
I have tried these Hymnorq bits off of Amazon and have been pleasantly surprised with them. https://www.amazon.ca/Migiwata-Extr...1647354524&sprefix=drill+bits,aps,164&sr=8-36
I think I used one bit on my install on my mill. The problem is they don't seem have a complete array of sizes.
It may not be a huge problem for me. 1/8 drills are pretty common. If I make 1/8 pilot holes, I can open them up with a regular drill before tapping. That's my thinking right now anyway.
Can't find any M on the casting anyplace. Prolly doesn't mean much unless it was there. Absence of proof is not proof of absence.......
Hoping carbide drill bits arrive tomorrow.
I tried a cobalt bit already and that didn't really help. But these guys have 1/8 and although that is a smidge too small for a 4mm tap, it will make a decent pilot hole. I have a #29 carbide arriving tomorrow.
Are you using a fixed speed drill? I've never burnt up a HSS bit drilling CI with a variable speed drill. It's slow going but eventually ends up deep enough.